Bacon 
 Louis 
 
 UNIVERSITY OF CALIFORNIA. 
 
 OXFT OF 
 
 HENRY DOUGLASS BACON. 
 
 1S77. 
 
 Accessions No. _/ 
 
 Shelf No.. . 
 
CALORIC 
 
 IN TWO VOLUMES 
 
 VOL I 
 
" To every form of being is assigned 
 An active principle : howe'er removed 
 From sense and observation, it subsists 
 In all things, in all natures, in the stars 
 Of azure heaven, the unenduring clouds, 
 In flower and tree, in every pebbly stone 
 That paves the brooks, the stationary rocks, 
 The moving waters, and the invisible air. 
 * * * from link to link 
 It circulates, the soul of all the worlds." 
 
 WORDSWORTH. 
 
CALORIC 
 
 ITS MECHANICAL CHEMICAL AND VITAL 
 
 AGENCIES IN THE PHENOMENA 
 
 OF NATURE 
 
 BY SAMUEL L. METCALFE M.D. 
 
 OF TRANSYLVANIA UNIVERSITY 
 
 VOL I 
 
 LONDON 
 
 WILLIAM PICKERING 
 
 1843 
 
<\ 
 
 \ 
 
PREFACE. 
 
 IN the primitive ages of the world, when men 
 gazed on the wonders of nature with the fresh- 
 ness of childhood, and before the vivid infor- 
 mation of the senses had become obscured by 
 fabulous traditions, all their physical and me- 
 taphysical theories were founded on the belief 
 that solar fire is the efficient cause of motion 
 and life throughout creation. This belief, 
 so manifestly the result of observation and 
 experience, was constantly forced upon their 
 minds with all the evidence of a living reality ; 
 and prevailed for thousands of years in every 
 quarter of the habitable globe. Nor is there 
 anything so strikingly obvious to the unso- 
 phisticated common sense of mankind, as the 
 omnipresent influence of the sun, which is 
 perpetually exerting a tranquil, yet omnipotent 
 energy, throughout the air, the ocean, and 
 the solid ground. He regulates all the phe- 
 nomena of climate and season, evaporation 
 and rain, the circulations of the atmosphere, 
 
 b 
 
VI PREFACE. 
 
 the flowing of waters, the transformations of 
 chemistry, the operations of vitality, and the 
 revolutions of the heavenly bodies. 
 
 But as the ancients never explained the 
 laws by which elementary caloric operates in 
 the generation of force and motion, nor the 
 manner in which it is related to electricity and 
 light; their speculations have exerted little 
 influence on the physical theories of modern 
 philosophers, who have, strangely enough, 
 disregarded nearly all that was most valuable 
 in the science of antiquity. At the present 
 time, it remains undecided, whether caloric is 
 an exceedingly subtile and active essence, as 
 maintained by the early Hindoos, Egyptians, 
 Phoenicians, Chaldeans, Persians, and Arabi- 
 ans, as well as the more enlightened Greeks 
 and Romans ; or whether it consists in mere 
 motion and vibration among the particles of 
 ponderable matter, as supposed by Bacon, 
 Boyle, Hooke, Rumford, Davy, Young, and 
 others. 
 
 One of the most important modern discove- 
 ries was that of latent or combined heat, by 
 Dr. Black. When he proved by accurate ex- 
 periments, that definite measures of caloric are 
 required to convert solids into liquids, and that 
 
PREFACE. vii 
 
 the same subtile fluid is obtained from the 
 atmosphere by respiration, he laid the foun- 
 dation of its true theory. But as he did not 
 extend his researches to its agency in the 
 mechanical, chemical, and vital phenomena of 
 nature, his labours have not been followed by 
 results corresponding with the magnitude of 
 his discovery, if we except the improvement 
 of the steam engine by Watt. 
 
 Nor has any one, either among the ancients 
 or moderns, ever attempted to give a regular 
 and systematic history of the mode in which 
 caloric operates in all the molecular and 
 aggregate forces of matter. Mr. Whewell 
 observes, in his late History of the Inductive 
 Sciences, that " we have no hypothesis regard- 
 ing thermotics, which, being assumed in order 
 to explain one class of phenomena, has been 
 found to account exactly for another." Yet 
 he adds, " it is one of the cardinal points on 
 which the doors of physical knowledge must 
 turn, which have hitherto remained closed." 
 
 Within the last hundred years, electricity 
 has been regarded by many persons as a key 
 by which to unlock all the secret cabinets of 
 nature. We have had electrical theories of 
 chemistry, of life, and of the universe. Yet 
 
Vlll PREFACE. 
 
 no one has explained what electricity is 
 whether a separate and distinct agent a modi- 
 fication of some other exceedingly refined and 
 more comprehensive principle or a mere 
 effect, condition, or property of ponderable 
 matter. The celebrated Faraday at one time 
 adopted the simple and rational theory of 
 Franklin, that it is a material fluid, definite 
 measures of which belong to each element of 
 ponderable matter. And yet he speaks of it 
 very often as if he considered it to be a com- 
 pound fluid. But when treating of its chemical 
 agency, he represents it as " a modification of 
 the exertion of chemical forces." 
 
 Again ; when by following up the discove- 
 ries of (Erstedt, Davy, Arago, and Schweig- 
 ger, who found that electricity is capable of 
 producing all the phenomena of magnetic 
 action on a small scale, he succeeded in 
 obtaining an electric spark from a permanent 
 magnet ; he arrived at the conclusion that 
 electricity and magnetism are identical ; ex- 
 cept that in the latter " the axis of power" is 
 greater than in the former. Yet, as if not 
 satisfied with any of the foregoing hypotheses, 
 he suggests, at another time, that electricity 
 may be resolved into undulations of an aether ; 
 
PREFACE. 1X 
 
 and, at another time, that all the more im- 
 portant electrical phenomena may be resolved 
 into polarization of the particles of ponderable 
 matter, or what has been called atomic polarity. 
 But he does not explain what he means by 
 the axis of power, and electric polarity ; nor 
 how chemical affinity and magnetism, which 
 are merely effects or modes of action, can 
 be identical with their cause; nor does he 
 inform us what causes the aether to vibrate. 
 Such have been the difficulties of this important 
 department of physical science, that its most 
 distinguished votaries have hitherto failed to 
 present us with a consistent theory of electrical 
 phenomena. But I hope to make it appear 
 that most of these perplexities have arisen 
 more from defective methods of inquiry, than 
 from any inherent obscurity of the subject. 
 
 Among the physical speculations of Oken, 
 light, heat, and weight, are represented as a 
 trinity of powers, to which all the phenomena 
 of nature may be referred : while it was main- 
 tained by Coleridge, that electricity, galvanism, 
 and magnetism, are the three fundamental prin- 
 ciples of action in nature, and identical with 
 the three primary dimensions of space length, 
 breadth, and depth. Yet, he observes, that 
 
X PREFACE. 
 
 "the sole factors in all electrical phenomena 
 consist in attractive and repulsive forces, inde- 
 pendent of any material substrate." Such is 
 the reverence of mankind for mysteries, that 
 the most obscure and visionary fancies are 
 often regarded as profound. It was long ago 
 remarked by Longinus, that darkness is a 
 source of the sublime : and it must be admitted 
 that objects are magnified by looming through 
 a fog. 
 
 In all ages of the civilized world, light has 
 been recognised as a powerful agent in the 
 work of the universe. As the great painter 
 of nature, it gives to the dome of heaven its 
 azure hue, to the rainbow, its gorgeous red, 
 brilliant yellow, refreshing green, and lovely 
 blue, shading into the softer violet. It is solar 
 light which touches the morning and evening 
 clouds with its celestial pencil, when they glow 
 with vivid tints of ruby, sapphire, and gold. 
 It adorns the flowery fields with an endless 
 variety ^ of beauteous colours ; while it is per- 
 petually modifying the taste, odour, and other 
 sensible properties of whatever it touches. 
 
 But it is still an unresolved problem, whether 
 light be a material substance, as maintained 
 by Pythagoras, Democritus, Leucippus, Em- 
 pedocles, Plato, Epicurus, Newton, and Brew- 
 
PREFACE. Xi 
 
 ster ; or whether it consist in the mere vibra- 
 tions of some unknown aether, as supposed by 
 Huyghens, Hooke, Euler, Young, Sir John 
 Herschel, Arago, and others. Nor is it yet 
 finally settled whether white light is composed 
 of seven primitive rays, as supposed by New- 
 ton, or of only three fundamental colours, as 
 maintained, with many cogent reasons de- 
 duced from experiment, by Sir David Brew- 
 ster. On the same subject, the advocates of 
 the undulatory or wave theory are equally at 
 variance among themselves : for while Huyg- 
 hens maintained that solar light is composed 
 of only two elementary colours, yellow and 
 blue, Hooke reduced all its modifications to 
 red and violet ; whereas Young reduced the 
 whole to red, green, and violet. 
 
 What is still more remarkable, neither of the 
 two great rival parties has ever yet attempted to 
 ascertain the relations of light to caloric and 
 electricity ; nor in what way they perform so 
 many wonderful effects in the moving drama 
 of the universe. But if they be connected in 
 action, they must be united in theory. And it 
 will be a leading object of the following work 
 to prove, by a careful generalization of facts, 
 that caloric and electricity are mutually con- 
 vertible into each other ; consequently, that 
 
Xll PREFACE. 
 
 they are modifications of one and the same 
 essence, which is the active principle in light, 
 and in all the phenomena of nature. 
 
 Since the time of Sir Isaac Newton, it has 
 been generally supposed that all the molecular 
 changes of matter may be referred to attractive 
 and repulsive forces. Yet the cause of attrac- 
 tion and repulsion has not been identified with 
 any known principle capable of demonstra- 
 tion. The orbits of planets, and the times of 
 their revolutions have been measured with 
 mathematical precision ; but the cause of their 
 eternal motion has never been clearly distin- 
 guished from projectile and gravitating forces. 
 The relative magnitudes of the particles or 
 atoms of ponderable matter have been, to a 
 certain extent, ascertained by the refined 
 analyses of modern chemistry : yet the cause 
 of chemical affinity is still confounded with 
 inherent properties, occult qualities, and unde- 
 fined powers. The composition of plants and 
 animals has been discovered, and their intimate 
 structure explored : yet the organizing prin- 
 ciple remains a profound mystery. What was 
 said by Descartes two hundred years ago, is 
 equally true at the present day. " In Philo- 
 sophia nihil adhuc reperiri, de quo non in 
 utramque partem disputatur." 
 
PREFACE. Xlll 
 
 It has been a complaint of long standing in 
 the world, that nature has spread a veil over 
 the first principles of things, which man can 
 never hope to remove. But there is reason 
 to believe that all the great truths of science 
 which are of the highest importance for us to 
 know, are no less remarkable for simplicity, 
 than for the wide extent of their application ; 
 and that when fully unfolded, they will be self- 
 evident propositions. It is true enough, that 
 the most familiar phenomena of nature, when 
 viewed separately, or through the mystical 
 interpretation of visionary theorists, are as 
 " inscrutable as the scattered leaves of the 
 Sibyl :" but when traced to their origin, the 
 hidden meaning of every thing is gradually 
 disclosed, and order springs from chaos. It was 
 profoundly observed by Sir Edward Bulwer, 
 that " the key to all mystery is the desire to 
 know," and that " there is only a single step 
 from a truism to a great discovery." 
 
 If we are destined ever to arrive at a per- 
 fect theory of nature, it must be founded on a 
 true history of the grand original, and a com- 
 plete knowledge of the prime mover. Nor 
 is it possible that men should avail themselves 
 fully of the powers which are in nature, with- 
 out knowing the cause of these powers. It 
 
PREFACE. 
 
 was from the elastic force of the latent caloric 
 that belongs to nitre, sulphur, and charcoal, 
 that man, unconsciously, obtained the power of 
 gunpowder ; the invention of which has essen- 
 tially modified the condition of the human race : 
 for it thenceforward secured the uninterrupted 
 progress of civilization, which can never again 
 be arrested by the incursions of barbarous 
 hordes, nor the light of knowledge be extin- 
 guished in embryo, as during the early periods 
 of history. It was by discovering that a piece 
 of metal called the loadstone, when horizon- 
 tally balanced on a pivot, is constantly directed 
 to certain points in the polar regions, that 
 commerce and civilization have been extended 
 to the remotest parts of the earth. But men 
 have yet to learn that the same principle 
 which directs the compass-needle to the poles, 
 guides the planets in their orbits, and fills 
 them with life. 
 
 It was by seizing the grand lever of nature 
 as a moving agent, that man was enabled 
 to create the steam-engine, which has brought 
 about a more important revolution in the con- 
 dition of nations, than all the united discoveries 
 of antiquity for thousands of years. Nor can 
 there be a reasonable doubt that a complete 
 
PREFACE. XV 
 
 knowledge of the same agent, as it operates 
 in all the phenomena of nature, would aug- 
 ment the resources of happiness a thousand 
 fold dispel the clouds of error which have so 
 long hovered over the sciences, and enlarge 
 the empire of man over the material world, 
 in an endless variety of ways. It is animating 
 to think how soon this grand result might be 
 brought about, if all the talents now wasted on 
 fruitless speculations were rightly employed 
 in the study of nature. 
 
 It may be right to inform the Reader that a 
 brief outline of the leading views contained in 
 the following chapters was first promulgated 
 by the Author in an Essay entitled " A New 
 Theory of Terrestrial Magnetism," published 
 at New York in 1833; and somewhat ex- 
 tended in a series of papers in the Knicker- 
 bocker Magazine of 1834-5. The Author also 
 feels it due to himself, and to those friends 
 who have been long expecting this Work, to 
 state, that the first three books were originally 
 intended to be published separately, and were 
 actually printed in 1837, the preliminary chap- 
 ter excepted. But as more enlarged views of 
 the subject opened to him, he clearly perceived 
 that a development of the physiological and 
 
XVI PREFACE. 
 
 pathological laws of caloric was essential to 
 the completion of his undertaking ; which at 
 that time he supposed would not require more 
 than twelve months : 
 
 " But more advanced, beheld, with strange surprise, 
 New distant scenes of endless science rise." 
 
 The performance of this task required a 
 vastly greater amount of laborious research 
 than he was prepared to expect, until he had 
 proceeded too far to desist. In the mean 
 time he had the satisfaction of perceiving that, 
 with every additional knowledge of facts, he 
 was conducted to a more elevated point of 
 view, and to more comprehensive generaliza- 
 tions : the consequence of which has been, that 
 in the Preliminary Chapter, he has entered 
 more fully into the rationale of geological and 
 astronomical phenomena, than he had ven- 
 tured to do in the second and third Books. 
 
 In addition to the many difficulties encoun- 
 tered at every step, much precious time was 
 lost owing to ill health, by which the work 
 has been still further and most painfully de- 
 layed, to the disappointment of the Pub- 
 lisher, whose liberality and forbearance merit 
 the grateful acknowledgments of the Author. 
 
GENERAL CONTENTS. 
 
 BOOK r. 
 
 Page 
 PRELIMINARY CHAPTER, being a Synopsis of the Work 1 46 
 
 CHAP. II. On the Atomic Constitution of Matter, and the 
 
 relative Quantities of Caloric in different Bodies. . . 46 96 
 
 CHAP. III. On the Forces of Caloric in elastic Fluids. 
 Theory of their Expansion and Contraction. Consti- 
 tution of Liquids 97 155 
 
 BOOK II. 
 
 CHAP. I. Theory of Cohesion, Conduction, and Radiation. 
 
 156195 
 
 CHAP. II. Chemical Attraction in general 196 224 
 
 CHAP. III. Theory of Solution, and of Freezing Mixtures. 
 
 225252 
 
 CHAP. IV. Theory of Capillary Attraction, and the Con- 
 nexion of molecular with aggregate Forces of Matter. 
 
 253279 
 
 BOOK III. 
 
 CHAP. I. Electricity atmospheric, identical with the Caloric 
 
 which causes Evaporation 280 32 1 
 
 CHAP. II. Theory of Winds, and their connexion with Elec- 
 trical Phenomena. Rationale of Tornadoes, Hail- 
 storms, &c 321 347 
 
XV111 GENERAL CONTENTS. 
 
 Page 
 CHAP. III. The Barometer. Theory of Dew, Mists, Fogs, 
 
 and of the Aurora Borealis 348370 
 
 CHAP. IV. Theory of Voltaic Electricity, and of Subterra- 
 nean or Volcanic Forces 37 1 417 
 
 CHAP. V. Hypothesis of two Electric Fluids examined. 
 
 Relations of Caloric and Electricity 418 454 
 
 BOOK IV. 
 
 CHAP. I. Life History of ancient and modern Opinions 
 
 concerning it 455 506 
 
 CHAP. II. Ultimate Elements of organized Bodies. Why 
 they unite into ternary and quaternary Compounds, so 
 as to form living Tissues. Spontaneous Generation. 
 Theory of Animal Heat, as connected with Respiration. 
 
 507559 
 
 CHAP. III. Influence of Respiration on the Temperature 
 and vital Energy of different Animals. Cause of the 
 Heart's Action, and of the Capillary Circulation 560 623 
 
 CHAP. IV. Theory of Digestion, Sanguification, Coagula- 
 tion, Secretion, Nutrition, Muscular Motion, Sensation, 
 and of Disease. Analogies of the Macrocosm and 
 Microcosm . . 624 689 
 
 BOOK V. 
 
 CHAP. I. Influence of Climate on the physical, intellectual, 
 
 and moral Character of the Human Race 690 728 
 
 CHAP. II. Origin of Races, Nations. Languages, and My- 
 thologies. Unity of the Human Race, and of Organi- 
 zation. Longevity of Nations 729 778 
 
GENERAL CONTENTS. XIX 
 
 Page 
 
 CHAP. III. Influence of Climate and Season on the Diseases 
 of Mankind. General Laws of Epidemics, and on the 
 Nature of Malaria, or bad Air 779827 
 
 CHAP. IV. Theory of Hybernation, suspended Animation, 
 
 warm and cold Bathing 828 852 
 
 BOOK VI. 
 
 CHAP. I. On Air and Exercise 853 886 
 
 CHAP. II. On Aliments, Wine, Spirits, and Malt Liquors. 
 
 887937 
 
 CHAP. III. Theory of Sleep. Influence of the Mind on 
 Health. Modus Operandi of Medicines and Morbific 
 Agents 938985 
 
 CHAP. IV. Theory of Temperaments. Of Hydrophobia, 
 
 Tetanus, and other Spasmodic Diseases 986 1032 
 
 CHAP. V. Theory of Fever, Inflammation, and other Dis- 
 eases, with the best Methods of Prevention and Treat- 
 ment . , 1033 1100 
 
CORRIGENDA. 
 
 THE Reader is requested to observe, that, as the Preliminary Chapter, and the 
 latter part of Chapter III. Book I. were cancelled after the Work was printed, 
 some few of the subsequent references to them will be found not to correspond 
 
 with the present paging. 
 
 Page Line 
 
 8, 4, (note) for Berkley read Berkeley. 
 
 27, 10, after or insert that. 
 
 46, 25, for bond read band. 
 
 94, 11, (note) for as it in read as it is. 
 
 113, 27, for its particles read particles of chlorine. 
 119, 3, after and insert those of. 
 129, 2, for its protoxide read protoxide of silver. 
 
 145, 16, (Table) for 21-62, read 34-32. 
 159, 8, for page 26 read page 4. 
 
 1 61 , 23, for page 24 read page 3. 
 
 163, 4, (note) for page 26 read page 6. 
 
 164, 2, for or read nor. 
 
 167, 5, omit the comma after the word Guyton. 
 
 168, 17, for page 28 read page 38. 
 175, 7, for freeze read frost. 
 
 177, 17, omit reference to page 106. 
 
 224, 19, after Chapter iii. insert Book i. 
 
 232, 2, for 70 read 90. 
 
 269, 16, for cubit read cubic. 
 
 271, 12, for solar attraction read planetary motion. 
 
 279, 23, for second causes read physical causes. 
 
 284, 3, for modified effects, read modifications. 
 
 290, 4, for attraction read nature. 
 
 397, 1, for Pouillet Scrope read Poullet Scrape. 
 
 398, 6, for his father read the elder Pliny. 
 407, 2, jor five to six read four to five. 
 426, 1, (n9te)fur ^Espinus read ^Epinus. 
 430, 11, for acception read acceptation. 
 
 432, 29, for second causes read physical causes. 
 
 445, 16, for numerous read many. 
 
 448, 15. for expected read supposed. 
 
CALORIC. 
 
 BOOK I. 
 
 PRELIMINARY CHAPTER. 
 
 " O that those who have both time and intellect at command 
 adequate to the investigation, might in perfect tranquillity, search 
 into nature, until they ascertain what quantities of heat are re- 
 quired to produce every action of matter ; that mankind might 
 then not only become masters of every kind of knowledge, but 
 of every kind of power." TELESIUS. 
 
 THAT the reader may perceive at once the 
 general scope and object of the present work, I 
 shall commence with a brief outline of the lead- 
 ing facts, which connect the various operations 
 of nature with the fundamental laws of caloric. 
 But as men of science are still undecided whether 
 caloric be a material agent, or the mere effect of 
 motion among the particles of ponderable matter, 
 it becomes necessary to examine the evidence on 
 which these opposite views have been founded. 
 
 Among the most enlightened nations of anti- 
 quity, elementary fire was regarded not only as 
 the most refined and spiritual of all the elements, 
 but as a universal and self active principle, 
 which they considered as identical with exist- 
 
 B 
 
2 VIEWS OF THE ANCIENTS. 
 
 ence or being. It has been amply proved by 
 Bryant, Calmet, and other learned etymologists, 
 that the Greek e*l, and the Latin csse, to be, like 
 our words essence and essential, were derived 
 from the Hebrew tPK Esh or Es, the fire ; and 
 that Vesta, the goddess of that element, had her 
 name from the Chaldee Nn&>N Eshta or Esta. 
 They have also shown that the word Dtf Am de- 
 noted both heat and existence, among the early 
 Egyptians ; who, believing it to be the cause of 
 motion and organization throughout nature, in- 
 scribed it on the great door of one of their temples. 
 We are further informed by the learned and 
 philosophical Parkhurst, that the sacred mystical 
 letters In Ie, which were inscribed over the door 
 of the temple at Delphi, dedicated to Apollo, (who 
 was a mythological personation of the sun or solar 
 fire,) were taken from the Hebrew IT Yeh or 
 Yah, signifying existence or being. Nor is it 
 unworthy of notice, that the Greek irvpfire, was 
 derived from the Hebrew "-ns pur, to break, dis- 
 solve, and separate; actions which clearly imply 
 mechanical and material agency. So much for 
 the primitive meaning of words employed by the 
 ancients to represent the essential nature of what 
 is called heat, but which I shall generally de- 
 nominate caloric, for the purpose of distinguishing 
 the cause from the mere sensation of heat. Let 
 us now examine the views which have been enter- 
 tained by the moderns on this important subject. 
 
OPINIONS OF BACON AND DAVY. 3 
 
 In the Novum Organum, and in his Treatise 
 entitled De Forma Calidi, it was maintained by 
 Lord Bacon, (whose opinion has been adopted 
 by a majority of philosophers since his day,) that 
 the very essence of heat is motion and nothing else. 
 In accordance with this doctrine, Sir H. Davy 
 observes, in his Chemical Philosophy, that " the 
 cause of heat is motion, and the laws of its 
 communication are precisely the same as the laws 
 of the communication of motion." But in the 
 Treatise on Life and Death, as also in his Natural 
 History, Bacon maintains that " there is in every 
 tangible body, a spirit or body pneumatical, 
 which fills the pores of all gross bodies : that it 
 is not some virtue, or action, or trifle, but a real 
 and quantitative substance, though rare, invisible, 
 and without weight." Moreover, that this spirit 
 or body pneumatical, was only another name for 
 what Hippocrates and other Greek authors called 
 0p/tov heat, (and sometimes ww^a spirit, y\$ equally 
 manifest from the fact, that Bacon represents it 
 as the cause of evaporation, and of many other 
 effects which are predicable of caloric alone. 
 And Sir Humphrey Davy observes in his Agri- 
 cultural Chemistry, that " whatever theory we 
 adopt, it is certain that there is matter moving in 
 the space between us and the heavenly bodies, capable 
 of communicating heat." It is therefore evident, 
 that neither of these distinguished men can be 
 fairly ranked as advocates of the immaterial 
 
4 HYPOTHESIS OF NEWTON. 
 
 theory ; and that, in reality, they had no fixed or 
 settled opinions on the subject. 
 
 The authority of Sir Isaac Newton has been 
 often cited in support of the doctrine, that caloric 
 is not a material substance. But it is worthy of 
 special notice, that in all the latest works of that 
 great man on physical science, he maintains the 
 existence of what he calls " an exceedingly sub- 
 tile and elastic ethereal substance, which is dif- 
 fused through all places, fills the pores of gross 
 bodies, and forms a large constituent of their 
 bulk or volume." In a letter addressed to the 
 celebrated Boyle in 1678, the object of which 
 was to explain his views of the aether, he repre- 
 sents it as " the cause of cohesion, capillary attrac- 
 tion, and of the force by which menstruums per- 
 vade and dissolve solid bodies." He adds in another 
 sentence, " I conceive the atmosphere to be com- 
 posed of the particles of all sorts of bodies of which 
 the earth consists, separated and kept at a distance 
 from one another by the same active principle"* 
 
 * The above views were still further expanded in a scholium 
 at the close of the second edition of the Principia, published in 
 1713; and in the form of queries, they were reiterated at the 
 close of the Optics, published in 1717. In both of these great 
 works, he represents the sether as the cause of gravity, cohesion, 
 capillary attraction, solution, elasticity, the emission, reflexion, 
 refraction, and inflexion of light. He also maintained that the 
 sether is the cause of animal motion. Yet he observes, that he 
 knows not what the aether is; and that " we have not that suf- 
 ficiency of experiments which are requisite to an accurate deter- 
 mination of the laws by which this subtile spirit operates." 
 
HYPOTHESIS OF NEWTON. 5 
 
 But if the aether be the cause of solution, and of 
 the elastic force of the atmosphere, it is mani- 
 festly identical with caloric. It is true that in 
 the fifth query, towards the close of the Optics, 
 Newton represents heat as consisting in a vibra- 
 tory motion among the particles of bodies, and 
 that the whole theory of the Principia was founded 
 on the hypothesis that space is a vacuum ; which 
 is certainly at variance with the foregoing views 
 of the aether. It is also inconsistent with his 
 doctrine of light, which he regarded as a material 
 substance, perpetually flowing from the sun and 
 fixed stars through space. But that caloric does 
 not consist in mere motion or vibration among 
 the particles of ponderable matter, would appear 
 from the following considerations: 
 
 1. That it may be added to and subtracted 
 from other bodies, and measured with mathe- 
 matical precision, as all good thermometers de- 
 monstrate : 
 
 2. That it augments the volume of bodies, which 
 are again reduced in size by its abstraction : 
 
 But if Newton had traced the word sether to its primitive roots, 
 he would have found that it was a Greek noun, which was 
 derived from two Phoenician or Hebrew words, Ath or Aith the 
 sun, and Ur fire, meaning the solar fire, a discovery which 
 probably would have modified all his physical investigations, 
 and have given a totally new aspect to the whole circle of the 
 Sciences. The truth is, that a complete Etymological Dictionary 
 would sweep away innumerable misconceptions, errors, and me- 
 taphysical subtleties, which have gradually arisen from the re- 
 volutions in language, and the adoption of words, the primitive 
 meaning of which has not been understood. 
 
O PROOFS THAT CALORIC IS 
 
 3. That it modifies the forms, properties, and 
 conditions of all other bodies, in an endless 
 variety of ways : * 
 
 4. That it passes by radiation through the 
 most perfect vacuum that can be formed by 
 means of the air pump, in which it produces the 
 same effects on the thermometer as in the atmos- 
 phere : 
 
 5. That it exerts mechanical and chemical 
 forces which nothing can restrain, as in volcanos, 
 the explosion of gunpowder and other fulmina- 
 ting compounds : 
 
 * It was first ascertained by Dr. Black, that on mixing a 
 pound of water at 172 F. with a pound of ice or snow at 32, 
 the latter was melted, when the temperature of the mixture stood 
 at 32 ; showing that 140 of caloric had been transferred to the 
 ice, and intimately combined with its particles. Since then it has 
 been found, as predicted by Black, that definite measures of 
 caloric are required to convert all other solids into the liquid and 
 gaseous states : that when a pound of steam at 212, is mixed 
 with 7 pounds of ice at 32, the latter is converted into water 
 of the same temperature; showing that 7 X 140, or 980 are 
 thus transferred from the steam to the ice, and employed in 
 melting it, without producing in it any elevation of tempera- 
 ture. This is what Black called the latent heat of water and 
 steam. It has also been discovered, that a cubic inch of water 
 at 212, is expanded to the dimensions of a cubic foot, or about 
 1720-fold on passing into the gaseous state, proving that 1719 
 parts by volume of steam at the same temperature, are occupied 
 by the caloric which surrounds its particles. The same fact is 
 still more remarkably illustrated in hydrogen gas, the volume of 
 which is nine times greater than that of the same weight of 
 steam, ceteris paribus : so that above 15,000 parts of the space 
 occupied by hydrogen, must be filled by that subtile form of 
 matter called heat. 
 
A MATERIAL AGENT. 7 
 
 6. That it operates in a sensible manner on 
 the nervous system, producing intense pain, and 
 disorganization of the tissues when in excess.* 
 
 But if caloric were a mere property or quality, 
 how could it be taken from one body and added 
 to another? Or if it augment the volume of 
 other bodies, must it not itself have volume, 
 occupy space, and therefore be a material agent? 
 Would it not be mere jargon to speak of the 
 radiation, reflexion, convection, and conduction 
 of a mere quality, or immaterial property ? And 
 if caloric were only the effect of vibratory motion 
 among the particles of ponderable matter, how 
 could it radiate from hot bodies without the 
 simultaneous transition of the vibrating parti- 
 cles? But it is certain that when iron, copper, 
 and other metals are heated to any temperature 
 below the point of ignition; like boiling water, 
 they give off caloric freely, without any sensible 
 loss of ponderable matter. 
 
 * The same reasoning on which is founded all belief in the 
 material existence of the outward universe applies equally to 
 caloric. No metaphysical sophistry can refute the belief of man- 
 kind, that whatever operates in a sensible manner upon material 
 organs, must be a material substance; for the obvious reason, 
 that " there can be no virtue without substance," as maintained 
 by Newton. It was an axiom among the ancients, that nothing 
 can be said to exist, unless it can be recognized by the senses. 
 " Nihil esse potest, nisi quod attigimus, aut vidimus." And 
 it was observed by an able writer in the Church of England 
 Review, that our words thing, and think, were derived from the 
 Greek verb Qiyy-tv, to touch; that is, a thing is what we first 
 
8 OBJECTIONS ANSWERED. 
 
 It has been said, that " the material theory 
 contains an inherent vice, by assuming the ex- 
 istence of a body, which has never been obtained 
 in the separate form." But if caloric do not 
 exist in a separate state while passing through a 
 vacuum, all our reasonings about it are fallacious 
 and unintelligible. Nor is it possible to explain 
 in a simple and satisfactory manner, any single 
 one of the phenomena ascribed to it by all par- 
 ties, in accordance with the hypothesis that it is 
 identical with motion, which is manifestly not 
 an agent, but merely some body in the act of 
 moving, and always implies the existence of a 
 mover. 
 
 If the vibratory theory were true, caloric ought 
 to be generated by all impulses which throw the 
 particles of bodies into a state of violent agitation. 
 But such is not the fact ; for if the atmosphere, 
 the ocean, and the solid strata of the earth, were 
 kept in a state of perpetual tremor, their tempe- 
 rature w r ould not be materially altered. The ad- 
 vocates of the immaterial theory have never ex- 
 plained what causes bodies to vibrate ; nor what 
 
 touch, and then think upon. And he adds that all impressions on 
 the senses are resolvable into touch. But there is nothing in na- 
 ture which operates so powerfully on the sense of touch as caloric. 
 
 " When Bishop Berkley said there was no matter, 
 And proved it 'twas no matter what he said." 
 
 And when men say that caloric is not matter, they reject the evi- 
 dence of their senses, subvert the foundation of all knowledge, 
 and pave the way to universal scepticism. 
 
OBJECTIONS ANSWERED. 9 
 
 keeps the particles of solids, liquids, and gases, 
 at a distance from each other while quiescent, or 
 free from vibratory motion.* And it is worthy of 
 special notice, that caloric is disengaged by pres- 
 sure, friction, or percussion, only so long as 
 bodies undergo condensation. For it has been 
 
 * It was supposed by Bacon, that the essential nature of heat 
 is motion, and nothing else, because it accompanies the motion 
 of friction, percussion, combustion, ebullition, violent exercise, 
 &c. Count Rumford was led to adopt the same opinion from 
 the following experiments : Into a cannon weighing 113 Ibs. and 
 cast solid, he caused a hole to be bored 3*7 inches in diameter, 
 and 7'2 inches in depth. Into this hole, he introduced a blunt 
 steel borer, that was made to rub against the bottom by horse 
 power, with a force equal to about 10,000 Ibs. avoird., the cylinder 
 being turned at the rate of thirty-two times per minute. At the 
 expiration of thirty minutes, when the cylinder had made 960 
 revolutions about its axis, its temperature was found to have 
 risen from 60 to 130 F. In another experiment, the cylinder 
 was wrapped round with flannel to prevent the loss of heat, and 
 inclosed in a wooden box containing 18*77 Ibs. of water, which 
 at the beginning was at the temperature of 60. After the ex- 
 periment had proceeded for an hour, it was raised to 107, in 
 thirty minutes more, to 142, in two hours, to 178, and in 
 two hours and a half, to 210. At the close of the experiment, 
 he found that 4145 grains of metallic dust and scales had been 
 detached from the bottom of the cylinder by the rubbing of the 
 borer, or above eight ounces. And as he found that the capa- 
 city, or what has been called the specific heat of the scales, was 
 the same as that of an equal weight of solid iron, he arrived at 
 the conclusion, that heat is not a material substance, but the 
 mere effect of motion. (Philosophical Transactions, 1798.) But 
 it will be shown hereafter, that what is called capacity or specific 
 heat, is not a measure of the quantity in different bodies ; and 
 that this mode of estimating their latent or combined caloric is 
 fallacious. 
 
10 OBJECTIONS ANSWERED. 
 
 proved by the experiments of Berthollet, Biot, 
 and Pictet, that when pieces of gold, silver, and 
 copper of the same size and shape, are suddenly 
 and forcibly struck, as when stamped in the pro- 
 cess of coining, they were condensed, and caloric 
 evolved, but more by the first than second blow ; 
 whereas after the third blow, when they had 
 arrived at the limit of condensation, there was no 
 perceptible increase of temperature. (Thomson 
 on Heat and Electricity, p. 339.) 
 
 In accordance with these facts, it is well known 
 that the smith often kindles his furnace by ham- 
 mering a piece of iron until it becomes red hot, 
 without any material loss of metallic dust or 
 scales ; and that after he has reduced it to the 
 limit of condensation, it becomes cold under the 
 hammer. It is therefore evident, that caloric is 
 not generated de novo, by the friction of rubbing 
 dry sticks of wood against each other, the pres- 
 sure of wire drawing, and by rubbing the hands 
 together ; but that it is merely forced out of the 
 pores of bodies, in the same way that water is 
 disengaged from the pores of a sponge by pres- 
 sure. And it will be proved hereafter, that the 
 caloric which is disengaged by rubbing the 
 hands together briskly, is resupplied by the 
 rapidly circulating blood, which obtains it by 
 respiration. 
 
 Should it be urged that caloric is disengaged by 
 rubbing two pieces of ice together in the vacuum 
 
OBJECTIONS ANSWERED. 11 
 
 of an exhausted receiver, as in the experiments 
 of Sir Humphrey Davy, I answer that there is 
 an enormous amount of caloric locked up in a 
 state of chemical combination with ice, as shown 
 by the rapidity with which it melts frozen mer- 
 cury, nitrate of potass, chloride of lime, chloride 
 of sodium, and many other salts which have a 
 strong attraction for caloric. There is, therefore, 
 no good reason why caloric should not be sepa- 
 rated from ice by friction as well as from other 
 solid bodies. And it may be asserted with con- 
 fidence, that if all the latent caloric contained in 
 a pound of ice could be transferred to the same 
 weight of gold, silver, iron, or copper, it would 
 raise them to a red heat, and perhaps convert 
 them into flame, or incandescent luminous 
 vapour. 
 
 That the particles of all bodies are surrounded 
 by an elastic medium, which prevents their actual 
 contact, is evident from their compressibility. 
 And that this medium is caloric is proved by the 
 facts already stated, that it augments the volume 
 of solids, liquids, and gases, which are again re- 
 duced to their former dimensions by abstracting 
 what was before added ; and by the large amount 
 of heat that is disengaged by friction, which is 
 transitive pressure, or by percussion, which is 
 sudden pressure; both of which cause condensa- 
 tion. It was estimated by Sir Isaac Newton, that 
 the pores of gold occupy about the same space as 
 
12 ALL BODIES FULL OF CALORIC. 
 
 its solid atoms ; and that in water, the pores are 
 about forty times greater than its solid particles. 
 (Optics, Book ii. p. 242.) If then it be true, that 
 all bodies are full of caloric, that it occupies 
 827 parts by volume of the atmosphere, and 
 1719 parts of steam, it must be obvious that it 
 constitutes by far the greater proportion by bulk, 
 of the solid globe we inhabit. And if when in- 
 timately combined with the particles of ponder- 
 able matter, its thermal properties are disguised 
 or hidden from the senses, the same thing is true 
 of water and the strong acids, the individual pro- 
 perties of which are concealed while they are in 
 a state of chemical union with rocks, salts, &c.* 
 
 Having thus proved that caloric is a material 
 agent, I now proceed to show that it is a self- 
 active principle, capable of moving itself, and of 
 generating motion in all other bodies. The car- 
 dinal facts which connect its agency with the 
 general theory of physics, may be reduced to the 
 following propositions : 
 
 1. That the activity or moving power of all 
 
 * The above facts will enable us, in some measure, to compre- 
 hend the theory of opacity and transparency, the cause of which, 
 Sir John Herschel thinks, has never yet been satisfactorily 
 explained. For as it is well ascertained that the particles of 
 the atmosphere, steam, gases, water, saline and metallic solu- 
 tions, like glass, and a great variety of crystalline solids, are 
 arranged in regular series, at considerable distances from one 
 another, the rays of light pass through them with slight in- 
 terruption, giving rise to the phenomena of transmission and 
 what, is called transparency. But when the regular arrange- 
 
GENERAL LAWS OF CALORIC. 13 
 
 bodies, is directly in proportion to the amount of 
 caloric around their particles : 
 
 2. That all molecular motions, whether centri- 
 fugal or centripetal, may be resolved into the law 
 
 by ivhich caloric repels its own particles, and at- 
 tracts those of ponderable matter, with forces that 
 vary inversely as the squares of the distance : 
 
 3. That the quantity of motion in the world, 
 whether mechanical, chemical, or vital, is in pro- 
 portion to the mean temperature of different lati- 
 tudes, ceteris paribus, and diminishes from the 
 equator to the poles : 
 
 4. That the centrifugal force by which planets 
 are impelled through their orbits, is directly in pro- 
 portion to the heating power of the sun ; and like 
 gravitation, is inversely as the squares of the dis- 
 tance : 
 
 5. That the aggregate vital energy of animals, 
 and the dev elopement of their organization, are ex- 
 
 ment of the particles of ice, glass, quartz, and other crystals, is 
 disturbed by unequal pressure, or unequal expansion by caloric, the 
 rays of light are transmitted imperfectly : and if their symmetrical 
 structure be broken down or deranged, as when they are reduced 
 to powder, their power of transmitting light is so far destroyed, 
 that they are rendered opaque. Sir Isaac Newton supposed that 
 opacity was owing to the largeness, and transparency to the 
 smallness of the particles and intervening pores of bodies. (Optics, 
 B. ii. p. 235.) But many salts, rocks, and metals, are transparent 
 when dissolved in water and the strong acids, although their par- 
 ticles are much larger than those of common ink and many other 
 bodies which are black and opaque. 
 
14 GENERAL LAWS OF CALORIC. 
 
 actly in proportion to the amount of caloric obtained 
 by respiration, and combined with their tissues : 
 
 6. That every variety of electricity is conver- 
 tible into caloric, and the latter again into electri- 
 city ; consequently, that they are modifications of 
 one and the same principle : 
 
 7. That the directive power of the compass needle 
 diminishes from the isothermal equator to the points 
 of lowest mean temperature, which are the magnetic 
 poles ; and that all its variations correspond with 
 the variations of terrestrial temperature : 
 
 8. That caloric is the active principle in light, 
 whether radiated from the sun, or generated by 
 ordinary combustion, friction, percussion, phos- 
 phorescence, or the electric discharge. 
 
 That caloric is a self-active principle, might 
 naturally be inferred from the fact, that every 
 change in the temperature of bodies is attended 
 with motion among their particles. It has also 
 the power of moving from one place to another, 
 and even through the vacuum of an air pump, 
 without any projectile impulse from the particles 
 of ponderable matter; as when it radiates from 
 hot bodies. And that it 4 has the faculty of ge- 
 nerating motion among the particles of other 
 matter, would appear from all the phenomena 
 of nature with which we are best acquainted. 
 
 For example, under the ordinary pressure of 
 the atmosphere, and at, or a little below the tem- 
 perature of 32, the particles of water exist in the 
 
CALORIC A SELF-ACTIVE PRINCIPLE. 15 
 
 solid and apparently fixed state. But if 140 of 
 caloric be added, their mobility is so far increased 
 that they glide freely over one another, and 
 assume the fluid form. If more be added, their 
 activity is still further augmented by every de- 
 gree of temperature, up to the boiling point, 
 when the whole is found to be in a state of rapid 
 intestine motion. And if at this stage of the ex- 
 periment, the water be kept over a furnace, until 
 it has received about 1000 more of caloric, the 
 boiling liquid is converted into steam, the moving 
 force of which is exalted by every addition of 
 this active principle, which has the power of con- 
 verting all other bodies from solids into liquids, 
 vapours, gases, and flame, or luminous incan- 
 descent particles. 
 
 If then it be true, that caloric alone gives to 
 the quiescent particles of ponderable matter 
 powers of motion which they do not possess 
 without it; and that their mobility is augmented 
 by every addition, and diminished by every 
 abstraction of the igneous principle it follows 
 with all the clearness of absolute demonstration, 
 that in the total absence of caloric, if such a con- 
 dition were possible, the universal system of nature 
 would be a motionless mass of inert and chaotic 
 matter. It also follows, that every thing in nature 
 is composed of two descriptions of matter, the 
 one essentially active, and the other passive ; as 
 maintained by many of the most distinguished 
 
16 ATTRACTION AND REPULSION. 
 
 philosophers of ancient Greece. Here is the foun- 
 dation of all physical logic, and a key to the 
 whole mechanism of nature. For as it is certain 
 that all the changes and transformations of matter 
 are the immediate effects of motion, it follows that 
 a complete knowledge of the prime mover would 
 lead to a perfect theory of physics. 
 
 Since the time of Sir Isaac Newton, attraction 
 and repulsion have been generally regarded as 
 ultimate principles of action, for which no reason 
 can be assigned.* But if it be a fact, that the 
 elastic force of bodies is augmented by every 
 addition, and diminished by every abstraction of 
 caloric, it is obvious that the entire privation of 
 
 * After referring to his theory of planetary motion, Newton ob- 
 serves in his Preface to the Principia, " many things induce me to 
 suspect, that all the rest of the phenomena of nature may depend 
 upon certain forces, by which the particles of bodies, by some 
 causes hitherto unknown, are mutually impelled towards each 
 other in regular figures, or are repelled and recede from one an- 
 other; which forces being unknown, philosophers have hitherto 
 attempted the investigation of nature in vain." Sir H. Davy also 
 observes, that " the various forms of matter, and the changes of 
 these forms, depend upon active powers, such as gravitation, 
 cohesion, calorific repulsion or heat, chemical attraction, and 
 electrical attraction." (Chemical Philosophy, p. 67.) Dr. Arnott 
 further states, that " attraction and repulsion are ultimate facts, 
 which admit of no explanation in the present state of science." 
 (Elements of Physics.) And Sir John Herschel adds, that " we 
 have no means of further analyzing the phenomena of cohesion 
 and elasticity, but must regard them, until we see reasons to the 
 contrary, as ultimate phenomena, referable to the direct agency 
 of an attractive and repulsive force." (Introduction to the Study 
 of Nat. Philosophy, s. 80.) 
 
ATTRIBUTES OF A PRIMARY CAUSE. 17 
 
 it, would destroy the repulsive power of their 
 particles. And as we have seen, that without 
 caloric, they could have no power of motion, it is 
 evident that they could neither approximate nor 
 recede from one another ; consequently, that both 
 attraction and repulsion are modified effects of 
 one and the same agent. Moreover, if it can be 
 proved that this agent is every where present in 
 the pores of bodies, as in the stellary spaces and 
 cannot be traced to any more comprehensive 
 principle it must be allowed to possess all the 
 attributes of a primary efficient cause. For, no- 
 thing can merit the title of a vera causa, unless 
 it be something which has the power of moving 
 itself, and of generating motion in other bodies. 
 
 It is equally evident, that whatever the cause 
 of attraction and repulsion may be, it must de- 
 termine all the phenomena of cohesion, chemical 
 affinity, crystallization, elasticity,* decomposition, 
 
 * If the particles of the atmosphere and other bodies were not 
 surrounded by caloric, there could be no vibrations, (in which 
 heat has been supposed to consist,) therefore no sound. And 
 here it is worthy of notice, that the velocity with which sound is 
 propagated through different media, is directly in proportion to 
 their elasticity, ceteris paribus. For example, it travels through 
 the atmosphere when at the temperature of 32, at the rate of 
 1090 feet per second; but when at 62, it travels 1125 feet per 
 second. It also moves at the rate of 3375 feet per second through 
 hydrogen gas, which contains a much larger amount of caloric 
 around its particles, than the same weight of atmospheric air, or 
 any other gas, as will be shewn hereafter. In accordance with 
 the above facts, it is well known that sound is transmitted more 
 
18 AGENCY OF CALORIC IN METEOROLOGY. 
 
 and recombination. When I come to treat of the 
 mode in which caloric produces opposite effects, 
 it will be found that in certain proportions it 
 causes the particles of ponderable matter to 
 separate, while in other proportions it forces 
 them to unite: that the aggregate force of at- 
 traction by which it tends to unite with the par- 
 ticles of gross matter, holds them together, and 
 maintains the earth in the globular form : in 
 short, that all the phenomena of nature may be 
 referred to the law by which caloric repels its 
 own particles, and attracts those of ponderable 
 matter. 
 
 That the quantity of evaporation and rain 
 throughout the earth is in proportion to the 
 heating power of the sun, ceteris paribus, would 
 seem to be a self-evident proposition. And it 
 will be shewn hereafter from numerous scientific 
 observations i that the annual average amount 
 
 distinctly, and rapidly, through light and resinous, or the more 
 combustible species of wood, than through such as are dense, less 
 elastic, and therefore contain less of the elastic sether termed caloric. 
 It also moves with greater velocity through water than glass, 
 and more swiftly through either than through rocks and metals, if 
 we make allowance for the greater density of the latter. For it 
 was found by MM. Biot and Colladon, that it was transmitted 
 through water at 46, at the rate of 4704 feet per second ; and 
 through cast iron at 61, at the rate of 1 1,090 feet per second. 
 But the specific gravity of cast iron is nearly eight times that of 
 water. And we shall find that it contains a far greater amount 
 of caloric around its particles than the same weight of iron, 
 although less than an equal bulk of iron. 
 
EVAPORATION AND RAIN. 19 
 
 of rain within the tropics, except in desert 
 places, is about 100 inches, or three times 
 greater than in the middle latitudes ; and about 
 nine times greater than in the polar regions. 
 Hence the enormous size of the tropical rivers, 
 compared with those of the higher latitudes. For 
 example, it has been found that the Orinoco, which 
 drains only 400,000 square miles of territory, dis- 
 charges more water into the sea than the Missis- 
 sippi, which drains 1,350,000 square miles.* It 
 will also be shewn, that the quantity of light- 
 ning throughout the earth, diminishes from the 
 torrid zone ; where during the rainy season, it 
 occurs almost every day, for nearly half the 
 
 * It has been estimated by geographers, that about thirty-three 
 cubic miles of water are discharged daily into the sea by all the 
 rivers of the earth. So that if this calculation be correct, or even 
 an approximation to the truth ; and if the same proportion of 
 rain falls into the sea as on a given area of dry land, it follows 
 that nearly 140 cubic miles of water must be carried into the 
 atmosphere every twenty-four hours, and again precipitated in 
 the form of rain and snow. Such are the vast forces which caloric 
 is continually exerting in the phenomena of meteorology, without 
 any reference to those violent commotions of the atmosphere 
 termed hurricanes, tornadoes, and other less impetuous winds. 
 Nor is it unworthy of passing notice ; that as the quantity of 
 water diffused through the atmosphere is in proportion to the 
 heating power of the sun, the barometer stands higher, on an 
 average, within the tropics than in the middle or polar latitudes ; 
 as proved by the observations of Erman, laid before the French 
 Academy of Sciences, after my chapter on the barometer had been 
 printed. More water is also converted into steam during the heat 
 of the day, and more steam is condensed into water during the 
 coldness of night, which is the most convenient period for rain, 
 as it does not then impede the labours of husbandry. 
 
20 THEORY OF WINDS. 
 
 year, on to the polar regions, where it scarcely 
 ever lightens. 
 
 But were it not for the union of caloric with 
 the particles of ponderable matter, there could be 
 no fluidity of the ocean, which would be station- 
 ary as the solid frame-work of the mountains. 
 Were it not for the heating power of the sun, 
 there could be no contractions and expansions of 
 the atmosphere, therefore no winds, nor fluctua- 
 tions of the barometer. But in the present order 
 of things, not an atom of the great aerial ocean is 
 wholly quiescent for a single moment of time. 
 Its tropical portions being constantly expanded 
 by the influence of a vertical sun, rise and give 
 place to the denser air of colder latitudes ; by 
 which a perpetual circulation is kept up, as de- 
 scribed in the 1st chapter of Ecclesiastes, v. 6. 
 " The wind goeth toward the south, and turneth 
 about unto the north : it whirleth about contin- 
 ually, and returneth again according to its cir- 
 cuits." 
 
 If the earth were of uniform surface and ele- 
 vation, there would be a gradual diminution of 
 temperature from the equator to the poles, and 
 the winds would be as regular as the movements 
 of the heavenly bodies. But owing to the pre- 
 sent distribution of land and sea, mountains and 
 valleys, plains and woods ; the temperature of the 
 globe is infinitely diversified, even in the same 
 latitudes ; by which the phenomena are rendered 
 proportionally complex. And as the changes of 
 
FORCES Of CALORIC. 21 
 
 weather depend chiefly on the direction of winds, 
 they cannot be predicted with invariable accu- 
 racy, without knowing all the circumstances 
 which modify the temperature of different and 
 distant places. It is not therefore surprising that 
 meteorology has never been reduced to the cer- 
 tainty of an exact science. 
 
 Were it possible to compute the aggregate forces 
 of caloric in all the mechanical, chemical, and 
 vital transformations which are for the most part 
 unobserved, we should be astonished at the re- 
 sult.* But men are so accustomed to the regular 
 course of nature, that they are less aroused by the 
 grandeur of the sun, rising in pomp and might, 
 filling the world with beautiful creations, and 
 diffusing everywhere the spirit of gladness, than 
 by a passing meteor of the night. 
 
 That the whole theory of geological dynamics 
 is in some way immediately connected with the 
 agency of caloric, is now generally admitted by 
 
 * It is in the torrid zone that nature exults in the plenitude of 
 her powers in modifying the surface of the earth, where the 
 forces of the volcano, the earthquake, and of universal chemistry, 
 are surpassed only by those which wheel the planets through their 
 orbits. For example, we are informed by Captain Burnes, that 
 during the Cutch earthquake of 1819, the Delta of the Indus was 
 elevated about ten feet, over an area of fifty miles in length, and 
 sixteen in breadth, in some places. We also learn from Mr. Lyell's 
 excellent work on Geology, that during the shocks of 1822 in 
 South America, the coast of Chili was raised about four feet, over 
 an area of 100,000 square miles. And it is well known that 
 similar movements are constantly taking place in different parts 
 of the earth, or beneath the ocean. 
 
22 VOLCANIC FORCES. 
 
 philosophers. But the general fact to which 1 
 would here invite attention is, that the number of 
 volcanos and the forces they exert are in proportion 
 to the heating power of the sun* For example, 
 among the 200 volcanos now in action in different 
 parts of the earth, about one half are confined to 
 the tropical regions. In the island of Java alone, 
 Mr. Lyell says there are thirty-eight : and there is 
 about the same number in other tropical portions of 
 the old world. Between latitudes 10 and 15, in the 
 Provinces of Guatimala and Nicaragua in South 
 America, there are twenty-one; while in Peru, 
 between latitudes 14 and 20, there are sixteen ; 
 and I know not how many in the West Indies. 
 
 Again ; that the subterranean forces by which 
 the dry land has been elevated from beneath the 
 ocean, have in all past ages been in proportion 
 to the heating power of the sun, would appear 
 from the relative heights of the earth in different 
 latitudes. Nearly the whole of tropical America 
 
 * In every point of view, a complete theory of volcanos is of 
 fundamental importance: for they regulate the distribution of 
 land and sea, the magnitude and elevation of continents, the 
 diversities of temperature in given latitudes, the character of 
 rivers, and modify the direction of winds, which are impeded 
 or deflected by mountain ranges. They are also the great ter- 
 restrial laboratories in which most of the precious gems are 
 formed, in which carbon is liquified, and by slowly cooling under 
 an immense pressure, assumes the crystalline form of that beau- 
 tiful ornament the diamond, which has been aptly designated as 
 " a lump of light." Nor is it unworthy of notice, that all the 
 richest gems and metals have been found in greatest abundance 
 in the tropical mountains, or among the materials washed down 
 from them by rains, rivers, and springs. 
 
RELATIVE HEIGHTS OF THE EARTH. 23 
 
 for 3,000 miles in length, and several hundred in 
 width, is one great system of mountains, separated 
 by plains, which, within the tropics, are from 
 twelve to fifteen thousand feet above the sea. 
 Near the equator, Sorato and Illimani tower to 
 elevations of 25,400, and 24,350 feet, according 
 to the measurements of General Pentland. As we 
 proceed northwards towards Mexico, the loftiest 
 peaks are those of Chuquibamba, Gualatiere, 
 Sahama, Cotopaxi, Sierra, Antissana, and others, 
 which vary from 19,000 to 22,000 feet, until we 
 arrive at the table lands of Mexico, which, between 
 latitudes 19 and 24 N. are from six to 8,000 feet 
 above the sea. 
 
 As we advance through the middle latitudes of 
 North America, the rocky mountains average 
 about 10,000 feet. And if we except St. Elias and 
 Mount Hooker, they never exceed 12,000 feet. 
 Nor do the table lands which slope from their 
 base exceed from three to 5,000 : while it is well 
 known that from latitude 60, the elevations dimi- 
 nish on to the polar sea. On the other side of the 
 equator, the highest mountains of Chili are the 
 Acongagua and Descabezado, which, between 
 latitude 32-28 and 35 S. rise to elevations of 
 23,200, and 2 1 , 1 00 feet, from which they all dimi- 
 nish on to Patagonia, and thence to Cape Horn.* 
 
 * It is said that Captain C. Ross has recently discovered in 
 S. lat. 80 a mountain 12,400 feet high. But a few such ex- 
 ceptions are too slight to invalidate the general law. 
 
24 RELATIVE HEIGHTS OF MOUNTAINS 
 
 If we turn to the old world, we shall find that 
 there is riot a single mountain chain of the first 
 magnitude throughout the middle latitudes of 
 Asia, Europe, New Holland, nor the islands of the 
 sea : that, as in South America, the highest 
 plains of India, between latitude 24 and 32, are 
 from twelve to 15,000 feet; while the Himalayas 
 rise to elevations of from twenty-three to 26,862 
 feet : that the long chains of the Altai, which 
 extend across Europe and Asia, in about the lati- 
 tude of 50, are generally from six to 8,000, and 
 rarely exceed 15,000 feet: that the mountains 
 of western Europe also diminish in height from 
 the Alps, the Appennines, and the Pyrenees of 
 the south, to the Carpathians, the Dofrines, and 
 Urals of the north ; which rarely exceed 6,000 
 feet : that the vast plains of central Asia, be- 
 tween the Altai and Himalaya mountains, are 
 from three to 5,000 feet above the level of the 
 sea; while the plains of Siberia decline gradually 
 on to the polar ocean : that in Greenland and 
 Spitzbergen the average height of the mountains 
 is about 5,000 feet ; while Hecla in Iceland is 
 only 4,980 feet. 
 
 If the mountains of Africa are less elevated 
 than those of southern Asia and tropical America, 
 they are far more numerous, and the amount of 
 high table lands is much greater than in any 
 other quarter of the globe. Extending from the 
 equator to 34 S. and 37| N. its central plateaus 
 are supported by an immense chain that crosses 
 
AND PLAINS IN DIFFERENT LATITUDES. 25 
 
 the continent from west to east ; between which 
 and its southern extremity, there are three other 
 parallel ranges that diminish in height on to the 
 Cape of Good Hope. The vast plains of Abys- 
 sinia and Nubia are also several thousand feet 
 above the ocean, and supported by innumerable 
 mountains of still greater magnitude than those 
 of Atlas in the west ; while the eastern coast is 
 flanked by a chain which extends, with few in~ 
 terruptions, from north latitude 10 to 32 S. But 
 it is evident that the elevation and extent of table 
 lands, (which are in fact widely extended moun- 
 tains,) afford a far more accurate measure of geo- 
 logical forces, than the height of a few isolated 
 peaks. 
 
 From the foregoing brief outline we perceive, 
 that all the highest mountains of the earth are 
 found within 32 of the equator : and, what is still 
 more important to observe that the average eleva- 
 tion of the table lands is about equal to that of the 
 mountains in the middle latitudes, where again, the 
 table lands are of nearly the same height as that of 
 the polar mountains. The conclusion is therefore 
 irresistible, that the aggregate force by which moun- 
 tains, islands, and continents, have been raised, from 
 beneath the ocean, like all the chemical transforma- 
 tions on the surface of our planet, is in proportion 
 to the heating power of the sun, ceteris paribus. 
 
 And that the same law prevails throughout 
 the planetary system, would appear not only from 
 
26 OBSERVATIONS OF SCHROETER. 
 
 analogy, but from a series of telescopic observa- 
 tions continued for ten years on the surface of 
 Venus, by the celebrated Schroeter, who has 
 estimated the height of its principal mountains 
 as varying from 10*84 to 22-05 miles. So that 
 after making due allowance for the uncertainty 
 of such observations, it is probable that he has 
 arrived at an approximation to the truth. For, 
 as Venus is 1-40 times nearer to the sun than the 
 earth, and as the heating power of the sun is in- 
 versely as the squares of the distance, Venus 
 must receive more caloric than a given area of 
 the earth, in the ratio of 1*96, or nearly as 2 
 to 1, because the square of 1*40 is 1-96. For 
 the same reason, as the heating power of the sun 
 is 6*959 times greater at Mercury than on the 
 earth, which is 2*638 times farther from the sun, 
 the mountains of Mercury ought to be of corres- 
 ponding magnitude. And as Mars is 1*494 times 
 farther from the sun than the earth, he must re- 
 ceive 2*232 times less caloric ; which must pro- 
 portionally modify all the conditions of his sur- 
 face. In like manner, as Jupiter is 5-157 times 
 farther from the sun than the earth, he must 
 receive 26*594 times less caloric. And so on to 
 the extremity of the solar system. 
 
 But in estimating the changes which the sur- 
 face of our planet has undergone during long 
 geological epochs, we must not overlook the in- 
 fluence of variations in the inclination of the 
 
PLANETARY INCLINATIONS. 27 
 
 earth's axis, in modifying the mean temperature 
 of different latitudes. It is generally supposed 
 to have been demonstrated theoretically by La- 
 place, that the total variation of the planetary 
 inclinations must be comprised within the nar- 
 row limits of 3. That in so vast and complicated 
 a problem as that of perturbation, geometers may 
 have overlooked some important elements in their 
 calculations, would seem highly probable from 
 the limited period since which accurate observa- 
 tions have been made ; for they admit that the 
 disturbing influence of all the planets and their 
 satellites upon each other is such, that millions 
 of years are required to bring about one cycle. 
 
 But if it w r ere wholly impossible to determine 
 the exact amount of variation in the plane- 
 tary inclinations, during the countless ages that 
 have past, geology affords the most conclusive 
 evidence, that at some remote period of the 
 earth's existence, the inclination of its axis must 
 have been far less than at present ; or the 
 equator and poles must have been reversed. For 
 it has been discovered that the secondary for- 
 mations at Melville Island, and other parts of 
 the polar regions, are filled with the fossil re- 
 mains of plants and animals, which could have 
 been produced only in a warm climate ; and that 
 the newest tertiary deposits in Siberia, abound 
 with bones of the Mastodon or mammoth, which 
 seems to have been as common in the higher 
 
28 RELATIONS OF GEOLOGY 
 
 latitudes of Asia and America, as elephants are 
 now within the tropics. The conclusion is there- 
 fore undeniable, that a warm climate once pre- 
 vailed in the arctic regions, and, perhaps, at| 
 several distant periods of time. Nor is it pos- 
 sible to account for such a state of things without 
 supposing that in the progress of long geological 
 epochs, the inclination of the earth's axis has 
 undergone very great changes. 
 
 That this inclination is now actually diminish- 
 ing at the rate of one minute in 126^ years, is ad- 
 mitted by all astronomers. It therefore follows, 
 that if it should go on decreasing in the same 
 ratio, without any oscillations or retrogradations, 
 it would wholly vanish in about 177,760 years, 
 when the sun would shine upon every part of the 
 earth with nearly the same force, and produce a 
 grand physical millenium,*or what may be termed 
 
 * In the tenth book of the sublimest song in our language, 
 Milton represents the earth as enjoying this happy exemption 
 from winter, before the fall of man : after which, the Creator 
 
 " Bid his angels turn askance 
 The poles of earth twice ten degrees and more : 
 ***** to bring in change 
 Of seasons to each clime ; else had the spring 
 Perpetual smiled on earth with verdant flowers. 
 These changes in the heavens, though slow, produced 
 Like change on sea and land. * * * * 
 Beast now with beast 'gan war, and fowl with fowl, 
 And fish with fish ; to graze the herb all leaving, 
 Devoured each other/' ***** 
 
TO ASTRONOMY. 29 
 
 a vernal period of the great year. For although 
 there would be perpetual summer at the equator, 
 and a gradual diminution of temperature on to 
 the highest latitudes, there would be no winter. 
 In short, the days and nights would be every 
 where of the same length, except immediately 
 around the poles, which would be always illumi- 
 nated, and there would be no variety of seasons, 
 but an unceasing verdure would everywhere 
 prevail. And that the earth may have fre- 
 quently passed through such a state, is highly 
 probable from the fact, that at the present 
 moment, the axis of Jupiter has very little if any 
 inclination. And that this inclination has an 
 extensive range of variation, would further ap- 
 pear from the fact, that in the case of Saturn it 
 is now 28 40', while in that of Mars it is 30 18', 
 according to Sir John Herschel. There is there- 
 fore no obvious reason why the inclination of 
 the earth's axis should not go on augmenting 
 until it arrives at the same angle.* 
 
 * In reality, it is more in accordance with analogy to sup- 
 pose that this variation may pass through an entire revolution, 
 than that it is confined within the narrow limits of 2 or 3. 
 Should such a revolution go on uniformly at the rate of 48" in 
 a century, its completion would require a period of 2,700,000 
 years, unless interrupted by a conjunction of all the planets ; an 
 event which the ancients regarded with dread, as the cause of 
 deluges, or some other signal catastrophe. We are informed by 
 Mr. Samuel Davis, that, according to the Surya Siddhdnta, the 
 oldest Hindoo work on Astronomy, the obliquity of the ecliptic 
 was 24, when it was written ; which must therefore have been 
 4000 years before the 19th century. (Asiatic Researches, vol. ii.) 
 
30 FUNDAMENTAL LAWS OF 
 
 But are we not further authorized to conclude, 
 that the equator may have gradually shifted to 
 the middle and even the polar latitudes? This 
 hypothesis would enable us to explain the high 
 and uniform temperature which prevailed through- 
 out the northern hemisphere when the higher lati- 
 tudes abounded with tropical plants and animals, 
 a great physical fact which cannot be satisfac- 
 torily accounted for in accordance with the 
 theory of Laplace. The truth is, that his ma- 
 thematical reasonings were founded on the sup- 
 position that all the planets move in nearly the 
 same plane ; whereas it is now admitted by 
 astronomers, that the orbit of Pallas is inclined 
 to the ecliptic at an angle of 34^, and that of 
 two satellites of Uranus at an angle of 78 58'. 
 But these cosmical bodies had not been dis- 
 covered when the Mecanique Celeste was written ; 
 nor had Geology then taken its legitimate rank 
 among the Sciences. 
 
 This brings us to the general theory of plane- 
 tary motion. The leading facts of the solar sys- 
 tem which connect the movements of the heavenly 
 bodies with the agency and laws of caloric, may 
 be reduced to the following propositions. 
 
 1 . That the sun is 882, 000 miles in diameter, 
 and revolves on his axis from west to east, in 
 about twenty-five days. 
 
 2. That planets revolve around the sun, satel- 
 lites around planets, and all of them upon their 
 
PLANETARY MOTION. 31 
 
 axes, in the same direction that the sun moves 
 upon his axis. 
 
 3. That the heating power of the sun dimi- 
 nishes in proportion as the squares of the dis- 
 tance increase.* 
 
 4. That the centrifugal force by which planets 
 and their satellites are impelled through their 
 orbits diminishes in proportion as the squares of 
 the distance from the centres of power increase. 
 
 5. That the centripetal force by which planets 
 are impelled towards the sun, and satellites 
 
 * For example, as Mercury is 1-888 times nearer to the sun 
 than Venus, he receives more caloric than Venus, in the ratio of 
 3-564 to one; because the square of 1-888 is 3-564. And as 
 Mercury is 2-638 times nearer to the sun than the earth, he 
 receives 6-959 times more caloric, or the square of 2-638. For 
 the same reason, as Mercury is 3-944 times nearer to the sun 
 than Mars, the latter receives 15-555 times less caloric: Ceres 
 25-157 times less; Jupiter, 185-259 times less on a given area; 
 Saturn 625 times less ; and Uranus 2500 times less. Or, if we 
 take our own planet as the standard of measure, the heating 
 power of the sun is 2-232 times greater at the earth than at Mars, 
 because he is 1-494 times farther from the sun; 7'371 times greater 
 than at Ceres; 26*594 times than at Jupiter ; 89-737 times than at 
 Saturn ; and 358-988 times greater than at Uranus. But as the 
 planets are impelled through their orbits by two equal and op- 
 posite forces that unite in support of each other, the velocities do 
 not diminish at the same rate as their mean distances from the 
 sun : for while Jupiter is 5*157 times farther from the sun than 
 the earth, his velocity is only about 2-30 times less. In like 
 manner, although Saturn is nearly 9J times farther from the sun 
 than the earth, his velocity is only about three times less ; and so 
 of all the other planets, as may be readily ascertained by com- 
 paring the times and distances in the following Tables, con- 
 structed from data furnished by Sir J. Herschel. (Treatise on 
 Astronomy.) 
 
32 
 
 OPPOSITE FORCES OF CALORIC. 
 
 towards their primaries, diminishes in the same 
 ratio. 
 
 6. That by the joint operation of two forces, 
 each of which varies inversely as the squares of 
 the distance, the celestial bodies are impelled 
 through their orbits with velocities which vary 
 in accordance with Kepler's third law, as shown 
 in the following tables : 
 
 TABLE I. 
 
 M6Tcuryi * 
 
 Mean distance 
 from the sun. 
 36000000.. 
 
 Periodic times 
 d. h. m 
 88 ... ... 
 . 224 ... 7 ... 
 . 365 ... 6 ... 
 687 ... ... 
 . 1681 ... 8 ... 
 . 4332 ... 14 ... 
 .10759 ... 5 ... 
 .30686 ... 20 ... 
 
 .. 27 ... 7 ...43 
 
 s. 
 ... 
 ... 
 ... 
 ... 
 ... 
 ... 
 ... 
 ... 
 
 ...11 
 
 Velocities Diame- 
 per hour. ters. 
 ...107,100... 3,200 
 ... 79,227... 7,800 
 ... 68,093... 7,912 
 ... 54,113... 4,189 
 ... 40,484... 
 ... 29,608. ..87,000 
 ... 21,899... 79,000 
 ... 15,356... 35,000 
 
 ... 2,271... 2,160 
 
 "Venus 
 
 68 000 000 
 
 Earth 
 Mars 
 Ceres 
 Jupiter 
 Saturn 
 Uranus 
 Dist. of moon 
 from the earth 
 
 . 95,000,000.. 
 . 142,000,000.. 
 . 260,000,000.. 
 . 490,000,000.. 
 . 900,000,000.. 
 . 1800,000,000.. 
 
 X 237,000. 
 
 TABLE II. 
 
 SATELLITES OF JUPITER. 
 
 Periodic times. 
 
 
 Mean dist. 
 
 d. 
 
 h. 
 
 m. 
 
 Velocities. 
 
 Diameters. 
 
 First Sat. 
 
 263,111 ... 
 
 1 ... 
 
 18 
 
 ... 28 
 
 ... 38,929 
 
 ... 2508 
 
 Second 
 
 418,620 ... 
 
 3 ... 
 
 13 
 
 ... 14 
 
 ... 30,860 
 
 ... 2068 
 
 Third 
 
 667,725 ... 
 
 7 ... 
 
 3 
 
 ... 43 
 
 ... 24,433 
 
 ... 3377 
 
 Fourth 
 
 1,174,413 ... 
 
 16 ... 
 
 16 
 
 ... 32 
 
 ... 18,423 
 
 ... 2890 
 
 TABLE III. 
 
 SATELLITES OF SATURN. 
 
 Periodic times. 
 
 Mean dist. d. h. m. Velocities. 
 First Sat. 132,364 ... ... 22 ... 38 ... 36,750 
 
 Second 
 Third 
 Fourth 
 Fifth 
 Sixth 
 
 169,850 ... 
 208,718 ... 
 269,350 ... 
 376,198 ... 
 872,199 ... 
 
 1 ... 
 1 ... 
 2 ... 
 4 ... 
 15 ... 
 
 8 
 21 
 17 
 12 
 
 22 
 
 ... 53 
 ... 18 
 
 '..'. 41 
 
 ... 32,503 
 ... 28,949 
 ... 25,739 
 ... 21,802 
 ... 14,320 
 
 Seventh 2,542,180 ... 79 ... 7 ... 55 ... 8,389-5 
 
DISCOVERIES OF KEPLER. 33 
 
 Three of the asteroids, and the satellites of 
 Uranus, have been omitted, because their ele- 
 ments have not yet been fully ascertained. 
 The third column in the tables was obtained by 
 multiplying the distances by 2 ; which gives 
 the diameter of the orbits. On multiplying this 
 by 3*1416, and dividing the product by the 
 periodic times, we get the velocities with a suf- 
 ficiently near approximation to the truth for our 
 present purpose. 
 
 After the establishment of the true solar system 
 by Copernicus,* the invention of the telescope, 
 and the discovery of Jupiter's satellites by 
 Galileo, the most important advance ever made 
 in Astronomy was that of the immortal Kepler, 
 announced in a work entitled " Harmonice Mun- 
 di" published in 1619. In that work, he demon- 
 
 * We are informed by Aristotle and Plutarch, that the sun was 
 recognized as the centre of our system by Pythagoras, who learned 
 it in Egypt There is also reason to believe that some of the 
 early Chaldean astronomers were acquainted with the same theory. 
 But as it was unknown to all the Greek philosophers, except 
 Pythagoras, or was rejected by them, the knowledge of it must 
 have been always confined to a very small number of the ancients. 
 It is stated by Josephus, that an imitation of the sun, moon, and 
 five planets, was represented in the Jewish Tabernacle ; and the 
 general system of nature, on the robes of the high priest : that his 
 mitre was a symbol of heaven ; (as it was of the sun among the 
 Egyptians ;) his breast-plate of the earth in the centre of the uni- 
 verse ; the twelve stones set in it, of the twelve zodiacal signs ; 
 and the ephod of the four elements. (Jewish Antiquities, Book 
 iii. Sect. 7.) 
 
34 DISCOVERIES OF NEWTON. 
 
 strated that " the squares of the periodic times of 
 any two planets are to each other, in the same pro- 
 portion as the cubes of their mean distances from 
 the sun, a law which has been found equally 
 true of satellites and their primaries, if we ex- 
 cept the mutual influence they exert upon each 
 other, termed perturbation. It also led to the 
 important discovery of Newton, that every particle 
 of matter in the universe attracts every other, ac- 
 cording to the law of the inverse square of the dis- 
 tance; a law which, independent of all hypo- 
 theses in regard to the cause of motion, was one 
 of the highest generalizations ever made in the 
 science of Nature. 
 
 In regard to what is called Newton's first law 
 of motion, various and opposite opinions have 
 been entertained. By Leibnitz and other phi- 
 losophers of the last century, it was rejected as 
 hypothetical. According to this law, as announced 
 in the first book of the Principia, " every body 
 perseveres in its state of rest or of motion, 
 unless compelled to change that state by forces 
 impressed thereon." On this law was founded 
 his theory of planetary motion, as developed in 
 the third book, in which he maintains, that 
 when first created, the earth and heavenly bodies 
 were projected into empty space, by the agency 
 of a primitive impulse, communicated at various 
 distances from their centres of gravity ; by which 
 their annual and diurnal revolutions have been 
 
HIS FIRST LAW OF MOTION. 35 
 
 ever since maintained, without any renewal of 
 the cause.* 
 
 But in all the operations of nature with which 
 we are best acquainted, force is always expended 
 in producing motion ; and if not as constantly re- 
 newed, is very soon exhausted. Nor have we the 
 slightest proof, that motion is ever generated 
 without the immediate agency of some active 
 principle. The power of steam is created by the 
 immediate agency of caloric, and ceases when- 
 ever the acting principle is withdrawn. The force 
 with which a horse shoe magnet of soft iron holds 
 on to the armature, is generated by the passage of 
 an electric current through the wires which are 
 coiled around it ; but ceases the moment the cur- 
 rent is arrested. The metallic wire that connects 
 the extremities of a voltaic battery, attracts iron 
 filings, and deflects a magnetic needle in its 
 vicinity, so long as the electric fluid is disen- 
 gaged by chemical action, but ceases whenever 
 that action is at an end. The powers of digestion, 
 secretion, nutrition, and muscular motion, are 
 generated by means of an active principle which 
 is obtained from the atmosphere by respiration ; 
 
 * Newton observes, " that the motions of the planets may 
 subsist an exceeding long time, it is necessary that the heavens 
 should be void of all resisting matter." And he adds in another 
 place, " by the vis insita of bodies, I mean nothing but their 
 vis inertia." (Princip. book iii.) 
 
36 VIEWS OF HERSCHEL AND WHEWELL. 
 
 but cease whenever that important function is 
 arrested ; as will be shown in subsequent parts of 
 this work.* 
 
 But if it be true that caloric is perpetually 
 radiated from the sun and fixed stars into the 
 boundless regions of space, it must constitute an 
 infinite ocean of aethereal essence ; consequently, 
 there can be no such thing as a vacuum, which, 
 as Aristotle rightly observed, would destroy all 
 motion. Nor is it less obvious, that if caloric 
 be a self-active principle, and is every where 
 present, there can be no such condition of matter 
 as vis inertia, which literally means the power 
 of not acting. And that a single impulse is not 
 competent to maintain the unceasing motion of 
 planets and satellites, is evident from Newton's 
 
 * Such facts have created very strong doubt in the minds of 
 philosophers in regard to the truth of Newton's first law of mo- 
 tion. For example, it is observed by Sir John Herschel that, 
 " to say matter has inertia, is only to say that the cause is ex- 
 pended in producing its effect, and that the same cause cannot 
 continue to produce its effect without renewal." (Nat. Philoso- 
 phy, sect. 234.) And it was humorously argued by the author of 
 Knickerbocker, that " as the projectile force has long since ceased 
 to operate, while its antagonist remains in undiminished potency, 
 the world ought, in strict propriety, to tumble into the sun." Nor 
 would it be difficult to demonstrate, that this catastrophe would 
 occur before it performed one fourth part of its annual revolution, 
 if the force of gravity were counteracted only by a single impulse 
 of equal force. Mr. Whewell also observes in his Bridgewater Trea- 
 tise on Astronomy, that " to say motion must continue the same 
 from one instant to another, because there is nothing to stop it, 
 seems to be taking refuge in words." But there is no one force 
 
ERRORS OF NEWTON. 37 
 
 own hypothesis, that they are impelled or drawn 
 with an equal force at right angles to the direction 
 of the original projection. Moreover, when New- 
 ton referred the centrifugal force to the immediate 
 agency of the Deity, and that of gravity to an 
 inherent property of matter, he departed from 
 that uniformity of nature and of causation, on 
 which all true science is founded. To be con- 
 sistent, he ought to have referred all physical 
 power to the immediate agency of the Deity, or 
 to the inherent properties of matter. 
 
 That the illustrious author of the Principia was 
 not ultimately satisfied with the data on which 
 his theory of planetary motion was founded, viz. 
 the projectile impulse, the vacuum of space, and the 
 vis insita of matter* is plain enough from what has 
 
 in nature which is not counteracted by another force. It is there- 
 fore evident that Newton's first law of motion does not apply, as 
 he originally intended, to the planetary revolutions. Mr. Whe- 
 well is equally explicit in renouncing the vacuum of space : for 
 when treating of the luminiferous aether, he says, " it must not 
 be merely like a material fluid poured into the vacant spaces of the 
 material world ; it must affect the physical, chemical, and vital 
 properties of whatever it touches, and be the means of communi- 
 cation between planets and systems/' (Book i. ch. xvii. and 
 book ii. ch. xi.) Yet he observes in another chapter, that " in the 
 machinery of the universe there is, so far as we know, no material 
 connection between the parts which act on each other." (Book 
 ii. ch. i.) 
 
 * It might as well be said that " opium causes sleep by means 
 of a dormitive property," as that the particles of bodies are held 
 together by means of an inherent power of attraction termed co- 
 hesion ; or that planets are maintained in their orbits by an in- 
 
38 ERRORS OF NEWTON. 
 
 been already said in the early part of this chapter, 
 concerning his views of the aether. But here 
 again he was unfortunate in his explanation of 
 the mode in which it produces the phenomena of 
 cohesion, capillary attraction, gravitation, &c. 
 For he supposed that " the aether was more rare 
 within the bodies of the sun and planets, than in 
 the celestial spaces between them ; and that its 
 density increases perpetually in proportion as the 
 distances increase from them, thereby causing the 
 gravity of those great bodies towards one an- 
 other, and of their parts towards each other, 
 every body endeavouring to go from the denser 
 parts of the medium towards the rarer." (Optics, 
 Queries 20, 21.) 
 
 The failure of this hypothesis has been already 
 exposed by Mr. Whewell, who justly observes 
 that all elastic fluids tend to an equilibrium ; 
 so that if the density of the aether increased 
 with the distance, the force of gravity would 
 diminish until the equilibrium was restored, 
 when it would cease ; while it is now generally 
 understood, that the density of all radiant matter 
 diminishes with every increase of distance from 
 
 herent power of gravity, without the agency of an intermediate 
 impelling principle. And if we admit that each of the eleven 
 planets and their fourteen satellites was projected into space by a 
 primitive impulse, is it not remarkable that the continuous force of 
 that impulse should precisely correspond with the heating power 
 of the sun, and be just equal to the power of gravity ? 
 
UNSETTLED VIEWS OF NEWTON. 39 
 
 any given centre. And it will be proved here- 
 after, that the aether is more dense within the 
 pores and around the particles of dense than of 
 light bodies, in which it is more dense than in 
 free space. On the whole, it is not very sur- 
 prising that Newton's views of the aether have 
 been generally regarded as chimerical, and in- 
 sufficient to explain the leading phenomena of 
 nature ; especially as he never identified it with 
 any known principle. And when he referred 
 the centripetal forces of matter to its agency, he 
 assigned no physical cause of the centrifugal 
 force. But if the centrifugal force of planets be 
 directly in proportion to the radiating power of 
 the solar orb, caloric must be the cause of this 
 force : for the essential character of a vera causa 
 is, that the effects it produces are a measure of 
 its intensity.* 
 
 Nor is it less certain, that if the caloric which 
 is perpetually radiated from the sun be not anni- 
 
 * Moreover, as the mean temperature of the earth has remained 
 the same for long periods of time, it follows that the planets must 
 give off by radiation the same amount of caloric they receive from 
 the sun. This amount must depend on their superficial area, and 
 on their distance from the sun. It therefore becomes an important 
 question, how far it may operate in producing the centrifugal 
 force of their satellites, just as the radiating power of the sun 
 generates the centrifugal force of the planets themselves. At the 
 same time it must be observed, that the motions of the satellites 
 are subject to the direct influence of the sun ; which, however, is 
 greatly diminished by his immense distance, compared to the 
 nearness of their primaries. For as Sir John Herschel observes, 
 
40 CIRCULATION OF THE AETHER. 
 
 hilated, it must either accumulate in the planetary 
 spaces, and thus raise their mean temperature ; or 
 it must return to the great fountain from which it 
 emanates. It also follows, that if the vast aethe- 
 real tide flow perpetually toward the sun, with 
 the same force which it exerts in maintaining 
 the centrifugal power of planets, there is no good 
 reason why it should not be the cause of the cen- 
 tripetal force which maintains them in their 
 orbits ; consequently, that the projectile and gra- 
 vitating forces of Sir Isaac Newton are owing to 
 one and the same principle which produces all 
 the contractions and expansions, separations and 
 combinations of the particles of ponderable mat- 
 ter ; as will be proved in the third chapter of this, 
 and the whole of the second book. Nor can there 
 be a rational doubt, that in the total absence of 
 solar radiation, all the mechanical, chemical, and 
 vital operations of the planets would be arrested ; 
 and that if the interstellary spaces were reduced 
 
 " the greatest part of the sun's attraction, which is common to 
 both, is exerted in retaining both primary and secondary in their 
 common orbit about himself, and in preventing them from part- 
 ing company ; the small excess of force acting only as a disturbing 
 power." And he states that, according to the calculations of 
 Newton, the mean value of this excess, in the case of the moon's 
 disturbance by the sun, does not exceed ^fo of the principal force 
 which retains the moon in its orbit. (Astronomy, sect. 493). It 
 must also diminish, relatively, as the magnitude and distance of 
 planets increase. Yet it is sufficient to give the orbits of their 
 satellites the character of somewhat zigzag circles. 
 
CAUSE OF THE SUN's MOTION. 41 
 
 to absolute zero, there could be no motion of the 
 heavenly bodies. 
 
 Moreover if it be true that there is an unceas- 
 ing circulation of aethereal matter throughout the 
 solar system, it will account for the revolution of 
 the sun on his axis ; a phenomenon which has 
 never yet been explained in accordance with the 
 Newtonian theory ; and the knowledge of which 
 is of fundamental importance to a right under- 
 standing of physical astronomy ; as it is in the 
 laws which regulate the actions of the sun, that 
 we must seek for the origin of planetary motion. 
 For example, it will be shewn hereafter, that the 
 tendency of caloric to unite with other bodies, is 
 in proportion to the quantity of matter they con- 
 tain, ceteris paribus. Hence it is that two pounds 
 of water will condense just twice as much steam 
 as one pound ; and that a small fire is quenched 
 by a large quantity of coal, with which the 
 caloric unites, and thus arrests the process of 
 combustion. We are therefore authorised to 
 infer, that the aggregate force by which the 
 aether of space tends to unite with the different 
 bodies of the solar system, is in proportion to their 
 mass, and inversely as the squares of the dis- 
 tance.* 
 
 * By glancing over the Tables, p. 32, it will be observed that 
 the velocity of planets round the sun does not depend upon their 
 magnitudes, but on their distance from him, and that the same 
 law applies to their satellites ; which accords with the discovery 
 
42 REVOLUTION OF THE SUN ON HIS AXIS. 
 
 If the sun were a perfect sphere, and not sur- 
 rounded with planets, the aether would press 
 with equal force upon all parts of his surface, 
 and thus maintain him in a perfectly fixed state. 
 But as he is not a perfect sphere, and as the 
 pressure of the aether upon him from every part 
 of the solar system, is modified by all the sur- 
 rounding planets and satellites, it is obvious that 
 the centripetal force of the aether must vary on 
 different parts of his surface, so as to give him a 
 rotary motion on his axis, a result which may 
 be owing in part to certain actions going on with- 
 
 of Galileo, that the velocity with which bodies fall to the earth is 
 the same, whether they be large or small, dense or light, when 
 the resistance of the atmosphere is removed. But if the distance 
 of planets from the sun were equal, the velocity of their satellites 
 would be in proportion to the magnitude of their primaries, and 
 inversely as the cubes of the distance. At the present distance of 
 the earth from the sun, the moon revolves around us at the rate 
 of 2,168 miles an hour, at the distance of 237,000 miles from the 
 earth. But if the earth were at the place of Jupiter, and if the 
 velocity of satellites diminish in the same ratio as that of their 
 primaries, on receding from the sun, the velocity of the moon 
 would be 2*303 times slower than at present, and only 941 miles 
 an hour. It must, however, be observed, that as the volume of 
 Jupiter is about 1.300 times that of the earth, his first satellite, 
 which is 263,111 miles from his centre, moves at the rate 
 of 37,140 miles an hour. And if his first satellite were only 
 237,000 miles from his centre, (the distance of the moon from the 
 earth,) it would move at the rate of 41,200 miles an hour, and 
 faster than the moon, (if the earth were at the place of Jupiter,) 
 in the ratio of nearly forty-four to one, a difference which must 
 therefore be owing to the difference between the magnitude of 
 Jupiter and that of the earth. 
 
DIURNAL REVOLUTION OF PLANETS. 43 
 
 in the sun himself, and on which his radiating 
 power depends.* 
 
 * The above views will also enable us to explain the diurnal 
 revolution of planets, the elliptical form of their orbits, the in- 
 clination of their axes, and all the phenomena of the tides. In 
 the first place, if the planets were perfectly round, and not in- 
 fluenced by each other, both the radiating power of the sun, and 
 the centripetal pressure of the aether, would be the same on all 
 parts of their surface, and they could have no rotary motion. Nor 
 could there be any elongations of their orbits, which would be 
 perfect circles, if the centrifugal and centripetal forces by which 
 they are impelled were always equal and the same. But as none 
 of the heavenly bodies are perfectly spherical, the solar radiation, 
 like the returning pressure of the sether, must operate with un- 
 equal force on different parts of their surface, and tend to give 
 them a rotary motion ; the rapidity of which may depend upon 
 the extent of their deviation from the perfectly spherical form, and, 
 perhaps, on the inclination of their axes : which, again arises from 
 their mutually disturbing influence upon each other, modified by 
 the difference between their equatorial and polar diameters. In 
 the case of Jupiter, this difference is as 107 to 100; whereas in 
 the earth, it is as 299 to 298. 
 
 There is another circumstance which may have an equally im- 
 portant influence on the elliptical form of the planetary orbits. 
 For example, we learn from the telescopic observations of Sir 
 William Herschel, that all parts of the sun are not equally lumi- 
 nous ; that at times, there may be seen on his surface spots, some 
 of which are so large as to measure 45,000 miles in linear diame- 
 ter, exhibiting the appearance of a dark, opaque, and solid 
 ground. It therefore follows, that different quantities of caloric 
 are radiated from different parts of his surface, so as to augment 
 and diminish within certain limits, the centrifugal force of the 
 planets, causing them to approximate the sun in certain parts of 
 their orbits, and to recede from him in other parts, with corres- 
 ponding accelerations and retardations in their annual motions, 
 and, perhaps, variations in their mean annual temperature. On 
 the other hand, as the centripetal pressure of the eether on 
 
44 PHYSIOLOGICAL AND PATHOLOGICAL 
 
 When I come to treat of the physiological and 
 pathological laws of caloric, it will be found that 
 the aggregate amount of life on our planet is in 
 proportion to the heating power of the sun, ceteris 
 paribus : that no seed ever germinates, and no 
 
 each of them is modified by the disturbing influence of all those 
 beyond, this also tends to alter the circular form of the orbits, 
 and render them more or less elliptical. Nor is it less ob- 
 vious, that the interference of the moon must cause a successive 
 diminution of gravity or sethereal pressure upon the earth, so as 
 to cause a corresponding elevation of the tides, which are still 
 further elevated by the influence of the sun when in conjunction 
 with the moon. Thus we perceive that as the mean temperature 
 of planets, (at least of the earth,) and of the spaces between 
 them, is uniformly the same, there must be a perpetual circula- 
 tion of caloric from and to the centre of the solar system, as from 
 and to the planets. We have also found that the heating power 
 of the sun is just equal to the centrifugal force of planets, and an 
 accurate equation of the gravitating force : from which it follows, 
 that whatever is true of the laws established by Kepler and New- 
 ton, must be equally true of the foregoing induction ; while it 
 has the additional advantage of assigning a well known principle 
 as the physical cause of the phenomena, and of thus affording 
 a resting place for the mind. 
 
 From all the foregoing facts and observations we are authorized 
 to conclude, that caloric is a self active principle which is per- 
 petually circulating throughout the universe, from suns to 
 planets, and back again to the great fountains from which it 
 emanates : in short, that it is what Homer called 
 
 " The golden everlasting chain, 
 Whose strong embrace holds heaven, and earth, and main." 
 
 That the movements of the heavenly bodies are in some way 
 immediately dependent on the heating power of the sun, appears 
 to me almost a self-evident proposition, and was so regarded by 
 many of the ancient sages of the east. It was also vaguely re- 
 
LAWS OF CALORIC. 45 
 
 egg is ever hatched, without a due supply of 
 warmth : that as the thermometer rises in spring, 
 so does the sap of plants ; and as the mercury 
 mounts up in summer, the forces of life augment, 
 but decline in autumn, and are wholly arrested 
 during winter : that as the annual rings of trees 
 correspond in thickness with the mean tempera- 
 ture of the growing season in the higher lati- 
 tudes, and are always thickest on the side ex- 
 posed to the sun, the germination, growth, and 
 
 cognized by Milton, who represents the sun as both eye and 
 soul of this great world, 
 
 " Toward which the planets 
 Turn swift their various motions, or are turn'd 
 By his magnetic beam, that gently warms 
 The universe, and to each inward part, 
 With gentle penetration, though unseen, 
 Shoots invisible virtue, e'en to the deep." 
 
 (Paradise Lost, b. iii.) 
 
 When rightly understood, caloric is capable of explaining all the 
 phenomena of attraction, repulsion, and planetary motion ; but 
 these will not explain the operations of chemistry, geology, 
 meteorology, vegetation, and animal life ; nor the generation of 
 steam, which has become so important an agent in spinning and 
 weaving our fabrics, propelling boats, ships, and carriages, work- 
 ing mines, and in nearly all the most useful arts. But we cannot 
 expect to comprehend fully the modus operandi of caloric in 
 any one class of phenomena, until we rise high enough to survey 
 the whole field of knowledge, and to perceive the intimate con- 
 nexion between all its various branches. It was truly observed 
 by Mr. Hume, that " the only expedient from which we can hope 
 for success in our philosophical researches, is to march up directly 
 to the capital or centre of the sciences, which being once mas- 
 tered, we may everywhere else hope for an easy victory." 
 
40 VITAL LAWS OF CALORIC. 
 
 decay of vegetation, constitute a natural thermo- 
 meter on a grand scale. It will also be found, 
 that organized bodies are composed chiefly of 
 those elements which contain the largest amount 
 of caloric around their particles ; by which they 
 are rendered proportionally active, and endowed 
 with the faculty of entering into vital combina- 
 tions, so as to form highly complex tissues : that 
 the vital energy of animals, the activity of their 
 functions, and the developement of their organs, 
 are in proportion to the amount of caloric which 
 circulates through, and is employed in combining 
 arterial blood with the solids. A right under- 
 standing of these laws is of vastly greater im- 
 portance than those of Geology, Astronomy, or 
 even Chemistry. For until we comprehend the 
 operations of life, health, disease, the modus 
 operandi of medicines and morbific agents, the 
 healing art can never take its appropriate rank 
 among the exact sciences ; nor be rescued from 
 the charge of mysticism, quackery, and igno- 
 rance of what is essential to the character of a 
 philosophical physician. But as " the strength 
 of a science is, like that of the old man's fagot, 
 in the bond," the candid seeker after truth is 
 requested to suspend his judgment, until he shall 
 have carefully examined the whole of the evi- 
 dence adduced in support of the author's peculiar 
 views. 
 
45* 
 
 CHAPTER II. 
 
 Atomic Constitution of Matter. 
 
 " Omnia in mensura, et numero, et pondere disposuisti." 
 
 Liber Sapientise, xi. 21. 
 
 BEFORE treating of the relative quantities of 
 caloric in different bodies, and of the law by 
 which it produces the opposite forces of attraction 
 and repulsion, combination and separation, con- 
 traction and expansion ; I shall present a brief 
 outline of what is known in regard to the ulti- 
 mate constitution of ponderable matter. The 
 doctrine that everything in nature is governed by 
 measure, number, and weight, seems to have been 
 recognized by Moschus of Sidon, and other ori- 
 ental sages, long before the time of Pythagoras 
 and Democritus, who maintained that all matter 
 is composed of exceedingly small, hard, and un- 
 changeable atoms, that vary in magnitude ; so 
 arranged and combined as to produce an end- 
 less diversity of mineral, vegetable, and animal 
 bodies. 
 
 The same theory was adopted by Bacon, Boyle, 
 Newton, and many other distinguished modern 
 philosophers, who very justly conceived that if 
 matter were infinitely divisible, all species would 
 be confounded. And it is obvious that if the 
 elements did not unite in definite proportions, 
 the laws of chemistry could not be understood, 
 
46* VIEWS OF BOSCOVICH. 
 
 nor its results be predicted with certainty. In 
 opposition to this simple and rational view of the 
 subject, it was maintained by Boscovich, that 
 the minutest portions of matter consist of mere 
 mathematical points, without extension or solidity, 
 surrounded by alternate immaterial spheres of at- 
 traction, and repulsion, by one of which, the said 
 mathematical points are drawn together, and by 
 the other kept asunder, so as to be prevented 
 from touching. 
 
 We are indebted to the researches of Wenzel, 
 Bergman, and Richter, for the discovery that 
 definite proportions of acids and alkalies are 
 required for mutual saturation ; and that many 
 other chemical combinations take place only in 
 fixed ratios. It was further maintained by Wil- 
 liam Higgins of Dublin, (in a work entitled " A 
 Comparative View of the Phlogistic and Anti- 
 phlogistic Theories," published in 1789,) that all 
 compounds are formed by the union of exceed- 
 ingly minute atoms, which are surrounded by 
 atmospheres of caloric ; and that oxygen unites 
 with nitrogen in proportions which are even mul- 
 tiples of the lowest. But to Dr. John Dalton of 
 Manchester, was reserved the distinguished ho- 
 nour of reducing the atomic theory to a systematic 
 form, in a work entitled " Chemical Philosophy," 
 published in 1808-10, aided by the subsequent 
 analyses of Thomson, Berzelius, Prout, Gay- 
 Lussac, Dulong, and many others. 
 
 The most general law of chemical affinity as 
 
THEORY OF DALTON. 47 
 
 announced by Dalton is, that the constituents of 
 ponderable matter, ichether simple or compound, 
 are capable of combining with each other only in 
 fixed or definite proportions by weight. 
 
 In a practical point of view, this law has been 
 of the highest importance to the manufacturing 
 chemist, independent of its connexion with the 
 whole theory of physical science. 
 
 Passing over the early and imperfect analyses 
 of Dalton, it has been established by the united 
 labours of the most accurate experimenters of 
 modern times, that water is always composed of 
 8 parts by weight of oxygen to 1 of hydrogen ; 
 that common salt is always composed of 36 parts 
 by weight, (in round numbers) of chlorine to 24 
 of sodium ; that carbonate of lime, whether in 
 the form of marble, chalk, or stalactites, is inva- 
 riably composed of 2*2 parts by weight of car- 
 bonic acid, to 28 of lime, &c. 
 
 It was by thus ascertaining the relative pro- 
 portions in which bodies combine chemically by 
 weight, that Dr. Dalton was lead to a perfectly 
 simple method of deducing the relative weights 
 of their ultimate chemical atoms. The theory 
 assumes, that in all cases, the lowest combining 
 proportion of bodies, whether simple or com- 
 pound, represents the weight of its particles ; 
 and that when ever a body combines with another 
 in two or more proportions, the larger is an even 
 multiple by some whole number of the smaller, 
 
48 THEORY OF D ALTON. 
 
 as 2 to 1, 3 to 1, 4 to 1, &c. ; fractional parts 
 seldom occurring in well ascertained cases. 
 
 By inspecting the following Table, it will be 
 seen that the smallest combining ratio of oxygen 
 is 8, compared with hydrogen as unity ; and that 
 when it combines with other elements in larger 
 proportions, they are 16, 24, 32, 40, or some 
 multiple of 8. Chlorine combines with mercury 
 in the ratio of 36, as in chloride of mercury, 
 (calomel), or of 72, as in the bi-chloride of mer- 
 cury, (corrosive sublimate) and so of carbon, 
 hydrogen, and other elements. 
 
 I have adopted the atomic numbers employed 
 by the majority of British chemists in preference 
 to those of Berzelius, chiefly with a view of avoid- 
 ing the inconvenience of fractions. I have also 
 chosen hydrogen as a standard of comparison 
 for the same reason. Berzelius has selected oxy- 
 gen 100.00 as a standard, on account of its great 
 abundance, and the vast variety of combinations 
 which it forms ; while Thomson and Ure have 
 employed oxygen as unity, by which hydrogen 
 is rendered 8 times less; or 0.125, carbon 0.75, 
 sulphur 2, mercury 25 or 12^, chlorine 4.5, and 
 so on ; both of which are unavoidably attended 
 with fractions that are difficult to remember. 
 
 Dr. Wollaston employed the terms chemical 
 equivalent, and Sir Humphrey Davy combining 
 proportion, to denote the atom of Dalton. I shall 
 generally use the term atom, or particle, as indi- 
 
CHEMICAL SYMBOLS. 4.9 
 
 eating the smallest chemical divisions of bodies ; 
 and molecule, as a small assemblage of atoms. 
 
 Berzelius represents the different elementary 
 bodies by the initial letters of their Latin names. 
 Thus, O. denotes oxygen, H. hydrogen, N. ni- 
 trogen, S. sulphur, P. phosphorus, Cl. chlorine, 
 Br. bromine, I. iodine, F. fluorine, C. carbon, 
 Au. gold, Hg. mercury, Ag. silver, Cu. copper, 
 PI. platina, St. tin, Pb. lead, Zn. zinc, Si. sili- 
 cium, Se. selenium, As. arsenic, Fe. iron, M. 
 manganese, Al. aluminum, Mg. magnesium, Ca. 
 calcium, Ba. barium, L. lithium, Na. sodium, K. 
 potassium, (or kalium), which are the most im- 
 portant. 
 
 The number of atoms in each element of a 
 compound is indicated by figures, as in the fol- 
 lowing formula. N. O 5 , represent 1 atom of ni- 
 trogen and 5 of oxygen, as in nitric acid : while 
 sulphuric acid, which is composed of 3 atoms of 
 oxygen and 1 of sulphur, is denoted by S. O 3 . 
 He has in many cases introduced symbols of 
 still more remarkable brevity arid convenience. 
 For example, the number of oxygen atoms in a 
 compound is designated by dots placed over the 
 letter, which indicates the element with which it 
 combines. Thus, the composition of water is 
 
 represented by the symbol, H ; carbonic oxide 
 by C ; carbonic acid by C ; protoxide of nitrogen 
 
 by N ; binoxide of nitrogen by N ; nitrous acid 
 
 E 
 
50 CHEMICAL SYMBOLS. 
 
 by N ; and nitric acid by N. This is a most 
 important improvement of chemical symbols, 
 when we reflect that oxygen enters into the com- 
 position of nearly all compound bodies. 
 
 Berzelius represents the number of sulphur 
 
 atoms by commas. Thus H indicates sulphu- 
 retted hydrogen ; and H, bisulphuretted hydro- 
 gen, &c. He also denotes various compounds by 
 the initial letters of their names. Aq. repre- 
 sents water : Cy. Cyanogen ; Ni. nitrate of potass ; 
 Am. ammonia, &c. It is sometimes convenient 
 to denote 2 atoms of an element by a dash under 
 
 its symbol. Thus Fe, denotes 2 atoms of iron 
 and 3 of oxygen, as in the peroxide of iron. 
 
 TABLE OF ATOMIC WEIGHTS, 
 
 AND OF THE SYMBOLS BY WHICH THEY ARE REPRESENTED. 
 Parts by weight. Parts by weight. 
 
 8 Oxyg. combine with 1 H. to form H 9 parts by weight of water. 
 
 16 O 2 1 H H 17 Binoxide of hydrogen. 
 
 8 O 6 C C 14 Carbonic oxide. 
 
 16 O 2 6 C C 22 Carbonic acid. 
 
 16 O* 16 S S 32 Sulphurous acid. 
 
 24 O 3 16 S S 40 Sulphuric acid. 
 
 8 O 14 N N 22 Protoxide of nitrogen. 
 
 16 O 2 14 N N 30 Binoxide of do. 
 
 24 O 3 14 N N 38 Hyponitrous acid. 
 
ATOMIC WEIGHTS. 51 
 
 Parts by weight. Parts by weight. 
 
 32 O 4 combine with 14 N, to form N 46 NitfOUS acid. 
 
 40 Q5 14 N N' 54 Nitric do. 
 
 8 O 36 Cl Cl 44 Protoxide of chlorine. 
 
 320 36 Cl Cl 68 Peroxide of do. 
 
 40 O 5 36 Cl. ... Cl 76 Chloric acid. 
 
 8 O 40 K K 48 Potass. 
 
 8 O 24 Na. . . . Na 32 Soda. 
 
 8 O 20 Ca. . . Ca 28 Lime. 
 
 8 O 8 Si. ... Si 16 Silex, silicic acid. 
 
 8 O 64 Cu. . . . Cu 72 Protoxide of copper. 
 
 16 O 64 Cu. . . . Cu 80 Binoxide of do. 
 
 8 O 200 Hg. . . . Hg 208 Protoxide of mercury. 
 
 16 O 2 200 Hg. ... Hg 216 Binoxide of do. 
 
 8 O 1 10 Ag. ... Ag 1 1 8 Protoxide of silver. 
 
 24 O 3 16 P P 40 Phosphoric acid. 
 
 8 O 28 M M 36 Protoxide of manganese. 
 
 8 O 28 Fe Fe 36 Protoxide of iron. 
 
 24 O 3 56 2 Fe Fe 80 Peroxide of iron. 
 
 8 O 12 Mg. . . . Mg 20 Oxide of magnesia. 
 
 8 O 10 Al. ... Al 18 Alumina. 
 
 24 O 3 12 C. C* 36 Oxalic acid, 
 
 36 Cl 1 H Cl H 37 Hydro chloric acid. 
 
 126 1 1 H 1 H 127 Hydriodic acid. 
 
 16 S 1 H H 17 Sulphuretted hydrogen. 
 
 32 S* 1 H H 33 Bisulphuretted hydrogen. 
 
 6 C 2 H 2 . . . C H 2 8 Light carburetted hyd. 
 
 12 C 2 2 H. , ,C H 14 Olefiant gas. 
 
 12 C* 14 N. ..CN 26 Cyanogen. 
 
52 ATOMIC WEIGHTS. 
 
 Parts by weight. Parts by weight. 
 
 36 Cl. combine with 24 Na. . . Cl Na 60 Chloride of Sodium. 
 24 O ....... 4 H ..... OH 4 28 jEtherine (En) 
 
 36 C<5 ....... 3 H . . . . C6 H 3 39 Bicarburet of hyd. 
 
 C<5 H5 41 Naphtha. 
 
 C 10 H* 64 Naphthalin. 
 
 C'5 H 4 94 Paranapthalin. 
 
 NH 3 17 Ammonia. 
 
 O Au 208 Protoxide of gold. 
 
 O Pb 112 Protoxide of lead. 
 
 O pi 104 Protoxide of platina. 
 
 36 C6 ....... 5 H. . 
 
 60 C 10 ...... 4 H .. 
 
 90 C 15 ...... 4 H 
 
 14 N ....... 3H 
 
 8 O ....... 200 Au . 
 
 8 O ....... 104 Pb. 
 
 8 O ...... 96 pi 
 
 8 O ....... 72 Bi . . . . O. Bi 80 Oxide of bismuth. 
 
 26 Cy ...... 1 H. 
 
 26 Cy ..... . 8 O. . 
 
 26 Cy ...... 40 S. 
 
 26 Cy ...... 36 Cl. 
 
 14 C* H ____ 9 Aq. 
 
 28C*H* ____ 9Aq. 
 
 .CyH 27 Hydro-cyanic acid. 
 
 Cy 34 Cyanic acid. 
 
 Cy S 66 Sulpho-cyanic acid. 
 
 Cy Cl 72 Chloro-cyanic acid. 
 
 R2H 23 Alcohol. 
 
 ^H^H 37 ^ther. 
 22 C ........ 1 7 N H 3 C N H 3 39 Carbonate of ammonia. 
 
 44 C'* ...... 48 K ____ C* K 92 Bicarb, of potass. 
 
 54 N' ...... 48 K ..... N' K 102 Nitrate of potass. 
 
 37 Cl H ____ 1 7 N H 3 . Cl H N H 3 54 Muriate of ammonia. 
 
 37 Cl H ____ 28 En. . Cl H En 65 Muriatic aether. 
 
 40 S ....... 32 Na ____ S Na 72 Sulphate of soda, 
 
 . 40 S . . , ---- 20 Mg . . .. S Mg 60 Sulphate of magnesia. 
 
 The lowest numbers in the two first columns 
 of the above Table down to oxide of bismuth 
 
ATOMIC WEIGHTS. 53 
 
 represent the atomic weights of simple bodies, 
 or multiples of them ; while the numbers of the 
 3rd column, including all those from hydrocyanic 
 acid in the 1st and 2nd columns, denote the 
 weights of compound particles or molecules. 
 Thus it will be found, that the atomic weight of 
 oxygen is 8 times that of hydrogen, carbon 6, 
 sulphur 16, nitrogen 14, chlorine 36, &c. that 
 the atomic weight of water is 9, of carbonic oxide 
 14, protoxide of nitrogen 22, which are binary 
 compounds ; whereas carbonic acid, sulphurous 
 acid, and all other bodies that are formed of 2 
 atoms of one element, and one of another, were 
 called ternary compounds by Dr. Dalton. For 
 the same reason, olefiant gas is a quaternary 
 compound nitrous acid a quinquenary com- 
 pound alcohol sexanary, being composed of 
 C 2 H 3 O. carbonate of ammonia septenary; while 
 nitrate of potass, aether, and many other bodies, 
 are still more complex, being formed of larger 
 numbers of simple atoms, united into compound 
 particles or molecules, which retain their indivi- 
 duality and specific relations to caloric, until de- 
 composed and again reduced to their constituent 
 particles. 
 
 Berzelius regards all organic bodies as com- 
 posed of definite ratios of their constituent ele- 
 ments an hypothesis which is rendered more 
 and more probable by the recent progress of or- 
 ganic chemistry. It has been ascertained by the 
 
54 ATOMIC WEIGHTS. 
 
 analysis of Gay-Lussac, Dr. Prout, and others, 
 that perfectly dried wood is composed of about 
 50 parts by weight of carbon, to 50 of oxygen 
 and hydrogen in the proportions that form water. 
 M. M. Petersen and Schodler have also found 
 recently, by an important series of experiments 
 on 24 different species of wood, that they are 
 composed of carbon, oxygen, and hydrogen, in 
 very nearly the same proportions by weight : and 
 it is certain that definite ratios of oxygen com- 
 bine with their carbon and hydrogen during com- 
 bustion. They found that lOOlbs. of lime- wood 
 absorb and combine with 140*523lbs. of oxygen 
 and that 100 Ibs. of beech, which required less 
 oxygen than any of the 24 species, combined with 
 130-834 Ibs. of oxygen. (Journal of Prac. Sci- 
 ence, Nov., 1836.) It was formerly maintained 
 by Gay-Lussac and Thenard, that vegetable 
 substances are acid when they contain a larger 
 proportion of oxygen than is required to form 
 water resinous, oily, or alcoholic, when the quan- 
 tity of hydrogen predominates and saccharine, 
 mucilaginous, &c., when there is no excess of 
 either oxygen or hydrogen. Though exceptions 
 have been found to their results, they are true in 
 so many cases, that it is well to bear them in 
 mind. 
 
 The recent progress of chemical science has 
 led to the discovery of some apparent excep- 
 thus to the law of multiples. The following ex- 
 amples have been indicated by Dr. Turner. The 
 
ATOMIC WEIGHTS. 55 
 
 peroxide of iron is composed of 12 parts oxygen to 
 28 of iron. Oxygen combines with manganese 
 in the same ratio, forming a sesquioxide, from 
 the latin word sesqui, one and a half. It also 
 unites with arsenic in the ratio of 12 to 38 of the 
 metal, as in arsenious acid ; and of 20 to 38, as in 
 the composition of arsenic acid. With phos- 
 phorus, it unites in the ratio of 4, 12, and 20, as 
 in hypophosphorous acid, phosphorous, and phos- 
 phoric acids ; which would seem to indicate, that 
 oxygen is capable of combining with the above 
 substances in the ratios of \, 1^, or 2-J- atoms. 
 
 This difficulty has been evaded by supposing 
 that 2 equivalents or atoms of one substance 
 unite with 3, 5, or more atoms $f another that if 
 2 atoms of phosphorus unite with 3, and 5 atoms 
 of oxygen, we obtain the ratios of 1-f- and 2-i- ; or 
 if one atom of iron unite with 1 of oxygen, and 
 another compound be formed of 2 atoms of iron 
 to 3 of oxygen, the latter would be in the propor- 
 tions of 1, and 1-f-, and so of other like cases. 
 
 When 1 atom of oxygen unites with 2 of lead, 
 they form a ternary atom of what is termed a 
 dinoxide, or a suboxide. Dr. Turner lays it down 
 as a general rule, that when a metal forms two 
 oxides, the oxygen of which is in the ratio of 
 I to 1^, the first is usually the protoxide, and the 
 second a compound of two atoms or equivalents 
 of the metal to 3 of oxygen, as in the oxides of 
 iron nickel, and chromium. 
 
 It is highly probable, that a more accurate and 
 
5f> ATOMIC WEIGHTS. 
 
 refined mode of analysis, will prove hereafter 
 that several of the present atomic numbers do 
 not represent the true weights of the atoms. But 
 it is also probable, that in nearly all cases where 
 this is not so, they represent either multiples, or 
 sub-multiples of them. 
 
 There are other exceptions to the law, that all 
 bodies combine chemically in fixed or definite 
 proportions by weight. Many of the metals 
 unite with each other in all proportions when 
 converted into the liquid state by heat, or elec- 
 tricity, forming alloys. 
 
 Water combines with alcohol, and with the 
 strong acids in unlimited proportions ; and it will 
 be shown further* on, that the ratios in which 
 sugar, numerous salts, oily, resinous, and gela- 
 tinous substances, unite with water by chemical 
 solution, are determined by the temperature of 
 the water, solubility of the bodies, &c. But in 
 all such cases, the affinity is comparatively weak, 
 and the changes of properties consequent on 
 combination inconsiderable. 
 
 Theory of Volumes. 
 
 In the year 1805, Gay-Lussac and Humboldt 
 proved by numerous experiments, that water is 
 always composed of 2 measures by volume of 
 hydrogen to 1 of oxygen, as had been previously 
 shewn by Higgins. By following up the inves- 
 tigation, Gay-Lussac found, that many other 
 
THEORY OF VOLUMES. 57 
 
 gases, both simple and compound, unite with 
 each other in very simple ratios by volume that 
 1 volume of A unites with 1, 2, 3, or more vo- 
 lumes of B ; and that the bulk of the resulting 
 compounds, always bears a very simple and de- 
 finite ratio to that of its constituents, or to that of 
 one of them.* 
 
 This law has been extended by Dr. Prout and 
 others, to vapours, and even to the supposed 
 vapours of bodies which do not exist in the 
 elastic form, except when united with the per- 
 manent gases. For example, if carbon be burnt 
 in 100 cubic inches of oxygen gas, (the weight 
 of which is 34*60 grains,) an equal volume of 
 carbonic acid is formed ; (which weighs 47*26 
 grains,) showing that 1 2*66 grains of carbon have 
 been dissolved and chemically united with 100 
 cubic inches of oxygen, which are thus converted 
 into the elastic state ; and that 2 atoms of oxygen 
 have united chemically with 1 of carbon. In 
 this way it was found, that the specific gravity of 
 carbon vapour is '416, compared with oxygen 
 1 1 1 1 , as determined experimentally by Dr. 
 Thomson.! It was also found that when sulphur 
 is chemically combined with oxygen by combus- 
 tion, an equal volume of sulphurous acid is 
 formed, the specific gravity of which is 2*222, or 
 
 * Memoires D'Arcuiel, 1809, Tom. II. 
 
 f Mitscherlich has maintained recently, that the specific gra- 
 vity of carbon vapour is double the estimate of Prout. He ob- 
 serves, that as it cannot be determined by direct experiment, it 
 
58 THEORY OF VOLUMES. 
 
 just double that of oxygen : therefore it is evi- 
 dent, that 100 cubic inches of sulphur vapour, 
 as it exists in sulphurous acid, are of the same 
 weight as 100 cubic inches of oxygen. Such 
 facts led to a new mode of ascertaining the 
 atomic weights of bodies, and threw much addi- 
 tional light on the ultimate constitution of matter. 
 For example, if sulphurous acid be composed of 
 2 atoms of oxygen to 1 of sulphur, it follows, that 
 the atom of sulphur must be just 16 times that of 
 hydrogen, and double that of oxygen. 
 
 By pursuing this method of investigation, Dr. 
 Thomson arrived at the conclusion, that carbon, 
 oxygen, and sulphur, are even multiples of hy- 
 drogen without fractions (Records of Science, 
 March, 1836) ; whereas Berzelius makes the 
 atomic weight of carbon 0-76438 ; that of sul- 
 phur 2-01165; and sulphurous acid 4-01165, 
 compared with oxygen 100. 
 
 ought to be deduced from analogy for example, if carbonic acid 
 consisted of equal volumes of carbon vapour and oxygen, he 
 maintains that they ought to combine without any condensation, 
 because in all other cases, when equal volumes of gaseous bodies 
 unite chemically, there is no contraction, as in binoxide of nitro- 
 gen, hydrochloric acid, hydriodic acid, &c. He thinks that con- 
 densation never takes place, unless the combining volumes are un- 
 equal ; therefore, that carbonic acid is composed of one volume of 
 oxygen to half a volume of carbon vapour, (the specific gravity of 
 which would be -832, instead of -416, or 12 times that of hydro- 
 gen.) But it is not very material whether we regard the specific 
 gravity of carbon vapour as 6 or 12 times that of hydrogen, as 
 either number is in accordance with the law of multiple ratios. 
 
THEORY OF VOLUMES. 59 
 
 Without pretending to decide which of these 
 illustrious experimenters has approximated most 
 nearly to the truth, it would appear from all the 
 lights of modern analysis, that when the atomic 
 numbers shall have been ascertained with perfect 
 accuracy, they will be found to constitute very 
 simple ratios. It is obvious, that if the atomic 
 weight of carbon is 6 times that of hydrogen, 
 oxygen 8, and sulphur 16, the above and many 
 other equivalent numbers of Berzelius cannot be 
 correct ; which is also the case with those of Dr. 
 Turner, who has adopted most of them. Whether 
 this be true or not, the simplicity of the atomic 
 theory, as adopted by the majority of British 
 chemists, has been greatly diminished by the 
 number of decimals which Berzelius has affixed 
 to his atomic weights. I concur most fully with 
 Professor Forbes, in the hope that philosophers 
 may dismiss that superfluity of decimal places 
 which has been recently introduced into several 
 branches of physical science. They have already 
 tended to shake the confidence of some, as to 
 the soundness of the atomic theory. 
 
 The important discovery of Gay-Lussac has 
 been so far extended and verified by the united 
 researches of modern chemists, that it may be 
 regarded as an established law, that all gaseous 
 bodies combine with each other in definite pro- 
 portions by volume, and in accordance with the 
 law of multiples. 
 
60 SPECIFIC GRAVITY OF GASES. 
 
 The following Table will show the connexion 
 between the specific gravity of gaseous bodies 
 and their atomic weights. The first column of 
 figures represents their specific gravities, com- 
 pared with common air as a standard, as de- 
 duced from the experiments of Thomson, Prout, 
 Berzelius, Dulong, Gay-Lussac,Ure, Dumas, and 
 Mitscherlich, under the ordinary pressure of the 
 atmosphere, and at the temperature of 60* F. with 
 the exception of phosphorus, sulphur, arsenic, 
 and such other bodies as require higher tempe- 
 ratures to convert them into the gaseous state. 
 The second column exhibits the number of 
 grains in 100 cubic inches ; while the third co- 
 lumn gives the relation of their specific gravity 
 to that of hydrogen as unity ; and is obtained by 
 dividing the numbers in the first column, by the 
 specific gravity of hydrogen. 
 
 Gases and vapours. Specific gravities. ^ ot &*\ ns in pared wiS 
 
 bes ' hydrogen. 
 
 Atmospheric air 1-000 31-01 15 
 
 Chlorine 2-500 Cl 76-20 36 
 
 Iodine vapour 8-7161 265*76 126 
 
 Bromine do 5-555 Br 169-29 80 
 
 Carbon vapour -416 C 12-68 6 
 
 Carburetted hydrogen -555 C H. 2 . . 17-30 8 
 
 Olefiant gas -981 C 2 H 2 . 29-90 14 
 
 ^Etherine vapour 1-963 C 4 H 4 .. 61-13 28 
 
 Carbonic oxide -972COorC 29-62 14 
 
 Carbonic acid . . 1-527 C . 47.26 . 22 
 
SPECIFIC GRAVITY OF GASES. 61 
 
 Gases and vapours Specific gravities. 
 
 Aqueous vapour ...... -625 H ---- 19-05 ------- 9 
 
 Alcohol vapour ....... 1-620 C 2 H 3 . 49-37 ...... 23 
 
 jEther do ......... 2-570 C 4 H 5 O 79-67 ...... 37 
 
 Cyanogen .......... 1-815 C 2 N.. 56-47 ...... 26 
 
 Sulphurous acid ...... 2-222 S . . . . 67-72 ...... 32 
 
 Sulphuric acid ........ 2 777 S .... 84-72 ...... 40 
 
 Protoxide of nitrogen . . 1-527 N . . . . 47-26 ...... 22 
 
 Nitrous acid ........ 3-19 N ____ 98-80 ...... 46 
 
 Nitric do ........... 3-75 N ____ 116-14 ...... 54 
 
 Hydrogen gas ........ 0-0690 H ---- 2-13 ...... 1 
 
 Phosphuretted hydrogen 1-185 PH.. 36-74 ...... 17 
 
 Nitrogen gas ........ -972 N ---- 30-16 ...... 14 
 
 Ammonia ............ - 590 N H 3 . 18-19 ...... 8.5 
 
 Hydrochloric acid .... 1 270 Cl. H . 39-36 ...... 18.5 
 
 Hydrocyanic do ....... -942 C 2 N H 29-30 ...... 13.5 
 
 Binoxide of nitrogen .. 1-041 N.... 32-13 ...... 15 
 
 Hydriodic acid ...... 4-409 I H .............. 63.5 
 
 Hydrobromic do ..... 2-812 Br. H ............ 40.5 
 
 Mercury vapour ...... 6-944 Hg ............... 100 
 
 Protochloride of mercury 8-204 Cl. Hg ............. 118.5 
 
 Bichloride of ditto ... 9'431 CPHg. .. ____ . ..... 136 
 
 Bromide of do ....... 9-665 Br. Hg ............. 140 
 
 Oxygen ............ 1-111 O .. 34-60 ...... 16 
 
 Phosphorus vapour . . . 4-444 P ................ 64 
 
 Arsenic vapour ...... 10-625 As ............... 152 
 
 Sulphur do ......... 6-666 S . ............... 96 
 
62 SPECIFIC GRAVITY OF GASES. 
 
 By comparing the numbers in the 3rd column 
 of the Table, down to nitrogen, with the atomic 
 weights in the preceding table, page 50, it will be 
 found that they are identical or, that the specific 
 gravity of the gases and vapours in the upper 
 department of the Table, corresponds with their 
 atomic weights, as deduced from the analysis of 
 compound bodies. From which it follows, that 
 equal volumes contain equal numbers of atoms. 
 
 This however is not the case with the next 
 class of gaseous bodies ; for it will be observed, 
 that from ammonia down to bromide of mercury, 
 the atomic weights in the 3rd column are just 
 half of what they ought to be, were the atom 
 and the volume the same that is, allowing the 
 atomic weights in the first Table to be the true 
 ones. 
 
 It will also be observed, that the specific 
 gravity of oxygen is 16 times that of hydrogen, 
 while its atomic weight is only 8 showing that 
 its specific gravity is double its atomic weight as 
 exhibited in the first Table. The difference is 
 still greater between the specific gravity of phos- 
 phorous vapour and its atomic weight, in the 
 ratio of 4 to Ior of 64 to 16. The same is true 
 of arsenic vapour, its specific gravity being 152 
 times that of hydrogen, and its atomic weight 
 only 38 while the specific gravity of sulphur 
 vapour is 6 times its atomic weight, the former 
 being 96, and the latter 16. 
 
COMBINATION OF GASES BY VOLUME. (j.'3 
 
 The following Table will show at once the 
 nature and importance of the facts on which the 
 theory of volumes is founded, and their con- 
 nexion with the atomic constitution of matter. 
 
 Vols. or cubic inches. Cubic inches. Vols. 
 
 200 H. combine 100 O. to form Aq. 200 of Aqueous vapour 
 300 H. . . do. . . 100 N. to form Am. 200 Ammonia. 
 200 H. . . do. . . 100 C. vapour CH 2 100 Light Carbur. hyd. 
 200 H. . . do. . . 200 C.. .do.. . C 2 H 2 100 Olefiant gas 
 400 H. . . do. . . 400 C. . do . . En. 100 jEtherine vapour 
 300 H. . . do. . . 600 C. . do.. . C 6 H 3 100 Bicarburet of hydr. 
 500 H. . . do. . . 600 C. . do. . . C 6 H 5 100 Naptha vapour 
 
 1000 Car. vapour 400 H C 10 H 4 100 Napthalin vapour 
 
 1500 C. . . do. . . 400 H C 15 H 4 100 Paranapthalin do. 
 
 200 Nitrogen do. 100 Oxygen. . N O 200 Protoxide of Nitr. 
 
 200 N do. 300 O N 200 Hyponitrous acid 
 
 200 N do. 400 O N 200 Nitrous acid 
 
 200 N do. 500 O N 200 Nitric acid 
 
 100 C. vapour do.200 O C 200 Carbonic acid 
 
 200 C. do. do. 100 N C 2 N 200 Cyanogen 
 
 400 Car. oxide. . 400 H C 4 H 4 Hydrous acetic acid 
 
 100 Olefiant gas 100 Aq. vap. C 2 H 3 O 100 Alcohol vapour 
 200 . . do 100 Aq. do. C 4 H 5 O 100 ^Ethereal vapour 
 
 100 Chlorine do. 100 H Cl. H. 200 Hydrochloric acid 
 
 100 C. vapour 100 O C 200 Carbonic oxide 
 
 1001 do. 100 H IH 200 Hydriodic acid 
 
64 COMBINATION OF GASES BY VOLUME. 
 
 Vols. or cubic inches. Cubic inches. Vols. 
 
 100 Cy. combine 100 H to form Cy. H 200 Hydrocyanic acid 
 
 100 Cy 100 Cl Cy. Cl. 200 Cyan u ret of chlorine 
 
 100 Cy 100 I Cy. I 200 Cyanuret of iodine 
 
 200 N 200 O N 400 Binoxide of nitr. 
 
 25 P 100 H PH lOOPhosphurettedhyd. 
 
 16 Sulphur vap. 100 H S H 100 Sulphuretted do. 
 
 16 S do. 200 O S 200 Sulphurous acid 
 
 16 S. . .. do. 3000 S 200 Sulphuric acid 
 
 By glancing over the above Table, we perceive 
 that the aggregate volume of the 1 8 first gases and 
 vapours, down to aether, is reduced during che- 
 mical combination from 3 to 2, 4 to 2, 3 to 1 , 4 to 1 , 
 (as in olefiant gas) from 8 to 1 , as in aetherine 
 from 9 to 1, in Faraday's bicarburet of hydro- 
 gen from 11 to 1 , in naptha vapourand from 
 14 and 1 9 to 1 , as in napthalin and paranapthlin 
 in all of which, the specific gravity and atomic 
 weight are the same. 
 
 The next class of gases and vapours in the '2nd 
 department of the Table, unite chemically with- 
 out any change of volume, such as chlorine and 
 hydrogen, to form hydrochloric acid gas, the 
 specific gravity of which is a mean of its consti- 
 tuents, and so of the other six gases and va- 
 pours, including binoxide of nitrogen in all of 
 which the specific gravity represents only one 
 half of their atomic weights. 
 
CONTRACTION AND EXPANSION OF GASES. 65 
 
 It will also be observed, that the volume of 
 phosphorus vapour is augmented from 25 to 100, 
 on uniting with hydrogen, and that of sulphur 
 from 16 to 100, as in sulphuretted hydrogen, sul- 
 phurous acid, &c. 
 
 Here is a most important series of phenomena 
 that have never been explained. 1. Why the 
 specific gravity of gaseous bodies does not always 
 correspond with their atomic weights, except in 
 accordance with the law of multiple or submul- 
 tiple ratios : 2. Why many gases unite chemi- 
 cally with contraction of volume and diminution 
 of elastic force : 3. others without contraction : 
 4. and some with expansion of volume, as the 
 vapours of sulphur, phosphorus, &c. 
 
 It will be shewn in the next chapter, that all 
 the phenomena of contraction, expansion, and 
 the elastic force of gaseous bodies, depend on 
 their relations to caloric, which surrounds every 
 atom of ponderable matter, and, by its transition 
 from one body to another, determines all the 
 chemical or physical changes which they un- 
 dergo ; that the elastic force of hydrogen, oxygen, 
 and nitrogen, (which depends on the relative 
 proportions of caloric and ponderable matter of 
 which they are composed,) is so great, that no 
 degree of force, except that of chemical attrac- 
 tion, has been adequate to condense them per- 
 fectly into the liquid form : but that on uniting 
 chemically with each other, and with carbon, 
 
66 WHY GASES CONTRACT AND EXPAND 
 
 phosphorus, sulphur, and various other bodies, 
 they are deprived of their elastic force, and in 
 many cases without any disengagement of 
 caloric. 
 
 The following observations will shew at once 
 how chemical affinity modifies the specific gra- 
 vity and elastic force of gases. It has been seen 
 that the specific gravity of chlorine is 36 times 
 that of hydrogen. Its elastic force is also small, 
 as it may be condensed by a pressure equal to 4 
 atmospheres, or even by cold without pressure. 
 But when 100 cubic inches of chlorine unite che- 
 mically with 100 cubic inches of hydrogen, (the 
 elastic force of which is immense), they form 200 
 cubic inches of hydrochloric acid gas, the elastic 
 force of which is equal to the pressure of 40 
 atmospheres, at the temperature of 50. During 
 this combination, the larger atoms of chlorine 
 take from those of hydrogen a definite ratio of 
 caloric, by which the elasticity of the hydrogen 
 is diminished, and that of the chlorine increased. 
 At the same time, the atoms of chlorine are re- 
 moved farther from each other, causing an altera- 
 tion of specific gravity in the resulting compound. 
 In like manner, when one volume of iodine va- 
 pour, the specific gravity of which is 8*75, unites 
 chemically with an equal volume of hydrogen, 
 the specific gravity of the resulting compound is 
 diminished to 4*385 and so of the rest, together 
 with many other like combinations not set down 
 in the Table. 
 
DURING CHEMICAL COMBINATION. 67 
 
 The volume of phosphorus, arsenic, and sul- 
 phur vapours is still further augmented on 
 uniting with hydrogen and other permanent 
 gases. The specific gravity of these vapours, as 
 deduced from the experiments of Dumas and 
 Mitscherlich,(who converted them into the gase- 
 ous state by heat,) are 4*444, 10-625, and 6'666 
 (see table, page 61); but when phosphorus vapour 
 unites with hydrogen, its volume is augmented 
 fourfold that is, from 25 to 100, as in phosphu- 
 retted hydrogen. Sulphur vapour is expanded 
 still more on uniting with hydrogen, viz. from 16 
 to 100, as in sulphuretted hydrogen, as before 
 stated. Now it must be remembered that the va- 
 pours of phosphorus, sulphur, mercury, and ar- 
 senic, have little or no elasticity, unless at high 
 temperatures ; from which it follows, that their 
 volume and elastic force are augmented on uniting 
 with hydrogen, by acquiring from it a sufficient 
 amount of caloric to produce the effect. These 
 views will be more fully expanded when I come 
 to treat of the natural forces of caloric. 
 
 When thus investigated in connection with the 
 cause which moves atoms, and the law by which 
 they are united and separated, the atomic theory 
 embraces the whole science of nature. But until 
 the mutual relations of sethereal and ponderable 
 matter shall be better understood, the theory of 
 atoms, and consequently that of chemistry, must 
 remain involved in profound obscurity a lifeless 
 
68 RELATION OF ATOMS TO VOLUMES. 
 
 mass of phenomena, for which no satisfactory 
 reason can be assigned. 
 
 In regard to several bodies termed elementary, 
 chemists have not yet been able to determine 
 whether we have obtained their true atomic 
 weights, or only multiples or submultiples of 
 them. At one time, it was supposed by Ampere 
 and Dumas, that equal volumes of all gases and 
 vapours, simple or compound, contain exactly 
 the same number of atoms. In order to sustain 
 this hypothesis, so beautiful from its simplicity, 
 Dumas imagined that when chlorine unites che- 
 mically with hydrogen to form hydrochloric acid 
 gas, their atoms undergo a division, by which 2 
 atoms of the acid are formed out of one of each 
 of its elements. It is needless to insist, that these 
 hypotheses have not been found in accordance 
 with established facts. 
 
 That equal volumes of all gases contain equal 
 numbers of atoms was inferred, first, from the 
 circumstance that all gaseous bodies are equally 
 expanded by the same additions of caloric, the 
 pressure being equal : and secondly, from the 
 supposed fact, (which has been termed the law of 
 Mariotte), that the volume of any gas whatsoever, 
 diminishes in proportion to the pressure exerted 
 upon it, the temperature being equal. It was 
 maintained, that if the number of atoms in each 
 gas were not the same, the diminution of volume 
 under the same pressure ought also to vary. 
 
RELATION OF ATOMS TO VOLUMES. 69 
 
 Recent experiments performed by (Erstedt and 
 Despretz, have proved that this is actually the 
 case that the volume of sulphurous acid, cyano- 
 gen, ammonia, and sulphuretted hydrogen, dimi- 
 nishes much more rapidly under an equally 
 increasing pressure, than oxygen and nitrogen, 
 as in common air consequently, that the law of 
 Mariotte is not true when applied to gases indis- 
 criminately ; but only to such as have the same 
 degree of elastic force. Despretz regards the 
 above deviation from the law of Mariotte, as 
 referable to some unknown law which regulates 
 the constitution of gases. 
 
 When I come to treat of the causes which 
 modify the elastic force of gases, it will be shewn 
 that their volume and compressibility are deter- 
 mined by their relations to caloric, and not by 
 the number of atoms in a given volume. 
 
 Berzelius maintains in a recent work, entitled 
 Des Proportions Cldmiques, that all gaseous bodies 
 in the simple state, contain the same numbers of 
 atoms, or that the atomic weights of simple bodies 
 are represented by their specific gravity in the 
 gaseous state : from which it would follow, that 
 the atomic weight of hydrogen is TT that of 
 oxygen, (instead of -0, corresponding with the 
 difference between their specific gravities. And 
 as it was found that water is always composed of 
 2 volumes of hydrogen to 1 of oxygen, it was in- 
 ferred by Davy, Berzelius, Prout, and others, that 
 
70 ABSOLUTE WEIGHTS OF ATOMS DOUBTFUL. 
 
 water is a ternary compound, of two atoms hydro- 
 gen to 1 of oxygen. 
 
 In like manner, when it was found that the 
 protoxide of nitrogen is composed of two volumes 
 nitrogen and one of oxygen, it was inferred that 
 it is a ternary compound of two atoms nitrogen 
 to one of oxygen. In accordance with this 
 view, Berzelius and many of the continental che- 
 mists regard the hydrogen atom of Dalton, and 
 the nitrogen atom of Thomson, Turner, Brande, 
 and other British authors, as double atoms, or 
 multiples of their real weights. But if it be true, 
 that the only combining proportions on which we 
 can depend, are such as the most accurate expe- 
 rimenters have found them to enter by weight 
 into the composition of compound bodies, we are 
 not authorized to adopt the numbers of Berzelius, 
 until verified by new and more accurate methods 
 of analysis. At the same time, I am free to con- 
 fess, that the great degree of elastic force in nitro- 
 gen, favours the opinion of Berzelius, that its 
 atomic weight is 7, compared with hydrogen, 
 instead of 14. It cannot, however, be supported 
 on the ground that equal volumes of gases and 
 vapours contain the same numbers of atoms; 
 for it is manifest, that while the atomic weight of 
 ammonia is 17 times that of hydrogen, its specific 
 gravity is only 8*5 ; that the atomic weight of 
 hydrochloric acid is 37, but its specific gravity 
 only 18*5, and so of various other gases. It is 
 
MINUTENESS OF ATOMS. 71 
 
 also evident, that whenever the specific gravity 
 of gases does not correspond with their atomic 
 weights, they vary according to the law of multi- 
 ples or submultiples, which renders the theory 
 of volumes nearly as simple as if the atom and 
 the volume were always the same. 
 
 It is exceedingly difficult, if not wholly impos- 
 sible, to explain the foregoing phenomena of che- 
 mical combination, without adopting the theory 
 of Newton, Higgins, and Dalton, that the ele- 
 ments of ponderable matter are composed of ulti- 
 mate atoms, which, however minute they may be, 
 must have both extension and weight. If they 
 were mere mathematical points, or mere centres of 
 force, without extension, as maintained by Bosco- 
 vich and Exley, they could not possibly form ex- 
 tended and massy aggregates. That ponderable 
 matter consists of incalculably small particles or 
 atoms, is evident from all the phenomena of solu- 
 tion, the diffusion of odours, and the minuteness 
 of organized animalcules. According to the ob- 
 servations of Ehrenberg, the monas, which has a 
 complicated stomach and other organs, is not 
 more than a 20-thousandth part of an inch in 
 diameter ; while other species have been disco- 
 vered, so minute, that a million of them have been 
 supposed not to exceed the magnitude of a single 
 grain of sand. 
 
 The phenomena of crystallization are not less 
 astonishing. When a drop of muriate of ammo- 
 
72 MINUTENESS OF ATOMS. 
 
 nia is magnified by an oxy- hydrogen micros- 
 cope, it is seen to shoot into many hundred thou- 
 sand small crystals, (each of which must contain 
 at least as many ultimate atoms,) which coalesce 
 into one symmetrical solid crystal ; yet are they all 
 governed and arranged by number, measure, and 
 weight. An ultimate particle of lead, which is 
 104 times larger than an atom of hydrogen, is 
 estimated by Dr. Thomson as only _-JL__th of 
 
 ^ ** olUjUuUjUUUjUUU 
 
 a grain. Yet, if the igneous ather which surrounds 
 these molecules be a material agent, its particles 
 must be inconceivably smaller. We can no more 
 measure the ultimate minuteness of this spiritual 
 and fiery essence than we can comprehend the 
 infinitude of space and duration. We are less 
 amazed on contemplating the vast cycles of geo- 
 logy and astronomy, than by attempting to follow 
 nature in her smallest proportions. We know not 
 the absolute weights of gravitating atoms, but we 
 know from the preceding facts, especially those 
 on which the law of multiples is founded, that 
 they vary in size. We know not the forms of 
 ultimate atoms, nor whether they are all of the 
 same density ; but as all bodies in the liquid 
 state are disposed to assume a round form, we 
 may conclude that they are spherical, and that 
 the various forms of crystalline bodies are deter- 
 mined by the modes in which their particles are 
 grouped and arranged. 
 
 Dr. Prout has recently maintained that the 
 
DR. PROUT'S HYPOTHESIS. 73 
 
 chemical molecules of oxygen, hydrogen, carbon, 
 &c. do not exist in a state of ultimate division ; 
 but that they are composed of many sub-mole- 
 cules, which he conceives are analogous in subtil ty 
 and refinement to imponderable matter.* It will 
 be shewn hereafter, that the electric spark, and 
 the spark from the collision of flint with iron, 
 steel, and other hard bodies, is imponderable 
 while in that state. It will be inquired further 
 on, whether ponderable matter in such a state 
 may not be more subtile than in the elementary 
 gaseous form ; and whether the different colours 
 of electric light, and of the flames of combustion, 
 may not depend on the different primitive colours 
 of ultimate atoms. 
 
 Relative Quantities of Caloric in Different Bodies. 
 
 This is one of the most difficult problems in 
 Physical Science, the very elements of which 
 have yet to be unfolded. If it be true, that the 
 whole material world is composed of gravitating 
 atoms which vary in size, and that they are sur- 
 rounded by an active, igneous, and aethereal prin- 
 ciple, which is immediately connected with all 
 their properties and changes, it is obviously an 
 object of primary importance to ascertain the 
 
 * Bridgewater Treatise, p. 90. 
 
74 CONSTITUENT, OR LATENT CALORIC 
 
 relative proportions of each, and the laws of their 
 operation upon each other. Without hoping fully 
 to develope a subject which has hitherto baffled 
 all the efforts of preceding philosophers, I shall 
 endeavour to shew, that the methods which have 
 been employed for the purpose of estimating the 
 constituent caloric of bodies are fallacious ; the 
 application of which, to the phenomena of com- 
 bustion, respiration, evaporation, and solution, has 
 been a constant source of error. 
 
 It has been known ever since the time of Dr. 
 Black, that different quantities of caloric are re- 
 quired to produce the same temperature, in equal 
 weights or volumes of different bodies that 1 Ib. 
 of water requires about double the quantity of 
 caloric to raise its temperature 50 or 100, that 
 1 Ib. of oil does and that, on cooling an equal 
 number of degrees, water gives out twice as much 
 caloric as an equal weight of oil : from which it 
 was inferred, that the same difference existed 
 between the latent caloric of oil and water at all 
 temperatures, down to their absolute zeros in 
 other words, that the whole amount of caloric in 
 water is double that of oil. 
 
 This difference of capacity for caloric, as it was 
 termed by Dr. Black and his disciples, which was 
 found to exist between all other bodies, has been 
 regarded by Crawford, Kirwin, Lavoisier and 
 Laplace, Leslie and Dalton, as a measure of the 
 relative quantities of caloric which is chemically 
 
OF DIFFERENT BODIES. 75 
 
 combined with them, and has been generally 
 termed specific heat. But it is now universally 
 conceded, that the whole subject is involved in 
 profound obscurity, and that nearly all the ex- 
 periments connected with specific heat, are at 
 variance with each other ; which alone is a suf- 
 ficient proof that the truth has not yet been fully 
 ascertained. 
 
 According to the above mode of deducing the 
 amount of caloric in bodies, water should contain 
 more caloric than an equal weight of any other 
 known liquid or solid, as it gives out a larger 
 quantity on cooling an equal number of degrees. 
 If capacity or specific heat were a true criterion of 
 what they contain, the latent caloric of aether, 
 alcohol, oils, wood, coal, and all those bodies 
 which are known to be the most combustible, 
 would be comparatively low; which is refuted by 
 all the phenomena of combustion. This ought to 
 have been inferred from the large proportions of 
 hydrogen that enter into the composition of such 
 substances, and from the well-known fact, that a 
 given weight of hydrogen gives out far more ca- 
 loric during combustion than any other known 
 body. Ever since the first discovery of hydrogen, 
 it has been regarded as an exceedingly igneous 
 substance. The older chemists termed it inflam- 
 mable air. At one time, Kirwin maintained that 
 it was identical with the phlogiston of Stahl, 
 which was in reality the undiscovered latent heat 
 of Black. 
 
76 LATENT CALORIC OF HYDROGEN 1 . 
 
 These vague hypotheses have been superseded 
 by the more definite views of the celebrated La- 
 voisier, who proved that hydrogen is composed of 
 a ponderable base, united with an igneous fluid, 
 which he termed caloric ; and which may be sepa- 
 rated from each other by chemical action. 
 
 According to the experiments of Dr. Dalton, 
 caloric enough is decomposed and given out dur- 
 ing the combustion of I Ib. of hydrogen gas, to 
 melt 3*20 Ibs. of ice. According to Crawford, 
 480 Ibs. of ice are melted by the heat given out 
 during the combustion of 1 Ib. of hydrogen ; which 
 Dr. Thomson thinks is about as far beyond the 
 truth, as Dalton's estimate falls short: conse- 
 quently, that 400 Ibs. may be regarded as the 
 mean quantity of ice that will be melted during 
 the combustion of 1 Ib. of hydrogen. If then we 
 admit with Dr. Black, that 140 of caloric are 
 required to melt 1 Ib. of ice, 56,000 of heat must 
 be given out during the combustion of 1 Ib. of 
 hydrogen. 
 
 It must however be observed, that during the 
 process, 2 volumes of hydrogen combine chemi- 
 cally with 1 of oxygen or that 1 atom of oxygen 
 combines with 1 of hydrogen ; and as the atomic 
 weight of oxygen is 8 times that of hydrogen, 
 8 Ibs. of oxygen must unite with 1 of hydrogen, 
 making 9 Ibs. of water. From which it is evi- 
 dent, that a certain proportion of the caloric dis- 
 engaged, is afforded by the oxygen ; for we find 
 
LATENT CALORIC OF HYDROGEN. 77 
 
 that the volume and elastic force of both gases 
 are destroyed on assuming the liquid form. 
 
 If equal volumes of all gases contained the same 
 quantities of caloric, as conjectured by Dr. Dai- 
 ton, we should have 37,334, as the amount of heat 
 disengaged from 1 Ib. of hydrogen, and 18,666 
 from the oxygen, or of 56,000, corresponding 
 with the difference between the specific gravity 
 of oxygen and hydrogen, which is as 1 6 to 1 (that 
 is, the volume of 1 Ib. of hydrogen is twice that 
 of 8lbs. of oxygen). In accordance with this 
 hypothesis, 1 Ib. of hydrogen should give out 16 
 times more caloric than an equal weight of oxy- 
 gen, coinciding with the difference between their 
 volumes. 
 
 But as it will be shewn hereafter, that equal 
 volumes, of the compound gases, which have a 
 greater density than that of hydrogen, contain 
 more caloric, I shall assume for the present, that 
 1 Ib. of hydrogen contains 8 times more caloric than 
 1 Ib. of oxygen, corresponding with the difference 
 betiveen their atomic weights ; for it would be con- 
 trary to all analogy to suppose, that an atom of 
 hydrogen, which is only \ the size of an oxygen 
 atom, should contain double, or any other greater 
 quantity of caloric.* 
 
 * It is therefore probable, that 1 Ib. of hydrogen evolves 28,000 
 of caloric during combustion, which would melt 200 Ibs. of ice at 
 32 and that 8 Ibs. of oxygen afford the same quantity. From 
 the large amount of caloric combined with hydrogen, we are en- 
 
78 LATENT CALORIC OF WATER. 
 
 This view of the subject is in accordance with 
 the hypothesis of Dulong and Petit, to be noticed 
 further on, who inferred from their experiments 
 that the atoms of all bodies contain equal quan- 
 tities of caloric. 
 
 Still, we are left in the dark in regard to the 
 amount of caloric which is retained around the 
 atoms of oxygen and hydrogen, after their con- 
 densation into the liquid form the knowledge of 
 which would constitute a valuable addition to the 
 present stock of physical science.* 
 
 When we consider the vast abundance and im- 
 portance of oxygen and hydrogen in the economy 
 of nature, it becomes obvious, that a correct mode 
 of ascertaining the relative quantities of caloric 
 which they contain, would throw new light on all 
 
 abled to comprehend why those bodies which contain much of it, 
 are so highly volatile and combustible, as, the different aethers, 
 alcohol, volatile oils, tallow, wax, turpentine, bituminous coal, 
 and nearly all other light bodies. 
 
 * If the volume of water were diminished in the same ratio at 
 all temperatures, by the abstraction of caloric, we might arrive at 
 a proximate estimate of the absolute quantity of caloric which it 
 contains. For example, it is known that water is diminished 
 about ^ of its volume on reducing its temperature 180, viz. 
 from 212 to 32. If then it be assumed that the pores of water 
 are 20 times greater than its solid atoms, (and Newton supposed 
 that they were double this estimate,) it would require the abstrac- 
 tion of 3,600, to deprive it of all its caloric, provided the volume 
 continued to diminish in the same ratio. But as it has been 
 found that below the freezing point of mercury, its volume con- 
 tracts in a greater ratio than at higher temperatures, it is pro- 
 bable that the same thing may be true of other bodies. 
 
THE IMPORTANCE OF OXYGEN. 70 
 
 the relations of aethereal and ponderable matter. 
 All the waters of the earth are composed of oxy- 
 gen and hydrogen, in the proportions of 8 to 1 
 by weight. When converted into vapour by solar 
 caloric, and diffused through the atmosphere, 
 water is connected with all the phenomena of 
 metereology. As a mechanical agent, running 
 water is perpetually wearing down mountains, 
 hills, and elevated plains, and transporting them 
 to valleys, lakes, and seas. 
 
 As a chemical agent, water is slowly but con- 
 stantly dissolving rocks, salts, and metals, which 
 are again precipitated in the crystalline or solid 
 state. It forms a large proportion of all animal 
 and vegetable bodies ; also, of many salts arid 
 rocks. As a constituent of the atmosphere, oxy- 
 gen is indispensable to all the phenomena of vi- 
 tality. It enters largely into the composition of 
 nearly all acids, alkalies, native ores, or metallic 
 bases ; and constitutes about \ of the earth's crust. 
 
 The importance of carbon is not less manifest; 
 forming, as it does, the basis of all organic matter. 
 In combination with hydrogen, it constitutes the 
 principal portion of the food by which we are 
 nourished, and of the fuel by which we are 
 warmed, and kept alive during winter. Accord- 
 ing to the analysis of Gay-Lussac, and of Dr. 
 Prout, it forms about one half of lignin, or per- 
 fectly dried woody fibre. It is the chief ingre- 
 dient in those immense subterranean forests of 
 
80 CARBON THE BASIS OF FOSSIL COAL. 
 
 ancient vegetation, termed fossil coal ; and which, 
 perhaps, exceed in quantity a hundred fold, all 
 the trees and plants that now cover the surface of 
 our planet. 
 
 Still greater is the quantity of carbon which is 
 locked up in a latent state of combination with 
 lime and other rocks ; for it constitutes about i 
 of the widely diffused strata of carbonate of lime, 
 which forms the basis of extensive territories in 
 every quarter of the world. Although it is now 
 fully established, that all the varieties of fossil 
 coal are of vegetable origin, geologists seem not 
 to have ascertained, or even inquired, why the 
 chemical constitution of coal is so various in dif- 
 ferent regions. In Wales, and in several moun- 
 tainous portions of the United States, there are 
 extensive deposits of hard coal, termed anthra- 
 cite, consisting almost entirely of carbon, which 
 burns slowly, and without flame ; while all the 
 other varieties of fossil coal are composed of car- 
 bon, united with various proportions of hydrogen, 
 oxygen, and in some cases of nitrogen, with the 
 exception of Cannel coal, which is without oxy- 
 gen. The following facts may tend to throw some 
 light on this obscure subject. 
 
 1 . So far as the knowledge of the writer ex- 
 tends, anthracite is confined to regions that have 
 been elevated by subterranean fire, and at Car- 
 bondale in Pensylvania presents every appear- 
 ance of having undergone the action of intense 
 heat. 
 
EXPERIMENTS OF DULONG AND PETIT. 81 
 
 2. It has been found by geologists, that where 
 beds of bituminous coal have been perforated by 
 mineral veins, (which were originally the con- 
 duit pipes for the escape of volcanic heat,) it has 
 been changed into coke, or nearly pure carbon. 
 
 3. That beds of anthracite are confined chiefly 
 to mountainous regions; whereas inflammable 
 coal belonging to the same geological epoch, is 
 found in vast quantities between horizontal strata 
 of sandstone and shale. But I must return from 
 this digression to the immediate subject of in- 
 quiry. 
 
 After all attempts to ascertain the specific heat 
 of bodies had proved discordant and fallacious, 
 a series of experiments was undertaken by MM. 
 Dulong and Petit, the object of which was to 
 discover what relation existed between the atomic 
 weights of various bodies and their capacities for 
 caloric. The result of their researches was, that 
 the specific heat of water was nearly three times 
 that of sulphur and several of the metals, in which 
 it was about one half less than in some other 
 elements, four times less than in others again, such 
 as phosphorus and iodine, while in carbon it was 
 nearly six times less than in water, or as 0*169 
 to I'OOO. They also found that there was no 
 uniform relation between the quantities of caloric 
 evolved during the combustion of different bodies, 
 and the specific heat of their resulting products, 
 the capacity of which was often the same before 
 as after the process. Yet they maintained that 
 
 G 
 
82 EXPERIMENTS OF THOMSON. 
 
 the atoms of all simple bodies have the same specific 
 heat; because when they vary, it is in multiple 
 or submultiple ratios, or nearly so ; and that the 
 atomic equivalents of all bodies which do not ac- 
 cord with this assumed law, ought to be altered 
 and made to agree with it. (Ann. de Chim. et 
 de Phys. torn, x.) 
 
 The recent efforts of Dr. Thomson to verify 
 the hypothesis of Dulong and Petit, have not 
 been more successful ; as will appear from the 
 following table, representing the atomic weight 
 of twenty-six simple substances, (compared with 
 oxygen as unity,) their specific heat, and the re- 
 sulting product. He observes, that " if the spe- 
 cific heat of bodies multiplied into their atomic 
 weights be a constant quantity, it will follow that 
 every simple atom is surrounded with the same 
 quantity of heat." (Records of Science, April, 
 1836.) 
 
 Atomic weight. Specific heat. Product. 
 
 Carbon 0.75 0-257 0-192 
 
 Silicon 1- ,... 0-187 .... 0-187 
 
 Aluminum 1-25 0-150 0-187 
 
 Oxygen 1 0-236 0-236 
 
 Chlorine 4-5 0'827 0-372 
 
 Bromine 10 0-472 0-437 
 
 Hydrogen 0-125 3-293 0-412 
 
 Nitrogen 1-75 .... 0-269 0-472 
 
 Sulphur 2 0-188 0-376 
 
 Arsenic 4-75 0-081 .... 0-385 
 
 Antimony 8 .... 0-047 9-376 
 
 Tellurium 4 0-091 0.364 
 
 Iron 3-5 .... 0-110 .... 0-385 
 
 Nickel 3-625 0-103 . . 0-375 
 
EXPERIMENTS OF THOMSON. 83 
 
 Atomic weight. Specific heat. Product. 
 
 Zinc 4-125 0-927 .... 0-383 
 
 Lead 13 0-029 0-377 
 
 Tin 7-25 0-057 .... 0-370 
 
 Copper 4 0-095 0-376 
 
 Bismuth 9 .... 0-040 0-360 
 
 Mercury 12-5 0-029 0-362 
 
 Gold 12-5 0-029 0.373 
 
 Platinum 12 0-310 0-372 
 
 Cobalt 3-25 0.150 .... 0-487 
 
 Phosphorus .. 2 0-385 .... 0-770 
 
 Silver 13-75 0-056 0'770 
 
 Iodine 15-75 0-89 .... 0-401 
 
 Mean of the whole 0-375 
 
 Dr. Thomson maintains, that if the atoms of 
 carbon, silicon, and aluminum were doubled, 
 and those of phosphorus and silver reduced one 
 half, their specific heat would be about the same 
 as the mean of the whole ; and that the other 
 deviations from this average, ought to be referred 
 to inaccurate experiments. But if for the sake 
 of argument we admit his assertion, it would 
 follow that an equivalent of water contains 5*85 
 times more caloric than one of carbon, silicon, or 
 aluminum ; 4*76 times more than an atom of 
 oxygen ; above two and a half times more than 
 one of hydrogen, nitrogen, iodine, or cobalt ; 
 and about 40 per cent, more than one of phos- 
 phorus or silver ; for the specific heat of water is 
 1-125 when multiplied by its atomic weight. And 
 that capacity is no measure of the relative quan- 
 tities of caloric in different bodies, would appear 
 from the experiments of Hay craft, Delarive, and 
 
84 EXPERIMENTS OF DULONG AND HESS 
 
 Marcet, who found that equal volumes of all gases 
 are equally heated and cooled by equal additions 
 and subtractions of caloric. 
 
 The following experiments of Dulong and 
 Hess, performed with a view of ascertaining the 
 relative quantities of caloric evolved during the 
 combustion of several gaseous bodies and a few 
 metals, will be found more instructive. 
 
 Grammes of 
 
 Atomic com- water raised 
 Substances employed position 1 centigrade. 
 
 Litre of Hydrogen 3,102 
 
 Light carburetted Hydrogen . H 2 C 1 9,587 
 
 Olefiant gas H 2 C 2 15,338 
 
 Carbonic oxide OlCl 3,130 
 
 Cyanogen C 2 N 1 12,269 
 
 Alcohol vapour C2H3O1 .. 14,375 
 
 jEther vapour C 4 H 5 O 1 . . 32,254 
 
 " Turpentine vapour .... C 10 H 8 70,607 
 
 Carbon vapour equal to 1 litre in the gaseous state .... 7,858 
 
 1 Litre of Oxygen gas with iron 6,2 16 
 
 1 Tin 6,508 
 
 1 Antimony 5,552 
 
 1 Zinc 7,577 
 
 1 Cobalt 5,721 
 
 1 Nickel 5,333 
 
 Mean of the six metals 6,151 
 
 To these may be added the results of M. Des- 
 pretz, who found, that during the combustion of 
 1 Ib. of different substances, caloric enough was 
 evolved to raise the following quantities of water 
 from 32 to 212. 
 
 Substances employed. Quantities of water. 
 
 1 Ib. of Hydrogen 236-4 Ibs. 
 
 Charcoal from wood . . 75 
 
ON THE COMBUSTION OF GASES. 85 
 
 Substances employed. Quantities of water. 
 
 1 Ib. of Olive oil 90 
 
 Wax 95 
 
 ^ther 80 
 
 Pure charcoal 78 
 
 Alcohol 67 
 
 ' Bituminous coal 60 
 
 Baked wood 36 
 
 Wood with 20 per cent, water ... 27 
 
 Turf, mean 27 
 
 From the table of Dulong and Hess we per- 
 ceive, that during the combination of one atom 
 of oxygen with two of hydrogen and one of car- 
 bon, as in light carburetted hydrogen, about 
 three times more caloric is evolved, than by the 
 combustion of the same volume of pure hydrogen ; 
 and that one atom of carbon vapour -, as it exists in 
 carbonic oxide, gives out almost precisely the same 
 amount of heat as an equal volume of hydrogen. 
 It would also appear from the same table, that 
 during the chemical union of oxygen with the 
 above metals, and its conversion into the state of 
 solid oxides, about twice as much caloric is 
 evolved as by the same bulk of hydrogen. So 
 that if nearly the whole is afforded by the oxygen, 
 it would be about eight times less than is given 
 out by the same weight of hydrogen, corres- 
 ponding with the difference between their atomic 
 weights ; for hydrogen is sixteen times lighter 
 than oxygen : from which it would follow, that 
 during the combination of oxygen with carbon 
 and hydrogen, the atom of each gives out the 
 same quantity of heat. 
 
86 THE REFRACTIVE POWER OF BODIES 
 
 We further perceive, that during the combina- 
 tion of oxygen with two equivalents of carbon, 
 and two of hydrogen, as in the combustion of 
 olefiant gas, above four times as much caloric is 
 evolved as by the union of one atom of oxygen 
 with one of hydrogen ; and that, although the 
 coincidence is less exact between the quantities 
 of heat evolved and the atomic constitution of the 
 remaining compound gases, it is sufficiently so to 
 prove that hydrogen and carbon contain more 
 caloric around their atoms than an equal weight 
 of oxygen ; and that equal volumes of the gases 
 do not afford the same quantities of caloric. It 
 must, however, be admitted, that the results of 
 Despretz are at variance with those of Dulong 
 and Hess, as he found that hydrogen evolves only 
 3-15 instead of 6 times more caloric than the same 
 weight of carbon. 
 
 Let us next inquire whether the power of bodies 
 to refract light may not afford a measure of the 
 relative quantities of caloric around their par- 
 ticles. It w r as suggested by Newton at the close 
 of both the Optics and Principia, that the power 
 of bodies to reflect, refract, and inflect light, is 
 in proportion to the quantity of aether that covers 
 their surface, and surrounds their particles; 
 which aether he also regarded as the cause of co- 
 hesion, elasticity, solution, capillary attraction, 
 and gravitation. For example, he found that in 
 spirit of wine, spirit of turpentine, olive oil, lin- 
 seed oil, camphor, and amber, which are highly 
 
A MEASURE OF THEIR CONSTITUENT CALORIC. 87 
 
 inflammable bodies, the power of refracting light 
 is two or three times greater, in respect to their 
 densities, than in salts, rocks, or any other stony 
 concretes, which are less combustible : and as it 
 was higher in the diamond than in any other 
 body which he tried, he arrived at the conclusion 
 that it was a sulphureous or unctuous body co- 
 agulated, and would be found inflammable. 
 (Optics, Book ii. 24050.) 
 
 That there is at least a nucleus of truth in this 
 hypothesis of Newton, would appear from the 
 numerous experiments of Brewster, Wollaston, 
 Biot, Arago, and Dulong, who have found that 
 in phosphorus and sulphur, as in all those bodies 
 which are composed chiefly of hydrogen and 
 carbon, with various proportions of oxygen and 
 nitrogen, the power of refracting light is much 
 greater in proportion to their specific gravities, 
 than^in any other bodies ; and we have the most 
 decisive proof that they contain proportionally 
 more caloric around their particles, as might 
 naturally have been inferred from all the phe- 
 nomena of their combustion, volatility, and ten- 
 dency to assume the gaseous state. But, so far 
 as I am informed, no one has attempted to ascer- 
 tain what relation exists between the latent caloric 
 of bodies and their refractive powers, except my 
 friend Mr. Dyer, whose views on the subject, if 
 ever carried out, have not been published. 
 
 The most important experiments on the re- 
 fractive power of gaseous substances with which 
 
88 EXPERIMENTS OF DULONG, AND THE 
 
 I am acquainted, are those of M. Dulong, pub- 
 lished in the Annales de Chimie et de Physique, 
 xxxi. 154; as in the following table, which re- 
 presents their refractive power and specific gra- 
 vity, at the same temperature and pressure of 
 the atmosphere, to which I have added their 
 atomic composition. 
 
 TABLE I. 
 
 Refractive Power. Specific Gravity. 
 
 Atmospheric air 1-000 1-000 
 
 Oxygen -924 1-026 
 
 Hydrogen .... 470 685 
 
 Nitrogen 1-020 976 
 
 Deutoxide of Nitrogen .. 1-030 O2Nl 1-039 
 
 Protoxide of Nitrogen ... 1-710 O 1 N 1 . . . 1-527 
 
 Carbonic Oxide M57 O 1 C 1 -972 
 
 Carbonic Acid 1-526 O2Cl 1-524 
 
 Marsh Gas 1-504 H2C1 -555 
 
 Olefiant Gas 2-302 H2 C2 -980 
 
 Hydrocyanic Acid 1-531 C2NlHl .... -944 
 
 Hydrochloric Acid 1-527 Cl. 1 H 1 '1-245 
 
 Ammonia 1-309 Nl H3 -591 
 
 Chlorine 2-623 2-470 
 
 Cyanogen 2-832 C2Nl 1-818 
 
 Sulphuretted Hydrogen.. 2-187 Si Hi 1-178 
 
 Sulphurous Acid 2-260 S O2 2-247 
 
 Hydrochloric .Ether 3-720 C 4 H 5 Cl. 1 2-234 
 
 Phosgene Gas 3-936 3-442 
 
 Sulphuret of Carbon .... 5-110 2-644 
 
 Sulphuric Either 5-197 2-580 
 
 From the above table we perceive, that there 
 is no uniform relation between the refractive 
 power of gases and what is called their specific 
 heat, as admitted by M. Dulong; while it is 
 
CONCLUSIONS TO WHICH THEY LEAD. 89 
 
 equally obvious, that it is not in proportion to 
 their specific gravity, nor to the size of their 
 particles. It will be observed, however, that the 
 refractive power of oxygen is nearly double that 
 of hydrogen, which is sixteen times lighter : 
 it therefore follows, that if their refractive powers 
 be a measure of their latent caloric, hydrogen 
 must contain 8*14 times more than an equal 
 weight of oxygen ; corresponding with the dif- 
 ference between their atomic weights, and the 
 relative quantities of caloric they evolve during 
 the process of combustion. It is much to be re- 
 gretted that we have no means of ascertaining 
 the refractive power of carbon, separately, in the 
 gaseous state. But as it is about three times 
 higher in marsh gas, and four times greater in 
 olefiant gas than in simple hydrogen, we are au- 
 thorized to conclude, that a pound of hydrogen 
 contains six times more caloric than the same 
 weight of carbon ; or that the particles of each 
 are associated with the same quantities of ca- 
 loric. 
 
 And as the refractive power of nitrogen is 2*17 
 times that of hydrogen, (the specific gravity of 
 which is fourteen times less than that of nitrogen) 
 it follows that hydrogen must contain 6'45 times 
 more caloric around its particles than the same 
 weight of nitrogen. Nor can there be a rational 
 doubt, that if the experiments were rigidly accu- 
 rate, the refractive power of hydrogen would be 
 just eight times that of oxygen, and seven times 
 
00 THE ATOMIC WEIGHT OF NITROGEN. 
 
 that of nitrogen ; consequently, that the true 
 atomic weight of nitrogen is 7 compared with 
 hydrogen, (as maintained by Dalton and Berze- 
 lius,) instead of 14, as supposed by the majority 
 of chemists. And if such be the fact, it follows, 
 that hydrogen, carbon, nitrogen, and oxygen, 
 (which are by far the most important of all the 
 elements, because the most active, and because 
 they are the principal constituents of organized 
 bodies,) contain the same amount of caloric 
 around their chemical atoms.* 
 
 A still more direct and cogent proof that the 
 refractive power of bodies is in proportion to the 
 
 * There is, therefore, reason to believe, that when the refrac- 
 tive power of all bodies shall be rightly ascertained, we shall have 
 a more certain method of determining their atomic equivalents, 
 many of which are acknowledged to be doubtful ; and that we 
 shall be able to correct errors in regard to the chemical compo- 
 sition of bodies, that have arisen from imperfect analyses. It 
 must, however, be admitted, that in the present state of science, 
 the refractive power of compound gases, liquids, and solids, does 
 not always correspond with that of their constituents in the se- 
 parate state; a circumstance which may be owing in part to 
 imperfect experiments, and partly to the fact, that during nearly 
 all chemical combinations and decompositions, caloric is either 
 absorbed or given out, as will be shewn hereafter. But as we 
 have found that in hydrogen, carbon, and oxygen, it coincides 
 so nearly with the quantities of caloric they give out during com- 
 bustion; and is nearly the same in several compound gases, 
 when deduced from the refractive power of their elements, the 
 subject is one that merits the most careful investigation. For if 
 there be no uniform ratio between the refractive power of bodies 
 and their specific gravities, while in the best ascertained cases, it 
 accords with the quantities of caloric they afford by combustion, 
 it is difficult to resist the conclusion that caloric is the cause of 
 refraction, as it is of attraction and repulsion. 
 
EXPERIMENTS OF BREWSTER. 91 
 t 
 
 amount of caloric around their particles is, that 
 it is higher in water than in ice, higher in fluid 
 than in solid sulphur, as it is in all those bodies 
 which are composed chiefly of carbon and hy- 
 drogen, such as alcohol, aether, the volatile and 
 fixed oils, than in water, the specific gravity of 
 which is greater, as will be seen from the fol- 
 lowing table, taken chiefly from the experiments 
 of Sir David Brewster. It will also be seen, 
 that it is higher in the diamond, which consists 
 of pure carbon (condensed by an immense pres- 
 sure,) than in any other solid body, if we except 
 phosphorus and sulphur, both of which are 
 highly inflammable, and afford very large quan- 
 tities of caloric by combustion. 
 
 /V 
 
 If T 7 T? 13 
 
 TABLE II. 
 
 Representing the Refractive power and Specific gravity of 
 different classes of bodies in the liquid and solid states. 
 
 Refractive Power. Specific Gravity. 
 
 Water 1-335 1-000 
 
 Ice 1-307 -980 
 
 Alcohol 1-372 -794 
 
 JEther 1-358 -700 
 
 Melted Bees Wax .... 1-450 -960 
 
 Spermaceti .... 1 -470 940 
 
 Oil of Lavender 1 -457 877 
 
 Caraway 1-491 940 
 
 Turpentine 1-475 890 
 
 Camphor 1-487 988 
 
 Lemon 1-481 847 
 
 Olives 1-470 910 
 
 Castor Oil 1-490 969 
 
 Melted Sugar 1-555 1-500 
 
 Gum 1-554 1-400 
 
396 1-062 
 
 395 1-090 
 
 396 1-450 
 
 406 1-480 
 
 440 1*840 
 
 92 EXPERIMENTS OF BREWSTER. 
 
 Refractive power. Specific gravity. 
 
 Acetic Acid 
 
 Malic Acid 
 
 Nitrous Acid 
 
 Nitric Acid , 
 
 Sulphuric Acid 
 
 Phosphoric Acid 1-544 2-687 
 
 Rock Salt 1-557 2-600 
 
 Quartz 1-548 2-600 
 
 Garnet 1-515 4-000 
 
 CalcSpar 1-665 2-700 
 
 Aragonite 1-693 2-900 
 
 Sapphire, blue 1-794 4-200 
 
 Arsenic 1-811 5-800 
 
 Calomel 1-970 7-200 
 
 Carbonate of Lead 2-084 6-400 
 
 Sulphur, native 2-038 2-033 
 
 melted 2-148 1-990 
 
 Phosphorus 2-224 1-770 
 
 Diamond.. 2-470 3-591 
 
 Chromate of Lead 2-926 6-000 
 
 Mercury 5*000* 13-500 
 
 * The refractive power of mercury was determined by M. 
 Arago from its power of reflecting light, in accordance with the 
 hypothesis of Newton that both are owing to the same cause, 
 and that the one is a measure of the other. Should this hypo- 
 thesis be well founded, we have an easy method of ascertaining the 
 refractive power of solid and opaque bodies. That M. Arago has 
 very closely approximated the truth in regard to mercury, would 
 appear from the high refractive power of calomel, as determined 
 by Brewster. And that it is nearly the same in lead as in mer- 
 cury, would appear from the high refractive power of its com- 
 pounds, as in the carbonate and chromate of lead ; while it 
 is well known that gold, platinum, silver, iron, tin, zinc, and 
 other dense metals, reflect a much larger proportion of light, 
 (when smoothly polished,) than the same surface of rocks, gems, 
 glass, or the lighter metals ; and the latter more than water, alco- 
 hol, sether, or the oils. It would, therefore, appear that the 
 denser metals contain from two to four times more caloric around 
 their particles than an equal bulk of water, but very much less 
 
THEORY OF ISOMORPHISM AND DIMORPHISM. 93 
 
 It has been recently discovered by the re- 
 searches of chemists, that many bodies composed 
 of different elements, the atoms or particles of 
 which vary in size, exhibit the same crystalline 
 form, as in the phenomena of isomorphism, from 
 laos, equal, and /uop</>i7, shape.* It has been also 
 ascertained that other bodies composed of the 
 same elements of ponderable matter in the same 
 proportions, assume totally different crystalline 
 forms, as in the phenomena of dimorphism. 
 
 For example, it was found by Scoresby, 
 that in the arctic regions water congeals in an 
 almost endless variety of geometrical figures, of 
 which he enumerates five classes; the lamellar, 
 the stelliform, (which is the most general, and 
 occurs chiefly when the temperature is near 32) ; 
 
 than an equal weight of water, sulphur, phosphorous, or any of 
 the compounds of oxygen, carbon, hydrogen, and nitrogen. 
 
 * In regard to the rationale of isomorphism, Mitscherlich laid 
 it down as a law, that " the same number of atoms combined in 
 the same way, produce the same crystalline form, which is deter- 
 mined by the number and position of the atoms, independent of 
 their chemical nature." According to this view, the arseniate 
 and phosphate of soda, the protoxides of iron, zinc, copper, 
 nickel, manganese, and some other salts, are of the same form, 
 because composed of the same number of particles arranged in the 
 same manner. But the atomic weight of arsenic acid is thirty- 
 eight, and that of phosphoric acid, forty. The seleniate of soda 
 is also identical in form with the sulphate of soda, although the 
 atomic weight of selenic acid is sixty-four, and that of sulphuric 
 acid, forty. It is therefore not easy to comprehend why they 
 produce the same form on uniting with soda, without supposing 
 that sulphuric acid contains a larger amount of caloric around its 
 particles, the volume of which would be thus increased, so as to 
 approximate the magnitude of those of the selenic acid. 
 
94 OBSERVATIONS OF SCORESBY. 
 
 the regular hexagon, which becomes thin, and 
 diminishes in size as the cold increases ; aggre- 
 gations of hexagons, which occur chiefly at low 
 temperatures ; and lastly, combinations of hexa- 
 gons with spines or radii. (Arctic Regions, vol. i. 
 p. 432.) It is therefore clear, that the form of 
 crystals depends on the arrangement of their 
 particles, and not on their essential nature. But 
 if it be a fact that caloric is the agent which regu- 
 lates the distance of atoms or particles from one 
 another, and causes all their movements, whether of 
 union or separation, it must obviously determine the 
 various modes of their arrangement, whether in the 
 solid, liquid, or gaseous states. And as the atomic 
 composition of water in every state is the same, 
 it is impossible to comprehend why it should 
 assume various crystalline forms, as observed by 
 Kepler, Cassini, and Scoresby, without admitting 
 that its particles are surrounded with different 
 quantities of caloric, on assuming these different 
 forms.* 
 
 * The various crystalline forms are now generally arranged in 
 six divisions or systems, as in the following classification by 
 Gustav Rose : 1. The cubic or tessular. 2. The square prismatic, 
 (in which the lateral edges, like the terminal planes, are parallel.) 
 3. The rhombohedric. 4. The right prismatic. 5. The oblique 
 prismatic. 6. The doubly oblique prismatic. 
 
 In all crystalline bodies the form is angular, and the arrange- 
 ment of their particles rectilinear. In those of which all the sides 
 and angles are alike, the expansion by caloric is equal in all direc- 
 tions, as in the cube, the regular octohedron, and the rhomboidal 
 dodecahedron ; and the refraction of light is single, when they are 
 of uniform temperature and density, as it in the transparent gases, 
 
CAUSE OF DIMORPHISM. 95 
 
 It has been also discovered by Rose, that at 
 the temperature of 50, carbonate of lime assumes 
 the form of rhombohedric crystals, as in calc 
 spar; whereas, at the temperature of 150, it 
 takes the cubic form, as in Aragonite, the com- 
 position of which is the same. And when rhombic 
 crystals of calc spar are heated to 212, they are 
 changed to the cubic form, without any change 
 in its chemical composition, if we except the 
 addition of caloric, which is the cause of all 
 molecular aggregations, and therefore the creator 
 of forms. Corresponding with the foregoing facts, 
 
 vapours, liquids, and glass. But in the square prismatic and rhom- 
 bohedric classes, the expansion by caloric is dissimilar in two direc- 
 tions ; while in the right prismatic, the oblique prismatic, and the 
 doubly oblique prismatic, it is dissimilar in three directions. And 
 when a ray of light is made to pass through any of these bodies, or 
 through glass unequally cooled, and solids of unequal density, 
 whether from unequal temperature or pressure, it is refracted in 
 two different pencils, more or less inclined to one another, accord- 
 ing to the molecular arrangement of the body, and the direction in 
 which the pencil is incident ; thus producing all the phenomena 
 of double refraction, which also occurs when it passes through 
 resins, gums, jellies, horn, shells, bones, elastic integuments, 
 and animal lenses. Whenever a ray of light is thus divided, 
 both the transmitted rays are said to be polarized ; that is, 
 its properties are so far changed that it is incapable of under- 
 going reflexion or refraction, except at certain angles ; or of 
 transmission through transparent bodies, except in particular 
 positions. For example, a plate of tourmalin permits the rays to 
 be transmitted in one position, but in a position perpendicular to 
 this it arrests and stifles them, because in these two rectangular 
 directions its particles are differently arranged. It is there- 
 fore manifest that all the phenomena of crystallization, the re- 
 flexion, refraction, double refraction, polarization, and doubtless 
 the diffraction of light, are immediately connected with the theory 
 of caloric. 
 
96 CAUSE OF DIMORPHISM. 
 
 Mitscherlich has shewn that the mutual inclina- 
 tion of the crystalline planes in calc spar is 
 altered eight and a half minutes of a degree be- 
 tween the temperature of 32 and 212; while in 
 other cases it varies nearly 1 in different speci- 
 mens of the same salt. For a full account of his 
 discoveries, see Ann. de Chym. et de Phys. torn, 
 xiv. 172; xix. 350; xxiv. 264, 355. 
 
 In accordance with the above facts, it has been 
 discovered that on crystallizing from solution in 
 the bisulphuret of carbon, or in oil of turpentine, 
 at temperatures below 100, sulphur assumes the 
 octohedric form, with rhombic bases ; but that 
 when melted by itself and allowed to cool slowly, 
 it takes the form of an oblique rhombic prism on 
 solidifying at 230. (Graham's Elements of Che- 
 mistry, p. 189.) It has also been ascertained 
 that pure carbon occurs in the form of regular 
 octohedrons, as in the diamond, but in six sided 
 plates in Graphite. And Professor Johnston has 
 recently shown that there is a large class of 
 bodies composed of the same elements in the same 
 proportions, which crystallize in two, if not more 
 primitive forms. But since the time of Dr. Black,- 
 chemists have attended so little to the agency of 
 caloric in the various transformations of matter, 
 that they have scarcely ranked it among their 
 elements, although it constitutes by far the largest 
 proportion by volume of solid bodies. 
 
 The phenomena of isomerism are no less re- 
 markable, as illustrating the influence of caloric 
 
EXAMPLES OF ISOMERISM. 97 
 
 in changing the chemical properties of bodies. 
 For example, if phosphoric acid be obtained dry 
 by evaporating its solution, and then fused, it 
 becomes what is called pyro-phosphoric acid. In 
 these two states, although composed of phosphorus 
 and oxygen in the same proportions, it produces 
 totally different salts, on uniting with equal pro- 
 portions of the same base. It has also been found, 
 that crystals of tartaric and raceinic acids, in their 
 ordinary class of salts, are both composed of oxy- 
 gen, hydrogen, and carbon, in the same propor- 
 tions, and are so modified by heat as to form dif- 
 ferent salts on uniting with the same proportions 
 of the same base : and so of many other acids. 
 
 Among the most civilized nations of antiquity, 
 it was supposed that everything in nature is 
 composed of four primitive elements, which they 
 termed earth, water, air and fire, to which 
 Aristotle added a fifth. But the tendency of 
 modern science has been to increase the num- 
 ber, until it has extended to fifty-four, all of 
 which are regarded as simple, because chemists 
 have not yet been able to resolve them into fewer 
 elements. There is reason, however, to believe 
 that none of our chemical atoms and elements 
 are perfectly simple, if we except caloric, which 
 also exists in a great variety of states, as will be 
 shown hereafter ; and that it is only in the sub- 
 tilized form of light that we can hope to discover 
 the ultimate constitution of ponderable matter.* 
 
 * For example, if it be true that all the reputed elements are 
 
 H 
 
98 PARTICLES OF LIGHT IDENTICAL 
 
 In accordance with the hypothesis advanced 
 by Newton in one of his Optical Queries, that 
 light and common matter are mutually convertible 
 into each other, it has been recently maintained 
 
 convertible into light, and that light is decomposable into seven 
 primitive rays by prismatic refraction, as maintained by Newton, 
 or into only three fundamental colours, when analyzed by ab- 
 sorbent transparent media, as maintained by Brewster, it will 
 follow that what we call simple bodies are composed of one, two, 
 three, or more of the primitive elements which constitute white 
 light. Now it is worthy of remark, that hydrogen is the most 
 elastic of all gaseous bodies, and affords during combustion an 
 almost perfectly blue light; while according to the experiments 
 of Newton, the blue rays are more refrangible than any others 
 except the violet, which is not a simple colour according to 
 Brewster, but composed chiefly of blue, with small proportions of 
 yellow and red; which he regards as the three primitive rays, and 
 the elements of all compound colours. It is therefore probable 
 that the blue and violet rays are more refrangible than the others, 
 for the same reason that hydrogen, of which they are formed, is 
 the most elastic of all known bodies; viz. because it contains 
 more caloric around its particles in proportion to their size. And 
 it was supposed by Newton that the atoms of light diminish in 
 size from the red to the violet extremity of the spectrum. Again, 
 as sulphur burns with a blue, and iodine with a violet light, 
 (which contains small proportions of the other rays,) they may 
 be composed chiefly of hydrogen, with some other base or bases ; 
 and cannot be otherwise decomposed than by expanding them 
 into the subtile form of light. On the other hand, during the 
 combustion and ignition of potassium, strontium, barium, lithium, 
 sodium, and magnesium, they afford chiefly red light, with small 
 proportions of the other coloured rays; therefore must all be 
 composed principally of one element, the primitive atoms of which 
 are red, while those of hydrogen (which is the basis of sulphur, 
 iodine, and perhaps some other bodies) are blue. Hydrochlorate 
 of calcined soda also affords an orange coloured light ; while in 
 that of chlorine, silver, copper, and some other bodies, there 
 is a predominance of greenish rays; so that if green light be 
 composed chiefly of yellow and blue, as maintained by Brewster, 
 
WITH THOSE OF PONDERABLE MATTER. 99 
 
 by Sir David Brewster, that " the particles of light 
 are identical with the ultimate atoms of bodies, and 
 that there is a specific affinity between definite atoms 
 and definite rays, though we do not understand 
 its nature." (Transactions of the Brit. Association, 
 vol. i. p. 231.) He also observes in another 
 work, that " when a portion of light enters a 
 body, and is never again seen, we are entitled to 
 say that it is detained by some power exerted 
 over it by the particles of the body ; that it enters 
 into chemical combination with them, and pro- 
 duces the various chemical effects by which their 
 colours are changed, and the juices of plants 
 elaborated," to which he adds, " It is not easy to 
 allow that such effects are produced by undula- 
 tions of an aethereal medium." (Optics, chap. 
 xxxiv.) 
 
 That every description of ponderable matter is 
 actually convertible into light by a sufficiently 
 intense heat, or by electricity, will appear from 
 the following undeniable facts : 
 
 1. That the quantity of light generated by 
 ordinary combustion, friction, or percussion, is 
 always in proportion to the rapidity with which 
 ponderable matter is ignited and volatilized. 
 
 2. That the colour of light thus produced always 
 depends on the species of matter employed. 
 
 all bodies that burn with a green light must be compounds of 
 two or more primitive elements ; while others, again, which afford 
 different proportions of all the coloured rays of the spectrum are 
 still more complex. 
 
100 CALORIC THE ACTIVE PRINCIPLE IN LIGHT. 
 
 3. That the electric spark (like that produced 
 by the collision of flint and steel) consists of ex- 
 ceedingly minute portions of ponderable matter 
 in a state of incandescence, as will be shown 
 hereafter by the decisive and beautiful experi- 
 ments of Fusinieri. 
 
 4. That when the electric fluid is transmitted 
 through the vacuum of an air pump, little or no 
 light is produced, as proved by the experiments 
 of De Luc, and afterwards by those of Sir H. 
 Davy. 
 
 5. That the most intense heat of a voltaic 
 battery never produces any light, except when 
 acting on ponderable matter ; consequently, that 
 light and heat are not identical,* as maintained 
 by some modem theorists ; and that neither of 
 them is generated by the mere vibrations of an 
 aethereal medium. 
 
 * That caloric is a constituent of light, (as it is of all other 
 bodies,) and is the active principle in its generation, is evident 
 from the fact, that the most refractory gems and metals are 
 transformed into luminous incandescent particles by a sufficiently 
 intense heat, definite measures of which are required to produce 
 the effect on different species of matter. It has also been proved 
 by the experiments of Hulme, Dessaignes, Macartney, and others, 
 that every species of phosphorescence is promoted (for a time) 
 by moderate heat, and always extinguished by the coldness of 
 freezing mixtures; while others have found that the light of 
 luminiferous insects is much greater in vessels of oxygen gas than 
 in common air. But that caloric is a distinct essence, and may 
 exist independent of light, is manifest from the fact, that it con- 
 verts solids into liquids, vapours, and gases, in the midst of per- 
 fect darkness ; while it radiates from the earth during night, as 
 it does from boiling liquids and other hot bodies, without being 
 attended with any light. 
 
CHEMICAL AGENCIES OF LIGHT. 101 
 
 Iii accordance with the foregoing facts, it has 
 been found that each of the primitive rays pro- 
 duces specific changes of colour in different bo- 
 dies; that the blue and violet rays of the spectrum 
 change the white chloride of silver to a dark 
 violet hue; whereas the red rays change it to a 
 rose colour; and that the same change of colour 
 is produced on the protochloride of lead and the 
 oxide of mercury, when moistened and exposed 
 to the red rays of the spectrum, as in the experi- 
 ments of Scheele, Sennebier, Davy, and Seebeck: 
 that a piece of white paper stained yellow with 
 a solution of guiacum in alcohol, was turned 
 green in five minutes by exposure to sunshine, 
 but remained unaltered for several months in the 
 dark ; and that when the yellow paper was made 
 green by exposure to the violet rays, its original 
 colour was restored by exposure to the red rays 
 of the spectrum, as shown by the experiments of 
 Wollaston. 
 
 The chemical agency of light is still more 
 strikingly illustrated in the production of those 
 accurate pictorial delineations of objects termed 
 Daguerreotypes, which are formed by the imme- 
 diate influence of the regal sun. Moreover, that 
 there is " a specific affinity between definite 
 atoms and definite rays," is evident from the 
 fact, that bodies repel and reflect certain rays, 
 while they attract and absorb others. For ex- 
 ample, it was found by Sir David Brewster, 
 that red transparent solutions and glasses per- 
 
102 DECOMPOSITION OF LIGHT. 
 
 mitted the red rays of the spectrum to pass 
 freely through them, but absorbed and oblite- 
 rated the other rays ;* that blue media permitted 
 rays of the same colour to pass through them, but 
 absorbed the other rays ; and that green media 
 absorbed the rays at both extremities of the spec- 
 trum, but the red most where it verges to blue, and 
 the violet most where it verges to yellow. Nor is it 
 more remarkable, that bodies should absorb one 
 or more primitive rays, and reflect or transmit 
 others, than that certain elements of ponderable 
 matter should have an elective affinity for some, 
 and an antipathy for other elements ; the rationale 
 of which is doubtless the same in both cases, and 
 must be sought in the fact, that as the different 
 rays of light are of different temperatures, so are 
 the elements of ponderable matter associated 
 with different quantities of caloric. And it will 
 be found hereafter, that no chemical union of 
 bodies ever takes place without the transition of 
 
 * If in our cathedrals, colleges, and other public buildings, 
 were judiciously placed a few windows composed of perfectly red, 
 yellow, and blue glasses, (to which might be added combinations 
 of these colours,) the mind would be elevated, refined, and 
 instructed, on beholding such a vivid display of all that is most 
 beautiful in light when thus decomposed, and reduced to its 
 primitive elements. Never shall the author forget the emotions 
 of delight and admiration he experienced on first looking at 
 the sky through a fine ruby glass, when it presented the 
 appearance of a vast dome of lurid flame ; and the whole face of 
 the earth, as if by enchantment, was suddenly dyed of a gorgeous 
 crimson hue. We little think how cheaply some of the highest 
 pleasures of existence may be purchased. 
 
WHAT BECOMES OF LIGHT. 103 
 
 caloric from one to the other, attended in most 
 cases, with a change of temperature. 
 
 But if the ultimate atoms of ponderable matter 
 be identical with those of light, and the latter 
 consist of seven primitive rays, as supposed by 
 Newton, it follows that the fifty-four elements 
 enumerated by chemists are not simple bodies^ 
 but compounds of two or more primitive elements, 
 as before suggested ; or, that if light consist of 
 only three primitive rays, united with caloric^ 
 everything in nature must be composed of four 
 elements. Nor is it possible to admit with New- 
 ton, that the blue and indigo are distinct primitive 
 rays ; while it is certain that all the known varie- 
 ties of colour may be produced by combinations 
 of red, yellow, and Hue ; which, as Brewster has 
 shewn, overlap each other, and extend quite 
 across the spectrum. 
 
 What then becomes of the enormous quan- 
 tities of light perpetually radiated throughout 
 the solar system ? This is doubtless one of the 
 most curious, important, and comprehensive pro- 
 blems in the whole range of physics, and deserves 
 the profoundest attention of philosophers. Thus 
 much is certain, that if light be matter, it cannot 
 be annihilated, any more than the great fountains 
 from which it emanates ; that whatever falls upon 
 the earth, and is not reflected or radiated from it 
 into surrounding space, must combine with, and 
 become a constituent portion of, its surface ; that 
 certain rays produce specific chemical and vital 
 
104 COSMICAL PHENOMENA OF LIGHT. 
 
 effects; while the various powers of different 
 bodies to decompose white light by absorption, 
 transmission, reflexion, refraction, and polariza- 
 tion, cause an endless diversity of colours. Light 
 then is not only a revelation of all that is grand 
 and beautiful in the outward universe, but the 
 agent by which all its operations are carried on. 
 It is therefore probable, that when fully under- 
 stood, it will enable us to explain whatever is 
 now mysterious in the ultimate mechanism and 
 laws of nature. 
 
 And if " the particles of light be indentical 
 with the ultimate atoms of ponderable matter," 
 (the Tr/owVi? v\rt of the ancients,) the question natu- 
 rally arises, whether all the planets and satellites 
 of our system may not be so many masses of 
 embodied light, which is first aggregated into 
 nebulae, and then into comets, that go on gradu- 
 ally augmenting in size, by constant additions 
 of light, until after enormous periods of time, 
 (compared with which our geological epochs 
 are mere fractions,) they arrive at maturity ; or 
 until, by the expenditure of his substance, the 
 sun is so far reduced in magnitude, that the cen- 
 trifugal power of his rays becomes inferior to the 
 centripetal pressure of the surrounding aether 
 when they would gradually approach, and finally 
 in succession fall into the sun ? In short, whether 
 the ponderable matter of the sun and fixed stars 
 is not perpetually expanded by caloric into the 
 subtile form of light, which is as constantly re- 
 
COSMICAL PHENOMENA OF LIGHT. 105 
 
 converted into the matter of planets and satel- 
 lites? 
 
 This theory enables us to answer the important 
 question, " What becomes of light?" while it 
 affords a more intelligible explanation of the 
 manner in which cosmical bodies are generated 
 and finally destroyed, than any merely meta- 
 physical hypothesis unless by metaphysics we 
 understand the universal Science of Ontology, 
 or of whatever exists.* It also enables us to 
 comprehend why the distances of the planets 
 from each other augment in nearly definite ratios, 
 from Mercury to Uranus; why they increase in 
 magnitude (if we except Mars and the asteroids) 
 from Mercury to Jupiter ; and why their equa- 
 torial exceeds their polar diameters. For ex- 
 
 * Nor is this altogether a new hypothesis : for it was main- 
 tained by the early Hindoo Cosmogonists, that there is a creation 
 and destruction of innumerable worlds in eternal succession ; that 
 they all emanate from the Divine Being, and after long periods 
 of time are resorbed into the primitive fountain of their existence ; 
 a doctrine which certainly had its origin in the general belief of 
 the ancients, that the sun was the Supreme Being. And we are 
 informed by Brucker, that the oriental theory of emanations was 
 adopted by some of the older Greek philosophers. Hence the 
 doctrine of Heraclitus, that all things were originally formed from 
 fire, (which is light or flame,) and must again return to the same 
 state. (Diogenes, lib. ix. s. 8, p. 552.) We are also told in 
 the first chapter of Genesis, that light was created before the 
 earth, or even the sun, moon, and stars. Nor is it more difficult 
 to comprehend the generation of worlds from the matter of light, 
 than that they should have been created out of nothing ; or from 
 a gradual contraction of the sun's atmosphere, as maintained by 
 Laplace. 
 
106 COSMICAL AGENCY OF LIGHT. 
 
 ample, it is obvious that if light obey the same laws 
 as other projectile bodies, a much larger proportion 
 of what is radiated from the sun would lose its 
 original force and velocity at the distance of Jupi- 
 ter, Saturn, and Uranus, than at that of any one 
 of the planets nearer to the sun ; so that a corre- 
 sponding amount of luminous matter would be 
 aggregated into comets, which may successively 
 fall into those great masses and their satellites, 
 in the same way that many thousand meteoric 
 stones, and showers of stones, have fallen from 
 unknown heights upon our planet, since the 
 historical era, a fact which clearly demonstrates 
 that the earth has been augmenting in size, inde- 
 pendently of the constant additions of matter it re- 
 ceives from the sun in the form of light. And as 
 it is equally evident that the tropical portion of 
 planets receives much greater quantities of light 
 from the sun than the middle and polar latitudes, 
 this fact affords a more satisfactory reason for 
 their equatorial protuberances than the prevalent 
 theory, which refers them to the rapid diurnal 
 motion of their equatorial zones. 
 
 If the foregoing views be well founded, it fol- 
 lows that light, in connexion with caloric, which 
 is the active principle in its generation, and 
 always forms a constituent portion of it, is the 
 primitive basis of all material existence, or the 
 physical Ens entium consequently cannot be re- 
 solved into the mere vibrations of an setherial 
 
RADICAL DEFECTS OF THE WAVE THEORY. 107 
 
 medium, as maintained by many distinguished 
 mathematicians of the present age.* 
 
 * That the vibratory theory of light is not a true representation 
 of nature, would further appear from the following considerations : 
 
 1. That it does not explain what the aether is, nor what causes 
 it to vibrate. 
 
 2. That light is propagated in straight lines, and will not pass 
 through a bent tube ; whereas vibrations move around interposing 
 bodies, which obstruct the passage of light, as maintained by 
 Newton. 
 
 3. That the wave theory does not explain the generation of 
 light by combustion, ignition, friction, and percussion ; how it is 
 connected with caloric and electricity; nor why ponderable 
 matter is essential to its production. 
 
 4. That it does not explain the decomposition of light by 
 prismatic refraction, absorption, and transmission ; nor how it 
 modifies the chemical and vital properties of ponderable matter ; 
 while " it leaves the whole subject of colours, both in opaque and 
 transparent bodies, involved in profound obscurity." (Whewell.) 
 
 5. That in adopting the theory of undulations, " we are called 
 on for acts of faith, and certain admissions must be made at 
 every step," as acknowledged by Sir John Herschel, who is 
 certainly one of its ablest advocates. 
 
 6. That as the different colours of light depend on the species 
 of ponderable matter employed in its generation, they cannot be 
 resolved into different numbers of aetherial vibrations. 
 
 7. That the radical defects of the wave theory have been 
 disguised by an imposing array of algebraical formulae ; while the 
 most important facts connected with its history have been over- 
 looked, or intentionally neglected; and that it is exceedingly 
 difficult to understand, as admitted by Mr. Whewell. And it 
 might as well be said that the first mover in the steam engine is 
 motion, as that light consists merely in the vibratory motions of 
 an aether. 
 
108 
 
 CHAPTER III. 
 
 On the Law by which Caloric produces the oppo- 
 site Forces of Attraction and Repulsion, Con- 
 traction and Expansion. 
 
 " That alone is true philosophy which repeats the words of the 
 universe with fidelity, and is written, as it were, by dictation of 
 the universe." BACON. 
 
 THE doctrine that every thing in nature is com- 
 posed of two descriptions of matter, the one essen- 
 tially active and aethereal, the other passive and 
 motionless, was recognized by the most acute 
 and profound sages of antiquity in every quarter 
 of the civilized world. But notwithstanding they 
 all regarded elementary caloric as the prime 
 mover, they seem to have overlooked the law by 
 which it repels its own particles, and tends to 
 combine with those of ponderable matter, with 
 forces that vary inversely as the squares of the 
 distance, so as to produce all the centrifugal and 
 centripetal forces of nature. The same obser- 
 vation applies equally to Bacon, Descartes, New- 
 ton, and other modern philosophers, who, although 
 they referred all the operations of nature to what 
 they called a spirit or pneumatical body, a materia 
 subtilis, a subtile &ther, &c. they never identified 
 it with any known principle, nor explained how 
 it causes both attraction and repulsion, union and 
 separation. 
 
CALORIC A SELF ACTIVE PRINCIPLE. 109 
 
 Why then does caloric repel its own particles, 
 and attract those of ponderable matter, with forces 
 that vary inversely as the squares of the distance ? 
 To this primary and leading question I answer, 
 that caloric repels its own particles because they 
 are of the same nature, and attracts those of pon- 
 derable matter because they are of a totally 
 different nature ; that in every variety of state 
 caloric is an essentially active principle, and 
 incomparably more refined than any description 
 of ponderable matter, even when expanded into 
 the subtile form of light ; for it permeates the 
 most dense and opaque bodies, which are wholly 
 impervious to light. And that the forces of 
 caloric diminish in proportion as the squares of 
 the distance augment, is obvious from the fact, 
 that all aethereal emanations are necessarily dif- 
 fused in the same ratio, on radiating from any 
 given centre.* 
 
 That caloric is a self-active principle has been 
 already shewn by its power of moving itself, and 
 of giving motion to other bodies, the activity of 
 which is augmented by every addition, and dimi- 
 nished by every abstraction of heat; proving, 
 
 * It would therefore seem to follow, that there must be a limit 
 to the diffusion of caloric; that it is not infinitely subtile and 
 divisible ; but that there must be a definite number 6f particles in 
 any given quantity of it. It is only by its extension throughout 
 illimitable space that it can be regarded as infinite ; for we shall 
 find that, while it governs all the operations of the material 
 universe, it is itself governed by invariable and necessarily fixed 
 laws. Yet there is reason to believe that its great activity depends 
 on its extreme subtilty and refinement. 
 
110 RELATIONS OF CALORIC AND P. MATTER. 
 
 that if the particles of ponderable matter could 
 be wholly deprived of caloric, they would be 
 passive and motionless. At the same time it is 
 highly probable, that if universal space were 
 filled with caloric alone, (without any ponderable 
 matter,) it would also be inactive, and constitute 
 a boundless ocean of powerless or quiescent aether, 
 because it would then have nothing on which to 
 act. And we shall find that, however inactive of 
 itself, ponderable matter has certain properties 
 by which it modifies and controls the actions of 
 caloric, both of which are governed by immutable 
 laws that have their origin in the mutual relations 
 and specific properties of each. 
 
 That atoms of the same nature repel one ano- 
 ther, and attract those of a different nature, would 
 appear from the best known phenomena of che- 
 mistry and physical optics. For example, it has 
 been long known that similarity of properties 
 among the elements of ponderable matter causes 
 them to repel each other, as if by a mutual anti- 
 pathy ; but that diversity of properties is favour- 
 able to chemical combination. We have also 
 found that transparent media transmit rays of 
 light of their own colour, but attract and absorb 
 those of different colours. 
 
 I now proceed to shew, that all the expansions 
 and contractions of gaseous bodies depend on the 
 relative proportions of caloric and ponderable mat- 
 ter of which they are composed ; and that the force 
 by which caloric tends to unite ivith the particles 
 
OF GASEOUS EXPANSION AND CONTRACTION. Ill 
 
 of ponderable matter is in proportion to their size, 
 ceteris paribus. For example, the atoms of hy- 
 drogen are smaller, and contain a larger amount 
 of caloric around them, than those of any other 
 gas ; the consequence of which is that its elastic 
 force is such, that no mechanical pressure hitherto 
 employed has been sufficient to condense it into 
 the liquid form.* And it was found by Perkins, 
 that atmospheric air (which is composed of oxy- 
 gen and nitrogen in a state of mechanical mix- 
 ture) may be submitted to a pressure equal to 
 1200 atmospheres, without being perfectly con- 
 densed into the liquid form. (Philosophical 
 Transactions, 1826.) 
 
 But when 3 volumes of hydrogen unite chemi- 
 cally with 1 of nitrogen, they contract into 2 
 
 * Under the pressure of the atmosphere, and at the tem- 
 perature of 60, hydrogen is 15,480 times lighter than water, the 
 pores of which are 40 times larger than its solid particles, accord- 
 ing to Newton. It is therefore evident, that the pores of hydrogen 
 exceed the diameters of its particles several thousand times, and, 
 perhaps, to the same extent, that the spaces between the different 
 planets exceed their mean diameters. What, then, is the cause of 
 the stupendous force by which the particles of hydrogen are kept 
 at such comparatively great distances from one another ? Is it 
 some virtue, property, or condition termed polarity? Or is it 
 owing to the existence of certain hypothetical immaterial spheres 
 of repulsion around its particles ? Is it possible that masses, and 
 the atoms of which they are composed, are capable of acting upon 
 each other at comparatively great distances without an intervening 
 medium ? That the volume of gaseous bodies is augmented by 
 every addition of caloric, has been proved by the experiments of 
 Gay-Lussac, who found that 1000 cubic inches of common air 
 were expanded to 1 375 cubic inches by raising its temperature from 
 32 to 2 1 2. It was further ascertained by Dulong and Petit, that 
 
112 EXPANSION AND CONTRACTION 
 
 volumes of ammonia, the elastic force of which 
 is so far diminished that it may be condensed 
 into the liquid state by a pressure equal to 6'5 
 atmospheres, or by cold alone at the tempera- 
 ture of 46 below F. And when 2 volumes of 
 nitrogen combine with 1 of oxygen, the elastic 
 force of the resulting compound gas is so far dimi- 
 nished, that it may be liquified by a pressure 
 equal to 44 atmospheres at the temperature of 
 32, as first shewn by the experiments of Sir H. 
 Davy ; or by a pressure equal to 50 atmospheres 
 at the temperature of 45, according to Faraday. 
 What then is the rationale of these curious phe- 
 nomena ? Is the sphere of repulsion in the ele- 
 mentary gases exchanged for one of attraction 
 as they unite chemically, with contraction of 
 volume and diminution of elasticity? Or how 
 many immaterial and imaginary spheres of at- 
 traction and repulsion are required to explain 
 the phenomena of solidity, liquidity, and gase- 
 faction ? The summary answer to these queries 
 is, that " the self repulsive power of caloric is 
 
 the same law of expansion is true of atmospheric air and hydrogen , 
 up to the temperature of 680 ; from which they concluded, that 
 it was true of all gases, and at all temperatures. (Ann. de Chim. 
 et Phys. vii. 120.) Dr. Dalton also found that the elastic force 
 of steam was equal to the weight of the atmosphere at 212, but 
 was equal to the pressure of 135 atmospheres when raised to 320. 
 And we learn from the experiments of Perkins, that when water 
 is confined in very strong vessels it expands with a force equal to 
 the pressure of 1050 atmospheres when raised to the temperature 
 of 419. 
 
OF GASEOUS BODIES. 1 13 
 
 counteracted and diminished by its affinity for pon- 
 derable matter y by which the (Ethereal atmospheres 
 are drawn into a smaller compass. The reduction 
 of volume and elastic force are referable wholly 
 to this one cause. 
 
 Perhaps the principle cannot be better illus- 
 trated than by a consideration of the statical and 
 dynamical changes that are produced on hydro- 
 gen and chlorine, by their mutual action upon 
 each other. 
 
 We have seen, that the specific gravity and 
 atomic weight of chlorine are 36, compared with 
 hydrogen as 1 ; and that the elastic force of hy- 
 drogen is immense. It has been also shown by 
 Faraday; that the elastic force of chlorine is low 
 that it may be liquefied by a pressure equal to 
 4 atmospheres at the temperature of 60 F.* 
 
 But when 1 volume of chlorine is made to unite 
 with 1 of hydrogen, they form 2 volumes of hydro- 
 chloric acid gas, the specific gravity of which is 
 18-5 ; or a mean between that of its constituents. 
 During this combination, the hydrogen loses the 
 greater part of its elastic force, while that of the 
 chlorine is greatly augmented. That is, a defi- 
 nite proportion of caloric is attracted by the heavier 
 atoms of chlorine from the lighter atoms of hydro- 
 gen, by which its particles are removed farther 
 
 * When combined with aqueous vapour it may be liquefied, and 
 even solidified, at the temperature of 32 F. 
 
 I 
 
114 CONTRACTION AND EXPANSION 
 
 from each other, and its elasticity increased at the 
 expense of the hydrogen. Nay more, it is by virtue 
 of this very attraction that the atoms of hydrogen 
 are forced into chemical union with those of chlo- 
 rine, and their separate individuality destroyed. In 
 other words, all the above changes, including that 
 by which the gases are united and identified, are 
 referable wholly to the transition of caloric from 
 the one to the other. 
 
 It will be shown hereafter, that no chemical 
 combination of any one body with another ever 
 takes place, without a simultaneous passage of 
 caloric or electricity from one to the other; that if 
 water and other liquids could exist as such without 
 caloric, (which is impossible,) they could not com- 
 bine with salts, metals, and rocks ; and that the 
 diminution of bulk which attends the combination 
 of liquids with solids, is owing to the same law 
 which determines the reduction of volume and 
 elastic force of gases and vapours. The most 
 simple illustration of combination effected by the 
 attraction of ponderable matter for caloric, is that 
 by which steam is condensed by water or ice, and 
 intimately combined with their particles. When 
 a certain proportion of steam is mixed with cold 
 water, its volume and elastic force are destroyed 
 by the same attraction of ponderable matter for 
 caloric which causes liquids to combine with, and 
 dissolve solids, or which causes gases to combine 
 chemically, with contraction of volume and dimi- 
 nution of elastic force. 
 
OF GASEOUS BODIES. 115 
 
 There is no limit to the application of this doc- 
 trine in the phenomena of chemistry. 
 
 If a piece of ice be introduced into a vessel 
 full of ammoniacal gas, the latter disappears ra- 
 pidly, and the ice is melted, forming a chemical 
 solution of ammonia (spirit of hartshorn). Now 
 it is obvious on a moment's reflection, that the 
 volume and elasticity of the ammoniacal gas are 
 destroyed by the attraction of ice for its caloric. 
 It is equally true, that the ammonia is chemically 
 combined with the ice by the same attraction, as 
 will be proved when I come to treat of chemical 
 solutions. Again, if one volume of hydrochloric 
 acid be mixed with one volume of ammoniacal 
 gas, they combine rapidly with evolution of much 
 heat, when they lose the gaseous or elastic state, 
 making a solid crystalline salt (sal ammoniac) 
 of a cubical or octohedral form. The atomic 
 weight of the acid is 37, and that of the alkali 
 17. (See Table of Atomic Weights, p. 5i.) 
 
 In this case, there is an attraction of caloric by 
 the larger particles of the acid, by which those of 
 the ammonia are forced into chemical combina- 
 tion with them, forming compound particles of 
 still larger size, the weight of which is 54, com- 
 pared with hydrogen as unity. 
 
 Thus it is evident that the repulsive poiver of 
 caloric, on which the volume and elastic force of 
 gases depend, is counteracted and diminished by 
 an affinity of ponderable atoms for caloric; and 
 that this attraction augments in a certain ratio as 
 
116 CONTRACTION AND EXPANSION 
 
 the size of the particles increases, until it ivholly 
 predominates over the repulsive force. The atoms 
 of hydrogen, nitrogen, oxygen, and light carbu- 
 retted hydrogen, retain a large amount of caloric 
 around them in proportion to their size ; the con- 
 sequence of which is, that the thermo-repulsive 
 force greatly predominates. But when they are 
 made to combine with each other chemically, or 
 with carbon, phosphorus, sulphur, chlorine, &c. 
 making gases of greater specific gravity and 
 atomic weight, their elastic force is diminished, 
 even in cases where little or no caloric is given 
 out, as in the combinations of nitrogen and hy- 
 drogen, nitrogen and oxygen, nitrogen and car- 
 bon, with numerous others, formed of these and 
 of sulphur, phosphorus, &c. 
 
 It has long been a matter of controversy whe- 
 ther the oxygen and nitrogen of the atmosphere 
 exist in a state of mechanical mixture, as main- 
 tained by Dr. Dalton, or in a state of chemical 
 combination. Dr. Thomson has recently main- 
 tained that it is composed of 80 parts nitrogen 
 to 20 of oxygen, constituting definite proportions 
 by volume ; therefore, that it is a chemical com- 
 pound. (Records of Science, vol. iii. page 184.) 
 This hypothesis does not accord with the best 
 established facts connected with the theory of 
 volumes. For example, in all the combinations 
 of oxygen and nitrogen that are known to be che- 
 mical, there is a reduction of volume and elasti- 
 
OF GASEOUS BODIES. 117 
 
 city, except in the case of the binoxide, which is 
 composed of equal volumes of each. Besides, it 
 would seem to be a general law, that, whenever 
 unequal volumes of gases unite chemically, there 
 is a diminution of their aggregate volume. This 
 view is supported by the facts presented in Table 
 III. page 63 ; while it is evident from the fore- 
 going details, that all such chemical combina- 
 tions are attended with a reduction of elasticity. 
 But the volume and elastic force of oxygen and 
 nitrogen, as they exist in atmospheric air, are the 
 same as when in a separate state, which would 
 seem to demonstrate, that air is a mechanical 
 mixture, and not a chemical combination. 
 
 The elastic force of light carburetted hydrogen 
 is less than that of simple hydrogen. When Mr. 
 Perkins submitted it to mechanical pressure, he 
 found that it began to liquefy under a force equal 
 to the weight of 40 atmospheres ; and that under 
 a pressure of 1200 atmospheres it was perfectly 
 condensed into the liquid form. Being composed 
 of 2 atoms hydrogen to 1 of carbon, its specific 
 gravity and atomic weight are to hydrogen in the 
 ratio of 8 to 1 . 
 
 When 2 atoms or volumes of carbon unite with 
 2 of hydrogen, they form bicarburetted hydro- 
 gen (olefiant gas), a compound, the specific gra- 
 vity and atomic weight of which are 14, compared 
 with hydrogen as unity. During this combina- 
 tion, the 4 volumes of hydrogen and carbon con- 
 tract into 1 volume, the elastic force of which 
 
118 CONTRACTION AND EXPANSION 
 
 has not been ascertained ; but from the foregoing 
 facts, there cannot be a doubt, that it is very low, 
 compared with that of carburetted hydrogen . 
 
 It cannot be maintained that there is less ca- 
 loric in 100 cubic inches of carburetted hydrogen, 
 or olefiant gas, than in an equal volume of hy- 
 drogen. On the contrary, it appears from the 
 results of their combustion, that they contain 
 much more. According to the experiments of 
 Dr. Dalton, caloric enough is evolved during the 
 combustion of 1 Ib. of carburetted hydrogen to 
 melt 85 Ibs. of ice ; while the same weight of 
 olefiant gas afforded heat enough to melt 88 Ibs. 
 of ice. Now, when it is remembered that the 
 volume of hydrogen is 8 times that of carburetted 
 hydrogen, and 14 times that of olefiant gas, weight 
 for weight, it becomes self-evident, that equal 
 volumes of these compound gases contain more 
 caloric than hydrogen. 
 
 The proportions of caloric in equal volumes of 
 alcohol vapour, aethereal vapour, nitrous acid, 
 cyanogen, &c., are still greater than in carbu- 
 retted hydrogen or in olefiant gas. Why then, I 
 repeat, is their elastic force so much less at the 
 same temperature? The obvious answer to this 
 question is, that the larger compound particles of 
 such gaseous bodies exert a stronger affinity for 
 caloric, by which it is drawn into a smaller space, 
 and chemically united, producing definite con- 
 tractions of volume, and consequently an increase 
 of specific gravity. 
 
OF GASEOUS BODIES. 119 
 
 If the self- repulsive force of caloric in these 
 compound gases were not counteracted by an 
 attraction between their particles and thermal 
 aether, their elastic force would be greater than 
 that of hydrogen in proportion to the greater 
 amount of their latent caloric. 
 
 This conclusion is rigorous ; and it is so im- 
 portant in its bearing upon the whole science of 
 chemistry and physics, that I have dwelt upon 
 it even at the hazard of repetition, with a hope 
 that by presenting the operation of the same 
 principle in different points of view, it might be 
 rendered clear and intelligible to the most ordi- 
 nary capacity. It explains why the expansive 
 force of steam is greater, other things being equal, 
 in proportion as the quantity of water employed 
 in its generation is less ; a thorough comprehen- 
 sion of which is destined to effect an immense 
 saving of fuel. 
 
 The law by which the elastic force of aethereal 
 matter is counteracted by the mutual affinity be- 
 tween it and ponderable matter, is still more strik- 
 ingly illustrated by the changes which are pro- 
 duced in the statical and dynamical properties of 
 hydrogen and sulphur, oxygen and nitrogen, 
 chlorine and nitrogen, with some others. 
 
 It was before noticed that the specific gravity of 
 sulphur vapour as determined by the experiments 
 of Mitscherlich, is 6*666, which is about 96 times 
 the specific gravity of hydrogen gas : and it re- 
 
120 CONTRACTION AND EXPANSION 
 
 quires a temperature of about 640 F. to maintain 
 it in the gaseous form, when not united with other 
 bodies. But if brought into contact with hydrogen 
 gas, or if sulphur be volatilized in contact with 
 hydrogen, they both undergo remarkable changes. 
 
 1. In the first place, 16 parts by weight of sul- 
 phur combine chemically with 1 of hydrogen, 
 forming hydrosulphuric acid (sulphuretted hy- 
 drogen), the specific gravity of which is 17 times 
 that of hydrogen, and its elastic force compara- 
 tively low. The particles of sulphur, which are 
 16 times larger than those of hydrogen, attract 
 from the latter gas a portion of the aether which 
 encompassed its atoms, by which they are inti- 
 mately united. 
 
 2. During this process, the particles of sulphur 
 acquire a much greater repulsive force, and are 
 removed so much farther from each other, that 
 they occupy 6 times the volume which they did 
 in the form of vapour, before combining with the 
 hydrogen. 
 
 3. The elastic force of the hydrogen is so far 
 diminished by uniting with sulphur, atom to 
 atom, that sulphuretted hydrogen maybe liquefied 
 by a pressure equal to 17 atmospheres at the tem- 
 perature of 50, according to the experiments of 
 Faraday. It was afterwards discovered by Davy 
 that when reduced to the temperature of 3 F., 
 the elastic force of its vapour was equal to the 
 pressure of only 14 atmospheres. 
 
OF GASEOUS BODIES. 121 
 
 When 2 atoms of sulphur 32, combine with 1 
 atom of hydrogen, the resulting compound is 
 a brownish yellow, and dense liquid, (specific 
 gravity 1-769), somewhat acid, of an oily and 
 tenacious consistence. If it be submitted to very 
 low temperatures, its specific gravity and cohesion 
 are still farther augmented, when it becomes an 
 exceedingly firm solid, like butter, tallow, and 
 innumerable other fluids and semifluids under the 
 same circumstances. When an atom of sulphur 
 16, combines with 2 atoms of oxygen 16 ; or when 
 sulphur vapour combines with oxygen, the elas- 
 ticity of the latter is nearly destroyed ; while the 
 atoms of sulphur are removed farther from each 
 other, and acquire a degree of elasticity at the 
 expense of the oxygen : for the specific gravity of 
 the sulphurous acid thus formed is only 2' 222, 
 which is just i of 6'666, that of the sulphur vapour, 
 in agreement with the law of multiples, which may 
 be traced in all the contractions and expansions 
 that gaseous bodies undergo during combination 
 and decomposition. 
 
 According to the experiments of Faraday, sul- 
 phurous acid may be liquefied by a pressure equal 
 to 2 atmospheres, at the temperature of 45 ; and 
 by cold without pressure, according to the ex- 
 periments of Bussy and others. It must be ob- 
 served, however, that during the combinations of 
 oxygen and sulphur, a portion of caloric is given 
 out, as in the union of oxygen and hydrogen to 
 
1*22 CONTRACTION AND EXPANSION 
 
 form aqueous vapour; which is one cause of the 
 diminished elasticity in sulphurous and sulphuric 
 acids. 
 
 A thousand examples might be adduced equally 
 calculated to illustrate the chemical force with 
 which aethereal matter is attracted by the atoms 
 of gravitating matter, and its idio-repulsive force 
 thus diminished or destroyed. 
 
 The same order of phenomena which marks 
 the union of sulphur and hydrogen, is exhibited 
 during the combination of phosphorus, iodine, 
 bromine, selenium, tellurium, &c. in the state of 
 vapour with hydrogen and other permanent gases. 
 The volume and elasticity of these dense vapours 
 are augmented by receiving from the lighter gases 
 a portion of the principle on which their volume, 
 &c. depend, during the very act of combining. 
 
 The specific gravity of phosphorous vapour is 
 4-444 at the temperature of 550 F. or about 64 
 times the specific gravity of hydrogen . But when 
 it combines with hydrogen, atom to atom, it be- 
 comes highly elastic, and its particles occupy 4 
 times their former space, as in phosphuretted hy- 
 drogen, the specific gravity of which is only 17 
 times tha of hydrogen. 
 
 The specific gravity of iodine vapour is 8' 75 
 at the temperature of 347 F. When it unites 
 with hydrogen, atom to atom, (that is, in the 
 ratio of 126 by weight to 1 of hydrogen,) hy- 
 driodic acid is formed, the specific gravity of 
 which is 4' 386, or about one-half that of iodine 
 
OF GASEOUS BODIES. 123 
 
 vapour, in accordance with the law of multiples 
 as shown in hydrochloric acid, ammonia, &c. 
 
 The same principle applies to the various com- 
 binations of hydrogen with the vapours of bro- 
 mine, cyanogen, arsenic and mercury, as in its 
 combinations with the vapours of sulphur, iodine, 
 &c. (See Table III. of the preceding Chapter.) 
 
 When 3, 4, or 5 volumes of oxygen combine 
 with 2 of nitrogen, the aggregate bulk and elastic 
 force of the resulting compounds diminish with 
 every additional dose of oxygen. Nitrous and 
 nitric acid may be liquefied by moderate degrees 
 of cold without pressure. Yet they contain nearly, 
 if not quite as much caloric as the oxygen and 
 nitrogen of which they are composed, when in a 
 separate state. It was long ago observed by 
 Higgins, that during those combinations no ca- 
 loric is given out and that during the union of 
 nitric acid with potass, very little heat is disen- 
 gaged.* 
 
 That this is really true, would appear from the 
 immense quantity and intensity of the heat evolved 
 by the deflagration of nitrate of potass with char- 
 coal and sulphur, as in gunpowder and other de- 
 flagrating mixtures formed of nitre, phosphorus, 
 naphtha, turpentine, and various combustibles. It 
 is generally known, that during their combustion 
 with nitre, nearly as much caloric is given out, 
 
 * It is also known that when nitrous acid is passed through a 
 red hot iron tube, it is decomposed into its constituent elements, 
 which resume their original volumes and elastic force. 
 
124 PHILOSOPHY OF 
 
 even in vacuo, as when burnt in atmospheric 
 oxygen ; which proves that a large amount of 
 caloric is concentrated around the particles of the 
 nitric acid of the saltpetre, and set at liberty 
 during its decomposition. 
 
 Philosophy of Explosion or Detonation. 
 
 Immediately connected with the foregoing 
 theory, is the rationale of explosion, a pheno- 
 menon which has never been explained, and 
 has been often adduced as an argument against 
 the materiality of caloric. It has been supposed 
 that the quantity of heat given out during explo- 
 sion, and that which is requisite to convert gun- 
 powder into the gaseous state, could not have 
 existed in a state of combination with its particles. 
 
 This has arisen from not attending to the law 
 by which caloric is concentrated around the atoms 
 of ponderable matter, with a force that increases 
 in proportion to the augmentation of their size, 
 other things being equal ; and by which its self- 
 repulsive force is counteracted. I have shown 
 that the elastic force of nitrogen is equal to a 
 pressure of 1200 atmospheres; but that when 5 
 volumes of oxygen are combined with 2 of nitro- 
 gen, they contract into 2 volumes of nitric acid, 
 without any material loss of caloric, and yet that 
 the elastic force of nitric acid is very small ; that 
 when 5 atoms of oxygen 40, unite with an atom 
 
EXPLOSION OR DETONATION. 125 
 
 of nitrogen 14, they form compound molecules of 
 nitric acid, the weight of which is 54, compared 
 with hydrogen 1 : from which, and the foregoing 
 facts, we are bound to infer, that the repulsive 
 force of the aether which surrounded the atoms of 
 oxygen and nitrogen, is counteracted and nearly 
 vanquished by the attraction of the larger particles 
 of the compound for caloric.* 
 
 By referring to Table I. page 51, we perceive 
 that the atomic weight of potass is 48, compared 
 with hydrogen as unity. One atom of nitric acid 
 54, combines with 1 of potass 48, making com- 
 pound molecules of nitrate of potass, the weight 
 of which is 1 02 ; and the attraction of which for 
 caloric has so far overcome its idio-repulsive force, 
 that they are aggregated into a crystalline solid 
 of a cubical form. Let us then examine the com- 
 position of gunpowder. It consists of 1 atom of 
 nitre 102, 1 of sulphur 16, and 3 of charcoal 18, 
 
 * It was before shown that when 2 volumes of hydrogen com- 
 bine with one of oxygen to form water, an immense quantity of 
 caloric is disengaged, and that the aeriform state is merged in 
 that of the liquid state. But as the combinations of oxygen and 
 nitrogen retain nearly the same amount of caloric as their con- 
 stituents, they also retain the gaseous form at ordinary tempera- 
 tures, though their aggregate bulk and elasticity are greatly dimi- 
 nished. This fact is very remarkable ; for the particles of nitric 
 acid are larger than those of water in the ratio of 54 to 9 ; or 6 
 to 1. It is difficult to conceive why they retain the elastic state, 
 unless they retain around them a large amount of the same 
 eethereal matter which belongs to their elementary constituents : 
 whereas oxygen and hydrogen give out a large proportion of it 
 on combining to form water. 
 
126 PHILOSOPHY OF 
 
 in a state of intimate mixture. When perfectly 
 dry, and heat is applied, the nitre is decomposed 
 into its original constituents, with a tremendous 
 force of explosion, which is owing principally to 
 the elastic force of the nitrogen, on being released 
 from its combination with the oxygen and potass 
 of the nitre. During this rapid process, 2 atoms 
 of oxygen combine with 1 of sulphur, making sul- 
 phurous acid gas ; while the other 3 atoms of 
 oxygen that existed in the nitric acid, combine 
 with 3 atoms of charcoal, forming carbonic oxide 
 and carbonic acid. But as the elastic force of 
 these gases is comparatively low, the explosive 
 action must depend chiefly on the sudden ex- 
 pansion of nitrogen on assuming the gaseous 
 state. The whole is nothing but an instanta- 
 neous combustion of sulphur and charcoal, ac- 
 companied by the disengagement of heat and 
 light, as in ordinary combustion, and by the sud- 
 den liberation of nitrogen, which, in the separate 
 state, exerts an elastic force equal to a pressure 
 of 16800 Ibs. to the square inch. The force is 
 also greatly increased by the caloric given out 
 during the formation of carbonic oxide and car- 
 bonic acid, the quantity of which is by no means 
 inconsiderable. 
 
 This is a most instructive exemplification of the 
 law by which caloric exerts two opposite forces, 
 the one or the other prevailing according to 
 circumstances. At ordinary temperatures, the 
 particles of nitre, sulphur, and charcoal, retain 
 
EXPLOSION OR DETONATION. 127 
 
 caloric around them with a greater force than that 
 by which it repels its own particles; but when 
 they are decomposed and subdivided into smaller 
 particles, the repulsive force of their aethereal con- 
 stituent acquires the ascendency. 
 
 The same principle applies to all fulminating 
 compounds, whether solid, liquid, or aeriform, as 
 chlorate of potass, fulminating mercury, gold, 
 silver, platina, &c. ; iodide and chloride of ni- 
 trogen, protoxide and peroxide of chlorine, and 
 some other detonating compounds, all of which 
 are attended with expansion of volume and dis- 
 engagement of heat, during their decomposition. 
 
 Chlorate of potass is composed of chloric acid 
 and potass. When triturated with sulphur, phos- 
 phorus, and charcoal, it forms a deflagrating com- 
 pound. In the ratio of 3 parts of the chlorate to 
 1 of sulphur, it explodes violently when gently 
 heated, or struck with a hammer. If 2 grains of 
 the chlorate be mixed with 1 of phosphorus, in 
 a bit of paper, and struck with a hammer upon 
 an anvil, there is a violent explosion. The chloric 
 acid is decomposed in all such cases ; the chlorine 
 unites with the combustible ; and the oxygen 
 being liberated expands with a force proportional 
 to its elasticity in the gaseous state, for the same 
 reason that nitrogen expands when separated 
 from the nitre of gunpowder,. 
 
 Fulminating mercury is composed of oxygen 
 and cyanogen, combined with the protoxide of 
 mercury, in the proportions of 1 atom of each. 
 
128 PHILOSOPHY OF 
 
 When exposed to a temperature of 300 F., it is 
 suddenly decomposed ; from which it is evident 
 that the self-repulsive force of the caloric is re- 
 strained by its affinity for the particles of the com- 
 pound, until a further supply of thermal aether is 
 added, when the elastic force prevails, and the 
 compound is resolved into its constituents with 
 a violence sufficient to indent or lacerate iron. 
 During the process, oxygen combines with the 
 carbon of cyanogen, forming carbonic acid, while 
 the nitrogen of the cyanogen, being released from 
 its confinement, expands, causing the explosion. 
 The same effect is produced on bringing concen- v 
 trated nitric or sulphuric acid in contact with it, 
 the oxygen of which combines with the carbon of 
 the cyanogen, leaving the nitrogen at liberty to 
 exert its expansive force.* 
 
 * It is only by contemplating the elastic force of caloric in 
 oxygen and nitrogen, while in the state of simple gases, that we 
 are enabled to appreciate the stupendous force of attraction by 
 which it is concentrated around the molecules of ponderable 
 matter. If we take the experimental result of Rumford, that 15 
 grains of gunpowder expand when ignited, with a force equal to 
 the pressure of 400,000 Ibs. or 200 tons weight, it follows from a 
 simple calculation, that the elastic force of caloric in 1 Ib. of gun- 
 gunpowder, is equal to the pressure of 102,400 tons weight. This 
 enormous force is restrained by the attraction of caloric for the mole- 
 cules of gunpowder and all detonating compounds that contain ni- 
 trogen, until decomposed, when it expands with an energy far sur- 
 passing the most elastic steam, for the same reason that the oxygen 
 of chlorates expands with irresistible violence when decomposed. It 
 is therefore certain, that a more perfect knowledge of the application 
 of gunpowder and other fulminating compounds, must lead to a far 
 more effectual and rapid mode of destroying life than the steam gun. 
 
EXPLOSION OR DETONATION. 
 
 Fulminating silver is composed of oxygen and 
 cyanogen, united with its protoxide. When 
 gently heated, it is decomposed and resolved 
 into its constituents. At the same moment, oxy- 
 gen combines with the carbon of the cyanogen, 
 forming carbonic acid, leaving the nitrogen at 
 liberty to expand with explosive violence. And 
 so of fulminating gold and platina, which are 
 composed of ammonia, combined with the oxides 
 of these metals. When decomposed by heat, the 
 electric spark, or by percussion, their oxygen 
 unites with hydrogen of the ammonia to form 
 water, when the nitrogen expands as before. 
 
 Of all the detonating compounds, chloride of 
 nitrogen affords the most simple and striking 
 example of the opposite effects exerted by caloric 
 under different circumstances. It is composed of 
 3 atoms or volumes of chlorine to 1 of nitrogen, 
 which, on uniting, condense into a heavy and oily 
 liqiiid, the specific gravity of which is 1*6. While 
 its elements are united, the elastic force of the 
 caloric in nitrogen is restrained by the greater 
 force with which it is attracted around the atoms 
 of chlorine. These two opposite forces are so 
 nearly balanced, that by adding a small amount 
 of caloric to the chloride it is decomposed, the 
 nitrogen expanding with its accustomed force, 
 when reduced to the separate state. The chlorine 
 also assumes the gaseous state, with evolution of 
 heat and light . The chloride m ay be decomposed 
 
 K 
 
130 PHILOSOPHY OF 
 
 by the volatile oils, naphtha, phosphorus, and 
 various other combustibles, which unite with 
 chlorine, when it explodes as when heated to 
 212 F. 
 
 Euchlorine, peroxide of chlorine, and deutoxide 
 of hydrogen, also expand with explosion and evo- 
 lution of heat and light on being decomposed, 
 because the affinity of their particles for caloric is 
 diminished by reducing their size. The more 
 completely ponderable matter is divided, the less 
 power it has of concentrating, or retaining sethe- 
 real matter around its particles. Hence, the 
 quantity of caloric given out during ordinary com- 
 bustion, other things being equal, is in proportion 
 as the decomposition is complete. When coal or 
 wood is but partially decomposed, gross vapours 
 are formed, constituting smoke, the particles of 
 which are much larger than those of flame, and 
 which retain and carry off a considerable amount 
 of the caloric that is given out by radiation when 
 the combustion is perfect. 
 
 The whole theory of combustion is founded on 
 the various degrees of force with which ponder- 
 able matter attracts t/termo tztkereal matter, under 
 different circumstances. Caloric is more con- 
 centrated around the atoms of dense, than of light 
 gases and vapours ; and greatly more so around 
 the larger compound particles of liquids and 
 solids. In short, all the absorptions of caloric 
 by which it combines with and becomes latent in 
 
COMBUSTION AND DEFLAGRATION. 13' 
 
 ponderable matter, result from their mutual affi- 
 nity : while the escape of caloric during com- 
 bustion, or deflagration, results from the dimi- 
 nution of that affinity, for the same reason that 
 the volume and elastic force of hydrogen and 
 nitrogen greatly augment on the decomposition 
 of ammonia. 
 
 There is nothing more"clearly demonstrable in 
 science, than that all the caloric evolved during 
 the decomposition of ponderable matter, whether 
 solid, liquid, or gaseous, is only a liberation of 
 what was previously concentrated around the 
 atoms of the materials employed. When the 
 particles of solids are separated and subdivided 
 by friction, or collision, a portion of their con- 
 centrated caloric is disengaged, producing incan- 
 descent sparks, or streams of fire. 
 
 A machine is exhibited at the Hall of Practical 
 Science in London, which illustrates the enor- 
 mous quantity of caloric in steel, and its evolution 
 by decomposition, in the most beautiful and strik- 
 ing manner. A circular plate of soft iron is made 
 to revolve at the rate of 5000 times per minute, 
 when the hardest steel on being applied to its 
 edge is cut through rapidly, and reduced to in- 
 conceivably small particles, which are still farther 
 expanded by the caloric thus liberated, into a 
 shower of metallic flame and sparks. This kind 
 of ignition proceeds equally well in vacuo, as in 
 the atmosphere. 
 
132 PHILOSOPHY OF 
 
 Mr. Brande observes, in the last edition of his 
 Manual of Chemistry, page 390, that the exist- 
 ence of nitrogen in nearly all the powerfully 
 detonating bodies, is a singular fact ; and that 
 explosion must remain unexplained until we as- 
 certain the cause of the detonating power of such 
 compounds. He also adds, that at present the 
 phenomena are at variance with the usual expla- 
 nation of the evolution of heat and light during 
 combustion, which have been supposed to be the result 
 of union and condensation, instead of expansion and 
 decomposition. 
 
 The truth is, that in a large majority of cases, 
 combustion, as well as explosion, is attended 
 with expansion of the materials employed. La- 
 voisier, who maintained that gaseous oxygen was 
 the source of heat and light in all cases of com- 
 bustion, supposed that it was always condensed 
 on combining with combustibles. This partial 
 view of the subject has been incorporated with 
 so many works on Chemistry and Natural Phi- 
 losophy, that it has become a very general opi- 
 nion, that oxygen is the only supporter of com- 
 bustion, and the source of heat and light, instead 
 of the bodies with which it unites. 
 
 We have already seen, that during the combi- 
 nation of oxygen with hydrogen, they are both 
 condensed into the liquid state; which conden- 
 sation is attended with the evolution of caloric 
 and light. But a large proportion of the caloric 
 
COMBUSTION AND DEFLAGRATION. 133 
 
 thus given out is disengaged from the hydrogen, 
 which is therefore as much a supporter of com- 
 bustion as the oxygen. 
 
 Oxygen is also condensed, and even solidified on 
 combining with metals during their combustion 
 in it, by which they are converted into oxides. 
 In such cases, it is doubtless the principal source 
 of caloric. It is however not the only supporter 
 of metallic combustion ; for cyanogen, chlorine, 
 bromine, iodine, sulphur, phosphorus, and some 
 other solid bodies unite rapidly with metals when 
 they are heated together, with evolution of heat 
 and flame. 
 
 The combustion of carbon, sulphur, and phos- 
 phorus in oxygen gas, is attended with intense 
 heat ; yet they are greatly expanded without any 
 condensation of the oxygen : for the carbonic, sul- 
 phuric, and phosphoric acids produced, have the 
 same volume as that of the oxygen. 
 
 During the combustion of aether, alcohol, oils, 
 resins, wood, coal, and other inflammable bodies 
 in oxygen, the volume of the gaseous products 
 exceeds that of the oxygen ; yet the process is 
 attended with the production of immense quan- 
 tities of heat and light. 
 
 There is a mixture prepared at the Military 
 Academy of Woolwich, called the Carcass com- 
 position, that burns with great violence, some- 
 what like the detonating compounds, which 
 cannot be quenched with water, and has been 
 supposed to resemble the Greek fire. 
 
134 PHILOSOPHY OF 
 
 I am indebted to Dr. Faraday for the following 
 mode of preparing it. 
 
 lb. oz. 
 
 Nitrate of potass .... 6 4 
 
 Sulphur 2 8 
 
 Powdered antimony . . 10 
 
 Powdered resin 1 14 
 
 Tallow 10 
 
 Venice turpentine .... 10 
 
 The resin, tallow, and turpentine, are melted 
 together. The sulphur and nitre are then added, 
 being kept hot all the time and well stirred about. 
 The powdered antimony is then added and 
 worked well in it, when it may be formed into 
 the shape required. 
 
 The combustion of this mixture is truly terrific, 
 and the quantity of heat evolved enormous. It 
 also goes on in vacuo as well as in the air, which 
 is true of all deflagrating and detonating com- 
 pounds. All such combustions are attended 
 throughout with expansion of the burning bodies 
 instead of condensation. 
 
 The explosive power of gunpowder may be 
 lessened by augmenting the proportions of char- 
 coal and sulphur. Fuses, which burn with a 
 gradual, or continuous deflagration, are composed 
 in the ratio of 
 
 lb. oz. 
 
 Nitre 4 4 
 
 Sulphur 1 
 
 Common gunpowder ground into meal. . 1 12 
 
COMBUSTION AND DEFLAGRATION. 13-5 
 
 From the foregoing facts and observations, we 
 perceive how partial and erroneous is the pre- 
 valent notion, that under all circumstances ca- 
 loric is a repulsive agent. We find that the 
 caloric of explosion, like that of ordinary combus- 
 tion, is only a liberation of what was previously 
 concentrated around the particles of ponderable 
 matter, and diffused during its dissolution. 
 
 Such is the beautiful simplicity of nature, that 
 a clear comprehension of the law by which the 
 molecules of a salt are aggregated and dissolved, 
 affords a miniature representation of the mecha- 
 nism by which the universe is kept in motion, 
 from the law of gravitation to the no less impor- 
 tant transformations of chemistry. 
 
 It has been shown, that cold, or the abstrac- 
 tion of caloric, produces the same effect on gases 
 as mechanical pressure that is, it diminishes 
 their volumes and condenses them into liquids or 
 solids ; which is effected by lessening the ratio 
 of sethereal or elastic matter, while the quantity 
 of ponderable matter remains the same. If we 
 suppose that the repulsive force of this sether in 
 hydrogen is equal to the weight of 2000 atmos- 
 pheres, it must be attracted with a still greater 
 aggregate force, by the atoms of sulphur and 
 other bodies : for we have seen that when 1 atom 
 of sulphur combines with I of hydrogen, the re- 
 sulting compound, sulphuretted hydrogen, may 
 be liquefied by a pressure equal to 17 atmos- 
 
136 EXPANSION AND CONTRACTION. 
 
 pheres at 60 F. while the bisulphuretted hydro- 
 gen becomes liquid, or semi solid, without any 
 pressure. 
 
 By the affinity of ponderable matter for caloric, 
 its atoms are approximated and held together : 
 by its elastic or self-repelling property, it sepa- 
 rates them from each other, as in gasefaction, 
 explosion, and all decompositions. The fact that 
 Philosophers have overlooked this affinity by 
 which caloric is concentrated around the parti- 
 cles of liquids and solids, resolves the problem of 
 contradictions by which the theory of caloric has 
 been so long perplexed, and explains why many 
 have doubted its materiality why the phenomena 
 of combustion, explosion, cohesion, and chemical 
 affinity have not been understood. 
 
 I have shown, that caloric is the cause of re- 
 pulsion in steam and all gases ; in vaporization, 
 combustion, and the expansive force of detonating 
 compounds : and that this elastic force is coun- 
 teracted and diminished, or vanquished by its 
 affinity for gravitating matter. 
 
 The ancient philosophers of Greece often re- 
 ferred to an agency, by which they supposed 
 that all nature was perpetually tending to a ge- 
 neral dissolution: but being restrained by the 
 overpowering concord of things, (by which they 
 meant attraction,) the result of the conflict was 
 the beautiful order and harmony of the world. 
 This doctrine throws a clear and full light on 
 
EXPANSION AND CONDENSATION. 137 
 
 all the powers, motions, combinations and de- 
 compositions of the elements by which we are 
 surrounded and sustained ; and, when perfectly 
 unfolded in all its relations, will be found to fur- 
 nish a simple and rational interpretation of the 
 book of nature. 
 
 Constitution of Liquids. 
 
 It has been shown in the preceding chapter, 
 that there is an intimate relation between the 
 elastic force of gases, and the proportions of igne- 
 ous aether which surrounds their atoms that 
 hydrogen contains a larger amount of caloric, in 
 proportion to the quantity of ponderable matter, 
 than any other known body, and possesses a cor- 
 responding degree of expansive force : but that 
 when it unites chemically with oxygen, it gives 
 out a large proportion of caloric, by which its 
 volume and elasticity are diminished. 
 
 It has also been shown, that other things being 
 equal, the elastic force of other gaseous bodies 
 is in proportion to the amount of igneous matter 
 which is combined with any given quantity of 
 ponderable matter. 
 
 I shall now proceed to show, that the lightest 
 and most volatile liquids are composed of ele- 
 ments which contain a large proportion of caloric 
 around their atoms. I am not aware that any 
 one, since the time of Boyle and Newton, 
 
138 CONSTITUTION OF LIQUIDS. 
 
 has attempted to explain why liquids differ so 
 greatly in their volatility. Boyle supposed that 
 their tenacity was owing to the grossness of their 
 particles, while Newton referred their volatility 
 to the smallness of their particles. Neither of 
 these hypotheses, which are nearly the same, 
 is in accordance with the present state of science. 
 The proximate atoms of water are less than those 
 of alcohol, asther, and various other liquids that 
 are more elastic and volatile at the same tempe- 
 ratures. The atoms of nitrous and nitric acids, 
 of sulphuretted and phosphuretted hydrogen, of 
 chlorine, hydrochloric acid, and many other gase- 
 ous bodies, are larger than those of carbon, sul- 
 phur, phosphorus, silicium, calcium, &c. Yet 
 the former are much more volatile and elastic 
 than the latter. The atoms of aetherine, sulphu- 
 rous acid, muriatic aether, (which is composed of 
 astherine and hydrochloric acid) protoxide of 
 chlorine, &c. are larger than those of water or 
 hydrocyanic acid, the elasticity of which is much 
 inferior.* 
 
 Such facts prove conclusively, that the elastic 
 force of gases and liquids is not determined alone 
 
 * Lucretius observes that light passes through scraped horn, 
 which wine and water will not do, because the particles of the 
 latter are too large ; but that water and wine percolate strainers 
 more readily than oils, because the latter are composed of larger 
 particles, or of particles that are hooked. (De Natura Rerum, 
 Book II.) 
 
CONSTITUTION OF LIQUIDS. 139 
 
 by the size of their proximate atoms, but by their 
 relations to a self-repelling fluid. 
 
 There is a class of liquids which are composed 
 chiefly of hydrogen and carbon, that seem to 
 form a connecting link between gases and more 
 fixed bodies. They are generally much lighter 
 than water, and exceedingly volatile. Such are 
 Faraday's aetherine and bicarburet of hydrogen, 
 spirit of gum elastic,parafiine,and naphtha. jEther, 
 alcohol, pyro-acetic spirit, acetic aether, and most 
 of the essential oils, which are composed of car- 
 bon and hydrogen, united with small proportions 
 of oxygen, are lighter than water, and some of 
 them highly volatile. There are also a few com- 
 binations of hydrogen and carbon with nitrogen, 
 chlorine, and even iodine, that are very volatile, 
 as nitrous aether, hydrocyanic acid, muriatic, and 
 hydriodic aethers. There cannot be a doubt that 
 all such liquids owe their volatility to the same 
 cause which determines the elastic force of gases. 
 Accordingly, we find, that aetherine, the lightest of 
 them all, boils or expands rapidly into the gaseous 
 state, under the pressure of the atmosphere below 
 32. Common aether boils at 96, muriatic aether at 
 60, nitrous aether at 60, and acetic aether at 105, 
 while alcohol boils at 173.* Butwhen thepressure 
 of the atmosphere is removed, as under an ex- 
 
 * With a view of ascertaining how far the rationale of such 
 phenomena had occupied the attention of philosophers, I took an 
 opportunity of asking a distinguished professor and author in 
 
140 CONSTITUTION OF LIQUIDS. 
 
 hausted receiver, the elastic force of the caloric 
 which surrounds their particles, expands them 
 rapidly into vapour at 145 below their boiling 
 points under the pressure of the atmosphere. In 
 all such cases, liquids are expanded into the 
 gaseous state by the elastic force of their latent 
 constituent caloric, which is thus diffused and 
 carried off, by which intense cold is produced. 
 In vacuo, pure aether is rapidly expanded into 
 vapour at 46, alcohol at 28, and water at 67 
 from which it follows, that they are all elastic 
 fluids like gases, but in a less degree ; and that 
 if their elasticity were not restrained by the 
 pressure of the atmosphere, they would boil at 
 ordinary temperatures, until the process were 
 checked by the pressure of their own atmos- 
 pheres, 
 
 By reference to a subsequent Table, it will 
 be seen that aether is composed of 5 atoms of 
 hydrogen, 4 of carbon, and 1 of oxygen ; or 2 
 atoms of olefiant gas to one of water ; and that 
 
 London, why sether, alcohol, &c. were more volatile than water, 
 and the latter than sulphuric acid : after pausing a few moments, 
 he replied, that " he supposed it was owing to the smallness of 
 their cohesion" the reason of which remained in statu quo. 
 
 I have thought proper to relate this circumstance, because the 
 present systems of chemistry and physics are full of such defini- 
 tions and explanations, the fundamental reason of things being 
 overlooked. When a teacher is asked by his pupil why men can 
 see through water, glass, and many other hard dense bodies, he 
 answers with the utmost self-complacency, because they are 
 transparent, and there is an end of the matter. 
 
CONSTITUTION OF LIQUIDS. 141 
 
 alcohol is composed of 3 atoms hydrogen, 2 of 
 carbon, and 1 of oxygen while water is com- 
 posed of 1 atom hydrogen to 1 of oxygen. Hence 
 the difference between their specific gravities and 
 boiling points the specific gravity of pure aether 
 being about -700, and that of alcohol -794, com- 
 pared with water 1000, which congeals at 32 F. 
 while aether and alcohol are exceedingly difficult 
 to congeal.* 
 
 That light and volatile liquids contain more 
 caloric than water and some others which are 
 more dense and tenacious, might be inferred from 
 the large amount of hydrogen which they con- 
 tain, and from their highly combustible property. 
 So highly inflammable is aetherine, that it takes 
 fire on the first approach of a lighted taper. 
 
 It has been often stated gravely by chemical 
 writers, that cold results from evaporation, because 
 vapours have a greater capacity for caloric than, the 
 liquids from which they are formed, but this is 
 mere verbiage, and does not explain how liquids 
 
 * It was said that alcohol had been frozen by Hutton; and 
 Fourcroy supposed that he had frozen aether at 46. But neither 
 Thenard nor Bussy were able to congeal it : from which it is pro- 
 bable, as observed by Mr. Brande, that the aether employed by 
 Fourcroy was not pure. It is now certain however from the ex- 
 periments of Thilorier, that both may be congealed. 
 
 When alcohol and water are mixed, they combine chemically, 
 with diminution of their aggregate volume and disengagement of 
 heat. Proof spirit is composed of about equal weights of each, 
 the specific gravity of which should be -916. 
 
142 CONSTITUTION OF LIQUIDS. 
 
 are expanded into vapour. The coldness results 
 from the elastic force of their latent caloric, by 
 which it is expanded over a larger space ; yet 
 without being separated from their particles and 
 radiated as during combustion. 
 
 When an open vessel of water is placed over a 
 fire, its temperature never rises above 212 F. 
 however hot the fire may be, because at 212, 
 the elastice force of caloric in water overcomes 
 the pressure of the atmosphere, and expands it 
 into steam, the bulk of which is 1720 times that 
 of water. But when water is enclosed in a strong 
 vessel like Papin's Digester, and prevented from 
 expanding into steam, its temperature rises to 4 
 or 500. If a vessel could be obtained strong 
 enough, water might be made red hot, and if 
 again permitted to expand, its temperature would 
 immediately fall in proportion to the diffusion ; 
 and so of all other vapours. 
 
 The production of cold during the exhaustion 
 of a receiver, as reported by Leslie and Dalton, 
 is referable to the same cause, and not to an in- 
 crease of capacity f o?' caloric in rarefied air, as they 
 supposed. That is, a large proportion of caloric 
 is carried off in combination with the air which is 
 pumped out ; so that what remains is greatly dif- 
 fused by virtue of its elasticity, producing a cor- 
 responding reduction of temperature. When car- 
 bonic acid, ammonia, cyanogen, chlorine, and 
 other elastic fluids are converted into the liquid 
 
CONSTITUTION OF LIQUIDS. 143 
 
 or solid state by pressure, a still greater reduction 
 of temperature results from their sudden expan- 
 sion on removing the pressure. 
 
 M. Thilorier has recently invented an apparatus 
 by which he can form large lumps of solid car- 
 bonic acid, the rapid expansion of which, causes 
 a reduction of temperature 132. When alcohol 
 was poured upon them, it was immediately con- 
 verted into a hard, brittle ice ; while aether was 
 congealed to the consistence of sodden snow. M. 
 Bussy has also congealed alcohol, (sp. gr. *850) 
 by the evaporation of liquid sulphurous acid in 
 vacuo. (Ann. de Chim. for May, 1824.) 
 
 When aether is dropped upon the hand, the 
 caloric of the living body expands it into vapour, 
 and is carried off in an invisible form, causing 
 great coldness. In the same way, the caloric of 
 the solar rays is continually expanding the water 
 of the earth into vapour, and diffusing it through 
 the atmosphere, (to be given out in colder re- 
 gions) by which the sultry heats of summer are 
 diminished. 
 
 That all odoriferous emanations consist of ex- 
 tremely minute particles of bodies diffused 
 through the atmosphere by caloric, need scarcely 
 be mentioned, being obvious from the fact, that 
 at very low temperatures, they are not produced. 
 Excessive cold puts a stop to all volatilization and 
 decomposition of matter. 
 
 That the numerous facts connected with the 
 
144 CONSTITUTION OF LIQUIDS. 
 
 constitution of different liquids may be the more 
 readily understood, I have presented them in a 
 tabular form. 
 
 The second column of the first table exhibits 
 the number of carbon atoms in the various com- 
 pound liquids, with the letter C annexed, the 
 second column, the number of hydrogen atoms 
 the third, of oxygen, and the fourth, of nitrogen ; 
 while the fifth column represents their united 
 equivalents, or proximate atomic weights, com- 
 pared with hydrogen as unity. The sixth column 
 gives the specific gravity of the liquids, compared 
 with water 1000, and the seventh, their boiling 
 points. The remaining numbers give the rela- 
 tive proportions of their constituents in the 1 00 
 parts by weight, as derived from the best analyses 
 of modern chemists. By inspecting the first table, 
 it appears that all the most spirituous and vola- 
 tile liquids contain large proportions of hydrogen 
 and carbon that most of them are lighter than 
 water, and boil at lower temperatures. 
 
 Naphtha is composed of 5 atoms hydrogen and 
 6 of carbon, or of 87.75 parts by weight of car- 
 bon, to 12.25 of hydrogen in the 100. It is also 
 more dense than aetherine, and less volatile. 
 Hence it would seem, that the elasticity of 
 aetherine exceeds that of naphtha, for the same 
 reason that the elastic force of olefiant gas is 
 greater than that of aetherine ; or that the elas- 
 ticity of hydrogen exceeds that of olefiant gas. 
 
145 
 
 TABLE I. 
 
 Representing the Atomic Constitution, Specific Gravity, and Boiling 
 Points of various Volatile Liquids, fyc. 
 
 
 1 
 
 at 
 
 o 
 
 Hydrogen. 
 
 a 
 O 
 
 ^ 
 
 Proximate 
 atom. 
 
 O 
 
 Cu 
 
 ce 
 
 ffg 
 I 1 
 
 32 
 
 60 
 
 70 
 105 
 
 80 
 96 
 160 
 186 
 120 
 132 
 150 
 148 
 180 
 173 
 102 
 200 
 212 
 
 210 
 112 
 
 Relative Proportions by Weight in 
 100 Parts. 
 
 ^Etherine, 
 Sp.of caoutch. 
 Mur. aether 
 Nitrous aether 
 Acetic aether 
 Ess. ofJemon 
 Hydrocy. acid 
 Comn. aether 
 Naphtha 
 Bicarb, of hyd. 
 Paraffine 
 Pyro acetic sp. 
 Pyroxilic spirit 
 Hydriod. aether 
 Hydrcy. aether 
 Alcohol 
 Bisul. of carb. 
 Chi. of sulphur 
 Chi. of nitr. 
 [odideof nitr. 
 
 tf.acid,concen- 
 Mu. acid,conc. 
 Tartaric acid 
 Citric acid 
 Hydriodic acid 
 Acetic acid 
 Cyanic acid 
 Sul. cyan, acid 
 Perchloric acid 
 
 Sul. acid, CODC. 
 Water 
 
 C 4 
 
 O 4 
 3 4 
 3 8 
 
 5 s 
 3 2 
 
 C 4 
 C 5 
 o 6 
 
 C 3 
 
 34 
 
 C 4 
 C 6 
 
 H2 
 
 S 2 
 
 N. 
 N. 
 
 N* 
 C1.H 
 
 d 4 
 
 34 
 
 I 
 Ac. 
 
 
 
 S 
 
 H 4 
 H 
 H 5 
 H 3 
 H 8 
 H 4 
 H 
 H 5 
 H 6 
 H 3 
 H 
 H 2 
 H 5 
 H 5 
 H 5 
 H 3 
 S 2 
 Cl. 
 Cl 3 
 
 I 3 
 
 Aq 2 
 Aq 
 H 2 
 H 2 
 H 
 Aq. 
 
 S 2 ' 
 O 7 
 
 
 
 ci 
 
 O 4 
 O 4 
 
 
 
 N 
 
 N 
 
 28 
 
 *65 
 75 
 88 
 34 
 27 
 37 
 36 
 39 
 
 28 
 45 
 154 
 55 
 23 
 38 
 68 
 122 
 392 
 
 72 
 91 
 
 627 
 640 
 874 
 880 
 
 847 
 705 
 700 
 750 
 850 
 870 
 792 
 804 
 1.92 
 700 
 794 
 1-272 
 1-6 
 1-6 
 
 1-5 
 1-6 
 
 C. 
 
 85-15 
 
 36-9 
 32-00 
 54-55 
 88-1 
 44-4 
 64-87 
 87-75 
 
 H. 
 
 14-25 
 
 7-7 
 6-67 
 9-09 
 11-9 
 3-7 
 13-51 
 12-25 
 
 0. 
 
 55-4C1. 
 42-67 
 36-36 
 
 21-62 
 
 N. 
 
 18-66 
 51-8 
 
 Parts. 
 100 
 
 100 
 100 
 100 
 100 
 100 
 100 
 
 6 
 
 O 2 
 
 i. 
 o 
 
 b 
 o* 
 
 o 
 b 
 
 .. 
 ... 
 
 N 
 
 85-02 
 
 14-98 
 
 ... 
 
 ... 
 
 ... 
 
 
 
 
 
 
 15-60 
 65-5 
 52-17 
 15-79 
 
 3-15 
 9-1 
 13-51 
 84-21 S 
 
 81-251 
 21-62 
 
 25-4 
 
 100 
 100 
 100 
 100 
 
 11-5 n 
 3-6 n 
 
 75- N' 
 
 88-5 Cl. 
 94-4 I. 
 
 25 Aq. 
 
 ... 
 
 ... 
 
 100 
 100 
 
 
 
 
 
 
 
 ... 
 
 ... 
 
 ... 
 
 
 127 
 60 
 34 
 59 
 92 
 
 58 
 9 
 
 1-7 
 1-062 
 
 1-022 
 1-6 
 
 1-84 
 1-000 
 
 260 
 
 
 
 
 
 
 
 
 217 
 
 392 
 
 620 
 212 
 
 35-2 
 
 45-8O 
 
 41-10 
 54-2 S. 
 
 23-7 n. 
 
 ... 
 
 ... 
 
 81-63S 
 
 18-37Aq 
 11-9 
 
 88-1 
 
 ::: 
 
 100 
 100 
 
TABLE II. 
 
 Representing the ultimate Constitution of the Volatile and Fixed 
 Oils, with some other Compounds, their Specific Gravity, 
 Boiling Point, fyc. 
 
 
 e3 
 
 Q 
 
 Hydrogen- 
 
 o 
 
 * 
 
 Proximate 
 atom. 
 
 5 
 
 & 
 
 n 
 
 M . 
 
 .S c 
 
 3* 
 
 Relative Proportions by Weight in 
 100 Parts. 
 
 Camphene, 
 Oil of Anise, 
 Peppermt. 
 Lavender, 
 Rosemary, 
 Camphor, 
 Caraway, 
 Juniper, 
 Cinnamon, 
 Sassafras, 
 Benzule, 
 Naphthalin, 
 Paranaphthal. 
 Creosote, 
 Petrolene, 
 Oilofbitr.alm. 
 Cloves, 
 Spermaceti, 
 Hogslard, 
 Tallow, 
 Castor oil, 
 Linseed oil, 
 Olive oil, 
 Resin, 
 Beeswax, 
 Camphor, 
 Sugar, 
 Gum, 
 Starch, 
 Gluten, 
 Lignin, 
 Sulphovinic t 
 acid, S 
 Hea. oil of win. 
 Sulphonaph- 
 thalic acid, 
 
 c* 
 
 C 10 
 C 10 
 
 H 8 
 H 6 
 H 10 
 
 
 
 o 
 
 
 
 68 
 72 
 78 
 
 860 
 985 
 920 
 877 
 890 
 988 
 940 
 911 
 1-350 
 1-094 
 
 312 
 
 C. 
 
 88-1 
 81-4 
 77-3 
 
 H. 
 11-9 
 7-98 
 12-6 
 
 O. 
 
 10-62 
 10-1 
 
 N. 
 
 Parts. 
 100 
 100 
 100 
 
 
 
 
 
 
 ... 
 
 
 
 
 
 
 
 
 
 
 79-28 
 
 10-36 
 
 10-36 
 
 
 100 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 C 14 
 
 C 10 
 C 15 
 
 H 5 
 H 4 
 H 4 
 
 O 2 
 
 
 105 
 64 
 94 
 
 
 
 
 
 
 
 1-037 
 1-043 
 
 410 
 572 
 397 
 536 
 
 89-00 
 
 11-00 
 
 ... 
 
 
 100 
 
 72-42 
 88-5 
 79-56 
 70-02 
 79-5 
 79-098 
 78-996 
 74-000 
 76-01 
 77-21 
 75-94 
 80-60 
 
 8-12 
 11-5 
 5-56 
 7-42 
 11-6 
 11-146 
 11-700 
 10-29 
 11-35 
 13-36 
 10-71 
 11-47 
 
 14-46 
 
 14-88 
 22-56 
 8-9 
 9-756 
 9-304 
 15-71 
 12-63 
 9-42 
 13-33 
 7-93 
 
 ... 
 
 100 
 100 
 100 
 100 
 100 
 100 
 100 
 100 
 100 
 100 
 100 
 
 C a> 
 
 C 14 
 
 C 20 
 
 c 
 c 
 c 
 c 
 c 
 c 
 
 H 16 
 H 6 
 H' 3 
 H 
 H 
 H 
 H 
 H 
 H 
 
 O 2 
 O 5 
 
 o 
 
 
 
 o 
 o 
 o 
 o 
 
 :: 
 
 128 
 106 
 173 
 
 
 ... 
 
 
 
 
 
 
 
 
 
 ... 
 
 600 
 
 
 
 
 
 
 
 C 10 
 C 12 
 C 13 
 C 7 
 
 H 8 
 H 11 
 H 12 
 H 
 
 o 
 
 O 11 
 
 o 12 
 o 
 
 ... 
 
 76 
 171 
 186 
 96 
 
 988 
 
 400 
 
 42-1 
 41-94 
 43-75 
 57-7 
 50-00 
 
 6-4 
 6-5 
 6-77 
 7-8 
 50- Aq 
 
 51-5 
 52-1 
 4968 
 22-00 
 
 14-5 
 
 100 
 100 
 100 
 100 
 100 
 
 
 
 
 
 
 En 
 
 En 2 
 
 N. 
 
 S 2 
 S 2 
 S 2 
 
 ... 
 
 ... 
 
 108 
 136 
 208 
 
 
 
 1.333 
 
 
 
 
 
 
 
 
 
 
 
 
 
COHESION OF LIQUIDS. 147 
 
 It has been found, that several of the essential 
 oils ate hydrocarbons, as the essence of turpen- 
 tine, lemons, copaiva, burgamot, and camphene, 
 or camphogen ; but that most of them are com- 
 posed of hydrogen and carbon, united with oxy- 
 gen ; or that they are oxides of hydrocarbons, as 
 they have been termed by Dumas. 
 
 The oil of mustard contains sulphur and nitro- 
 gen ; the oil of bitter almonds also contains some 
 nitrogen, according to Liebig and Wohler. When 
 perfectly pure, it is composed of 1 atom benzule 
 (Bz.) and 1 of hydrogen, the proximate atom of 
 which is 106. Their atomic weights have not 
 been accurately ascertained, owing to the fact, that 
 they do not combine with bases without decom- 
 position. They are of a pungent aromatic taste 
 and odour ; and many of them pass into the form 
 of vapour at the temperature of boiling water; 
 but some of them require a much greater heat. 
 Dumas observes, that the density of the volatile 
 oils is proportional to the quantity of oxygen they 
 contain. 
 
 The specific gravity and chemical constitution 
 of the fixed oils are nearly the same ; yet they 
 require a temperature of about 600 F. to vola- 
 tilize them. Why then, it may be naturally in- 
 quired, if they consist chiefly of carbon and 
 hydrogen, is their cohesion greater than that of 
 aether, alcohol, water, and the essential oils? 
 The following facts may tend to throw some 
 gree of light on this question. 
 
148 COHESION OF LIQUIDS. 
 
 By adverting to the second table, it will be 
 found that camphene, or camphogen, is composed 
 of lOc. to 8h. united into 1 compound atom, the 
 weight of which is 68, compared with hydrogen : 
 whereas, the essence of lemon is composed of 5c. 
 to 4h. making a proximate atom equal to 34, or 
 one-half that of camphene. The consequence 
 of which is, that the latter is much more volatile 
 than the former, though their specific gravities 
 are nearly the same. Camphene requires a tem- 
 perature of 312 F. to make it boil, while the 
 essence of lemon is highly volatile like naphtha. 
 Camphene is the principal ingredient in oil of 
 turpentine and camphor, both of which are oxides 
 of camphene. Common camphor is composed of 
 1 atom camphene to 1 of oxygen. There is also 
 an artificial camphor, composed of hydrochloric 
 acid 1 atom, united with 1 of camphene. While 
 3 atoms of water and 1 of camphene make the 
 hydrate of camphene ; and 5 atoms oxygen to 1 
 of camphene, camphoric acid. Petrol ene, which 
 is obtained from petroleum by distillation, ac- 
 cording to Boussingault, is composed of carbon 
 and hydrogen in the same proportions as cam- 
 phene ; but its proximate atom being just double 
 that of camphene, corresponding with the diffe- 
 rence between the specific gravity of their va- 
 pours, it possesses the consistence of a fixed oil, 
 requiring a temperature of 536 F. to convert it 
 into vapour. The product (asphaltine), which 
 
COHESION OF LIQUIDS. 149 
 
 remains after the distillation, is still more tena- 
 cious. 
 
 Naphthalin is composed of lOc. 4h. united into 
 1 atom 64. It is a highly tenacious liquid, re- 
 quiring a temperature of 400 for its volatiliza- 
 tion. 
 
 According to Dumas and Laurent, there is a 
 combination of carbon and hydrogen in the ratio 
 of 15c. 4h. (equivalent 94) which has been called 
 paranaphthalin. It is one of the last products 
 from the distillation of coal tar, and is less vola- 
 tile than naphthalin. The atomic weight of sul- 
 phuric acid is 40, and that of naphthalin 64. 
 When 2 equivalents of the former unite with 2 
 of the latter, the compound equivalent is 208 of 
 sulpho naphthalic acid, (according to Faraday) 
 forming a hard and brittle solid, that is soluble 
 in water, alcohol, and oils. 
 
 Naphthalin also forms a dense and tenacious 
 compound with chlorine. With cyanogen, sul- 
 phur, iodine, bromine, &c. it forms dense semi- 
 liquids, the cohesion of which augments in 
 proportion to the increased magnitude of their 
 compound equivalents. 
 
 From the atomic constitution of camphene, oil 
 of turpentine, cloves, peppermint, anise, naphtha- 
 lin, &c. there can scarcely be a doubt that their 
 cohesion, and that of the fixed oils, is greatly mo- 
 dified, if not wholly determined by the number 
 and relative proportions of elementary atoms 
 
150 COHESION OF LIQUIDS. 
 
 which combine into complex atoms or particles 
 of larger size. Hence, aetherine is more vola- 
 tile than naphtha, and the latter than camphene. 
 Camphene is more volatile than naphthalin, and 
 the latter than paranaphthlin, although they are 
 all composed of carbon and hydrogen. The 
 atomic equivalent of camphene exceeds that of 
 naphthalin, while the latter is less volatile : but 
 this is owing to the fact, that camphene contains 
 just double the ratio of hydrogen. 
 
 By looking over the preceding tables, we per- 
 ceive that the most volatile liquids are composed 
 largely of hydrogen, and of .other elastic gases, 
 such as hydrochloric aether, nitrous aether, acetic 
 aether, hydro-cyanic and hydriodic aethers, chlo- 
 ride of nitrogen, nitric acid (anhydrous,) pyroacetic 
 spirit, &c. all of which expand into the gaseous 
 state at temperatures below 212 F., notwithstand- 
 ing their proximate equivalents are large: but 
 it was also shown, that carbon, phosphorus, sul- 
 phur, iodine, bromine, and even arsenic, may be 
 converted into permanent gases by combining 
 chemically with hydrogen that they attract from 
 it a portion of caloric by which their elastic force 
 is increased, and that of the hydrogen diminished 
 that their volume and elasticity decrease in pro- 
 portion to the size of their proximate atoms, until 
 they assume the liquid or solid form. The most 
 embarrassing circumstance connected with this 
 subject is, that carbon should not be elastic at all 
 
COHESION OF LIQUIDS. 151 
 
 temperatures, like oxygen, nitrogen, hydrogen, 
 and their combinations. Considering the large 
 amount of caloric which it contains, there is some- 
 thing very mysterious about the fixedness of char- 
 coal at high temperatures. 
 
 The whole theory of distillation and sublima- 
 tion is founded on the different degrees of vola- 
 tility in the various ingredients of solid and liquid 
 bodies, from the rectification of the aethers, al- 
 cohol, and the volatile oils, to the distillation of 
 coal, by which its carbon, hydrogen, and oxygen 
 are volatilized in a state of carburetted hydrogen, 
 olefiant gas, carbonic oxide, &c. as in coal gas. 
 
 That the proximate atoms of the fixed oils, (such 
 as olive oil, castor oil, spermaceti, lard, tallow, 
 and other bodies which are difficult to volatilize, 
 as tar, resin, beeswax,- petroleum, &c.) are larger 
 than those of the volatile oils, would appear from 
 a variety of considerations. 
 
 1. They are generally opaque, and many of 
 them obtained by expression from the seeds of 
 plants from which it is probable that they con- 
 tain a mixture of gross particles, united with more 
 volatile particles and that they differ from es- 
 sential oils in a manner somewhat analogous to 
 the difference between smoke, which is composed 
 of gross vapours, and the pure gases, which are 
 transparent and invisible. 
 
 2. In its ordinary state of impurity, oil of tur- 
 pentine volatilizes slowly at 300 F., when a limpid 
 
152 COHESION OF LIQUIDS. 
 
 oil passes over. At 360 it boils but on losing 
 its essential oil, it becomes more tenacious, and 
 requires a temperature of 500 F. to make it boil 
 thus, passing from the state of a volatile to that 
 of a fixed oil. 
 
 The oil of anise is composed of 10 atoms carbon, 
 6 of hydrogen, and 1 of oxygen, making its proxi- 
 mate atom equal to 74 while the oil of pepper- 
 mint consists of C 10 H 10 O, making its compound 
 equivalent 78: so that in their atomic constitution 
 they resemble naphthalin, forming a medium be- 
 tween the more volatile oil of lemons, and those 
 termed fixed. 
 
 According to Dumas, the oil of cloves is com- 
 posed of 20 atoms carbon, to 13 of hydrogen, and 
 5 of oxygen, making its proximate atom 173. It 
 is accordingly very difficult to volatilize, like the 
 fixed oils from which it is probable, that their 
 atomic constitution is similar, and determines 
 their tenacity. 
 
 When the volatile oils are exposed to the atmos- 
 phere, they absorb oxygen, by which they become 
 resinous and concrete. The oil of turpentine is 
 thus converted into rosin. By absorbing oxygen, 
 the fixed oils become rancid, and much more 
 rapidly in warm than cold weather during which 
 process, carbonic acid is produced, and heat 
 evolved, as in fermentation. Hence, the spon- 
 taneous combustion of cotton goods which have 
 imbibed oily matter. They all give out great 
 
COHESION OF LIQUIDS. 153 
 
 quantities of caloric during combustion, and are 
 very bad conductors of heat and electricity. 
 
 Query. May not the mild and un irritating pro- 
 perties of the fixed oils depend chiefly on the size 
 of their proximate atoms, by which they retain 
 around them their latent caloric, so that when 
 taken into the stomach, they produce no burning 
 sensation or inflammation? And may not their 
 refusal to combine with cold water be owing to 
 the same cause ? for it will be seen hereafter that 
 no chemical combination ever takes place without 
 a transition of caloric from one body to another. 
 
 It would be a matter of the highest interest and 
 importance to ascertain the cause which deter- 
 mines the specific agencies of the aethers, alcohol, 
 and its combinations with water, as brandy, gin, 
 &c. on the living body, what gives them their 
 tonic and exhilarating properties why the vola- 
 tile oils are pungent and aromatic, while the fixed 
 oils are bland, producing no sensation of heat 
 when taken into the stomach. The modus ope- 
 randi of hydro-cyanic, oxalic, nitric, and sul- 
 phuric acids, together with all active medicines, 
 which are poisons, is still involved in profound 
 darkness. A thorough investigation of this whole 
 subject, physiologically and pathologically, under 
 the guidance of broad and fundamental principles, 
 would create a new era in medical science, and 
 rescue it from the opprobrium of mysticism and 
 uncertainty which have long rendered its utility 
 
154 COHESION OF LIQUIDS. 
 
 more than doubtful among men of the soundest 
 views. 
 
 That nitric, sulphuric, and phosphoric acids, 
 owe their active properties to the igneous prin- 
 ciple with which they are associated, cannot be 
 doubted ; as their action is attended with an in- 
 tense heat, as when mixed with oils, sugar, and 
 alcohol; and is accompanied by the formation of 
 new chemical compounds. It is the prevalent 
 opinion of medical men, that hydro-cyanic acid 
 destroys life by a sedative influence ; but I have 
 satisfied myself by inspecting the stomachs of 
 individuals who have been destroyed by it, that 
 it produces a high degree of active inflammation. 
 There never was a stomach more injected with 
 blood, than one exhibited in Guy's Hospital, pro- 
 duced by swallowing a large dose of prussic acid. 
 
 It has been discovered by the recent researches 
 of chemists, that there are several combinations 
 of carbon and hydrogen, the relative proportions 
 of which are the same, while they differ greatly 
 in their physical properties: for example, olefiant 
 gas is composed of 2 atoms carbon, united with 
 2 of hydrogen, forming a bicarburet of hydrogen, 
 which is permanently elastic at all temperatures ; 
 while setherine is a quadri- hydro-carbon, con- 
 sisting of 4 atoms carbon, to 4 of hydrogen, united 
 into 1 compound atom, the weight of which is 28, 
 compared with hydrogen as unity ; or just double 
 the atomic weight of oletiant gas. Accordingly, 
 
COHESION OF LIQUIDS. 155 
 
 we have seen, that although aetherine is a highly 
 volatile liquid, it is far less elastic than olefiant 
 gas. 
 
 Such bodies have been termed isomeric, by Ber- 
 zilius, (from KTOC equal, and /tcpoc part.) Dr. Turner 
 explains the difference between the properties of 
 these bodies by supposing that their particles 
 are differently grouped together. (Page 238, 
 Chem. 5th edit.) This is no doubt true, but 
 does not explain why their particles contract 
 into a smaller space, and why the specific gravity 
 and elastic force of setherine and olefiant gas are 
 different. I have already proved that the repul- 
 sive force of caloric in hydrogen is counteracted 
 and diminished in proportion to the quantity of 
 carbon united with it, and that the igneous aether 
 is concentrated around the larger atoms of ethe- 
 rine by virtue of their mutual affinity. May not 
 the arrangement of their particles, and the varia- 
 tion in their chemical properties result from the 
 same cause? Such queries open a wide field of 
 speculation to the philosophical chemist, and 
 their solution is of fundamental importance to a 
 right understanding of chemical philosophy. 
 
156 
 
 BOOK II. 
 
 CHAPTER I. 
 
 On the Cause of the Forces which regulate the 
 Constitution of Solids. 
 
 IT was long since observed by Lord Bacon, that 
 the most important facts connected with the fun- 
 damental constitution of nature, had been quite 
 overlooked ; such as " the cause of heat and light, 
 weight and density ', hardness and softness, solidity 
 and fluidity, fermentation and putrefaction, ger- 
 mination and organization" Novum Organum. 
 Although more than two centuries have elapsed 
 since Bacon pointed out the radical defects of 
 science, and the true mode of its regeneration, 
 with profound sagacity, and a soul-stirring elo- 
 quence never surpassed, scarcely one of the above 
 problems have been resolved in a satisfactory 
 manner. Philosophers are still as much divided 
 in regard to the cause of heat and light as they 
 were in the time of Bacon, Galileo, and Boyle ; 
 or the still more remote period of Plato and 
 Aristotle. 
 
COHESION OF SOLIDS. 157 
 
 Sir Isaac Newton devoted many years to the 
 investigation of light, and really accomplished 
 much towards an elucidation of its physical pro- 
 perties ; but without ever having inquired into 
 its connexion with heat, or its wonderful agency 
 in the work of the universe. 
 
 The same illustrious author resolved the cohe- 
 sion of solids and the tendency of heavy bodies 
 towards the centre of the earth, into the same 
 law which determines the aggregation of planets, 
 and their revolutions around the sun : but he 
 did not identify the cause of universal attraction 
 with any known agent. In short, he did not 
 distinctly unfold the fundamental principle of 
 action in nature of expansion and contraction, 
 density and lightness, hardness and softness, so- 
 lidity and fluidity, chemical union and decom- 
 position. There is nothing more remarkable in 
 the history of science, than that the phenomena 
 of attraction should have been so far unfolded and 
 generalized, without any definite knowledge of 
 its cause. It would seem that one of the first in- 
 quiries of the philosopher ought to be, what is 
 the agent or cause of force, by which the atoms 
 of matter are held together? and that the most 
 natural answer would be, that which surrounds 
 and fills the spaces between them. 
 
 It can no longer be disguised, that in regard to 
 the cause of cohesion, capillary attraction, arid 
 gravitation, Sir Isaac Newton has expressed him- 
 self with so much ambiguity as to leave his fol- 
 
158 COHESION OF SOLIDS. 
 
 lowers in great doubt whether he had any settled 
 opinion on the subject. In the first edition of 
 the Principia, he maintained that universal space 
 is a vacuum ; or that it ivas void of all sensible 
 matter, and that the ultimate particles of bodies 
 are endowed with inherent forces, or powers of at- 
 traction and repulsion. 
 
 That he afterwards renounced the vacuum of 
 space and the self motive power of a toms, is evident 
 from the scholium which he added to the second 
 edition of the Principia, his letter to Boyle, and 
 from the whole tenor of the Opticks in each of 
 which, he maintains the existence of an exceed- 
 ingly subtile, active, and elastic aether as pervad- 
 ing universal space and the pores of all bodies 
 that it was the cause of cohesion, capillary at- 
 traction, and of the force by which menstruums 
 dissolve solids in fine, that it was the moving 
 power of nature. 
 
 It is also universally known, that he regarded 
 light as a material substance, capable of being 
 attracted and repelled by gravitating matter; 
 which alone is sufficient to prove, that he had 
 abandoned the hypothetical vacuum of space. 
 He further supposed that light and common mat- 
 ter were convertible into each other an hypo- 
 thesis which I shall endeavour to show hereafter 
 by an appeal to nature, and the most decisive 
 experiments, is susceptible of positive demon- 
 stration. 
 
 Considering the almost unbounded influence 
 
COHESION OF SOLIDS. 159 
 
 of Newton's authority on nearly all subjects 
 connected with the science of nature, it is im- 
 portant that his real opinions should be distinctly 
 understood. I shall, therefore, proceed to prove, 
 by his own words, that he did not regard attrac- 
 tion as an ultimate law of nature, resulting from 
 the inherent properties of atoms. In addition to 
 the passages before quoted, in page 26 of this 
 work, he observes, in the advertisement to the 
 second edition of the Opticks, " to show that I do 
 not take gravity for an essential property of 
 bodies, I have added one question concerning its 
 cause, choosing to propose it by way of question, 
 because I am not satisfied about it for want of 
 experiments."* 
 
 The same view is still further expanded in the 
 third book of the Opticks, page 365. After ob- 
 serving that " all matter, even light, seems to be 
 composed of exceedingly small, hard, and un- 
 changeable atoms, which in the densest bodies 
 touch only in a few points," he adds, " how they 
 can stick together so firmly as they do without 
 the assistance of something which causes them 
 to be attracted or pressed towards one another, 
 is very difficult to conceive." He remarks, in 
 another passage, page 369, " there are agents in 
 nature capable of causing the particles of matter 
 to stick together by very strong attractions, and 
 
 * The above sentence refers to the cether, which, in the second 
 edition of the Principia, he proposed hypothetically as the cause 
 of universal attraction. 
 
160 CONSTITUTION OF SOLIDS. 
 
 that it is the business of experimental philosophy 
 to find them out." Yet it is an undoubted fact, 
 that nearly all the most distinguished followers 
 of Newton have represented him as teaching the 
 vacuum of space that the sun operates upon 
 the planets without any intervening mechanical 
 medium and that the gravitating matter of which 
 planets is composed, is held together by virtue of 
 inherent powers, or innate forces, which Newton 
 expressly says that he could not conceive. 
 
 It was truly observed by Bacon, that "the 
 doctrines of great and original minds are often 
 degenerated and embased by time that while 
 the lighter parts of their labours float down the 
 stream of time, the weightier and more valuable, 
 frequently sink into oblivion."* This remark 
 applies with great force to the misconception and 
 perversion of the ancient systems of philosophy, 
 the most important features of which are but 
 vaguely and imperfectly comprehended by the 
 moderns. When Greece was the centre of light 
 and civilization to the whole world, nearly all her 
 most distinguished sages maintained the existence 
 of an igneous principle, which extended through- 
 out the universe. This powerful and omnipre- 
 sent agent was regarded by them as the life of 
 nature, and the cause of all concord and discord, 
 (by which they evidently meant attraction and 
 
 * Advancement of Learning. 
 
DOCTKINE OF THE ANCIENTS. 
 
 repulsion,) by virtue of which the celestial bodies 
 were preserved in their respective courses, and 
 connected as by an invisible everlasting chain ; 
 and without which there could be no generation 
 or dissolution of bodies, 
 
 Such were the opinions of Pythagoras, Par- 
 menides, Democritus, Heraclitus, Plato, and 
 many others. Hippocrates termed it " a strong 
 but invisible fire which rules all things without 
 noise, and is never in repose; which actuates 
 and animates the whole system of nature." 
 Here is a definition of heat in accordance with 
 the discoveries of Dr. Black, but still more com- 
 prehensive and important. 
 
 Like the ancient Greek philosophers, Bacon 
 reduced all matter to two classes, active and 
 passive ; the first of which he describes as rare, 
 invisible, and without weight, though a real and 
 quantitative substance, pervading and filling the 
 pores of all gross bodies. I have already shown 
 that this active spirit, to which Bacon referred 
 all the motions and transformations of matter, is 
 only another name for caloric. (See page 24.) 
 But if this pneumatical power be the cause of all 
 the changes of living and dead matter, it must 
 be the cause of attraction, as well as repulsion ; 
 of decomposition and recombination. 
 
 In his treatise on the Wisdom of the Ancients, 
 Bacon further maintains that the attraction of 
 matter was typified among the early Greek phi- 
 
 M 
 
162 DOCTRINE OF THE ANCIENTS. 
 
 losophers and poets, by the elder Cupid, or prin- 
 ciple of love ; that it was the primitive cause of 
 force, or the moving power of elementary atoms, 
 which formed and organized the universe of things 
 out of chaos. He adds, by way of commentary 
 on this ancient allegory, that " there is doubtless 
 a primary and universal law of nature, which re- 
 gulates the circular revolutions of the celestial 
 bodies, and to which are owing all contraction 
 and expansion of matter." 
 
 In the third book of his treatise on the Ad- 
 vancement of Learning, he says, that whoever 
 shall attentively observe the appetences of matter, 
 shall receive clear information concerning ce- 
 lestial objects from things which are constantly 
 seen around us; and that it is the object of 
 science not only to ascertain the number, situ- 
 ations, and periodic motions of the heavenly 
 bodies, but the physical cause of their mutual 
 action upon each other, which he terms living' 
 astronomy, to distinguish it from that which is 
 vulgar and empirical. 
 
 It was also maintained by Newton, that all 
 the phenomena of nature are resolvable into 
 attraction and repulsion, which he referred to 
 the agency of an all pervading cethereal substance, 
 capable of contraction and dilatation, that this 
 cether preserves the particles of the atmosphere and 
 all gaseous bodies at a distance from each other. 
 But, as it is now demonstrable, that caloric alone 
 is the cause of expansion and the elastic force of 
 
HYPOTHESES OF BACON AND NEWTON. 163 
 
 gases, vapours, and volatile liquids, there can no 
 longer be the shadow of a doubt that it is iden- 
 tical with the aBther of Newton, the pneumatical 
 power of Lord Bacon, and the universal igneous 
 principle of the ancient Greek philosophers. 
 Nor is it possible to doubt that Newton regarded 
 this principle as the proximate cause of cohesion, 
 capillary attraction, chemical affinity, and of 
 universal gravitation ; all of which he viewed as 
 modified effects of one and the same agent.* 
 It was owing to the vague and imperfect account 
 which he gave of its modus operand^ that philo- 
 sophers have even doubted the reality of its ex- 
 istence, and treated it as a chimera of the author's 
 imagination, invented for the purpose of sus- 
 taining his theory of nature ; the consequence 
 of which has been, that the law of gravitation 
 has been regarded as a comprehensive gene- 
 ralization of aggregate movements, for which no 
 definite reason can be assigned : while the great 
 and noble science of chemistry, which, in a 
 practical point of view, is far more important 
 than astronomy, consists of an immense collection 
 of facts and experiments, the connection of which 
 with the phenomena of heat, light, electricity, 
 
 * It is now universally admitted, that the force with which 
 menstmums dissolve, and combine with solid bodies, is an 
 exertion of chemical attraction ; a force which Newton referred 
 to the aether, as I before stated, page 26 ; and I shall demon- 
 strate hereafter, that caloric is not only the universal solvent of 
 nature, but that it is the only agent by which liquids are enabled 
 to combine chemically with solids. 
 
164 NEWTON AND BLACK. 
 
 cohesion, capillary attraction, and gravitation, 
 has never been distinctly understood, or reduced 
 to fundamental laws. 
 
 Had Newton discovered the simple law by 
 which the aether produces the opposite effects of 
 contraction and expansion, he would probably 
 have traced its agency in the phenomena of 
 combustion, solution, vaporization, and all the 
 molecular changes of matter: or had Dr. Black, 
 and his successors, fully comprehended that 
 universal law of caloric by which it attracts pon- 
 derable matter with a force that augments in 
 proportion as bodies are deprived of it, they 
 would have found that it is as capable, under 
 such circumstances, of becoming a powerful bond 
 of cohesion, as it is, under other circumstances, 
 of dissolving their union, and of converting them 
 into elastic fluids. But they have all overlooked 
 the force of attraction, by which this subtile fluid 
 is concentrated around the particles of gravitating 
 matter, and thus rendered latent ; and by which 
 its self-repulsive force is counteracted or des- 
 troyed. 
 
 So imperfectly has Sir Isaac Newton's theory 
 of attraction been understood, that while some 
 of his followers have considered gravitation as a 
 distinct and primary agent, others have regarded 
 it as a fundamental and universal property of 
 matter, by which all bodies tend to a common 
 centre : but I have shewn that Newton referred 
 
BUFFON AND DALTON. 165 
 
 attraction, repulsion, and heat, to the agency of an 
 cether. Not being able to comprehend how one 
 and the same agent could produce such opposite 
 effects, Buffon maintained that the powers of 
 nature, which are known to us, may be reduced 
 to two : that which causes weight, and that which 
 causes heat, that to the power of attraction, 
 joined to the cause of heat, may be referred all 
 the phenomena of living and dead matter. Still 
 the cause of attraction remained unexplained. 
 Had Buffon advanced but one step further, he 
 would have resolved all the forces of nature into 
 one and the same cause. 
 
 Since the discovery of latent heat by Dr. 
 Black, nearly all philosophers have viewed it as 
 the antagonist of that universal force by which 
 all things are held together. When treating of 
 liquids, Dr. Dalton observes, that they must be 
 considered as bodies under the control of two 
 most powerful agents, attraction and repulsion, 
 the last of which he refers to caloric. Sir H. 
 Davy also observes, that heat, or the power of 
 repulsion, may be considered as the antagonist 
 of cohesion ; the one tending to separate, and the 
 other to unite the particles of bodies. (Chemical 
 Philosophy, page 30.) Still the important ques- 
 tion recurs, what is the cause of attraction? 
 Newton says, it is an effect of some unknown 
 aethereal agent, and that it is the business of 
 philosophy to find it out. 
 
166 NEWTON AND DAVY. 
 
 What then is the internal constitution of mat- 
 ter ? Are the pores of bodies void of all sub- 
 stance ? or are they pervaded by subtile and 
 active matter ? If so, what is it, and what are 
 the laws by which it operates ? It is quite cer- 
 tain, that until these important queries are re- 
 solved, the science of nature can never be 
 established on the solid rock of first principles ; 
 but must remain, as heretofore, imperfect and 
 vacillating.* 
 
 It requires no extended series of argument to 
 prove, that whatever the cause may be which 
 moves atoms, must also be the cause which moves 
 the largest bodies, for the simple and obvious 
 
 * It was supposed by Epicurus and his followers, that " the 
 atoms of fluids were smooth and spherical, by which they were 
 enabled to glide freely over each other ; but that the atoms of 
 solids were hooked/' as if their forms could change on passing 
 from the liquid to the solid state. He also maintained that the 
 pores of bodies were void of all matter. (De Natura Rerum, 
 book ii.) Others have supposed that the particles of bodies are 
 glued together by an immaterial cement, as bricks are held 
 together by mortar. (Baxter on the Immateriality of the Soul.) 
 The Rev. W. Jones referred cohesion to the pressure of a cold 
 ather y from the fact that liquids are converted into solids by 
 cold. This he thought was demonstrated by the expansion of 
 water during the process of freezing ; an effect which is obviously 
 owing to the arrangement of its particles in the crystalline form. 
 Ampere, Berzelius, and some other modern philosophers have 
 maintained that the atoms of bodies are endowed with electric 
 polarity, or that their opposite sides are in different states of 
 electricity ; while the great body of chemists regard the whole 
 subject as involved in profound obscurity. 
 
LAPLACE AND MORVEAU. 167 
 
 reason that they are made up of atoms. If it be 
 true, that cohesion, capillary attraction, and 
 chemical affinity, be only modifications of gra- 
 vity, as maintained by Newton, Laplace, Buffon, 
 Guy ton, Morveau, and other philosophers, it fol- 
 lows, that the whole theory of nature, whether 
 mechanical, chemical, or physiological, is re- 
 solvable into that of atoms, and the cause by 
 which they are surrounded, attracted and re- 
 pelled, united and separated. If we are capable 
 of discovering the cause which holds together 
 the particles of a pebble, or crystal of ice, and 
 can demonstrate that it is a universal constituent 
 of ponderable matter, we are also capable of 
 comprehending the cause which binds all things 
 together by gravity. Newton expressly affirms, 
 that " the drops of fluids affect a round form by 
 the mutual attraction of their parts, as the earth 
 affects a round form by the mutual attraction of 
 its parts by gravity." (Opticks, book iii. page 
 370.) 
 
 It is self-evident, that if the particles of bodies 
 be not endowed with inherent powers of motion, 
 they must be impelled by some other agent ; 
 that is, they must act upon each other at a dis- 
 tance, without the agency of any physical tie, 
 or by something intimately connected with them. 
 Thus it will be found, that the primary object of 
 science is to ascertain the cause which moves 
 atoms, and the mode in which it produces so 
 
168 CAUSE OF COHESION. 
 
 many and diversified effects ; that chemistry and 
 natural philosophy are only different branches 
 of one great science, which cannot be studied 
 apart from each other, without departing from 
 the unity and simplicity of nature, every ope- 
 ration of which is governed by the same code of 
 physical laws, from the aggregation of a crystal 
 to that of suns, planets, and their satellites. 
 
 It is still a problem with philosophers, whether 
 the particles of bodies are drawn together, or 
 pressed together. Newton supposed, that the 
 aBther, which I have shewn to be identical with 
 the cause of heat, was more rare within the sub- 
 stance of dense than light bodies ; and more 
 dense in the spaces beyond them, than around 
 their particles, by which they are pressed to- 
 gether. (See page 28, chap. 1.) But I have 
 shewn the reverse of this to be the fact ; that a 
 cubic inch of carburetted hydrogen, which is 
 eight times the specific gravity of simple hydro- 
 gen, contains a greater amount of aethereal matter 
 around its particles, because they are larger, and 
 have a stronger attraction for it. For the same 
 reason, equal volumes of olefiant gas contain 
 more of the igneous ther around its atoms than 
 light carburetted hydrogen, while the vapours of 
 alcohol, aether, naphthalin, setherine, and many 
 other gaseous bodies, attract and retain around 
 their particles still larger quantities, correspond- 
 ing with their greater size. 
 
CAUSE OF COHESION. 169 
 
 I have proved, that when chlorine, or the 
 vapours of carbon, sulphur, phosphorus, &c, are 
 brought into contact with hydrogen, they di- 
 minish its elastic force by withdrawing from it a 
 portion of its caloric ; and that all gaseous bodies 
 are combined chemically, with contraction of 
 volume, by virtue of their attraction for caloric, 
 for the same reason that steam, ammoniacal gas, 
 and the vapours of alcohol, aether, nitrous acid, 
 hydrocyanic acid, &c. are condensed by contact 
 with cold water, and chemically united with the 
 water. 
 
 I have shewn, in the foregoing chapters, that 
 the atoms of all bodies are surrounded with sub- 
 tile and active matter, without which they could 
 neither approximate nor recede from each other; 
 consequently, would be passive and motionless ; 
 that the various forces, movements, and changes 
 of form which bodies undergo, are determined 
 by the relative proportions of aethereal and pon- 
 derable matter of which they are composed ; 
 that when the active principle predominates, they 
 are decomposed, or expanded into gases, vapours, 
 or even flame, which is luminous aether; but 
 that when the ratio of gravitating matter pre- 
 dominates, its attraction for caloric counteracts 
 its self-repulsive force, by which gases are che- 
 mically united into vapours, with contraction of 
 volume and diminution of elasticity, or condensed 
 into liquids and solids. 
 
170 CAUSE OF SOLIDITY. 
 
 It still remains to prove that the cohesion of 
 metals, rocks, and all other solid bodies, is de- 
 termined by the various degrees of force with 
 which they attract caloric ; and that it is resolv- 
 able into the same cause which produces the 
 contraction and chemical combination of gases, 
 or reduces them to the form of liquids. If it can 
 be established as a general law, that the particles 
 of all bodies are held together, with forces which 
 vary according to the different degrees of their 
 affinity for caloric, and that this affinity varies 
 with every change in the relative proportions of 
 caloric and ponderable matter, the problem of 
 attractions will be greatly simplified ; for it will 
 be evident that cohesion is not the result of 
 pressure, as conjectured by Newton, but that 
 contraction and expansion, density and lightness, 
 solidity and fluidity, are modified effects of one 
 and the same agent ; in fine, that all the ope- 
 rations of nature depend on the relations of sethe- 
 real and ponderable matter. 
 
 A thorough comprehension of the law by which 
 caloric is chained down in a state of intimate 
 combination with the ponderable matter of the 
 earth, and thus prevented from expanding 
 throughout the universe, would banish from the 
 science of Physics all those vague and absurd 
 speculations, which have been founded on hypo- 
 thetical data, such as innate forces, immaterial 
 properties, occult qualities, inertia of atoms, &c. 
 
CAUSE OF SOLIDITY. 171 
 
 Surely there are mysteries enough in science, 
 without our going beyond the range of expe- 
 rience and observation. Perhaps the most fruit- 
 ful source of error in physics, has been owing to 
 partial and limited views of nature ; and the con- 
 founding of phenomena or effects with the cause 
 which produces them. Some modern writers on 
 natural philosophy, speak of gravitation as though 
 it were " the animating principle of nature." In 
 the fifth volume of the Cabinet Cyclopedia, we 
 are told that, " all the great changes and revo- 
 lutions of the bodies which compose our system, 
 can be traced to, or derived from this principle." 
 But if gravitation were a universal principle of 
 action in nature, it ought to explain the pheno- 
 mena of solution, repulsion, evaporation, the 
 expansive force of gases and fulminating com- 
 pounds ; in short, it ought to account for all the 
 operations of chemistry, geology, and meteor- 
 ology, which is not the fact. It therefore follows, 
 that there must be a principle of action in nature 
 ulterior to that of gravitation, as admitted by 
 Newton. 
 
 It might as well be said that repulsion is the 
 animating principle of nature, as the general 
 attraction termed gravitation. The true state of 
 the case is, that both attraction and repulsion are 
 subordinate, though universal effects of an all- 
 pervading principle that surrounds every particle 
 of matter in the universe, to which may be 
 
172 GRAVITY AN EFFECT. 
 
 referred the phenomena of heat, electricity, light, 
 evaporation, and combustion, together with all 
 the diversified transformations of matter. 
 
 If the atoms of ponderable matter were wholly 
 deprived of this principle, they would no longer 
 be capable of attracting and repelling each other ; 
 consequently, there could be no cohesion, and 
 if cohesion be only a modification of universal 
 attraction, it is idle to regard gravitation as the 
 first of secondary causes, from which all the 
 phenomena of motion may be deduced ; while 
 it is only an expression of the general fact, that 
 bodies tend towards each other with forces which 
 vary inversely as the distance. When the vacuum 
 of space, and the projectile force of planets, on 
 which the Newtonian theory was originally 
 founded, shall have sunk into oblivion ; the 
 above fact will remain a monument of lofty gene- 
 ralization until time shall be no more. 
 
 It was by confounding the external world with 
 the impressions which it produces on the senses, 
 that Berkeley was led to resolve the universe of 
 matter into mind or spirit. The mathematical 
 theory of Boscovich before noticed, is equally 
 beyond the power of human comprehension. In 
 the same spirit of metaphysical subtlety, the 
 celebrated Kant denied the existence of ultimate 
 atoms, by assuming that they were without 
 extension or solidity : while he resolved heat, 
 light, electricity, and magnetism, into the power 
 
BERKELEY AND KANT. 173 
 
 of attraction and repulsion, as if such powers 
 could exist without substance. Not less obscure 
 is the modern doctrine which resolves light, heat, 
 and electricity, into vibrations of some unknown 
 hypothetical aether. Who can grapple with 
 such shadowy and unsubstantial data ? 
 
 It has been already shewn, that caloric is not 
 an effect, condition, or property of other matter, 
 but an all-pervading and independent active 
 principle, without which there could be no vi- 
 brations. Had Bacon, Boyle, Newton, and 
 Hooke, been aware of the law by which aethereal 
 and active matter is attracted and concentrated 
 around the particles of ponderable matter, and 
 thus disguised from the senses, as shewn by Dr. 
 Black, they could never have confounded the 
 cause of heat with motion and vibration ; or had 
 Count Rumford recognised the vast force of 
 attraction by which caloric is concentrated 
 around the particles of iron and other metals, 
 he would not have been at a loss to account for 
 the heat evolved by the friction of boring a 
 cannon. 
 
 It is an exceedingly partial and superficial 
 view of caloric to regard it merely as the cause 
 of temperature, fluidity, vaporization, decompo- 
 sition, &c. ; for it is self-evident that if the at- 
 traction of caloric for metals, ice, and other 
 bodies, augments in proportion as they are de- 
 prived of it, it must be an attractive as well as a 
 
174 RATIONALE OF COHESION. 
 
 repulsive agent an ethereal bond of cohesion, 
 the force of which varies according to the relative 
 proportions of caloric and ponderable matter. 
 Every alteration in these proportions produces a 
 change in the physical, chemical, and even vital 
 properties of all bodies. 
 
 That the force with ivhich caloric combines 
 with, and is concentrated around the particles of 
 ponderable matter, augments in proportion as they 
 are deprived of it, may be regarded as a funda- 
 mental axiom, derived from the general experience 
 of mankind ; and is founded on a law of nature 
 which connects all the phenomena of molecular 
 attractions with the theory of latent caloric. 
 Without the recognition of this important truth, 
 it is impossible to comprehend the most familiar 
 phenomena of every day life : why, for example, 
 the atmosphere abstracts from animal bodies 
 their vital heat, with a rapidity proportional to 
 the reduction of its temperature ; or why caloric 
 is rendered a latent constituent of all matter. 
 The attraction of ice for caloric exceeds that of 
 water, because it contains less of it than water ; 
 the consequence of which is, that the particles 
 of water are drawn closer together, and main- 
 tained in the solid form with a corresponding 
 force of cohesion. If it be objected that water 
 expands during congelation, it may be answered 
 that its particles are arranged in series, forming 
 angles of 60 and 120, making large pores or 
 
RATIONALE OF COHESION. 175 
 
 cavities. Were it not for this, the volume of ice 
 and other crystalline bodies, would diminish on 
 assuming the solid form. That the volume of 
 ice is actually reduced, and its cohesion greatly 
 augmented by the abstraction of caloric, is 
 evident from the large fissures found in bodies 
 of ice after an excessive freeze in rigorous cli- 
 mates, and from the rocky firmness which it 
 exhibits. Were it possible to reduce the tem- 
 perature of ice 1000, its attraction for caloric 
 would be immense, with a corresponding aug- 
 mentation of its density and cohesion. 
 
 If the atoms of gold, silver, copper, iron, lead, 
 tin, and other metals, be surrounded with caloric 
 alone, and if it have a definite degree of attraction 
 for each, it must hold them together with a 
 corresponding force of cohesion, for the obvious 
 reason, that " nothing can act where nothing is." 
 Or if the atoms of oxygen, hydrogen, and 
 carbon, of vegetable matter be surrounded with 
 caloric, and nothing else, it must be the cause 
 of their contraction and expansion, of their 
 chemical union and decomposition, unless the 
 atoms be endowed with inherent powers of at- 
 traction and repulsion which is hypothetical 
 and contrary to all analogy. 
 
 If it be maintained, that electricity is a con- 
 stituent of all bodies, I answer, that latent elec- 
 tricity, as it exists in a state of combination with 
 the particles of ponderable matter is identical 
 
176 ELECTRICITY WHAT. 
 
 with caloric. For the proofs of this identity, the 
 reader is referred to the next book, where it will 
 be demonstrated that solar caloric is the basis 
 of lightning ; and that under all circumstances, 
 however various the phenomena of electricity, 
 they are only modified effects of the same agent 
 which produces evaporation and solution. 
 
 The general recognition of this important truth 
 will banish from the science of nature an im- 
 mense mass of obscure and metaphysical jargon, 
 by divesting it of that complexity which has 
 hitherto baffled every attempt to explain in a 
 satisfactory manner, the connexion of heat and 
 electricity with cohesion and chemical affinity. 
 The absurdity of supposing that the atoms of 
 bodies are surrounded with two distinct aethereai 
 agents, one of which draws them together, while 
 the other repels them asunder, is too obvious to 
 require a serious refutation, 
 
 By the attraction of caloric for ponderable mat- 
 ter, it unites and holds together all things ; by its 
 self repulsive agency, it separates and expands all 
 things. 
 
 To whatever portion of nature's wide domain 
 we turn our attention, we recognize the operation 
 of this universal law. Hence it is, to use the 
 significant language of Bacon, that " heat and 
 cold are nature's two hands ;" which is a general 
 though vague enunciation of the above law : for 
 
THEORY OF COHESION. 177 
 
 it is certain that in a philosophical sense, the 
 words heat and cold are only relative terms, 
 which indicate different proportions of the same 
 aethereal agent. 
 
 It is because the attraction of caloric for solids 
 exceeds that of liquids, that their cohesion is 
 'greater than that of liquids. It is because the 
 attraction of mercury for caloric exceeds that of 
 water, that its particles are held together with a 
 greater force of cohesion. When reduced to the 
 temperature of 39, the attraction of mercury 
 for caloric is so far augmented that it assumes 
 the solid form : but the most important fact con- 
 nected with this change is, that it acquires a 
 corresponding power of attracting other bodies, 
 the temperature of which is higher. It was 
 before stated, (page 106,) that when the hand is 
 applied to frozen mercury, its caloric is rapidly 
 withdrawn. They are also held together with 
 great force, as iron is attracted by a powerful 
 magnet when charged with electro-caloric by a 
 voltaic battery. It is therefore highly probable, 
 that if the temperature of mercury were reduced 
 100, it would abstract from animal bodies their 
 vital heat with a force and rapidity resembling 
 an electric shock ; and that if it were possible 
 to reduce its temperature two thousand degrees 
 below zero, the force of its attraction for caloric 
 would surpass all means of computation ; while 
 
 N 
 
178 THEORY OF COHESION. 
 
 its cohesion and density would be proportionally 
 augmented.* 
 
 It is owing to the attraction of caloric for 
 gravitating matter, that when the hand is applied 
 to iron, copper, gold, silver, and other dense 
 metals at very low temperatures, it adheres fast, 
 and cannot be disengaged without lacerating the 
 skin ; or that when a portion of melted zinc is 
 poured upon a solid plate of the same metal, 
 there is a rush of caloric from the liquid to the 
 solid, by which their particles are drawn to- 
 gether ; or that when water is poured upon a 
 block of ice 15 or 20 below zero, it is imme- 
 
 * It is because iron, copper, gold, silver, platinum, and other 
 dense metals, have a stronger attraction for caloric than silks, 
 furs, down, woollens, resins, bitumens, sulphur, coal, iodine, 
 bromine, dry wood, potassium, sodium, with innumerable other 
 light bodies, that they abstract it more rapidly from warm-blooded 
 animals, and consequently feel colder to the touch. It is because 
 the dense metals exert a powerful attraction for caloric, that it is 
 concentrated and held around their particles with immense force, 
 and cannot be disengaged from them, even in small proportions, 
 without the application of great mechanical pressure. Accord- 
 ingly, we find that they are good conductors of caloric, and 
 cohere together with a corresponding force of aggregation. Their 
 cohesion and conducting power are also augmented in proportion 
 to their condensation by pressure, as in wire drawing ; from 
 which it follows, cateris paribus, that their affinity for caloric, on 
 which their cohesion and conducting power depend, increases 
 with their density and loss of caloric. It is equally true of all 
 other bodies, without a single exception, that their cohesion and 
 conducting power are determined by the relative degrees of their 
 attraction for caloric, which augments in proportion as they are 
 deprived of it. 
 
THEORY OF COHESION. 179 
 
 diately converted into the solid state, and incor- 
 porated with the ice by virtue of the same force 
 ^ which causes universal attraction. 
 
 It is by the attraction of caloric for ponderable 
 matter that it combines with different bodies 
 and produces their liquidity ; it is also by virtue 
 of the same attraction, that liquids are enabled 
 to dissolve and combine with other bodies. Phi- 
 losophers have generally assumed, that cohesion 
 is the antagonist of chemical affinity, and that 
 they are produced by different causes : but the 
 most obvious phenomena of nature demonstrate 
 that they are produced by one and the same 
 cause, and that all molecular combinations result 
 from the attraction of caloric for ponderable mat- 
 ter. The only difference between cohesion and 
 chemical attraction is, that the one is exerted 
 between homogeneous atoms, and the other 
 between heterogeneous atoms, which vary in 
 size, and in the degrees of their affinity for 
 caloric. It is owing to the attraction of caloric 
 for ponderable matter, that when a piece of tin 
 is laid on a portion of melted lead, the tin is dis- 
 solved, and its particles intimately blended with 
 those of the lead. In all such cases, it is un- 
 deniable that the atoms of the liquid are forced 
 to combine with those of the solid, by the agency 
 of caloric alone ; for the obvious reason, that no 
 other agent has been employed to produce the 
 effect. 
 
180 THEORY OF COHESION. 
 
 It is in this way that all metallic alloys are 
 formed. If six drachms of solid zinc be brought 
 in contact with an ounce of melted copper, there 
 is a transition of caloric from the one to the 
 other, by which the particles of zinc are trans- 
 ported from their original place, and intimately 
 combined with those of the copper, by the same 
 power which unites the atoms of individual 
 metals. The simple matter of fact is, that all 
 the elements of nature may be united by fusing 
 them together, and again separated by larger 
 proportions of the same agent. If a mass of 
 granite, or basalt, were plunged into a cauldron 
 of burning lava, they would be intimately in- 
 corporated throughout by the transition of caloric 
 from the lava to the solid rock. It is scarcely 
 necessary to add, that the various materials of 
 which all volcanic rocks are formed, are thus 
 united and held together, by the same power 
 which maintains the solidity and cohesion of the 
 earth. 
 
 The internal constitution of metals is so far 
 modified by their different degrees of purity, 
 that no two series of experiments hitherto per- 
 formed for the purpose of ascertaining their 
 respective degrees of cohesion and conducting 
 power have presented the same results. Ac- 
 cording to Emmerson, the cohesion of gold wire, 
 one-tenth of an inch in diameter, supports 500 
 pounds weight, and iron wire of the same size, 
 4-50 pounds ; whereas other experimenters have 
 
THEORY OF COHESION. 181 
 
 found the tenacity of iron to exceed that of gold 
 and all other metals. 
 
 That the cohesion of metals is determined by 
 the relative degrees of their affinity for caloric, 
 would appear from a variety of considerations. 
 It was ascertained by Buffon, that when equal 
 quantities of tin, lead, silver, copper, gold, and 
 iron were heated to an equally high temperature, 
 the tin and lead cooled in the shortest time; 
 silver next, then gold, copper, and lastly iron ; 
 corresponding very nearly with the relative de- 
 grees of their cohesion, as determined by Mr. 
 George Rennie. (Phil. Transactions for 1818.) 
 But, as observed before, the cohesive force of 
 different metals has been so variously stated by 
 different individuals, that little reliance can be 
 placed in any of them. It will be seen hereafter, 
 that the radiating power of different bodies, 
 cceteris paribus, is inversely as their attraction for 
 caloric ; from which it will follow, that if iron 
 require a longer time to cool a given number of 
 degrees than copper, gold, silver, tin, and lead, 
 it must have a stronger attraction for caloric. 
 It is for the same reason, that when these metals 
 are reduced to a very low temperature, iron and 
 copper abstract caloric from the living body 
 more rapidly than mercury, lead, tin, arsenic, 
 potassium, sodium, and all other bodies, the co- 
 hesion and conducting power of which are small, 
 and the radiating power of which is proportion- 
 ally great. 
 
182 
 
 THEORY OF COHESION. 
 
 The art of plating bars of iron, copper, &c. 
 with gold, silver, zinc, tin, and other metals, is 
 founded wholly on the cementing power of 
 caloric, which forces them together, by what 
 may be termed chemical cohesion, to distinguish 
 it from the aggregation of simple bodies. Plates 
 of gold are made to unite with bars of iron, and 
 other metals, by being^ pressed together, and 
 placed in a stove or furnace. 
 
 When bars or plates of iron are thoroughly 
 cleaned and polished until quite bright, and 
 immersed in melted tin, they are soon covered 
 over with a thin white coat ; or if a slip of copper 
 be perfectly cleaned and polished, then heated, 
 and rubbed over with a piece of tin, a portion of 
 the latter metal combines with the copper, 
 giving it a silvery coat, which adheres to it for 
 the same reason that the hand adheres to frozen 
 mercury, or other metals, when reduced to very 
 low temperatures. 
 
 The common mode of tinning copper vessels, 
 is to make the surface bright by scraping and 
 washing them with a solution of muriate of am- 
 monia. They are then wanned, when the tin is 
 melted and poured into them, by which it incor- 
 porates with every part of their surfaces, and 
 when cold remains firmly united. In the same 
 way, iron vessels are coated with zinc. It is 
 well known that silex cannot be made to com- 
 bine with potass or soda to form glass without 
 the agency of heat, which is equally essential to 
 
THEORY OF COHESION. 183 
 
 the welding of iron, and to the soldering of all 
 other metals. The adhesive property of wax, 
 gum, sugar, &c. when in a state of fusion by 
 caloric is equally familiar to every one. 
 
 The truth is, that all the internal and external 
 properties of bodies, whether mechanical or che- 
 mical, such as hardness and softness, density and 
 lightness, tenacity and firmness, volatility and 
 combustibility, are determined by their relations 
 to caloric. 
 
 It is well known to spinners and weavers, that 
 the fibres of cotton, wool, flos-silk, and flax, are 
 brittle during cold weather, and that if their 
 rooms are not kept at a proper temperature, 
 their threads often break. On the other hand, 
 some of the most brittle substances in nature, 
 such as glass, may be spun into thread almost 
 as fine as that of the silk- worm, when in a state 
 of fusion by heat ; while butter, lard, and many 
 other substances that are soft and tenacious 
 when warm, become hard and brittle at very low 
 temperatures. The same is true of iron and 
 some other metals, which become brittle like 
 glass or ice during excessively cold weather. 
 The rationale of this will appear from the general 
 fact already established, that the attraction of 
 caloric for bodies augments in proportion as they 
 are deprived of it ; the consequence of which is, 
 that it is more concentrated around their par- 
 ticles, which cohere with a corresponding force, 
 producing great hardness ; but when by a blow, 
 
184 THEORY OF COHESION. 
 
 or any sudden force, they are removed in the 
 slightest degree from their place, the cohesion is 
 broken, and they fly asunder. In the state of 
 liquids, their particles glide freely over each 
 other, without losing their hold, as one magnet 
 glides over another. This is the case with all 
 the maleable metals, and with the tenacious oils, 
 gums, glue, &c. until reduced to very low tem- 
 peratures, when they all become more or less 
 brittle like ice. It is owing to the augmented 
 cohesion and hardness of very cold iron that it 
 will not bend, but snaps asunder, that is, its 
 particles refuse to glide over each other ; while, 
 at higher temperatures, the greater extent of the 
 igneous atmospheres that surround them, holds 
 on to them at greater distances, though with less 
 force, causing toughness or tenacity. 
 
 When two pieces of lead, tin, zinc, or any 
 other soft metal, are pressed together with suf- 
 ficient firmness, their atoms are brought within 
 the range of this attractive medium. The same 
 is true of the hardest substances, when softened 
 by heat. Even polished plates of glass, marble, 
 wood, and many other bodies, when brought into 
 close apposition, cohere, but still better when 
 fused together by heat. 
 
 It was before stated that the aethers, alcohol, 
 and many other liquids, have no cohesion what- 
 ever at ordinary temperatures ; and when released 
 from the pressure of the atmosphere, are ex- 
 
THEORY OF COHESION. 185 
 
 panded into vapours by the repulsive power of 
 their latent caloric. They are accordingly very 
 bad conductors, like silks, woollens, furs, and 
 other light bodies, that are full of caloric. Yet 
 by a sufficient reduction of temperature, their 
 attraction for the igneous principle is so far aug- 
 mented, that their particles are drawn closer 
 towards each other, and bound together in the 
 solid form ; and if their temperature could be 
 reduced 2000 F. there is every reason to believe 
 that their cohesion would equal that of salts, 
 rocks, or even the denser metals. 
 
 From all the foregoing facts and arguments 
 it is evident, that hardness and softness, solidity 
 and liquidity, are not essential conditions of 
 bodies, but depend on the relative proportions of 
 aethereal and ponderable matter of which they 
 are composed ; that the most elastic gas may be 
 reduced to the liquid form by the abstraction of 
 caloric, and again converted into a firm solid, 
 the particles of which would cling together with 
 a force proportional to their augmented affinity 
 for caloric. On the other hand, it is equally 
 evident, that by adding a sufficient quantity of 
 the same principle to the densest metals, their 
 attraction for it is diminished, when they are 
 expanded into the gaseous state, and their co- 
 hesion destroyed. 
 
 As the author has met with a few individuals 
 who cannot readily conceive how a self-repulsive 
 
186 THEORY OF COHESION. 
 
 agent can operate as a bond of cohesion between 
 the particles of ponderable matter, it may be 
 proper to shew by a few familiar examples, that 
 the force with which liquids hold together the 
 particles of solid bodies, is not in proportion to 
 the attraction of their own particles for each 
 other, but in proportion to their affinity for the 
 solids. 
 
 It is well known that at ordinary tempe- 
 ratures of the atmosphere, the particles of water 
 cohere with very slight force. It is also known, 
 that when granite, lime, clay, and marie, to- 
 gether with all other rocky and earthy bodies, 
 are reduced to the condition of a perfectly dry 
 and impalpable powder, their particles glide 
 freely over one another, having little or no at- 
 traction for each other. On adding to this pow- 
 der a due proportion of water, they are found to 
 unite together by a very strong attraction, form- 
 ing dense and highly tenacious mortar. The 
 less water such ingredients contain, the stronger 
 is their attraction for it. Hence it is, that the 
 cohesion of mortar augments in proportion as it 
 is deprived of water by drying ; or that when 
 the earth has been parched by a long drought, 
 it attracts and absorbs more rapidly a shower of 
 rain, than when in a moist state, in the same 
 way that all bodies attract and absorb caloric 
 with a force and rapidity in proportion as they 
 are deprived of it. In like manner, the cohesion 
 
THEORY OF COHESION. 187 
 
 of mortar is diminished by adding to it larger 
 proportions of water, in the same manner that 
 the cohesion of ice, metals, and other bodies, is 
 lessened by increasing their temperatures that 
 is, by altering the relative proportions of caloric 
 and ponderable matter. 
 
 Innumerable liquids might be mentioned, the 
 atoms of which have no cohesion among them- 
 selves, which, nevertheless, operate as a bond of 
 union among the particles of various other solids 
 when in the state of powder. It is by virtue of 
 the affinity between wheat flour and water, that 
 they form a cohesive dough ; and so of a thou- 
 sand other bodies, the particles of which have little 
 attraction for each other, without the medium 
 of a liquid ; but if caloric be indispensable to 
 fluidity, it must be the ultimate and efficient 
 cause of attraction between fluids and solids. It 
 is the caloric of melted wax, glue, paste, gum, 
 melasses, &c. by which they are enabled to 
 combine with and hold together the particles of 
 solid bodies, for the same reason that the caloric 
 of melted metals, rocks, &c. enables them to 
 combine with solids, and to hold them together. 
 If sulphate of lime be reduced to the state of 
 powder, its particles have scarcely any cohesion 
 for each other ; but if converted into mortar by 
 the admixture of water, they cohere into a rocky 
 cement, the firmness of which is in proportion 
 to the force of attraction between the water and 
 the lime. 
 
188 THEORY OF COHESION. 
 
 In fine, the more profoundly we scrutinize the 
 operations of nature, the more evident it becomes, 
 that all the modifications of force by which the 
 particles of bodies are united, depend on the 
 various degrees of their attraction for a self-re- 
 pulsive aether ; and that they cohere with a force 
 proportional to their affinity for caloric. It is 
 therefore ridiculous to maintain, that an agent 
 which repels its own particles, cannot hold toge- 
 ther the particles of other bodies. 
 
 Theory of Conduction and Radiation. 
 
 The most general and well established fact 
 connected with conduction is, that all the lightest 
 bodies in nature are bad conductors of caloric 
 and electricity ; such as furs, eider down, silks, 
 woollens, cottons, resins, lac, bitumins, phos- 
 phorus, dry w r ood, &c. among solids ; and aether, 
 alcohol, oils, and water, among liquids; while 
 gases are still worse conductors whereas, the 
 densest known bodies are good conductors, such 
 as gold, silver, platina, mercury, copper, &c. 
 Next to the pure metals in conducting power, 
 are rocks, gems, flint glass, porcelain, and the 
 denser liquids, as solutions of the acids and 
 alkalies. Owing to their extreme fusibility, it is 
 difficult to determine the conducting power of 
 potassium and sodium; but it is certain that 
 
THEORY OF CONDUCTION. 189 
 
 they are bad conductors of caloric, and probably 
 worse than water, in proportion to the difference 
 between their specific gravities. 
 
 It has also been proved in the preceding 
 chapter, that all the lightest known bodies are 
 composed of large proportions of caloric, (which 
 repels its own particles,) compared with the 
 quantity of ponderable matter that all vegeta- 
 ble and animal compounds are composed chiefly 
 of oxygen, hydrogen, carbon, and nitrogen, in 
 various ratios. 
 
 It has been further shewn, that the attraction 
 of all bodies for caloric, increases in proportion as 
 they are deprived of it. If then it be true, that 
 the conducting power of bodies is only a modifi- 
 cation of their attraction for caloric, (a proposi- 
 tion that cannot be doubted,) it becomes obvious 
 that the conducting power of bodies is inti- 
 mately connected with the relative proportions 
 of aethereal and ponderable matter of which they 
 are composed. Other things being equal, it is 
 attracted most strongly by those bodies which 
 contain the least of it, and repelled by those 
 which are full of it. The atoms of gases being 
 surrounded by extensive atmospheres of caloric, 
 (that repels its own particles,) have very little 
 affinity for caloric, and are therefore bad con- 
 ductors. The same thing is true, though in a 
 less degree, of all the lighter liquids and solids. 
 
 On the other hand, the atoms of the metals 
 
190 THEORY OF CONDUCTION. 
 
 which contain less caloric around them in pro- 
 portion to their size, and being closer together, 
 attract and conduct it from one to the other, 
 with different degrees of rapidity ; modified by 
 the arrangement of their atoms, and perhaps by 
 other circumstances not yet fully understood. It 
 is, doubtless, owing to the crystalline structure of 
 ice, that it is a worse conductor of electricity 
 than water. May it not be owing to the same 
 cause that glass, resins, sulphur, and some other 
 bodies, are better conductors of electricity in the 
 liquid, than in the solid state ? 
 
 That the conducting power of all bodies 
 augments in proportion as they are deprived of 
 caloric, may be regarded as a self-evident pro- 
 position. 
 
 The conducting power of metals is increased 
 in proportion to their condensation by pressure, 
 for the same reason that it is augmented by a 
 reduction of temperature, that is, owing to the 
 loss of a portion of their latent caloric. Caloric 
 has a stronger attraction for pure metals than 
 for their oxides, chlorides, fluorides, bromides 
 and iodides ; their specific gravity, cohesion, and 
 conducting power are also greater. * 
 
 * Lord Bacon observes, in the Second Book of the Novum 
 Organum, that it should be inquired why metals and stones, feel 
 colder to the living body than the fur of animals, silks, woollens, 
 feathers, wood, &c. ; whether the latter contain more inherent 
 heat than the former; and if so, whether it be owing to their 
 
THEORY OF RADIATION. 191 
 
 The connexion of this subject with the philo- 
 sophy of radiation is exceedingly important, and 
 seems never to have been rightly understood. It 
 was ascertained by Leslie as a very general fact, 
 that the radiating power of bodies was inversely 
 as their conducting power. This result was sup- 
 ported by a great variety of experiments per- 
 formed by Dr. Wells, with a view of explaining 
 the production of dew; and still farther con- 
 firmed by the recent researches of Melloni. It 
 was found by Dr. Wells, that eider down, wool, 
 cotton, grass, the leaves of trees, and all vege- 
 table substances, parted with their caloric more 
 rapidly by radiation, than rocks and metals 
 that while dew collected in large quantities on 
 the former, during clear nights, there was gene- 
 rally little or none on the latter. But no one 
 seems to have suspected, that the radiating 
 power of bodies was determined by their latent 
 
 oily nature, or to the air which they contain. Dr. Thomson 
 thinks that it is owing to the air within their pores ; while the 
 great mass of writers on Chemistry and Physics, resolve the whole 
 mystery by telling us, that they are bad conductors of caloric, 
 which is the very thing to be explained. The hypothesis of Dr. 
 Thomson is so far from affording a solution of the difficulty, that 
 he does not explain why air is a bad conductor. The simple 
 matter of fact is, that all those articles of clothing which retain 
 the caloric of the body most effectually, contain a large amount of 
 the igneous principle, and are therefore bad conductors. For the 
 same reason, they are highly combustible ; and, when submitted 
 to friction, afford abundance of the electric aether on which ac- 
 count^ they have been called electrics. 
 
192 THEORY OF RADIATION. 
 
 caloric, or that it was even modified by their 
 attraction for it. 
 
 It was supposed by Prevost, whose opinion 
 has been adopted by a majority of writers on 
 Chemistry and Natural Philosophy, that the 
 tendency of all bodies to an equilibrium of tem- 
 perature, is owing to a perpetual exchange of 
 caloric from one to the other by radiation : but 
 it is evident from the foregoing facts, that the 
 motions of caloric by which it passes out of one 
 body into another, are owing to its attraction 
 for ponderable matter, as well as to its self- 
 repulsive or radiating power. When a hot body 
 is placed in vacuo, and at a distance from other 
 bodies, it parts with caloric by radiation alone, 
 with a rapidity proportional to temperature. 
 When placed in atmospheric air, it loses the 
 same quantity of caloric by radiation, while an 
 additional portion is abstracted by the contiguous 
 particles of air. 
 
 It is generally stated, that bodies cool about 
 twice as fast in air as in vacuo. Count Rumford 
 found that a thermometer cooled from 212 F. 
 to 32, in vacuo, in .... 10m. 5 sec. 
 in air 7 3 
 
 water 1 5 
 mercury 36 
 
 But if it be true that all bodies attract and absorb 
 caloric, with a force and rapidity in proportion 
 as they are deprived of it, it is obvious that in 
 
THEORY OF RADIATION. 193 
 
 air, 50, the thermometer would sink much 
 more rapidly. It is equally obvious, that when 
 placed in water, mercury, and other dense liquids, 
 the effect is produced wholly by their attraction 
 for caloric, and without radiation. 
 
 It was before stated, that the metallic oxides 
 have but little attraction for caloric, compared 
 with the pure metals ; and that their cohesion, 
 specific gravity, and conducting power, are ac- 
 cordingly small. The experiments of Leslie 
 prove that their radiating power is much greater. 
 He found that while the radiating power of clean 
 lead was only 19, it rose to 45 when tarnished 
 by oxidation ; that the radiating power of plum- 
 bago was 75, and deutoxide of lead (red lead) 80. 
 He also discovered, that while the radiating 
 power of gold, silver, copper, and polished tin, 
 was only 12, that of crown glass was 90, sealing- 
 wax 95, resin 96, writing-paper 98, and lamp- 
 black 100. 
 
 In short, all light bodies, which are full of 
 latent aethereal fire, and therefore bad conductors, 
 are proportionally good radiators ; while the 
 denser metals, which contain less of it, hold on 
 to it for a longer time, under the same circum- 
 stances. But as their affinity for caloric di- 
 minishes in proportion as they acquire more of 
 it, they also radiate freely at very high tempe- 
 ratures. On the other hand, if the dense metals 
 could be reduced 1000 below zero, they would 
 
 o 
 
194 THEORY OF RADIATION. 
 
 attract and conduct it with a force and velocity 
 like lightning. 
 
 Whatever may be the influence of colour on 
 the radiating power of bodies, it is trifling com- 
 pared with the relative proportions of sethereal 
 and ponderable matter of which they are com- 
 posed. 
 
 It has been long known that metallic vessels, 
 such as tea-urns, retain their temperature much 
 longer than vessels of stone, earthenware, wood, 
 &c. which have less affinity for calorie than 
 metals ; and that the same metallic vessels retain 
 their temperature longer when highly polished 
 than when rough. The latter effect would seem 
 to be owing to the closer proximity of the par- 
 ticles composing a smoother surface ; for it has 
 been found, that when wood is reduced to saw- 
 dust, it radiates more rapidly than in the solid 
 state ; that locks of wool, cotton, flos-silk, &c. 
 radiate better than the same materials when 
 spun and woven, by which their fibres are brought 
 closer together. So when the particles of a 
 metallic surface are brought near to each other, 
 they exert a stronger affinity for caloric than 
 when more distant, and thus prevent it from 
 flying off, for the same reason that the cohesion 
 and conducting power of metals are augmented 
 by condensation as in wire drawing. Is it not 
 owing to the same cause, that electricity escapes 
 more rapidly from rough surfaces which consist 
 
THEORY OF RADIATION. 195 
 
 of innumerable points, than from such as are 
 smooth and highly polished ? 
 
 Connected with this subject, is another fact 
 that has never been explained, and which may 
 appear at variance with the above theory of 
 radiation, until duly considered. It has been 
 ascertained by Leslie and other experimenters, 
 that the reflecting power of bodies is inversely as 
 their radiating power ; and that their power of 
 absorbing caloric is proportional to their radiating 
 power. 
 
 It was discovered by Newton, that the surfaces 
 of glass and polished marble are covered over by 
 an invisible and repulsive medium, which pre- 
 vents their actual contact, even when pressed 
 together with great force. It is doubtless owing 
 to this elastic and repulsive aether, which adheres 
 to polished metals by a still stronger attraction, 
 that when water is poured upon them, it glides 
 over, without wetting or touching them ; and 
 that steel needles are enabled to float on the 
 surface of water, notwithstanding their greater 
 specific gravity. It is this thermo-electric aether 
 which prevents polished metals from absorbing 
 caloric, and causes it to rebound from their sur- 
 faces by reflection ; while light bodies, and metals 
 that are rough or uneven, which contain less of 
 the repulsive medium over their surfaces, absorb 
 more, and reflect less caloric. 
 
196 
 
 CHAPTER n. 
 
 Chemica I At tra c tion . 
 
 " Of the great and comprehensive laws, which rule over the 
 widest provinces of natural phenomena, few have yet been dis- 
 closed to us." WHEWELL. 
 
 A COMPLETE history of Chemistry would em- 
 brace an account of all the molecular transforma- 
 tions perpetually going on throughout nature, 
 by which matter is maintained in a state of un- 
 ceasing motion, as if pervaded by a principle of 
 universal life. Every process of combustion, 
 solution, fermentation, putrefaction, and recom- 
 bination, are only modified exertions of chemical 
 action, by which the face of the earth is per- 
 petually renovated, and without which, the 
 great frame of nature would fall into an eternal 
 sleep or death. 
 
 Whether in a practical or philosophical point 
 of view, a perfect theory of chemistry would be 
 of far higher importance than that of universal 
 gravitation ; for it would lead to a knowledge of 
 all the properties of the elements by which we 
 are surrounded, and of their application to the 
 extension of human happiness. Yet there never 
 was a period in the history of science, when 
 
CHEMICAL ATTRACTION. 197 
 
 greater uncertainty prevailed in regard to the 
 primary cause of chemical action, than at the 
 present time. The celebrated (Erstedt regards 
 the science of chemistry as in the same condi- 
 tion now, that mechanical philosophy was in the 
 age of Galileo, Descartes, Huygens, and New- 
 ton ; and maintains that no general principle has 
 been discovered which governs all affinities. (Sur 
 1'Identite des Forces Chimiques et Electriques.) 
 Notwithstanding the recent progress of atomic 
 chemistry, Dr. Prout observes, that this great 
 science " is founded solely on experience, for 
 tne phenomena of which we can assign no rea- 
 son." (Bri.dgewater Treatise, p. 29.) On the 
 same subject, the language of Professor Whewell 
 is still more emphatic and precise. In the con- 
 cluding chapter of his Treatise on Astronomy, 
 he states, that " no one has pointed out any common 
 feature between chemical affinity and the attractions 
 of which we know the exact effects ; and that we 
 are still more profoundly ignorant of the vital 
 principle" Alas ! if this be a true representation 
 of the actual state of human knowledge, is it 
 not high time that men should awake from their 
 lethargy, and observe more attentively all the 
 circumstances connected with chemical action ? 
 It was profoundly observed by Bacon, that " in 
 all generation and transformation of bodies, we 
 should inquire what is added, what remains, and 
 what is lost, ivhat is united, and what is sepa- 
 
198 CHEMICAL ATTRACTION. 
 
 rated, -what hinders, what commands, and tv/iat 
 gives the motion." (Novum Organum.) 
 
 This is the true foundation of the inductive 
 philosophy ; careful observation, rigid analysis, 
 the rejection of all hypotheses, and the undue 
 authority of distinguished names, must ultimately 
 lead to the discovery of all causes. It is doubt- 
 less an object of great practical importance to 
 know the proportions in which the elements of 
 ponderable matter unite to form water, alcohol, 
 aether, acids, alkalies, salts, rocks, &c. ; but it 
 is still more important to know what the agent is, 
 by which they are brought together and main- 
 tained in a state of intimate combination. 
 
 It is already well known, that all chemical 
 action is resolvable into attraction and repulsion, 
 or combination and decomposition. I have also 
 shewn, that every particle of ponderable matter 
 is surrounded by an active, subtile and igneous 
 fluid, which in one proportion exerts a prodigious 
 force of attraction for them, and thus holds them 
 together ; while in larger proportions, it sepa- 
 rates them by a counteracting and idio-repulsive 
 force that every change in the dimensions, 
 powers, and aptitudes of different bodies, is at- 
 tended by an addition or subtraction of this 
 sethereal principle ; that all liquids, vapours, and 
 gases are solutions of ponderable matter in caloric, 
 with which they are intimately united by a 
 mutual affinity. 
 
CHEMICAL ATTRACTION. 199 
 
 The proximate agency of caloric in chemical 
 affinity would have been long since recognised, 
 but for the difficulty of comprehending how a 
 self-repulsive agent could become a cause of 
 attraction. But it is self-evident, that if a 
 globule of ice be composed of oxygen, hydrogen, 
 and caloric ; and if there be an attraction 
 between the particles of ice and caloric, they 
 must be held together with a force equal to that 
 attraction ; and so of all other bodies. Besides, 
 if it were demonstrated, that some other aethereal 
 fluid, such as electricity, surrounds the particles 
 of ice, it must have an attraction for them like 
 caloric, or it could not become a bond of union. 
 It therefore follows, that in either case, the 
 effect results from one and the same fundamental 
 law, which involves an identity, or unity of 
 causation. In addition to what was before stated, 
 page 186, the following facts will further illus- 
 trate the manner in which a self-repulsive fluid 
 becomes a bond of union between the particles 
 of ponderable matter, which have no inherent 
 affinity for each other. 
 
 It is well known, that the particles of aether, 
 alcohol, and many other volatile liquids, repel 
 each other with such force, that when the pres- 
 sure of the atmosphere is removed, they fly 
 asunder, and assume the form of elastic vapours, 
 thus presenting the character of an idio-repulsive 
 agent. It is also known that when the particles 
 
200 CHEMICAL ATTRACTION. 
 
 of resin, charcoal, and hundreds of other bodies, 
 are reduced to the state of an impalpable powder, 
 like the dust of our roads after a long drought, 
 they have little or no attraction for each other : 
 but if they be brought into contact with the 
 above volatile liquids, they cohere with consider- 
 able force. Why ? Undoubtedly because there 
 is a mutual attraction between the liquids and 
 powders, which counteracts the repulsive force 
 of the liquids, and prevents them from flying oft' 
 in the form of vapour. 
 
 If the particles of dust had no cohesion for 
 each other whatever, they would represent the 
 condition of ultimate atoms wholly deprived of 
 caloric, which could neither approximate nor 
 recede from each other. At the temperature of 
 67 F. water is an elastic fluid in vacua ; but if 
 a thin film of water be placed between two 
 plates of glass in an exhausted receiver, they 
 cohere together, because the water is more strongly 
 attracted by the glass, than repelled by its own 
 particles. However imperfect such illustrations 
 may be, they are sufficient to prove that a self- 
 repulsive agent may become a bond of attraction 
 to other bodies. But the fact which must for 
 ever set this question at rest is, that the attraction 
 of all bodies for caloric augments, cceleris paribus, 
 in proportion as they are deprived of it, and that 
 their cohesion augments in the same ratio. 
 
 To those philosophers who have regarded elec- 
 
CHEMICAL ATTRACTION. 201 
 
 tricity as the proximate cause of molecular at- 
 traction, it may be somewhat surprising that I 
 have proceeded so far without an examination of 
 the facts on which the electro-chemical theory 
 was founded. 
 
 To this I answer, that no general law of elec- 
 tric action has ever yet been pointed out capable 
 of explaining all the phenomena of molecular 
 forces in short, that nearly all the leading facts, 
 connected with the theory of electricity, are 
 involved in the utmost obscurity and uncer- 
 tainty. 
 
 I have shown that caloric is a universal and 
 independent agent, which may be everywhere 
 recognized as a source of power and motion 
 of contraction and expansion of solution and 
 recombination that it is an essential principle 
 of action in all the proceedings of nature. 
 
 But, in regard to electricity, we are not in- 
 formed by those who assign it as the cause of 
 chemical action, whether it be a material agent 
 which may be added to, and subtracted from 
 ponderable matter, or a mere effect resulting 
 from the inherent properties of common matter. 
 The electro-chemical theory of Sir Humphrey 
 Davy was founded on the well known fact, that 
 when bodies are in different states of electricity, 
 they attract each other. Starting from this 
 point, he assumed, first, the existence of two 
 electric fluids, each of which has an attraction 
 
202 CHEMICAL ATTRACTION. 
 
 for the other, and repulsion of its own particles ; 
 secondly, that all bodies which combine che- 
 mically, are in opposite states of electricity. 
 Finding that the atoms of oxygen, chlorine, 
 fluorine, iodine, and bromine, were attracted by 
 the positive pole of the voltaic battery, he in- 
 ferred that they were combined with negative 
 electricity : while all those bodies that were at- 
 tracted to the negative extremity of the battery, 
 were supposed to be electro-positive ; and that 
 in consequence of the attraction existing be- 
 tween such bodies, they rushed into a state of 
 chemical combination, when the two electrici- 
 ties assumed the form of light, or fire. (Phil. 
 Transactions for 1806.) 
 
 It would be an irksome and endless task to 
 detail all the objections that might be urged 
 against this ingenious hypothesis. That it was 
 not understood by Sir H. Davy himself, is mani- 
 fest from the fact, that, in the same Lecture, he 
 asks the question, " May not the remote cause 
 of electrical energy be identical with chemical 
 affinity, and an essential property of matter?" 
 He also observes, in the Chemical Philosophy, 
 that " electricity seems to result from the general 
 powers and agencies of matter." How is it 
 possible to reconcile or comprehend such vague 
 and contradictory views ? 
 
 Had not this distinguished chemist attached 
 himself in early life to the hypothesis, that " ca- 
 
CHEMICAL ATTRACTION. 203 
 
 Joric was a mere effect," instead of being an all- 
 pervading and sufficient cause of motion, his 
 own experiments would have led him to per- 
 ceive that caloric and electricity are mutually 
 convertible into each other; for he was among 
 the first to demonstrate that electricity is capable 
 of producing the same effects which are usually 
 ascribed to caloric. By means of a wire, con- 
 nected with the poles of a battery, he caused 
 water and other liquids to boil. 
 
 1. Let us examine briefly some of the conse- 
 quences which flow from the hypothesis that 
 caloric results from the combination of two elec- 
 tric fluids, admitting for the present, (what has 
 never been established,) that electricity consists 
 of two mutually attractive fluids. 
 
 The hypothesis assumes in the first place, 
 that all the elements of ponderable matter are 
 reducible to two classes, one of which is united 
 with positive, and the other with negative elec- 
 tricity, the mutual attraction and combination 
 of which, produce the phenomena of heat, and 
 the chemical union of bodies. But it is self- 
 evident, that if heat result from the union of 
 two electric fluids, all simple bodies must be 
 without caloric, until they unite chemically, 
 which is contrary to matter of fact ; for it has 
 been demonstrated in the preceding part of this 
 work, that all bodies are composed of caloric and 
 ponderable matter a fact which cannot be pre- 
 
204 CHEMICAL ATTRACTION. 
 
 dicated of electricity, unless we admit, that, in 
 its latent or combined state, it is identical with 
 the omnipresent igneous fluid. It is impossible 
 to imagine any thing more at variance with 
 common sense and the universal experience of 
 mankind, than the supposition that caloric is 
 the offspring of electricity-r-or that a universal 
 agent should be the effect of any other power 
 which is not universal. It would be quite as 
 rational to maintain that the ocean, from which 
 all the waters of the earth are derived, is pro- 
 duced by the perpetual influx of rivers from the 
 dry land. 
 
 2. Another objection to the electro-chemical 
 theory arises from the fact, that bodies which 
 are assumed to be in the same electric state, 
 unite chemically. 
 
 For example, oxygen combines with chlorine, 
 fluorine, iodine, and bromine, making chloric, 
 fluoric, iodic, and bromic acids ; while sulphur, 
 phosphorus, carbon, hydrogen, and the metals, 
 which are considered to be in an opposite state 
 of electricity from the above elements, combine 
 chemically with each other as well as with 
 oxygen, chlorine, &c. Besides, it is not true 
 that oxygen, chlorine, iodine, and bromine, are 
 uniformly in the same electric state ; for it is 
 very well known that when chloric acid is de- 
 composed, its elements are conveyed to different 
 poles of the battery that when sulphurous and 
 
CHEMICAL ATTRACTION. 20-3 
 
 sulphuric acids are decomposed by the pile, 
 sulphur goes to the negative pole ; but that 
 when sulphuretted hydrogen is decomposed, 
 sulphur goes to the opposite pole that when 
 carbon, selenium, arsenic, and tellurium are 
 united with oxygen, they are positive, but ne- 
 gative with hydrogen proving that bodies are 
 neither essentially positive nor negative, and that 
 they vary in this respect according to circum- 
 stancesconsequently, that all classifications of 
 bodies founded on their electric polarities are 
 fallacious. 
 
 Dr. Thomson observes, that " if chemical affi- 
 nity were merely the result of different states 
 of electricity, bodies could not remain united 
 unless these different electrical states were per- 
 manent. But if the positive and negative elec- 
 tricities combine and fly off in the form of fire, 
 there must be an end of the different electrical 
 states which caused them to unite, and of course 
 the union must cease, which is contrary to 
 matter of fact. (Thomson on Heat and Elec- 
 tricity, p. 335.) 
 
 3. A still more fatal objection to the electro- 
 chemical theory is, that it affords no explana- 
 tion whatever of cohesion or simple aggrega- 
 tion ; whereas I have demonstrated that the 
 particles of homogeneous bodies are held to- 
 gether by the same cause which maintains the 
 chemical union of heterogeneous elements that 
 
206 CHEMICAL ATTRACTION. 
 
 the particles of copper are held together by the 
 same agent that causes it to combine with zinc 
 and other metals : but who has ever maintained 
 that the atoms of homogeneous bodies are in 
 different states of electricity ? 
 
 It is not surprising that M. Becquerel, who 
 follows Davy and Berzelius in referring chemi- 
 cal attraction to electricity, should have ad- 
 mitted that cohesion is a stumbling block, (la 
 pierre d'achoppement), in the way of every at- 
 tempt hitherto made to connect the theory of 
 chemistry with that of electricity. (Traite de 
 L'ectricite et du Magnetisme, vol. iii. p. 369.) 
 
 4. Those who regard caloric and electricity as 
 distinct agents, and the latter as the cause of 
 chemical affinity, make caloric the cause of 
 repulsion. Nothing could be more absurd than 
 such partial and contradictory views of nature. 
 Has it not been known, ever since electricity 
 was first studied as a science, that it possesses 
 the power of repulsion as well as caloric ? I 
 have also proved that the effects of caloric are 
 not limited to its self-repulsive agency that 
 it has a universal attraction for ponderable mat- 
 ter, and repulsion of its own particles, by virtue 
 of which it binds bodies together, or tears them 
 asunder, according as it pervades them in 
 greater or less proportions and it will be shewn 
 hereafter^ that all the motive powers of elec- 
 tricity, whether of high or low tension, are 
 
CHEMICAL ATTRACTION. 207 
 
 governed by the same fundamental law ; that 
 all the most powerful displays of electric action 
 are only modified effects of that all -pervading 
 spirit of matter which warms in the life-giving- 
 solar beams, and preserves the universe in a 
 state of unceasing motion. 
 
 It is because philosophers have not suffi- 
 ciently examined the relations of heat and elec- 
 tricity, and the law by which they are con- 
 nected with ponderable matter, that almost every 
 department of Physics has become involved in 
 profound obscurity. It is self-evident, that if 
 electricity be a bond of union between the par- 
 ticles of bodies, it must have an attraction for 
 them a circumstance which has been over- 
 looked by Davy, Berzelius, Ampere, and their 
 followers. Dr. Thomson observes, that " with 
 respect to the unknown link which unites elec- 
 tricity to atoms, and keeps it united with them, 
 we are quite in the dark." (Inorganic Che- 
 mistry, vol. i. p. 40.) 
 
 Never can the science of chemistry be re- 
 duced to the simplicity of established principles, 
 until men shall recognize the relations of caloric 
 and electricity, and the universal law by which 
 they are connected with ponderable matter. 
 
 When a bar of iron is charged with the elec- 
 tric aether, it attracts iron filings, which collect 
 around it in large bunches, each particle cling- 
 ing to the others, like bees suspended from the 
 
208 CHEMICAL ATTRACTION. 
 
 branch of a tree. But if electricity be a self- 
 repulsive agent, it must have a still stronger 
 attraction for the particles of iron, or it could 
 not become a temporary bond of union between 
 them and that it is the true cause of magnetic 
 attraction in soft iron, is obvious from the fact, 
 that when it is withdrawn the attraction is de- 
 stroyed, and they fall asunder. 
 
 At the same time, it is equally evident that 
 electricity is not the generic principle of action 
 in nature. If so, it ought to be everywhere 
 present under all circumstances ; but so far is 
 this from being the fact, that in its most co- 
 pious and concentrated form, (that of lightning,) 
 its manifestations are only occasional and mo- 
 mentary. Besides, if electricity were the pri- 
 mary moving power of matter, it ought to be 
 the cause of fluidity, evaporation, gasefaction, 
 and those expansions of the atmosphere on 
 which all its circulations depend. It is true 
 that when sufficiently concentrated, it produces 
 the same phenomena which are universally 
 ascribed to caloric that is, it raises the tem- 
 perature of bodies, converts solids into liquids, 
 vapours, and gases, ignites combustibles, and 
 produces the chemical union of bodies. 
 
 If then there be any truth in the great fun- 
 damental axiom, that the same effects must be re- 
 ferred to the same cause, it is clear that electri- 
 city is only a modification of the omnipresent 
 
CHEMICAL ATTRACTION. 209 
 
 igneous principle. This identity is indicated 
 by the fact, that when a current of the electric 
 fluid is made to combine with metals, until they 
 are melted or ignited, its properties are so far 
 changed, that it no longer produces a shock, 
 but in all respects exhibits the same pheno- 
 mena which result from the heat of combustion. 
 Dr. Hare attributes the explosive power of gun- 
 powder and other fulminating mixtures to elec- 
 tricity ; which is wholely unintelligible on the 
 supposition that caloric and the electric fluid 
 are distinct agents; for it is demonstrable that 
 the expansive force of all such compounds is 
 owing to their sudden conversion into gases, and 
 that gases are expanded by caloric as certainly 
 as that the elastic force of steam is due to the 
 same power. 
 
 A thousand facts might be adduced to prove 
 that without caloric there could be no electricity. 
 Those light and highly combustible bodies which 
 afford the largest amount of caloric by friction, 
 such as furs, silks, woollens, resins, sulphur, 
 c. also afford the largest proportions of elec- 
 tricity during the same process, and therefore 
 have been termed electrics. Moreover, the 
 strong acids, which give out the most heat 
 during chemical action, afford the largest sup- 
 ply of electricity when acting on the metallic 
 plates of a voltaic battery. 
 
 Again, those bodies which have the strongest 
 
210 CHEMICAL ATTRACTION. 
 
 attraction for caloric, such as metals, conduct 
 it most freely. The same is true of electricity. 
 Hence it is that both caloric and electricity 
 disappear most rapidly when in the vicinity of 
 good conductors, being attracted by them and 
 incorporated with their substance. It is thus 
 that flashes of lightning are absorbed by the 
 earth and rendered latent. Or if a light feather 
 be charged with electricity, and suspended in 
 the still air of a room, at equal distances from 
 sticks of resin, sulphur, glass, and metals, it will 
 approach the latter in preference to the former, 
 cteteris paribus, with a force and rapidity that 
 varies inversely as the squares of the distance. 
 
 If it be true that caloric and electricity be 
 only modifications of the same agent, the elec- 
 tro-chemical theory becomes intelligible, and 
 may be reconciled with the chemical agency of 
 caloric. For example, those bodies which have 
 the strongest tendency to unite chemically with 
 each other, are said to be in opposite states of 
 electricity. It is also certain, that the same 
 bodies which contain different quantities of 
 caloric, are most disposed to unite chemically; 
 while those which have nearly the same re- 
 lations to caloric have little attraction for each 
 other, such as sulphur and phosphorus, potas- 
 sium and sodium the reason of which is, that 
 a transition of caloric from one body to another 
 is indispensable to all chemical combinations. 
 
CAUSE OF CHEMICAL ATTRACTION. 21 1 
 
 Every chemist knows, that he cannot carry 
 on his distillations, separations, and recombi- 
 nations without the agency of heat. But re- 
 garding this as an incidental circumstance, he 
 resorts to the agency of electricity for a solution 
 of the problem, without inquiring into the source 
 of this mysterious power, or whether it could 
 have any existence independent of the igneous 
 principle. 
 
 The controlling agency of caloric in the phe- 
 nomena of chemistry, may be traced in all the 
 decompositions and recombinations that are per- 
 petually going on throughout nature. The truth 
 of this proposition is attested by the vast amount 
 of chemical action within the torrid zone, and 
 within the temperate latitudes during summer ; 
 while in the regions of perpetual congelation 
 there is no chemical transformation. It is well 
 known, that animal and vegetable matter may 
 be preserved without alteration for unlimited 
 periods of time, in conservatories of ice or snow.* 
 
 * Nothing could more clearly illustrate this fact, than the 
 account of a huge elephant (or mammoth,) discovered in the 
 midst of a large mass of ice on the shore of the frozen ocean, 
 near the mouth of the river Lena in Siberia ; where it must have 
 remained for thousands of years, as it belonged to an extinct 
 species. When first discovered, in 1799, by a Tonguiese fisher- 
 man, the carcass was perfectly fresh and entire, parts of which 
 were given by the neighbouring Jackouts to their dogs ; while 
 the remainder was devoured by wild beasts, after its disengage- 
 ment from the ice, when its skin, bones, and teeth were removed 
 
212 CAUSE OF CHEMICAL ATTRACTION. 
 
 It is therefore obvious, that if the earth could be 
 wholly deprived of solar heat, all its chemical mo- 
 tions and changes would cease. It was admitted 
 by Dr. Black, that " heat is indispensable to che- 
 mical action, by overcoming the cohesion of bodies, 
 and thus enabling them to exert their attractive 
 powers." But I have demonstrated that the 
 agency of caloric is not confined to the mere 
 separation of bodies ; that the same agent which 
 expands them into vapours and gases, enables 
 them to unite chemically with each other, to 
 form new compounds, in obedience to the same 
 law by which liquids are enabled to dissolve and 
 unite chemically with solids ; that is, by the at- 
 traction of caloric for ponderable matter. 
 
 The most extraordinary fact connected with 
 the history of modern science is, that while 
 caloric is constantly employed in all the operations 
 of chemistry, and the arts of everyday use, 
 several distinguished modern philosophers have 
 refused it a separate numerical station among 
 the elements ; treating it as an incidental or 
 subordinate effect of those powers and changes 
 of which it is the primary and efficient cause. 
 
 to Petersburgh. Its neck was covered with a long main, and 
 the rest of its body with black hairs and a reddish fur or wool. 
 The tusks were nine feet long, and weighed 350 pounds. For 
 further particulars in regard to this curious discovery, see Cu- 
 vier's account, extracted from the Memoirs of the Petersburg 
 Academy, and quoted by Bertrand in his Revolutions of the 
 Globe. 
 
BECCHER AND STAHL. 213 
 
 When Count Rumford and Sir H. Davy sup- 
 posed that heat was motion, they mistook the 
 effect for the cause ; for I have shewn that all 
 the contractions and expansions of bodies, whe- 
 ther solid, liquid, or gaseous, result from their 
 various relations to caloric. If a portion of al- 
 cohol or water be put into a Florence flask, 
 their particles remain comparatively tranquil ; 
 but when placed over a burning lamp, a rapid 
 intestine motion begins, and augments in pro- 
 portion to the increase of temperature, until they 
 are driven off in the form of steam. Nothing, 
 however, could be more absurd, than to confound 
 the motion of ebullition with its cause, which is 
 evidently something derived from the lamp ; for 
 when the source of heat is removed, the ebul- 
 lition and vaporization cease. 
 
 When Lavoisier pointed out the extensive 
 agency of oxygen in combustion and ferment- 
 ation, he overlooked the still more important 
 fact, that the chemical power of all bodies is 
 augmented by every addition of caloric ; and 
 when Davy observed, that combustion was the 
 solution of bodies in oxygen gas, he overlooked 
 the fact, that all gaseous bodies are solutions of 
 ponderable matter in caloric, without which they 
 could not dissolve and combine chemically with 
 other bodies. 
 
 It was maintained by Beccher and Stahl, that 
 all bodies contained within them an exceedingly 
 
214 WHAT IS PHLOGISTON ? 
 
 subtile, elastic, and active principle, which they 
 termed phlogiston, and which was disengaged 
 during the process of combustion, producing the 
 phenomena of heat and light, or fire. Many and 
 long were the disputes of philosophers concerning 
 the nature of phlogiston. While many main- 
 tained that it was a material substance, Lavoisier 
 is supposed to have demonstrated that it was 
 only an imaginary something, invented for the 
 purpose of explaining the mystery of combustion. 
 That Stahl regarded phlogiston as the cause of 
 heat and inflammation, is evident from the name 
 he gave it, which in the Greek language signifies 
 heat or fire. 
 
 From what is reported of Dr. Black's unpub- 
 lished Lectures on Respiration, it would seem 
 that he confounded phlogiston with the carbon 
 secreted from the lungs ; for he maintained, that 
 a portion of atmospheric air unites with phlogis- 
 ton in the lungs, and that animal heat was dis- 
 engaged during the process. (Leslie on Animal 
 Heat.) 
 
 The celebrated Scheele supposed that heat was 
 composed of 'phlogiston and empyreal air, (oxygen,) 
 and that light was composed of phlogiston and 
 heat : while Kirwin supposed that phlogiston was 
 identical with inflammable air (hydrogen). Such 
 were the vague and contradictory opinions of 
 philosophers in regard to the nature of heat, light, 
 
I/AVO1S1EK*S THEORY OF COMBUSTION. 215 
 
 and phlogiston, during a great part of the pre- 
 ceding century. 
 
 After the discovery of latent heat by Dr. Black, 
 and of oxygen by Priestley, the theory of Stahl 
 was gradually superseded by that of Lavoisier. 
 This celebrated chemist maintained that oxygen 
 consisted of caloric and light, united with a 
 ponderable base, and that during every case of 
 combustion this base combined with the burning- 
 body, by which its volume was diminished; while 
 the caloric and light of the oxygen were given 
 out in the form of fire. 
 
 It is scarcely necessary to add, that this theory 
 was also found to be exceedingly defective and 
 erroneous in nearly all its essential conditions ; 
 that atmospheric oxygen is not indispensable to 
 the process of combustion, nor the exclusive 
 source of caloric and light ; that all bodies contain 
 definite quantities of caloric in a latent or com- 
 bined state, and may be expanded into flame or 
 light by a sufficient quantity of the same prin- 
 ciple.* He was equally mistaken in supposing 
 
 * When carbon, sulphur, phosphorus, boron, and the metals 
 are heated in vacuo, they become luminous without the agency 
 of oxygen. Another decisive proof that oxygen is not the only 
 source of light is, that its colour varies according to the nature 
 of the combustible. Hydrogen affords a bluish light ; potassium, 
 and many other bodies, burn with a red light. Hence it is, that 
 bituminous coal burns with a bluish light when only partially 
 ignited, because the hydrogen alone is volatilized, while its carbon 
 
216 LAVOISIER'S THEORY OF COMBUSTION. 
 
 that the condensation of oxygen was always ne- 
 cessary to combustion. 
 
 It is doubtless true, that during the chemical 
 union of gaseous oxygen with metals, its volume 
 is greatly diminished, and a large amount of 
 heat disengaged, by which the metals are ex- 
 panded into the luminous state when the process 
 is rapid. But it is equally certain, that the com- 
 bustion of wood, coal, naphtha, alcohol, aether, 
 and a thousand other bodies, is attended with 
 expansion instead of contraction of the combining 
 materials, as illustrated in the third chapter, 
 when treating of explosion and deflagration. It 
 is here worthy of special attention, that while 
 Lavoisier pointed out the vast abundance and 
 importance of oxygen in combustion, respiration, 
 acidification, and fermentation, he did not ex- 
 plain the cause of oxidation, which is indispens- 
 able to a theory of combustion. 
 
 The most direct and compendious method of 
 
 remains fixed. Hence also it is, that around the bottom of a 
 candle flame, where the heat is not sufficient to ignite the carbon, 
 there is always a circle of bluish light, which proceeds from the 
 combustion of hydrogen. When potassium is thrown upon 
 water, it enters into a state of vivid combustion ; the water is 
 decomposed, and the metal expanded into red light. At the 
 same time, a portion of the hydrogen thus decomposed, unites 
 with the potassium, producing a beautiful purple and rose co- 
 loured flame; that is, the blue and red colours on combining 
 produce a reddish purple. Query, May not all the diversities 
 in the colours of heterogeneous light resulting from combustion 
 be thus accounted for in a very simple manner ? 
 
EXTENSIVE AGENCY OF CALORIC. 217 
 
 arriving at the proximate physical cause of che- 
 mical action, would be a careful history of all 
 the circumstances which accompany the gene- 
 ration and dissolution of compound bodies 
 that is, to " observe what is added, what remains, 
 and iv hat is separated, what commands, and ivhat 
 gives the motion,'" as recommended by Bacon. 
 
 It is obviously impossible to make any im- 
 portant progress in the science of nature, with- 
 out ascertaining the cause of motion. But I 
 have already demonstrated that the particles of 
 ponderable matter, per se, have no inherent 
 powers of motion a doctrine which was clearly 
 admitted by Sir Isaac Newton consequently, 
 that all attempts to explain the phenomena of 
 expansion and contraction by the innate forces 
 of atoms must be given up as hypothetical and 
 untenable. 
 
 I have also proved, that cohesion and the 
 chemical union of atoms do not result from the 
 external pressure of an aBther, as supposed by 
 Newton ; but from the mutual attraction of aethe- 
 real and ponderable matter that the particles 
 of gross matter are surrounded by an active and 
 igneous fluid, which holds them together, or 
 repels them asunder, according as it pervades 
 them in greater or less proportions without 
 which there could be no expansions and con- 
 tractions of the atmosphere, therefore no winds 
 no evaporation and condensation, conse- 
 
218 EXTENSIVE AGENCY OF CALORIC. 
 
 quently, no rain, snow, hail, dew, or frost; and 
 no lakes, rivers, and springs, therefore, no ani- 
 mal or vegetable growth no earthquakes and 
 volcanoes, therefore no mountains. 
 
 It is impossible to realize the absence of ca- 
 loric, while it is perpetually emanating from the 
 great fountain of physical existence throughout 
 the solar system ; and intimately combined with 
 all matter, whether organic or inorganic. The 
 greatest cold of the polar regions, or of the 
 planetary spaces, is only a diminution of the 
 igneous principle, which is for ever changing 
 the forms, properties, and powers of all things. 
 
 Every change and movement of the atmos- 
 phere is immediately connected with changes 
 of temperature, from the gentlest breeze to the 
 most desolating tempests of lightning, thunder, 
 and rain. In like manner, all the chemical 
 changes that mark the course of nature, are 
 attended with changes of temperature, from 
 the slowest process of fermentation to the most 
 rapid combustion that is, all the decomposi- 
 tions and recombinations of matter are attended 
 by the addition or subtraction of caloric. With- 
 out the continual agency of the solar fluid, the 
 vital air, the ocean, and the solid ground, would 
 become a motionless mass of inert and chaotic 
 matter. Without the reception of caloric from 
 the atmosphere by respiration, the wonderful 
 mechanism of animal motion, sensation, and 
 
CALORIC THE CAUSE OF OXIDATION. 219 
 
 life, could not go on. Nay, more, all the phe- 
 nomena of health and disease are immediately 
 connected with temperature, from the slightest 
 invasion of a chill, the coldness of cholera or 
 the black death, to the most scorching fever. 
 
 Nearly all the phenomena of Chemistry may 
 be referred to combustion and solution. Every 
 process of fermentation, respiration, and putre- 
 faction, are slow combustions, to which caloric 
 is equally essential, as to every case of solution, 
 vaporization, and gasefaction. It is well known 
 to every practical chemist, that water is gene- 
 rated by combustion that nitrogen, carbon, sul- 
 phur, phosphorus, selenium, chlorine, iodine, 
 boron, arsenic, and some other bodies, have no 
 affinity for oxygen at very low temperatures ; 
 but that when caloric is added in sufficient 
 quantities, a rapid oxidation takes place, as in 
 ordinary combustion, by which acids are gene- 
 rated that when potassium, sodium, barium, 
 lithium, calcium, magnesium, and strontium, 
 are heated in atmospheric air, they combine 
 rapidly with its oxygen, forming alkalies that 
 when aluminum, glucinum, yttrium, thorinum, 
 and zirconium, are heated with oxygen gas, new 
 compounds are generated, termed earthy bases 
 and that when the other metals are exposed 
 to a high temperature, they are converted into 
 acids and metallic oxides. 
 
 At the temperature of 32 F. iron has no per- 
 
220 CALORIC THE CAUSE OF OXIDATION, 
 
 ceptible attraction for atmospheric oxygen ; 
 hence it is that in the polar regions, and during 
 excessive winters in the middle latitudes, metals 
 are not corroded by oxidation, but speedily ac- 
 quire a coating of rust in tropical climates.* The 
 process of oxidation augments with every ad- 
 dition of caloric up to the fusing point. It is 
 therefore preposterous to maintain, that the at- 
 traction of metals for oxygen is owing to some 
 inherent property of their particles, or that ca- 
 loric operates merely by overcoming their cohe- 
 sion, and thus enabling their chemical forces 
 to come into play. So powerful is the attraction 
 of iron for oxygen when raised to a white heat, 
 that it takes it from potassium, which, at ordi- 
 nary temperatures, is the most oxidable of all 
 the metals. As the attraction of potassium for 
 oxygen is known to be augmented by .every 
 increase of temperature, there is every reason 
 to believe that its latent caloric is the primary 
 and efficient cause of the chemical force by 
 which it is enabled to decompose water, and 
 even ice and that if its temperature could be 
 r 
 
 * If a piece of cold polished iron be inserted into fluid mer- 
 cury, there is little or no attraction exerted between them ; but 
 if the iron be made red hot before immersion, it acquires a coat- 
 ing of mercury, which adheres firmly. Even gold, which ad- 
 heres to mercury at common temperatures, attracts it still more 
 powerfully when heated, and so of other metals. 
 
AND OF ALL OTHER AFFINITIES. 221 
 
 sufficiently reduced, its affinity for oxygen would 
 be destroyed. 
 
 In accordance with this view of the subject, 
 it is well known that phosphorus, sulphur, and 
 the most combustible compounds of hydrogen 
 and carbon have no affinity for oxygen at very 
 reduced temperatures, but attract it rapidly 
 when assisted by heat. It would therefore be 
 a waste of time to multiply proofs that caloric 
 is the cause of oxidation. There is not a sub- 
 stance in nature with which it may not be made 
 to unite under the influence of heat. 
 
 Finding it impossible to overlook the agency 
 of caloric in chemical affinities, Sir H. Davy 
 maintained that " it gave freedom of motion to 
 the particles of bodies, and exalted their elec- 
 trical energies." (Phil. Transactions, Nov. 1806.) 
 
 It is also observed by Berzelius, that " a great 
 number of bodies seem to possess but feeble 
 affinities at ordinary temperatures of the atmos- 
 phere, which acquire very active powers of at- 
 traction when raised to high temperatures." (Des 
 Proportions Chiiniques, p. 57.) 
 
 This illustrious chemist might have added, 
 that the chemical power of all bodies is exalted 
 by every addition of caloric and diminished by 
 its abstraction. All the destructions and rege- 
 nerations of matter may be referred to, or de- 
 rived from that law of caloric by which it repels 
 
2*22 LIGHT OF COMBUSTION. 
 
 its own particles, and is attracted by ponderable 
 matter. By its self- repulsive property, caloric 
 dissolves, expands, and decomposes all things: 
 by its affinity for ponderable matter it contracts, 
 unites, and holds together all things thus caus- 
 ing the centrifugal and centripetal forces of 
 nature. By the agency of heat, chlorine, fluo- 
 rine, iodine, and bromine, are made to combine 
 with sulphur, phosphorus, metals, &c. by which 
 new compounds are generated, termed chlo- 
 rides, fluorides, iodides, and bromides. When 
 carbon, sulphur, phosphorus, and other bodies 
 are heated with metals, they are converted into 
 carburets, sulphurets, and phosphurets. By the 
 agency of solar heat the oxygen of the atmos- 
 phere is made to combine with the elements of 
 dead animal and vegetable matter, which are 
 thus constantly undergoing a, slow combustion 
 or dissolution during summer, termed putrefac- 
 tion ; and by which new combinations are 
 formed. 
 
 It has been said, that iron and other metals 
 may be kept in a state of ignition for unlimited 
 periods of time without any loss of their sub- 
 stance. Nothing could be more unfounded. 
 The truth is, that the incandescence or lumi- 
 nosity of all bodies, cater is paribus, is in pro- 
 portion to temperature ; while they are volati- 
 lized and dissipated in the same ratio. Ignition 
 is only a modification of combustion. When 
 
LIGHT OF COMBUSTION. 223 
 
 iron is raised to a red heat, the oxygen of the 
 air combines with it, as in cases of ordinary 
 combustion, by which the process is kept up; 
 but if they are heated in vacuo, the ignition 
 ceases when the heat is withdrawn. 
 
 It is necessary to distinguish the quantity of 
 light produced by combustion from its intensity. 
 When carbonate of lime and many other fixed 
 bodies are submitted to the high temperature of 
 an oxy-hydrogen blow-pipe, they are slowly 
 dissipated, with the disengagement of a most 
 dazzling and intense light, but in small quantity; 
 whereas, if aether, alcohol, naphtha, wax, tallow, 
 oils, resins, phosphorus, sulphur, cotton, paper, 
 silk, and many other inflammable compounds, 
 are submitted to one third of the above tempe- 
 rature, a far greater quantity of light is produced, 
 but of much less intensity : yet we are informed 
 by Dr. Lardner, " there is reason to believe that 
 all bodies begin to be luminous when heated, at 
 the same temperature." (Treatise on Heat, p. 
 24.) On the other hand, when charcoal is exposed 
 to the concentrated heat of a large voltaic bat- 
 tery, it is expanded into light that in splendour 
 almost rivals that of the solar beams ; yet not 
 in great quantity, as during the combustion of 
 more volatile bodies. The concentrated heat of 
 a forge while acting upon iron and other metals 
 that are difficult to volatilize, creates a light so 
 intense, that it strikes upon the eye-balls like 
 
2*24 QENERAL CONCLUSIONS. 
 
 finely comminuted sand. But the same degree 
 of heat acting upon an equal weight of oil, wood, 
 or bituminous coal, would produce one hundred 
 times the quantity of light, though of much less 
 intensity. 
 
 That modification of light termed phosphores- 
 cence, is generally the result of a slow combustion. 
 Being produced at very low temperatures, it is 
 both small in quantity, and of low intensity. 
 
 From all the preceding facts and observations 
 it would appear, 
 
 1. That the heat of combustion results from 
 the disengagement of that principle which holds 
 the particles of bodies together. 
 
 2. That the attraction of ponderable matter 
 for caloric is modified by every chemical change 
 which it undergoes, whether of combination or 
 decomposition, contraction or expansion. (See 
 Chapter III.) 
 
 3. That the light of combustion, or flame, results 
 from the ultimate division of ponderable matter 
 by caloric, which is diffused in all directions by 
 radiation with extreme velocity ; and that with- 
 out the volatilization of combustible matter, there 
 could be no artificial light. 
 
225 
 
 CHAPTER III. 
 
 Chemical Solution. 
 
 ** Veniet tempus quo posteri nostri apperta DOS nescisse mi- 
 renter." SENECA. 
 
 THE vast importance of chemical solution is 
 sufficiently obvious when we reflect, that it is 
 immediately connected with all the most im- 
 portant operations of nature. Could we take in 
 at one view the whole system of nature, we 
 should behold throughout, one vast theatre of 
 solution and crystallization, of decomposition 
 and recombination. 
 
 We should perceive that the atmosphere al- 
 ways contains an immense quantity of water 
 diffused through it in a state of invisible trans- 
 parent solution, until it meets with colder cur- 
 rents of air, when it is condensed and precipitated 
 in the form of rain, snow, or hail, by the ab- 
 straction of its solvent principle ; that all lakes, 
 rivers, and springs, contain greater or less pro- 
 portions of the rocks, salts, and metals that 
 compose the crust of the earth through which 
 they pass, in a state of chemical solution ; that 
 are carried down by running water and depo- 
 
 Q 
 
226 CHEMICAL SOLUTION. 
 
 sited on different parts of the great 
 floor." 
 
 We should observe many thousand hot springs, 
 issuing from the sides of mountains, and from the 
 bottom of the sea, charged with enormous quan- 
 tities of earthy and metallic bodies in solution ; 
 which are precipitated as they cool down, form- 
 ing new strata of rocks and earthy deposits. 
 
 Could we look through the earth as through a 
 great crystal, and behold all its molecular mo- 
 tions and changes, as we do the formation of 
 a salt by the aid of an oxy-hydrogen micros- 
 cope, we should be transported with admiration 
 of a scene at once so grand, simple, and beautiful. 
 The exquisite mechanism by which crystals are 
 generated, is carried on by the regular arrange- 
 ment of atoms in series and aggregates, the forms 
 of which are determined by the most exact ma- 
 thematical laws, by the adjustment of atoms by 
 far too small to be discerned with the most 
 powerful microscope. During the crystallization 
 of a drop of muriate of ammonia, magnified three 
 million times, and reflected on a large white 
 ground, many thousand small crystals are seen 
 shooting in every direction as the solution eva- 
 porates, which coalesce and form one solid 
 crystal. Still more admirable is the process of 
 organization by which the particles of dead 
 matter are converted into plants and animals, 
 endowed with irritability, sensibility, and the 
 power of attracting nourishment for their sup- 
 
CALORIC A UNIVERSAL SOLVENT. 227 
 
 port; while solution or fluidity is essential to 
 every vital process.* 
 
 * A complete history of the Mississippi river, would afford an 
 instructive example of the power of water in slowly dissolving 
 rocks, and transporting them to distant regions. Receiving as it 
 does, many large tributaries, that are fed by a thousand smaller 
 streams, which drain more than a million square miles of territory, 
 they pass through every variety of rocky strata. Some of its largest 
 tributaries, such as the Ohio, Missouri, Kentucky, Cumberland, 
 and Tennessee rivers, meander through extensive regions, based 
 on secondary limestone, which extends with occasional interrup- 
 tions, from Alabama to the falls of Niagara ; and varying from 
 500 to 2000 feet in depth. Through these immense beds of an- 
 cient limestone, they have furrowed channels from 200 to 400 
 feet deep. By their chemical solvent power, hundreds of sub- 
 terranean caverns have been gradually formed in the long lapse 
 of ages, with all those beautiful calcareous crystals termed sta- 
 lactites, with which many of them are so gorgeously decorated. 
 All valleys and river beds are slowly formed by the chemical and 
 mechanical agency of running water. Many springs also contain 
 in solution large quantities of carbonate of iron, which, as well 
 as lime, make a cement that binds into solid masses the beds 
 of loose sand through which they pass, forming sand stone. 
 Were we to follow out this subject in a geological point of view, 
 we should find that a great portion of the solid materials that 
 have been thus removed from the numerous valleys drained by 
 the Mississippi, have been transported to the gulf of Mexico, 
 which it is slowly filling up ; while the rest is conveyed by the 
 gulf stream into the wide Atlantic to form new rocks, after 
 having travelled thousands of miles in a state of invisible solu- 
 tion. The amount of soil, gravel, and sand, which are washed 
 down from mountains, hills, and plains, into the valleys during 
 floods of rain is enormous. The greater part of Louisiana, which 
 contains about 48,000 square miles, is composed of vegetable 
 mould, pebbles, gravel, sand, and clay, that have been conveyed 
 by this great river into the gulf of Mexico. Immense masses of 
 floating trees are also deposited on its banks and islands, and at 
 its mouth, which are covered by sand and clay, where they will 
 be gradually converted into beds of coal. Thus it is that every 
 thing in nature is in a state of perpetual transition and revolution. 
 
228 CALORIC THE UNIVERSAL SOLVENT. 
 
 That caloric is the universal solvent of nature 
 is evident from the fact, that all solid bodies are 
 convertible into liquids and gases or vapours, by 
 a sufficiently high temperature, and reconverted 
 into solids by its abstraction. It is equally clear, 
 that if caloric be the cause of all liquidity, 
 vaporization and gasefaction, it must be the men- 
 struum by which liquids and elastic fluids are 
 enabled to dissolve other bodies. 
 
 The most remarkable facts connected with 
 solution, may be reduced to the following propo- 
 sitions: 
 
 1. That all fluids are chemical combinations 
 of caloric with ponderable matter. Water is 
 composed of oxygen, hydrogen, and caloric ; 
 sulphuric acid of oxygen, sulphur, and caloric, 
 and so of other liquids, the elements of which 
 are chemically combined with it in definite pro- 
 portions : 
 
 2. That no solution of a solid in a fluid ever 
 takes place, without a transition of caloric from 
 the solvent to the solvend : 
 
 3. That the solvent power of water and other 
 menstruums is exalted by caloric, and dimi- 
 nished by its abstraction : 
 
 4. That the solutions of animal, vegetable, and 
 mineral substances in water and other fluids, are 
 strictly chemical combinations. 
 
 It therefore follows according to the most 
 rigid principles of logic, that if caloric be the 
 cause of solution, it must also be the physical 
 
HOT SPRINGS. 229 
 
 cause of chemical attraction, by which salts, 
 rocks, and metals, are held in a state of intimate 
 combination with fluid menstruums. 
 
 It may be objected, that caloric is not the 
 universal solvent of nature, because lime and 
 magnesia are more soluble in water at 60 F. 
 than at 212. But if it be true that lime and 
 magnesia, like all other bodies, are dissolved in 
 unlimited proportions by hot springs, such ex- 
 ceptions disappear, and therefore cannot invali- 
 date the general fact. 
 
 It is stated by Mr. Lyell, to whom the science 
 of Geology is so largely indebted, that the warm 
 springs which supply the baths of San Filippo, 
 near Rome, contain in solution so large a quan- 
 tity of calcareous and magnesian rocks, that they 
 have been known to deposit in a pond, a mass 
 thirty feet thick in twenty years. (Principles of 
 Geology, vol. i. p. 204.) 
 
 Mr. Lyell seems to suppose that the carbonic 
 acid contained in hot springs, is the chief cause 
 of their solvent power. But it is well known 
 that sulphate of lime, and many other rocks, are 
 dissolved by hot springs without the aid of car- 
 bonic acid. It is therefore evident, that the 
 solubility of lime and magnesia is augmented by 
 heat, as certainly as that the fusibility of all 
 other rocks and metals is augmented by it. It 
 is highly probable, that the carbonic acid found 
 in hot springs, has been driven off from a state 
 of combination with lime, during the process of 
 
230 HOT SPRINGS. 
 
 solution, by the agency of intense heat. Few 
 geologists are aware how large a proportion of the 
 calcareous, magnesian, and silicious rocks distri- 
 buted over our planet, have been deposited from 
 hot springs. Mr. Lyell has shewn, that various 
 parts of Italy and Sicily are covered over by 
 strata of limestone thus formed, several hundred 
 feet deep in many places. 
 
 It is impossible to have enlarged views of 
 chemical science, if we confine our observations 
 to the petty operations of an artificial laboratory. 
 Those who do so might conclude, that silex is 
 insoluble, or nearly so, in water. But those 
 who look to the great laboratory of subterranean 
 chemical action, where the heat is far more in- 
 tense than man can produce, will find that silex 
 is there dissolved as copiously as sugar in boil- 
 ing water ; and that it is deposited in vast quan- 
 tities by hot springs, such as the geysers of Ice- 
 land, the valle das furnas of St. Michael, and 
 innumerable others that issue from volcanic 
 regions, forming opal, chalcedony, and various 
 silicious gems. 
 
 The flinty deposits found in the chalk beds 
 of Europe, have doubtless been derived from 
 submarine hot springs. Many of the marine fos- 
 sils found in the chalk, are composed of silica, 
 a fact which cannot be otherwise accounted for.* 
 
 * It is related by Mr. Barrow, in his Visit to Iceland in 1834, 
 that the streams which proceed from the geysers of Iceland, de- 
 posit a white silicious rock, of a close compact texture, resemb- 
 
SILICIOUS PETRIFACTIONS. 231 
 
 It was discovered by Gay Lussac, that the 
 solubility of sulphate of soda in water, is aug- 
 
 ling white marble. This is an exceedingly interesting and im- 
 portant fact to the geologist. The author was once greatly 
 embarrassed on finding beautiful strata of perfectly white siiicious 
 rocks, which had been obviously deposited from water, inclosed 
 between masses of basalt, greenstone, and other volcanic rocks in 
 the mountains of North Carolina, more than 4000 feet above the 
 ocean level. As all the other portions of those mountains con- 
 sisted of granite, gneiss, porphyry, and other igneous rocks which 
 had been elevated by subterranean heat, the existence of the 
 white sedimentary rocks remained a mystery, until the agency of 
 hot springs was investigated. 
 
 The geysers rise up through volcanic rocks, in an island where 
 the eruptions of lava are so enormous, as to fill up gorges many 
 hundred feet deep, and two hundred feet wide. When not confined 
 in narrow valleys, they expand into broad lakes of melted rocks 
 that vary in thickness. Were such eruptions to cover the white 
 siiicious strata deposited by the geysers, (as they undoubtedly 
 have done, and will do again,) they would be inclosed between 
 igneous rocks, like the snow-white flinty strata in the mountains 
 of North Carolina. All animal and vegetable petrifactions com- 
 posed of silex, have been doubtless formed in waters holding this 
 mineral in solution, from the most minute animalcules and deli- 
 cate moss agates, to the largest fragments of silicified wood. Mr. 
 Barrow states, that on the margins of the numerous little streams 
 in the neighbourhood of the great Geyser, every description of 
 wood, bones, the horns of animals, and even paper, worsted 
 stockings, handkerchiefs, &c. were found in a silicified state. 
 
 The steam emitted from volcanos is charged with a great variety 
 of rocks, salts, and metals, in a state of solution, which are de- 
 posited in the crystalline form as the solutions cool down. When 
 melted silex cools under the pressure of a mass of lava, making 
 rock crystal, a portion of steam is sometimes inclosed within its 
 centre, and condensed into water, where it remains for unlimited 
 periods of time. All geodes are probably formed by the cooling 
 down of lava, that contained steam or other gaseous fluids within 
 their interior, that escape by percolation, if the rocks be porous, 
 leaving their centres hollow. 
 
232 SALINE SOLUTIONS. 
 
 mented by every addition of temperature from 
 32, to about 70, and then diminishes up to 
 212 F. (Ann. de Chim. et de Phys. xi. 296.) 
 
 It is also generally known, that chloride of 
 sodium (common salt) is not more soluble in 
 water at 212 than at 60. Whatever may be 
 the cause of such anomalies, they do not afford 
 the slightest proof that caloric is not the solvent, 
 for this plain reason, that when a solution of 
 common salt is exposed to great cold, it is preci- 
 pitated, and the water becomes nearly fresh 
 that is, when the agent which held it in a state 
 of chemical combination with the water is with- 
 drawn, it falls down which clearly proves that 
 the chemical attraction of water for the salt is 
 owing to its caloric. Hence it is, that sea water 
 is deprived of nearly all its salt by congelation, 
 as demonstrated experimentally by Danes Bar- 
 rington, a fact which the author has seen veri- 
 fied on a large scale. In the month of January, 
 1834, when the Bay of New York was frozen 
 over, the ice that covered it was found to be but 
 slightly brackish. It is therefore evident, that 
 if the ocean could be frozen throughout, it would 
 not be capable of holding its salt in a state of 
 chemical combination, but that it would fall 
 to the bottom, constituting a solid stratum, vary- 
 ing in thickness with the depth of the ocean. 
 Dr. Turner states, that common salt dissolves 
 in twice and a half its own weight of water at 
 
OBJECTIONS ANSWERED. 233 
 
 t>0 from which, and the preceding facts, it 
 follows, that if the ocean were saturated with 
 salt and afterwards frozen, it would deposit a 
 stratum more than one-third its depth. 
 
 It is likewise obvious, that the tropical ocean 
 must contain more salt in suspension than the 
 Polar seas, especially during winter, and in the 
 vicinity of icebergs, or other frozen masses.* 
 
 If it be maintained that caloric is not the 
 solvent of sulphate of soda, lime, and magnesia, 
 because they are more soluble in water at 60 
 than at 212, the same mode of reasoning would 
 prove that caloric is not the solvent of sulphur, 
 which is well known to be perfectly liquid at 
 230 F., but becomes viscid at 300, and con- 
 tinues so up to 400. In reply to such objec- 
 tions, it may be stated in the first place, that 
 no chemical union ever takes place until one 
 at least of the combining bodies is reduced to 
 the fluid state, and that caloric is essential to 
 all fluidity : secondly, that the chemical force 
 by which water is enabled to dissolve and com- 
 bine with animal, vegetable, and mineral sub- 
 stances, is exalted by every addition of tem- 
 
 * It can hardly be denied, that sugar is chemically combined 
 with cyder by the agency of caloric ; for it is well known that 
 during the congelation of sweet cyder, its sugar falls down, and 
 may be found at the bottom of the vessel which contains it, in the 
 state of a highly concentrated syrup. But if afterwards ex- 
 posed to warmth, it is again taken up and recombined with its 
 watery solvent, which thus acquires its original properties. 
 
234 BERZELIUS AND DR. ARNOTT. 
 
 perature, in a thousand cases for one exception 
 and I have shown that the above examples 
 afford no real exceptions to the principle, but 
 confirm it that sulphate of soda and common 
 salt are far more soluble in water at 60 than 
 at 32 that lime and magnesia are perfectly 
 soluble in hot springs, which owe their solvent 
 power to intense subterranean heat. 
 
 Berzelius supposes that the greater solubility 
 of lime and magnesia in cold than boiling water, 
 is owing to a portion of carbonic acid that is 
 almost always found combined with cold water ; 
 but which is driven off at a high temperature. 
 Whether this be regarded as a true explanation 
 of the fact or not, it is generally admitted by 
 chemists, that carbonic acid augments their 
 solubility in water. This however does not fully 
 resolve the problem, since the solubility of sul- 
 phate of soda increases with the temperature 
 from 32 to 70 F. and then diminishes slightly, 
 up to 212. 
 
 Dr. Arnott admits, that the solution of a solid 
 in any gas or fluid menstruum is merely another 
 mode of melting it by heat that the menstruum 
 itself is fluid only because of the heat which it 
 contains. (Elements of Physics, vol. ii. p. 47.) 
 
 This is a true statement as far as it goes ; 
 and it is highly probable, that if this philoso- 
 pher had renounced the inherent attractive pro- 
 perties of atoms, as Newton did on second 
 
INFUSIONS MADE BY CALORIC. 235 
 
 thoughts, he would not have added the follow- 
 ing sentence. " A menstruum dissolves other 
 bodies, merely because its attraction for them 
 brings their particles into union with the heat 
 which already exists in it." Why then should 
 water at 212 exert a stronger attraction for salts 
 than water at 32? Why should hot water 
 ascend through porous solids, and capillary 
 tubes more rapidly than cold water? Why 
 should boiling water dissolve 18 times more 
 nitrate of potass than ice-cold water? and 20 
 times more chlorate of potass? Why should 
 boiling water attract and dissolve, or combine 
 chemically with the aromatic constituents of 
 tea, coffee, and a thousand other vegetable pro- 
 ducts more rapidly than cold water, if caloric 
 be not an attractive agent ? or why are the che- 
 mical affinities of all bodies modified by every 
 addition and subtraction of caloric, if it be not 
 the ruling principle of action in all solutions? 
 
 That caloric is the medium by which water 
 is enabled to combine chemically with salts, 
 will appear from another view of the subject. 
 For example, those salts which have the greatest 
 affinity for caloric, have also the strongest attrac- 
 tion for water. The consequence of which is, 
 that they absorb it from the atmosphere, produc- 
 ing what is termed their deliquescence and 
 when dissolved in water they absorb its caloric, 
 by which cold is produced. 
 
236 CONGEALING POINT OF SOLUTIONS. 
 
 It is likewise owing to the powerful attraction 
 of such salts for caloric, that when dissolved in 
 water they are so difficult to congeal that is, 
 they require an intense degree of cold to ab- 
 stract from them that portion of caloric which 
 maintains them in a state of chemical com- 
 bination with water. When I come to treat of 
 freezing mixtures, it will be seen that solutions 
 of potass and chloride of lime, formed by mixing 
 them with snow, remain liquid at 82 and 83 
 below the freezing point of water. 
 
 The same thing is true of many other salts, 
 though to a less extent. It is owing to the at- 
 traction of common salt for caloric, that sea 
 water will not freeze at 32, but requires a 
 farther reduction of temperature to produce the 
 effect, when it gives up a portion of its heat and 
 the salt falls down. When 30 per cent, of 
 common salt is dissolved in water, its freezing- 
 point is reduced to 0. Moreover, the cohesion 
 of the solution is so far augmented, that its 
 boiling point is raised to 224 F. 
 
 In like manner, all those salts which have a 
 strong attraction for caloric, and therefore pro- 
 duce cold during their solution, lower the con- 
 gealing point of water, and elevate its boiling 
 point ; such as nitrate of potass, nitrate of soda, 
 acetate of soda, tartrate of potass, muriate of 
 ammonia, and many others.* 
 
 * It is owing to the affinity of sulphate of soda for caloric, 
 
COHESION OF SOLUTIONS. 237 
 
 Dr. Lardner states, that the solution of a salt 
 in water diminishes the cohesive force of the liquid, 
 and therefore lowers its freezing point. (Trea- 
 tise on Heat, p. 194.) 
 
 The fact however is just the reverse, for a 
 saturated solution of chloride of calcium in water 
 requires 42 more caloric to overcome its cohe- 
 sion than pure water that is, it requires a tem- 
 perature of 264 F. to make it boil. In other 
 words, the particles of water, which are held 
 in a state of chemical union with the salt by ca- 
 loric, have a stronger attraction for the particles 
 of chloride of calcium, than for each other ; 
 therefore cannot be separated and driven off in 
 the form of vapour without an augmentation of 
 temperature. 
 
 From the preceding facts and observations we 
 are brought to the general conclusion, that the 
 deliquescence of salts, the production of cold 
 
 that when dissolved in hot water, and tightly corked up in a 
 phial, it cools down without crystallizing, if kept perfectly still. 
 But if shaken, a portion of the caloric which held it in a state 
 of combination with the water is disengaged, when the phial 
 becomes warm, and the solution crystallizes. If the cork be 
 withdrawn, the same effect is produced, owing to the mechanical 
 pressure of the atmosphere, which forces out of the solution a 
 portion of its caloric. By inserting into it a piece of ice, or any 
 salt that has an affinity for caloric, crystallization is produced 
 for the same reason that all other fluids are congealed by the 
 abstraction of their caloric. It has been said that a film of oil 
 retards the crystallization, which is no doubt the fact, because a 
 bad conductor of caloric, and therefore prevents its ready escape. 
 
238 COHESION OF SOLUTIONS. 
 
 during their solution in water, the low tempera- 
 tures at which they congeal, and the high tem- 
 peratures at which they boil, are all determined 
 by their affinity for caloric, which holds them 
 in a state of chemical combination with water. 
 
 Theory of Freezing Mixtures. 
 
 It was before stated that no solution of a solid 
 in a liquid ever takes place without a transition 
 of caloric from the solvent to the solvend. The 
 truth of this proposition is strikingly illustrated 
 by the phenomena of freezing mixtures. 
 
 When water is congealed into snow or ice, it 
 has a stronger affinity for caloric than in the 
 liquid state. Hence it is that when a Ib. of 
 water, at the temperature of 172F. is mixed 
 with a Ib. of ice or snow, the latter is dissolved, 
 and the mixture brought to the temperature of 
 32 proving that 140 of caloric have been at- 
 tracted from the water by the snow, and inti- 
 mately combined with it in a latent state during 
 the process of liquefaction. 
 
 But there are many salts which abstract ca- 
 loric from snow, by which they are dissolved, 
 or chemically combined with the snow. Such 
 is the affinity of common salt for caloric, 
 that when mixed with its own weight of 
 snow, both at the temperature of 32, there 
 
THEORY OF FREEZING MIXTURES. 239 
 
 is a transition of caloric from the snow to 
 the salt, by which they are intimately united, 
 and the temperature of the mixture reduced 
 9, or 41. Again, so powerful is the at- 
 traction of chloride of calcium for caloric that 
 when 3 parts of it are pulverized and mixed 
 with 2 of snow, both at 32, the temperature 
 and congealing point of the mixture are reduced 
 50 : and if 4 parts potass be mixed with 3 
 of snow, the temperature falls 51 or 83 in 
 all. But if 2 parts chloride of calcium and 1 of 
 snow be reduced 9, and put into the solution 
 of snow and salt, the temperature and freezing 
 point of this new mixture are reduced 74. 
 
 That such salts attract caloric from snow is 
 evident from the fact, that if the chloride of 
 sodium and snow be cooled to 9, and then 
 mixed together, no solution or farther reduction 
 of temperature takes place and that if chloride 
 of calcium and snow be cooled from 32 to 50 
 before they are mixed, no chemical solution, 
 nor change of temperature occurs, because there 
 is no transition of caloric from one to the other. 
 
 Many other salts have the power of absorbing 
 caloric from water, acids, and from snow, such 
 as nitrate of potass, nitrate of soda, muriate of 
 ammonia, muriate of zinc, sulphate of soda, &c. 
 If nitrate of ammonia be pulverized and mixed 
 with its own weight of water, at 50 F. the tem- 
 perature is reduced 46, that is down to 4, which 
 
240 THEORY OF FREEZING MIXTURES. 
 
 is 28 below the freezing point of water and if 
 the same quantity of carbonate of soda be added, 
 the temperature is reduced 7, or 39 below 
 32. If then such salts can abstract caloric from 
 water at 4, and even below zero, it follows a 
 fortiori, that they can take it from snow at 32. 
 
 Dr. Turner observes, that when salt and snow 
 are mixed, the salt causes the snow to melt by 
 reason of its affinity for water. But if the snow 
 and salt be cooled down 9 there is no attrac- 
 tion between them, and therefore no solution 
 nor reduction of temperature. The truth is, that 
 all freezing mixtures are dissolved by caloric 
 as certainly as that snow is dissolved by boiling 
 water ; for the simple and sufficient reason, that 
 caloric is indispensable to all fluidity, without 
 which there can be no chemical combination. 
 " Corpora non agunt, nisi sint soluta" When snow 
 is dissolved in the strong acids, there is a rapid 
 transition of caloric from the acids to the snow, 
 by which they are chemically combined, with 
 a reduction of temperature, as in the solutions 
 of ice or salts in water. If 8 parts of snow be 
 dissolved in 5 of muriatic acid, there is a re- 
 duction of temperature from 32 to 27: or 
 if 7 parts of snow be dissolved in 4 parts of 
 diluted nitric acid, the mixture falls 30. The 
 same effects are produced by mixing pulve- 
 rized salts with the strong acids. 
 
 After having demonstrated that caloric is the 
 
THEORY OF FREEZING MIXTURES. 241 
 
 universal solvent of nature, and that solution is 
 strictly a chemical process, it would be needless 
 to insist that the strong acids owe all their che- 
 mical properties to the heat which is combined 
 with their atoms. Like all other liquids, they 
 are solidified by the abstraction of caloric, and 
 when frozen, their burning caustic properties 
 are greatly impaired, together with their powers 
 of combining with other bodies.* 
 
 It may be regarded as a fundamental axiom 
 in science, that the laws of nature are uniform 
 throughout her boundless dominions, and through 
 all her diversified changes and revolutions ; and 
 that the same effects must be ascribed to the same 
 
 *JLs 
 
 cause. 
 
 Whatever hypothesis is opposed to this great 
 principle, should be at once rejected as un- 
 sound. 
 
 Some modern philosophers, of high reputa- 
 
 * When this subject shall have been more fully investigated, 
 it will be found that the melting point of tin, bismuth, and lead, 
 when united into an alloy, is reduced for the same reason that 
 the melting point of chloride of sodium, chloride of calcium, 
 potass, and other salts, is lowered on mixing them with snow. 
 This would appear from the fact, that when 217 grains of lead, 
 118 of tin, and 284 of bismuth, are finely powdered and mixed 
 with 1617 grains of mercury, the temperature of the mass falls 
 from 64 to 18 F, proving that there is a transition of caloric 
 from one to the other which is true, in fact, of all chemical 
 changes. Besides, when 3 parts lead, 2 of tin, and 5 of bis- 
 muth are pulverized and mixed together, they melt at 197<> F. 
 
242 PROUT AND LLOYD. 
 
 tion, have taken a different view of this im- 
 portant subject. In his late Bridgewater Trea- 
 tise, Dr. Prout observes, that "the world itself 
 before arriving at its present condition, has not 
 only undergone a progressive series of different 
 states ; but in these different states, different laws 
 of nature have prevailed." (Book I. Section 4.) 
 
 It is also maintained by the Rev. Mr. Lloyd, 
 that " the forces by which the world was brought 
 into its present form, were originally far more 
 energetic, before the appetences of matter for 
 matter had been so extensively satisfied. Shall 
 we expect (he adds,) to find the same activity 
 in a neutral salt, as in its separate elements 
 before chemical combination?" (Transactions 
 of the British Association for 1835.) 
 
 In answer to such hypotheses, it may be 
 stated, that they are not only unsupported by 
 the slightest evidence, but are contradicted by 
 all analogy. The truth is, that unless the laws 
 of nature were uniform throughout all her 
 changes and transformations, there could be no 
 established principles of science. Old things 
 pass away, and all things become new, but 
 the properties and laws of the primitive ele- 
 ments never change. Memphis and Thebes, 
 Nineveh and Babylon, Balbec and Jerusalem, 
 with their gorgeous palaces and solemn temples, 
 have passed into other forms of existence 
 
ALL ROCKS FORMED FROM SOLUTION. 243 
 
 yea, the " everlasting mountains" have silently 
 mouldered into ruins, and been transported to 
 other regions ; but nature remains for ever fresh 
 and vigorous, as in the morning of creation. 
 
 The " sun himself may waste away, grow dim 
 with age," and pass into other modes of exist- 
 ence still, there is not the slightest evidence 
 that the primitive constituents of matter ever 
 change. Mr. Lyell has done a most important 
 service to the science of geology by proving, 
 that all the revolutions of the earth have been 
 brought about by existing causes. 
 
 If then it be true that caloric is indispensable 
 to the existence of gaseous oxygen, and to its 
 combination with other bodies, as in combustion, 
 fermentation, and putrefaction to the genera- 
 tion of water, and its power of uniting with salts, 
 it is equally essential to the generation of acids, 
 and to their chemical combination with the al- 
 kaline, earthy, and metallic oxides, as in the 
 formation of salts and rocks. 
 
 It is quite evident, that all solid bodies have 
 been formed from a state of chemical solution. 
 Volcanic rocks have been formed from a state 
 of fusion by subterranean caloric; while sedi- 
 mentary rocks have been formed from a state 
 of solution in water ; and I have proved that the 
 solvent power of water is owing wholly to ca- 
 loric that those bodies which are insoluble in 
 
244 TEA DRAWING, A CASE OF ATTRACTION. 
 
 cold or even boiling water, become so at still 
 higher temperatures.* 
 
 It was observed by Lord Bacon, that " we 
 should inquire how far infusions may be made, 
 by the help of attractions." The truth is, that 
 all infusions, like the solutions of salts in water, 
 are obtained by the attractive power of caloric. 
 Cold water has no attraction for tallow, butter, 
 and other oily substances ; but the cook under- 
 stands practically, that when water is raised to 
 a boiling temperature, it will extract and com- 
 bine with the gelatinous and oleaginous ingre- 
 dients of animal bodies, making soups and 
 gravies consequently, that the combining power 
 is not in the water, but results from the agency 
 of heat. 
 
 The chemical power of water is so far exalted 
 by caloric, that, when raised to the temperature 
 400, as in Papin's Digester, it dissolves nearly 
 all animal matters, except the bony phosphate 
 
 * The familiar process of drawing teas depends simply on the 
 attractive power of heat, to which we owe all our infusions, 
 medicinal extracts, emulsions, &c. The superior cleansing 
 property of hot over cold water, is owing to its power of com- 
 bining chemically with the various impurities that adhere to 
 clothing, &c. It is also known that metals are deprived of their 
 drossy combinations, and thus purified by the agency of heat. 
 Hence, among the nations of antiquity, it was regarded as the 
 type of purity a term derived from the Greek word Trvp, signify- 
 ing heat or fire. 
 
VAST FORCE OF THIS ATTRACTION. 245 
 
 of lime, together with the oily and resinous 
 portions of wood, which are but slightly soluble 
 in boiling water. 
 
 Caloric enables water to combine with salts 
 and the various ingredients of organic com- 
 pounds, for the same reason that it enables 
 wood, coal, and all other combustibles, including 
 the metals, to attract oxygen from the atmos- 
 phereor for the same reason that it enables 
 melted metals to dissolve and unite with solid 
 metals. 
 
 All solutions of salts in water, or metals in 
 acids, are the results of an attraction between 
 the solvent and the solvend. But if this at- 
 traction augments with every addition of ca- 
 loric, it cannot be an inherent property of the 
 menstruum.* 
 
 * Nothing could more strikingly illustrate the immense aggre- 
 gate force of chemical attraction than the phenomena of solution. 
 For example, it is well known that when sugar or salts are dis- 
 solved in water, and metals in acids, the liquids undergo very 
 little augmentation of volume consequently, their density must 
 be greatly increased. But it is evident from the experiments of 
 Perkins, that a mechanical pressure equal to 2000 atmospheres, 
 is not capable of reducing the volume of water more than -^th, 
 if so much. What then must be the force of attraction by which 
 salts and metals are united during the process of chemical solu- 
 tion ? By attracting from the liquids a portion of their caloric, 
 the solids are dissolved, or chemically united, with diminution of 
 volume, for the same reason that the bulk and elastic force of 
 gases are lessened on combining chemically. 
 
246 CHEMICAL FORCES HOW EXERTED. 
 
 It was before shewn, that when tin, lead, cop- 
 per, silver, and other metals, are converted into 
 the liquid state by heat, their power of combining 
 with each other is greatly augmented ; and that 
 whenever a melted metal unites with a solid 
 metal, there is a transition of caloric from the 
 one to the other. 
 
 In like manner, when mercury, gold, silver, 
 &c. are converted into vapour, under plates of 
 copper, iron, and other solid bodies, there is a 
 transition of caloric from the former to the latter, 
 by which the particles of metallic vapour are 
 transported to, and intimately combined with the 
 solids, for the same reason that melted tin unites 
 chemically with copper and iron vessels when 
 poured into them, as in the process of tinning ; 
 or for the same reason that aqueous vapour is 
 attracted by cold bodies, and combined with 
 them in the form of dew or frost ; that is, by 
 virtue of an attraction of their caloric for bodies 
 that contain less of it. 
 
 But if the attractive power of all bodies be 
 modified by every change in their relations to 
 caloric, it is unphilosophical to refer the effect to 
 electricity, unless it be a modification of caloric ; 
 
 The force of chemical attraction is equally evident from the 
 manner in which it overcomes the cohesion of solid bodies. The 
 attraction of nitric acid for the atoms of silver, copper, and iron, 
 must exceed that of their cohesion ; for it tears them asunder, 
 but iu an almost imperceptible manner, and atom by atom. 
 
CHEMICAL FORCE OF THE ACIDS. 247 
 
 and still more absurd to confound attraction with 
 the innate properties of ponderable matter. 
 
 That the strong acids owe their activity and 
 chemical properties to caloric, is evident from 
 the following facts : 
 
 1 . They all become solid by the abstraction of 
 caloric, when their burning caustic properties are 
 greatly diminished, together with their power of 
 dissolving other solid bodies. 
 
 2. Their power of dissolving metals is greatly 
 augmented by raising their temperature. 
 
 Concentrated sulphuric acid acts very feebly 
 on iron, until made boiling hot. Copper is dis- 
 solved rapidly by sulphuric acid when raised to 
 the boiling point. Lead, which is not affected 
 by sulphuric acid when cold, is readily dissolved 
 by it at 212 F. Its solution in nitric and acetic 
 acids is also greatly augmented by raising their 
 temperature. But it would not be philosophical 
 to maintain that an agent which is indispensable 
 to all fluidity, and which increases the solvent 
 power of acids, is different from the primary and 
 efficient cause of solution.* 
 
 3. When the earthy, alkaline, and metallic 
 
 * The first part of the process by which metals are dissolved 
 in the strong acids, is decidedly one of combustion. For ex- 
 ample, when nitric acid is poured upon plates of iron, copper, 
 &c. a portion of its oxygen unites chemically with them, by 
 which they are converted into oxides, with disengagement of 
 heat, (as when poured on volatile oils, and other inflammable 
 bodies,) after which, they are dissolved like salts in water. 
 
248 CRYSTALLIZATION 
 
 oxides are dissolved in the acids, they are che- 
 mically united with them, and thus maintained 
 in a state of transparent solution, like salts in 
 water, in opposition to their specific gravity ; 
 and may be crystallized by evaporation or by 
 cold.* 
 
 Could we clearly explain why sugar, gums, 
 
 * Philosophers have never yet determined fully, why innu- 
 merable bodies arrange themselves in the crystalline form, on 
 passing from the fluid to the solid state. But it is known, that 
 when salts, rocks, and many metals, are converted into the 
 liquid form, whether by the direct agency of caloric alone, or by 
 means of a chemical menstruum, their particles arrange them- 
 selves in regular series, at various angles, forming symmetrical 
 aggregates, that cohere in definite forms as they cool down. 
 When sulphur, iodine, camphor, benzoic acid, with many other 
 simple and compound bodies, are converted into the gaseous 
 state, they also crystallize in regular forms on cooling down, like 
 solutions of salts in water, or metals in acids. 
 
 From some recent experiments performed by M. Bequerel and 
 Mr. Cross, it has been supposed that electricity is the agent by 
 which crystals are aggregated. But if electricity be regarded as 
 a distinct power sui generis, and the only cause of crystallization, 
 why does water and a thousand other liquids assume the solid 
 and symmetrical form on merely reducing their temperatures ? 
 There can be no doubt, that when a current of voltaic electricity 
 is directed for days, weeks, and months, upon salts and rocks, 
 as in the experiments of Mr. Cross, it decomposes and transports 
 their elements to the extremities of the battery, where they will 
 assume the crystalline form : but it is equally certain, that crys- 
 tallization is constantly going on in the laboratory of nature, 
 where no electric action can be detected by the most delicate 
 tests. 
 
 The whole of this problem is resolvable into one of still higher 
 importance and generality; that is, whether electricity be only 
 
MODIFIED BY TEMPERATURE. 249 
 
 starch, gelatine, albumen, and some salts, are 
 more soluble in water than in alcohol ; why sul- 
 phur, phosphorus, resins, &c. are more soluble 
 in alcohol than in water ; and why some bodies 
 are soluble in oils that are insoluble in other 
 liquids ; why one acid dissolves metals which 
 another will not ; and why some metals are more 
 
 a modification of that universal principle of action, which I have 
 endeavoured to shew, is capable of producing all the contractions 
 and expansions of matter. 
 
 As yet, philosophers are but partially acquainted with the 
 circumstances which determine the numerous diversities in the 
 forms of the same substance : why, for example, there should be 
 several hundred varieties in the crystalline arrangement of car- 
 bonate of Jime. But it has been ascertained by the recent 
 researches of Mitscherlich and Haidinger, that various pro- 
 portions of water unite with many substances at different tempe- 
 ratures, during the process of crystallization, producing a corres- 
 ponding diversity of forms ; that seleniate of zinc unites with 
 three different portions of water, and assumes three different forms, 
 according as its temperature is cold, lukewarm, or hot; and so 
 of other solutions. They also found that moderate degrees of 
 temperature, such as that of the solar rays, produced a decided 
 change in the molecular arrangement of solid crystals. 
 
 Not less remarkable and unexpected was the discovery of 
 Mitscherlich, that many bodies differing in chemical composition, 
 assume the same crystalline forms, which are determined by the 
 relative number and position of their atoms ; in other words, that 
 the same number of atoms, united in the same way, produce the 
 same crystalline form; that the protoxides of iron, copper, zinc, 
 nickel, and manganese, crystallize in the same form ; which is 
 also true of the neutral phosphate of soda, arseniate of soda, and 
 many other compounds that vary in chemical composition. 
 Such bodies have been therefore termed isomorphous, meaning 
 identity of form. 
 
250 ELECTIVE AFFINITIES. 
 
 soluble in diluted than in concentrated acids; 
 the obscurities of Chemical Science would ra- 
 pidly disappear. 
 
 If, however, it be true, that caloric is the uni- 
 versal solvent, without which liquids could not 
 combine chemically with solids, we must en- 
 deavour to resolve the remaining difficulties, by 
 carefully investigating the circumstances which 
 determine the relative attractions of caloric for 
 different bodies, and its transition from one to 
 another. 
 
 Between water in the state of ice, and tallow, 
 or oils, there is no affinity whatever. But when 
 water is raised to the boiling point, it unites 
 readily with all oleaginous substances; and at 
 still higher temperatures dissolves resins, and 
 various other bodies. The solubility of sulphur 
 and phosphorus in alcohol is also augmented by 
 temperature. 
 
 All solutions and precipitations are owing to 
 the transition of caloric from one body to another. 
 What is termed elective affinity is owing to the 
 stronger attraction of one body for caloric than 
 another. By the solvent power of caloric in 
 nitric acid, it is enabled to combine chemically 
 with silver, the particles of which are diffused 
 equally throughout the menstruum, making a 
 transparent solution of nitrate of silver. But if 
 a portion of mercury be poured into the solution, 
 the silver is precipitated as the mercury dissolves. 
 
ELECTIONS AND PRECIPITATIONS. 251 
 
 It therefore follows, that if the caloric of nitric 
 acid enabled it to dissolve and combine with the 
 silver, it must have a still stronger attraction for 
 the particles of mercury, or it would not desert 
 the atoms of silver for them ; in short, that the 
 silver is separated from its combination with the 
 acid by an abstraction of caloric, for the same 
 reason that salts dissolved in water are precipi- 
 tated by a reduction of temperature. 
 
 The same principle must apply to all other 
 elections and precipitations, modified, however, 
 by circumstances not yet fully understood. 
 
 Lead precipitates mercury, and copper lead, 
 which is again thrown down from a state of com- 
 bination with nitric acid by iron ; all of which 
 changes are attended with transitions of caloric 
 from the solvent to the solvend. 
 
 The art of coating metals with other metals 
 by precipitation, is founded on the above law, 
 such as gilding, silvering, tinning, &c. If a 
 plate of copper or iron be immersed in a solution 
 of nitrate of mercury, a coating of the latter 
 metal is precipitated on them, for the same 
 reason that aqueous vapour is precipitated on 
 cold bodies, and coheres to them in the form of 
 frost or ice. If nitrate of silver be dissolved in 
 water, and a plate of clean copper be inserted 
 into the solution, a beautiful coating of silver is 
 precipitated on the copper ; or, if a polished iron 
 rod be immersed in a solution of nitro-muriate 
 
252 CALORIC THE CAUSE OF ALL AFFINITIES. 
 
 of gold, the latter is precipitated on it in the 
 metallic form ; for the same reason that melted 
 tin, zinc, bismuth, silver, &c. are attracted by 
 solid metals, and thus chemically united with 
 them, as in the process of plating. Hence it 
 follows, that if caloric be indispensable to the 
 solution of metals in acids, their precipitation 
 must be owing to its abstraction by the solid 
 metals. 
 
 From a general view of the preceding facts 
 and observations, it is evident, that caloric is the 
 cause of all oxidation ; that water and the strong 
 acids are generated by its agency, and chemically 
 united with the earthy, alkaline, and metallic 
 oxides, forming salts and rocks : in short, that 
 combustion, fermentation, and solution, are mo- 
 dified effects of the same cause. Vinous fer- 
 mentation begins at about 59 F. and increases 
 up to 77, at which point acetous fermentation 
 begins, and ceases at 88. The difference be- 
 tween putrefaction and combustion is only in 
 degree. The former requires a temperature of 
 about 80, and augments up to 135 F. ; while 
 phosphorus enters into a slow combustion at 43, 
 and potassium at still lower temperatures. 
 
253 
 
 CHAPTER IV. 
 
 Capillary Attraction. 
 
 That very law which moulds a tear, 
 And bids it trickle from its source, 
 That law preserves the earth a sphere, 
 And guides the planets in their course. 
 
 ROGERS. 
 
 CONSIDERED in all its relations and bearings, 
 capillary attraction is one of the most important 
 processes in nature, and is immediately con- 
 nected with all the changes and modifications of 
 both living and dead matter. It is the force by 
 which solids and liquids are drawn and held 
 together; which causes plates of glass, wood, 
 metal, &c. to adhere with some force to the sur- 
 face of water and other liquids, when laid flat 
 upon them. It is by the force of capillary at- 
 traction, that the waters of the earth are conveyed 
 through its crust in opposition to that of gravity ; 
 for water is much lighter than the earthy and 
 rocky strata through which it descends ; and has 
 been found at the greatest depths to which 
 miners have penetrated, forming subterraneous 
 streams, which greatly augment after heavy 
 rains. During this transudation of water through 
 
254 CAPILLARY ATTRACTION. 
 
 the earth, it dissolves and combines chemically 
 with a portion of its mineral ingredients ; after 
 which, it is forced to the surface by hydrostatic 
 pressure, (on meeting with an obstruction to its 
 horizontal progress,) forming innumerable springs 
 and fountains of delicious water. 
 
 It is owing to the attraction of liquids for 
 solids that the dust of our roads, which, when 
 dry, has little or no cohesion, becomes so tenacious 
 after rain ; or that a rope when moistened with 
 water, contracts with great force. The com- 
 bination of tannin with leather, and colouring 
 matter with clothing, are due to a modification 
 of the same power that enables water to com- 
 bine with salts, or to permeate porous rocks. 
 
 Several distinguished philosophers have re- 
 cently conjectured, that a discovery of the cause 
 which determines the rise of liquids through 
 porous solids and capillary tubes, would unfold 
 the latent principle of action in all molecular 
 changes, whether chemical or vital. The trunks, 
 stems, leaves, and flowers of all the trees and 
 plants that adorn the earth, are composed through- 
 out, of exceedingly small capillary tubes and 
 pores that attract liquid nourishment from the 
 earth, and convert it into their own substance, 
 by the same power which causes the combina- 
 tion of other solids and liquids. And so of all 
 animals. Every muscle, gland, nerve, bone, 
 and blood vessel, is composed of imperceptibly 
 
CAPILLARY ATTRACTION. 255 
 
 small capillary tubes, through which the blood 
 is circulated by the same power which causes 
 universal attraction. 
 
 The subject of capillary attraction has been 
 laboriously investigated by many of the most 
 distinguished votaries of science, for the last 150 
 years ; but without any attempt to explain the 
 cause of the phenomena ; if we except a single 
 suggestion of Newton, contained in his letter to 
 Boyle, concerning the cetlier. He there refers 
 capillarity to the same agent which causes men- 
 struums to dissolve solids, a most important 
 hint, for which his successors have not given him 
 any credit. It must, however, be acknowledged, 
 that he never gave a satisfactory explanation of 
 what causes solution. Still, his views were more 
 just and comprehensive than those of the present 
 day. That he also referred vital attraction to the 
 same cause which produces ordinary capillary 
 attraction, is evident from the following observa- 
 tion : " The same principle which causes a sponge 
 to suck in water, causes the glands in animal 
 bodies to suck in the various juices from the 
 blood, according to their several natures and dis- 
 positions." (Opticks, page 367.) 
 
 In the time of Newton, it was ascertained ex- 
 perimentally by Hawkesbee, 
 
 1. That water rises to the same height in 
 capillary glass tubes of equal diameter, whether 
 the tubes be thin or thick. 
 
256 CAPILLARY ATTRACTION. 
 
 2. That it rises to the same height in vacuo, as 
 in atmospheric air. 
 
 3. That the velocity and elevation to which 
 water ascends in capillary glass tubes, cceteris 
 paribus, is inversely as their diameters. 
 
 4. That the upper surface of water, spirit of 
 wine, and various other liquids, in capillary glass 
 tubes, was concave ; which he rightly attributed 
 to a stronger attraction of the particles of water 
 in immediate contact with the glass for it, than 
 for each other. 
 
 In 1805, Dr. Young read a paper before the 
 Royal Society on the cohesion of fluids, in which 
 he reduced all the phenomena to the joint agency 
 of a cohesive and repulsive force, which in fluids, 
 he thought balanced each other. But as he does 
 not explain what causes the particles of liquids 
 to approach or recede from each other, his whole 
 theory is vague, and very difficult to compre- 
 hend. - 
 
 The following passage taken from a paper on 
 capillary attraction, by Professor Sang of Edin- 
 burgh, may be regarded as a specimen of the 
 obscure manner in which this interesting subject 
 has been generally treated ; and of the prevalent 
 opinion in regard to the recondite nature of the 
 cause which determines the attraction between 
 liquids and solids. He observes, that " the whole 
 of the phenomena are due to a change in the 
 corpuscular arrangement produced by the simple 
 
CAPILLARY ATTRACTION. 257 
 
 contact of heterogeneous substances, the laws 
 and nature of which change are, and perhaps for 
 ever, will remain unknown to us." (Edinburgh 
 Philosophical Journal, vol. viii. 253.) 
 
 Sir H. Davy maintained, " that water is com- 
 bined with rocks, earths, salts, wood, muscular 
 fibre, &c. by chemical attraction ; but that it 
 combines with glass, porcelain, &c. by cohesive 
 attraction." This is contrary to his own, and the 
 general view of chemical attraction, which is de- 
 fined as " the force that unites different ele- 
 ments, and as the antagonist of cohesion," which 
 is supposed to unite homogeneous elements. But 
 there is as much difference between water, and 
 glass or porcelain, as between water and salts, 
 rocks, wood, or muscular fibres. 
 
 There is no end to the ambiguities and con- 
 tradictions that have resulted from regarding 
 cohesion and capillary attraction, as referable to 
 a different cause from what produces chemical 
 affinity. I have already proved that the par- 
 ticles of water and other compound bodies, are 
 held together by the same agent which causes 
 the cohesion of gold, or any other homogeneous 
 body. The same power that unites the atoms of 
 quartz, feldspar, and mica, and holds them to- 
 gether in the form of granite or gneiss, main- 
 tains the cohesion of liquids. This principle has 
 been recognized by Laplace, in a supplement 
 to the 10th Book of the Mechanique Celeste, 
 
258 SIR DAVID BREWSTER'S EXPERIMENTS. 
 
 in which he treats of capillary attraction, as a 
 modification of chemical affinity. 
 
 That this is really the case, would appear from 
 various considerations : 
 
 1. Capillarity is the force by which liquids 
 and solids are made to cohere, whether homoge- 
 neous or heterogeneous. 
 
 2. Every solution of a solid in a liquid, is the 
 result of a chemical force, by which their par- 
 ticles are united. 
 
 3. The force of capillary attraction, by which 
 liquids permeate solids, is always in proportion 
 to their chemical affinity for each other for ex- 
 ample, water has a strong affinity for sugar. It 
 also rises rapidly through it by capillary attraction. 
 
 Considering the vast importance of the subject, 
 it is really surprising how imperfect and limited 
 the number of experiments that have been in- 
 stituted for the purpose of elucidating its nature. 
 Sir David Brewster has given the relative heights 
 to which fifty-two different liquids rose through 
 a capillary glass tube, the bore of which was 
 0,0561 of an inch the general result of which 
 was, that water rose to a greater height than any 
 other liquid. The next in order were muriatic, 
 nitric, and nitrous acids ; then the volatile oils ; 
 after which were alcohol and the aethers; and 
 lastly, sulphuric acid.* But if capillary attrac- 
 tion represent the force by which all liquids and 
 solids cohere, it is obvious, that before we can 
 
 * Edinburgh Encyclopaedia, Article Capillary Attraction. 
 
M. LINK'S EXPERIMENTS. 259 
 
 arrive at any just conclusion, the attraction of 
 innumerable other solids for as many liquids must 
 be ascertained. 
 
 As if to shew the futility, or uncertainty of 
 all experiments, M. Link states, that distilled 
 water, nitric acid, spirit of wine, sulphuric aether, 
 sulphuric acid, and the aqueous solution of pot- 
 ass, (1 oz. to six of water,) all rose to the same 
 height between glass plates. What is still more 
 remarkable, he states that the above liquids 
 rose to the same height between plates of cop- 
 per, zinc, copper and zinc soldered together ; 
 first, with the zinc surface opposed to the copper ; 
 next, the zinc surfaces opposed ; and then the 
 copper surfaces opposed.* 
 
 Mr. Challis observes, after recounting the above 
 experiments, that " the heights of ascent under 
 similar circumstances, would seem to be alike 
 independent of the liquids and solids." But if 
 this conclusion were well founded, water ought 
 to rise between plates of sulphur, bees-wax, gum 
 lac, resin, spermaceti, tallow, &c. as freely as be- 
 tween plates of glass, which is not the fact. The 
 truth is, that liquids rise most rapidly through 
 such porous solids as are most soluble in them 
 that is, bodies for which they have a strong 
 chemical affinity. Water rises freely through 
 sugar, salts, ashes, and porous rocks, because it 
 has a strong chemical affinity for them. For 
 
 * Transactions of the British Association, vol. iv. p. 293, 
 Report on Capillary Attraction, by the Rev. James Challis. 
 
260 SIR J. HERSCHELL AND ARISTOTLE. 
 
 the same reason, alcohol rises through all such 
 solids by capillary attraction, as are soluble in 
 it; and so of the strong acids. Tallow and 
 water have no tendency to unite chemically 
 when cold. For the same reason, when glass 
 plates are smeared with tallow, and brought 
 close together, water will not rise between them, 
 unless they be first wetted. But in this last 
 case, the water rises, owing to its attraction for 
 its own particles, for the same reason, that they 
 aggregate into spherical drops. 
 
 It was observed by Sir John Herschell, that 
 "the discovery of a new law or general fact is 
 scarcely announced when its traces are found 
 everywhere, by which unexpected lights are 
 shed over parts of science that had been aban- 
 doned in despair, and given over to hopeless 
 obscurity." (Discourse on the study of Nat. Phil, 
 p. 131.) Nothing could more aptly illustrate 
 this observation than the phenomena of capillary 
 attraction, the cause of which, when once pointed 
 out, may be traced everywhere around and within 
 us. But such is the blinding influence of custom, 
 that men disregard what is common and familiar, 
 though it be from analysing the most ordinary 
 phenomena, that the greatest discoveries have 
 been made, such as that of steam power, the art 
 of printing, rail-roads, &c. 
 
 It was said by Aristotle, that everything is best 
 seen in its smallest proportions. Such is the 
 admirable simplicity with which Infinite Wisdom 
 
NEWTON AND LAPLACE. 261 
 
 directs and governs the stupendous frame of 
 nature, that the physical cause of chemical 
 force, and of universal attraction may be recog- 
 nized in the smallest dew-drop that glitters on 
 the grass. 
 
 It has been shewn for example, that the atoms 
 of oxygen and hydrogen, are chemically united 
 by the agency of caloric, making compound par- 
 ticles of water, which are aggregated into the 
 spherical form by the attraction of cohesion and 
 that it adheres to solid bodies by capillary at- 
 traction all of which, according to Newton and 
 Laplace, are modified effects of the same cause 
 that actuates the vast machinery of the universe. 
 
 When a certain proportion of caloric is com- 
 bined with this little dew-drop, it assumes the 
 solid and crystalline form in another propor- 
 tion it renders it liquid, and enables it to com- 
 bine with other bodies while an additional 
 quantity of the same aethereal fluid which held 
 its particles together, separates and expands 
 them into thin air. 
 
 Again, the phenomena of a burning candle 
 demonstrate the agency of caloric in chemical 
 and capillary attraction, as effectually as a thou- 
 sand experiments, though contrived with the 
 greatest skill. By the application of heat to the 
 wick, it is ignited, when it attracts oxygen ra- 
 pidly from the atmosphere, causing combustion. 
 During this process, the tallow is rendered fluid, 
 and attracted by the burning wick, affording a 
 
262 ILLUSTRATIONS. 
 
 continual supply of melted matter, which is de- 
 composed, and expanded into flame, or dense 
 light.* 
 
 Other things being equal, the force and ra- 
 pidity with which the fluid tallow is drawn up, 
 is in proportion to the amount of caloric given 
 out by the wick. Thus, it would appear that 
 the rationale of oxidation, capillary attraction, 
 and the generation of light, are clearly exempli- 
 fied by a familiar process that has been over- 
 looked by the unreflecting million, and never 
 fully investigated by philosophers. With a view 
 of ascertaining the force of capillary attraction 
 caused by the heat of a burning candle, I per- 
 formed the following simple experiments : 
 
 1 . About five grains of the heaviest coal ashes 
 were placed around the wick of an ordinary 
 sized candle, every particle of which was drawn 
 up in a few minutes, adhering closely to the 
 wick. 
 
 2. I next put about the same quantity of iron 
 filings into the bole of a large candle, all of 
 which were soon drawn up and collected around 
 the wick, as in the former experiment. 
 
 There can scarely be a doubt that filings of 
 silver, lead, gold, and even platinum, would pre- 
 sent the same results under like circumstances; 
 
 * But if light and flame be identical, and if flame be gaseous 
 matter raised to a white heat, as maintained by Newton, Davy, 
 and others, it follows, that the light of combustion is an ex- 
 panded condition of ponderable matter by caloric. 
 
ILLUSTRATIONS. 263 
 
 nor is it a whit more remarkable, than that red 
 hot iron should attract oxygen, sulphur, mer- 
 cury, and other bodies more strongly than cold 
 iron. 
 
 In reply to the above facts, I have been told 
 by grave and learned men, that " fluidity is in- 
 dispensable to capillary attraction, and that the 
 only agency of caloric in the process is to cause 
 fluidity." But this does not explain why hot 
 water rises far more rapidly through lumps of 
 white sugar, salts, &c. than cold water, nor why 
 those bodies which have the strongest affinity 
 for caloric, attract and absorb water most ra- 
 pidly, such as the deliquescent salts that are 
 employed in freezing mixtures. 
 
 If it be urged that the absorption of water by 
 sugar and salts, is not owing to capillary attrac- 
 tion, but to chemical affinity, I answer, that hot 
 water passes through numerous porous solids 
 and capillary tubes, with a force and velocity 
 proportionate to its temperature when there is 
 no solution that boiling water passes much 
 more rapidly through a glass capillary syphon 
 than when cold. This fact may be verified in the 
 following simple manner. Take two bunches of 
 spun glass about four inches long ; insert the end 
 of one into water at 50 F. and the other at 180, 
 when the latter will be found to rise with far 
 greater force and rapidity than the former in 
 the ratio of at least 3 to 1. 
 
 The same is true of amianthus, flaxen thread, 
 
264 AN APPARENT EXCEPTION. 
 
 bunches of hair, hemp, and other textile fibres, 
 when arranged in a similar manner. But it would 
 be unphilosophical to maintain, that an agent 
 which augments capillary attraction, is different 
 from its primary and efficient cause. 
 
 It has been maintained by Laplace, that an 
 increase of temperature diminishes the elevation 
 of liquids in capillary glass tubes first, by aug- 
 menting their capacity, and secondly, by lessen- 
 ing the density of the liquid. He further re- 
 gards it as a general law, that the elevation of 
 any liquid that completely wets the sides of a 
 capillary tube at different temperatures, is in the 
 direct ratio of its density. This view of the sub- 
 ject has been partially corroborated by the ex- 
 periments of Sir David Brewster, who found that 
 cold water rose somewhat higher in a capillary 
 glass tube, than when hot. 
 
 Whatever may be the cause of this singular 
 fact, (which I have also verified by repeated 
 experiments,) it is opposed by a thousand others, 
 which demonstrate that the force and rapidity 
 with which liquids pervade porous solids and 
 capillary tubes, cceteris paribus, are proportional 
 to the temperature of the liquids. 
 
 When I come to treat of the agency of caloric 
 in the phenomena of life, it will be shewn that it 
 is the proximate physical cause of capillary cir- 
 culation throughout the animal and vegetable 
 world, without which there could be no absorp- 
 tion, secretion, nutrition, and growth ; that trees 
 
ENDOSMOSE AND EXOSMOSE. 265 
 
 and plants are mere aggregations of capillary 
 tubes and pores, through which many hundred 
 million tons of sap are forced up by the power of 
 vital attraction, under the immediate agency of 
 solar heat, and that all the phenomena of life, 
 (which result from an attraction between liquids 
 and solids,) are arrested by cold. The principal 
 difference between ordinary capillary attraction, 
 and the capillary circulation of plants and ani- 
 mals, is, that the vessels or tubes of the latter 
 are almost inconceivably small, while the force 
 of all attraction is inversely as the distance ; 
 hence the force with which a moistened rope 
 contracts, and raises immense weights ; or the 
 force and velocity with which blood and sap are 
 drawn through their minute vessels. 
 
 The mutual interchange of two different li- 
 quids, separated by a membrane or other porous 
 body, which has been referred by Dutrochet to 
 the operation of a peculiar force, termed by him 
 endosmose, and exosmose, according to their direc- 
 tion, is doubtless a modification of capillary at- 
 traction, or of the force which causes all che- 
 mical combinations. 
 
 There is another general fact which connects 
 the theory of capillary attraction with that of 
 heat. 
 
 Those bodies which have the least attraction 
 for caloric, have the least power of absorbing 
 water, such as furs, silks, woollens, cottons, 
 resins, sulphur, phosphorus, and other non-con- 
 
266 DEPRESSION OF MELTED METALS 
 
 ductors of caloric and electricity. Hence it is 
 that when water is poured on a perfectly dry 
 clean silk dress, it runs off, or collects in large 
 globules, while it is rapidly absorbed by linen, 
 which is a much better conductor of caloric. 
 For the same reason, a lock of wool, cotton, 
 down, or fur, will float on water a long time 
 without becoming wet. Or if one end of a 
 perfectly dry skein of silk be suspended in a 
 vessel of cold water, it remains for hours without 
 attracting the water through its fibres ; whereas 
 a skein of linen or hemp becomes very soon 
 wetted throughout. But if the water be made 
 hot, it rises through the silk also. 
 
 In accordance with the above facts, it has been 
 found that mercury, and other melted metals, 
 instead of rising through capillary glass tubes, 
 are somewhat depressed, because they have a 
 stronger attraction for their own particles than 
 for those of the glass. That they have also a 
 stronger attraction for caloric, is evident from 
 their greater conducting power. Hence, there 
 can be no transition of caloric from liquid me- 
 tals to the glass, for the same reason that there 
 is none from cold water to silks, resins, &c. there- 
 fore no attraction. But if plates of gold, silver, 
 and tin, be inserted into mercury, the latter is 
 attracted by them, rises above its level, and is 
 incorporated with them by virtue of the same 
 power that causes all other attractions between 
 
IN CAPILLARY GLASS TUBES. 267 
 
 liquids and solids. When mercury is poured 
 on a marble or wooden table, it collects in large 
 globules, for the same reason that water aggre- 
 gates into large drops when poured upon dry 
 silk, a duck's feathers, and other non-conduct- 
 ing bodies or for the same reason that when 
 plates of glass are smeared with tallow they do 
 not attract water unless previously wetted. 
 
 On the Connexion between Gravity and the 
 Molecular Forces of Nature. 
 
 IT has been said that the attraction of atoms is 
 not like that of gravitation, inversely as the 
 squares of the distance. This assertion is not 
 only refuted by all analogy, but by the well 
 established fact that the elevation and force with 
 which liquids rise in capillary tubes, cceteris pari- 
 bus, is inversely as their diameters. The prin- 
 cipal difference between the attraction of atoms 
 and that of masses is, that the former acts at 
 exceedingly small distances, corresponding with 
 the minuteness of atoms ; while the power of 
 masses extends to comparatively great distances. 
 The aggregate force of cohesion with which a 
 mass of granite is held together, other things being 
 equal, is proportional to the number of its ulti- 
 mate particles. The force of gravity with which 
 it presses upon the earth is in the same ratio. 
 
268 AGGREGATE FORCES 
 
 But if caloric be the physical cause of cohesion, 
 capillary attraction, and chemical solution, as I 
 have demonstrated ; and if gravitation result 
 from the aggregate action of atoms, as main- 
 tained by Newton, Laplace, and many other 
 philosophers, the annual and diurnal movements 
 of the heavenly bodies must be owing to a mo- 
 dified action of the same cause.f 
 
 We are so accustomed to the great powers and 
 movements which mark the course of nature, 
 that we are scarcely aware of their existence 
 until aroused by some extraordinary pheno- 
 menon. What can be more obvious and familiar 
 than the power of heat in modifying the surface 
 of our planet ? a power absolutely incommensu- 
 rable, though for the most part unobserved. Were 
 it possible to compute the aggregate forces of 
 capillary attraction in the circulation of the 
 
 f According to all the best established canons of philoso- 
 phizing, that is the most important principle in physics, to which 
 the greatest number of phenomena may be traced. But if we 
 admit that the accelerated motion of falling bodies, the aggre- 
 gation of planets, with their annual and diurnal revolutions, are 
 resolvable into the Newtonian law of gravity, it is certain that 
 many other equally important phenomena of nature cannot be 
 referred to the principle of gravitation, such as those of heat, 
 light, and electricity, together with the innumerable operations of 
 Chemistry, Geology, and Meteorology, all of which are immedi- 
 ately connected with, and may be traced to that law of caloric by 
 which it produces the opposite effects of contraction and expan- 
 sion, and without which, we cannot explain the most simple mo- 
 difications of molecular attraction. 
 
OF NATURE. 269 
 
 blood and sap of all the animals and plants that 
 inhabit the earth, we should be amazed at the 
 result. Yet they are all produced by the subtile 
 agency of caloric, a definite amount of which is 
 indispensable to all vital action, from that of the 
 insignificant moss or animalcule, to the most 
 perfect dev elopements of organized existence. 
 
 On beholding for the first time so grand a 
 spectacle as the falls of Niagara, the mind is 
 bewildered by an impression of irresistible power. 
 But if we compare this thundering exhibition 
 of might, with the vast but silent power of solar 
 caloric in evaporation, or of subterraneous caloric 
 in upheaving mountains, the ocean cataract 
 dwindles into a fractional item ; for it is demon- 
 strable, as before observed, that about 140 cubit 
 miles of water are daily converted into steam, 
 and carried into the atmosphere by the expansive 
 energy of solar heat, and that all the lakes, 
 rivers, and springs of the earth are supplied by 
 its precipitation. 
 
 We are sometimes aroused to a perception of 
 the wonderful powers that are in nature, by the 
 sudden and awful coruscations of the electric 
 fluid, when darting through the heavens like 
 arrows of Omnipotence, rending rocks, trees, and 
 dwellings. But few are aware that it is only a 
 concentrated exhibition of the same agent which 
 causes evaporation, solution, crystallization, and 
 the growth of vegetation. 
 
270 AGGREGATE FORCES 
 
 It is generally conceded by philosophers, 
 that all the operations of nature are referable to 
 attraction and repulsion, which I have proved in 
 the preceding chapters, are resolvable into the 
 agency of caloric alone. But if the stupendous 
 forces of chemistry, geology, and meteorology, 
 are determined by the agency of solar radiation, 
 why should it not be adequate to produce the 
 annual and diurnal revolutions of planets ? That 
 rays of subtile matter, capable of producing heat 
 and light, are continually proceeding from the 
 centre of our system, is self-evident from expe- 
 rience and observation. It would, therefore, be 
 contrary to all analogy, and the indications of 
 common sense, to refer the planetary motions to 
 some unknown hypothetical influence exerted 
 through a vacuum, while there is a known cause 
 sufficient to explain the phenomena. It is im- 
 possible to conceive how the sun could exert any 
 agency whatever upon the earth, independent 
 of his potent beams. Besides, what can be more 
 simple and natural than the inference, that the 
 same power which aggregates and holds together 
 the particles of planets, guides their movements 
 round the heavens? 
 
 It was laid down by Newton himself, as a 
 fundamental axiom, that no more causes of na- 
 tural things ought to be admitted, than such as 
 are both true and sufficient to explain the pheno- 
 mena. (Principia, Book iii.) 
 
OF SOLAR LIGHT. 271 
 
 The safest mode of investigating the cause of 
 planetary motion, is to follow the lights of ana- 
 logy. When it is found that the quantity and 
 force of light diminish inversely as the squares 
 of the distance, and that the sun operates upon 
 the planets by gravity in obedience to the same 
 law, it is difficult to avoid the conclusion that 
 they are connected together as cause and effect. 
 
 When commenting on the Newtonian law of 
 gravity, by which every particle of matter in the 
 universe is supposed to attract every other par- 
 ticle inversely as the squares of the distance, 
 Mr. Whewell asks, " Why do the attractions of 
 masses, or those of their constituent particles, 
 follow this law of the inverse square of the dis- 
 tance?" (Bridgewater Treatise, Chapter X.) 
 
 This question admits of a satisfactory answer, 
 in accordance with the hypothesis that solar 
 light is the cause of solar attraction, though we 
 may not fully comprehend the mode in which it 
 operates. The truth is, that the force of all 
 aethereal emanations is inversely as the squares 
 of the distance, for the obvious reason that they 
 are necessarily diffused in the same ratio. Other 
 things being equal, the repulsive force of caloric 
 in gases and vapours diminishes in the ratio of 
 the distance of their particles from each other. 
 Its heating power decreases in the same pro- 
 portion, while the attractive and repulsive forces 
 of electricity are known to follow the same law. 
 
272 CALORIC THE ACTIVE PRINCIPLE IN LIGHT. 
 
 That caloric is the active principle in solar 
 light would appear from the fact, that the quan- 
 tity of light produced by ordinary combustion, 
 c&teris paribus, is always in proportion to tempe- 
 rature ; and it will be shewn hereafter, that 
 without caloric there could be no electricity nor 
 light. 
 
 Newton maintained that light and common 
 matter were mutually convertible into each 
 other ; but seems not to have inquired whether 
 solar radiation was connected with the planetary 
 movements. So far was he from recognizing the 
 agency of the sun's heat in maintaining the life 
 of nature, that when speculating on the use of 
 comets, he hints that they may be wandering 
 magazines of vitality, which they distribute to 
 the planets, thus supplying its consumption by 
 vegetable and animal growth. 
 
 Such is the love of mankind for the mar- 
 vellous, that the most obvious causes of natural 
 phenomena are disregarded, and their explana- 
 tion sought after by resorting to such as are 
 hypothetical and remote, or obscure. Hence it 
 is, that our books on Natural Philosophy are 
 filled with speculations about the vacuum of 
 space, while visible and palpable floods of lu- 
 minous tether are continually pouring upon the 
 earth from the great fountain of physical motion 
 and life. When Sir H. Davy observed, that it 
 " was absolutely necessary for the explanation 
 
SPACE FULL OF SUBTILE MATTER. 273 
 
 of the planetary motions, to suppose space in the 
 universe void of all matter," he overlooked the 
 existence of solar light, and even of that subtile 
 medium, the vibrations of which are supposed 
 by some to constitute light. That he did so from 
 authority, and without reflection, would appear 
 from what he says in another part of the same 
 work. " It cannot be doubted that there is matter 
 in motion through space between the sun, and 
 stars, and our globe." (Chem. Phil. p. 67.) 
 
 There is no decisive evidence that any of 
 the ancient philosophers adopted the theory of a 
 perfect vacuum in nature. It was the opinion of 
 Bacon, that the ancient Pan, which all the 
 learned have regarded as an allegorical perso- 
 nation of the universe, " was represented as 
 hairy to denote the rays of things, because every 
 thing which acts at a distance may be said to 
 emit rays." (Wisdom of the Ancients.) 
 
 It was also maintained by Lucretius, who is 
 regarded as the advocate of a vacuum, that sub- 
 tile streams are perpetually flowing from every 
 thing, without which bodies could not be disco- 
 vered at a distance.* (DeNaturaRerum, Book vi.) 
 
 * That the regions of space are rilled with subtile matter can 
 no longer admit of doubt or controversy. By a train of analo- 
 gical reasoning, Pouillet has arrived at the conclusion, that the 
 quantity of heat annually received by the earth from the sun's 
 rays, is sufficient to melt a stratum of ice about forty-six feet in 
 depth over all its surface. (Elemens de Physique, Tom. ii. p. 
 204.) It therefore follows, that as the mean temperature of the 
 
 T 
 
274 IMPERFECT STATE OF PHYSICAL SCIENCE. 
 
 It has been repeated a thousand times, that by 
 reducing the phenomena of gravitation to a ge- 
 neral law, Sir I. Newton had revealed the whole 
 mechanism of the universe. But he entertained 
 a far more accurate estimate of what he had 
 done, when he compared himself to " a little boy 
 collecting a few choice pebbles and shells on the 
 sea shore ; while the great ocean of truth lay all 
 undiscovered before him." 
 
 When he resolved the aggregation of planets 
 into the action of their minutest particles, he left 
 his followers in doubt whether gravitation was a 
 primary agent, or only an expression of the mode 
 in which some universal cause is observed to 
 operate inversely as the squares of the distance ; 
 and whether it resulted from the pressure of an all 
 pervading aether, or from the inherent properties 
 of elementary atoms. (See Opticks, p. 351.) 
 
 globe is constant, an equal amount of caloric must be annually 
 radiated into the planetary spaces. Nay, it is highly probable, 
 that if the temperature of space could be reduced 1000 F. below 
 the minimum of the earth's surface, it would still be an exhaust- 
 less ocean of sethereal matter ; for it is impossible to conceive the 
 total absence of heat. Under all circumstances, it is perpetually 
 radiated from the sun and fixed stars throughout the boundless 
 regions of space. 
 
 In a more advanced condition of human knowledge, it will 
 become an object of inquiry, in what way the movements of the 
 heavenly bodies are connected with this omnipresent aether, 
 which is radiated from the sun to the planets, and reflected from 
 planets to their satellites, and actuates every atom of which 
 they are composed. 
 
HYPOTHESES OF NEWTON. 275 
 
 The power of generalization by which he traced 
 remote analogies, and reduced a vast multitude 
 of apparently opposite phenomena to the domi- 
 nion of one law, displayed an admirable faith in 
 the uniformity of nature. Yet the projectile force, 
 the vacuum of space, and the vis insita which he 
 represents as the cause of attraction and repul- 
 sion, were mere -hypotheses, wholly unsupported 
 by evidence. And that the illustrious author 
 himself was fully convinced of this during the 
 latter period of his life, is manifest from the 
 whole tenor of his speculations concerning the 
 aether, which, as I have already shewn, he finally 
 regarded as the primary physical cause of cohe- 
 sion, capillary attraction, and of gravitation ; but 
 without explaining how it produces the repulsion 
 of atoms, and the centrifugal force of the heavenly 
 bodies ; or in what way the phenomena of chem- 
 istry, geology, meteorology, and planetary mo- 
 tion, are connected with the influence of the im- 
 ponderables, and the relations of the latter to 
 each other. 
 
 But in the total absence of caloric, if such a 
 thing were possible, the whole material universe 
 would disappear no less completely than if anni- 
 hilated : for it is obvious that in their separate 
 state, the chemical atoms of ponderable matter 
 could not be recognized by the senses. And I 
 have proved that caloric is the organizing prin- 
 ciple by which they are aggregated into visible 
 
276 CALORIC THE CAUSE OF FORMS. 
 
 and tangible forms ; consequently, that it is the 
 self-active arid universal essence on which all the 
 manifestations of being or existence depend.* 
 
 Yet we are told that caloric is not a material 
 substance, because it is imponderable. It is 
 evident, however, that whatever the cause of 
 gravity may be, it must be imponderable without 
 gravity ; otherwise we must explain gravity by 
 itself, which would be absurd. The truth is, 
 that when reduced to a state of ultimate diffusion, 
 all matter is imponderable, as in the form of the 
 electric spark, flame, &c. And if caloric were 
 " motion and nothing else," as maintained by 
 Bacon and other philosophers, it would follow 
 that the prime mover in a steam engine, and 
 throughout all nature, is motion, a proposition 
 which involves the glaring absurdity of explain- 
 ing motion by itself. 
 
 But without plunging further into the profound 
 abyss of chaos, or practical non-existence that 
 would follow the entire extinction of the organ- 
 izing principle, it is the legitimate province of 
 science to ascertain how it produces all the 
 phenomena of nature in accordance with the 
 invariable laws of supreme intelligence. Nor 
 is it possible to predict the results which would 
 flow from a searching method of analyzing 
 facts. We often mistake our own inattention 
 
 * And if the particles of all bodies be surrounded by a self-active 
 principle, there can be no such thing as absolute inertia in nature. 
 
GRAVITY NOT AN ULTIMATE PRINCIPLE. 277 
 
 and indolence, or the mystical inventions of 
 fanciful theorists for impenetrable obscurities, 
 that would vanish before a bold and deter- 
 mined spirit of inquiry. Could the veil be 
 drawn aside which conceals from our inspection 
 the whole mechanism of the universe, nothing, 
 perhaps, would so much excite our astonishment 
 as its simplicity. 
 
 From a careful review of the foregoing Chap- 
 ters, the following conclusions may be deduced: 
 
 1. That cohesion, chemical affinity, and ca- 
 pillary attraction, are modifications of that uni- 
 
 In opposition to this view of the subject, we are informed by 
 Dr. Arnott, that " the greater part of the phenomena of nature 
 may be referred to four elementary truths, viz. atom, attraction, 
 repulsion, and inertia." He observes, that " inertia expresses 
 the fact, that atoms, as regards motion, have a stubbornness 
 about them, which tends always to keep them in their existing 
 state, whatever it may be." (Elements of Physics, Vol. I. page 
 1 and 2.) In what way atoms have been endowed with this ima- 
 ginary property has not been explained ; nor does Dr. Arnott 
 assign the cause of attraction. Until this is done, let no man 
 flatter the world, that even the foundation of physical science 
 has been established on the solid rock of fixed principles. 
 
 If it be true that caloric is the physical cause of attraction as 
 well as repulsion, and that cohesion and gravity are modifications 
 of the same power, it must be a primum mobile : it therefore 
 becomes the business of philosophy to investigate the mode of 
 its operation in maintaining all the molecular and aggregate 
 movements of nature. 
 
 The connexion of caloric with the phenomena of motion has 
 been virtually recognized by all those philosophers who have 
 regarded heat and motion as identical. But it is obvious that 
 there can be no motion without an agent; consequently, that 
 they have confounded the effect with its cause. 
 
278 GENERAL CONCLUSIONS. 
 
 versal force by which planets and all other bodies 
 are held together : 
 
 2. That the particles of all bodies are sur- 
 rounded by, and intimately combined with an 
 exceedingly subtile, active, and mobile prin- 
 ciple, which in certain proportions holds them 
 together, but in larger proportions separates or 
 decomposes them : 
 
 3. That the prevalent theory of physics which 
 ascribes the phenomena of attraction to the in- 
 herent, or immaterial properties of ponderable 
 matter, is fallacious, and wholly unsupported by 
 evidence : 
 
 4. That there is no such thing as a perfect 
 vacuum in nature ; neither in the pores of bodies, 
 nor in those widely extended pores of the uni- 
 verse, termed the planetary spaces: 
 
 5. That the inertia of matter is a philosophical 
 fiction, because there is nothing quiescent in 
 nature, or which possesses the poiver of not act- 
 ing neither in the starry heavens, nor in the 
 frame of the earth. The sun revolves on his 
 axis, and planets around the sun. The air, the 
 ocean, and the solid ground are for ever in motion. 
 The molecules of plants and animals are in a 
 state of rapid circulation and change. Yea, the 
 invisible atoms of inorganic matter are in a state 
 of perpetual oscillation and transformation: 
 
 6. That the " unknown hypothetical aether" 
 of Sir I. Newton is identical with a true phy- 
 
GENERAL CONCLUSIONS. 279 
 
 sical agent, the properties of which may be 
 ascertained by the various mechanical, chemical, 
 and physiological effects it produces that it 
 causes the aggregation and chemical union of 
 bodies, whether simple or compound, by virtue 
 of its attraction for ponderable matter, and not 
 by pressure, as supposed by Newton ; while it 
 causes evaporation, gasefaction, explosion, with 
 all the separations and expansions of matter by 
 virtue of its idio-repulsive power : 
 
 7. That if the earth were wholly deprived of 
 caloric, it would become a stupid mass of inert 
 and chaotic matter, without form, and void of all 
 power of attraction and repulsion, of solidity, 
 fluidity, &c. 
 
 8. That the total extinction of the solar fluid, 
 (if such a thing were possible,) would mark the 
 reign of everlasting stillness and death that the 
 same aethereal principle which lights up the uni- 
 verse with radiant glory, directs the planets 
 through their orbits, and preserves them in a 
 state of perpetual motion, circulation, and reno- 
 vation : finally, that caloric is the first of second 
 causes. 
 
BOOK III. 
 
 CHAPTER I. 
 
 Electricity. 
 
 " Nature will not deliver her oracles to the crowd, nor by 
 sound of trumpet. We must open our minds to her in solitude, 
 with the simplicity of children, and look earnestly in her face for 
 a reply." WALTER SAVAGE LANDOR. 
 
 THE grand requisite to a right understanding of 
 nature, is to watch attentively all the changes 
 that mark her progress, and the various circum- 
 stances by which they are attended. Perhaps 
 there is not a more striking characteristic of the 
 present age, than the vast amount of industry 
 and talent that are devoted to the cultivation 
 of separate branches of science, which cannot be 
 understood but as connected parts of one har- 
 monious system. The leading object of all 
 science is to reduce a multitude of phenomena 
 to some universal principle, or general law, which 
 pervades the entire constitution of matter. But 
 how is it possible to arrive at universal facts or 
 fundamental laws, without regarding nature as a 
 whole ? 
 
ELECTRICITY. "281 
 
 The more profoundly we scrutinize her ope- 
 rations, the more we discover of simplicity and 
 unity of power amidst all her diversified move- 
 ments and transformations. Who could have 
 suspected without a general survey of the widely 
 extended provinces of nature, that the aggre- 
 gation of liquids into spherical drops, and their 
 adhesion to solids, are resolvable into the same 
 power that determines the solidity and rotundity 
 of the earth ? which causes rain to descend from 
 on high, rivers to flow towards the sea, and 
 planets to revolve around the sun? yet these 
 various movements were traced by Newton to one 
 arid the same law. 
 
 What can be more unlike to the mass of man- 
 kind, than the opposite forces of attraction and 
 repulsion, contraction and expansion ? Yet I 
 have proved that they are both produced by one 
 and the same agent ; which in certain propor- 
 tions binds the atoms of ponderable matter to- 
 gether, as in cohesion and chemical union ; 
 while in other proportions it diminishes or de- 
 stroys their cohesion, as in liquefaction, vapori- 
 zation, combustion, &c., by which the forms, 
 properties, and powers of all bodies are perpe- 
 tually changed. I have shewn that combustion 
 is the disengagement of that principle by which 
 the earth is maintained in its present form ; that 
 it is for ever flowing from the sun throughout 
 the solar system ; and that as it is the spring of 
 
282 ELECTRICITY. 
 
 all motion and power throughout the earth, it 
 must also be the cause of the annual and diurnal 
 motions of planets. 
 
 If, then, caloric be a universal principle of 
 action in nature, and immediately connected 
 with all the phenomena of motion, what is elec- 
 tricity ? Is it a distinct fluid, sui generis ? or is 
 it a modification of the igneous principle ? These 
 questions, so intimately connected with the whole 
 theory of Physics, have never yet been satis- 
 factorily answered. If. electricity were the ge- 
 neric moving power of nature, it ought to be 
 every where present. But so far is this from 
 being the fact, that it is only under peculiar 
 circumstances that it is developed so as to be 
 appreciable by the senses ; whereas, it is impos- 
 sible to realize the absence of heat, which is 
 indispensable to all the phenomena of climate, 
 season, the growth of vegetation, and the life of 
 nature. (See page 208.) 
 
 As the subject is acknowledged by all philo- 
 sophers of the present day to be involved in the 
 utmost obscurity, I shall offer no apology for 
 endeavouring to place it in a new light. While 
 many regard electricity as the cause of all mo- 
 lecular attractions, aftd others as the vital prin- 
 ciple, almost everything connected with its origin 
 and laws, is either debatable or unintelligible ; 
 some maintaining with Franklin, that it is a 
 subtile and inconceivably refined species of mat- 
 
ELECTRICITY. 283 
 
 ter, diffused throughout nature ; others, that it is 
 a compound of two fluids, each of which repels 
 its own particles, and is attracted by the other ; 
 while a third party maintains that it is neither, 
 but a mere effect or property of ponderable 
 matter. 
 
 Such differences of opinion are alone suffi- 
 cient to show how vaguely and imperfectly it is 
 understood. Since the time of Franklin, many 
 thousand experiments have been repeated, with- 
 out affording any precise or satisfactory informa- 
 tion in regard to its origin, or the mode of its 
 operation in the work of the universe. The 
 discoveries of Galvani, Volta, Davy, Oerstedt, 
 and Faraday, have opened to us an immense 
 store of new facts ; but where is the general 
 principle which connects them with the theory 
 of cohesion, capillary attraction, chemical solu- 
 tion, vaporization, and the elastic force of gases ? 
 What the present state of the science requires, 
 is not the repetition of experiments that have 
 been performed a thousand times, but a more 
 comprehensive and profound investigation of 
 those properties which connect electricity with 
 the laws of heat and light, and with the general 
 phenomena of nature. 
 
 If ever we shall be enabled to lift the veil 
 which nature has spread over the first principles 
 of things, and behold the secret spring of her 
 simple and sublime mechanism, we must first 
 
284 ELECTRICITY. 
 
 learn the relations of caloric and electricity. If 
 it can be shewn, that under all circumstances 
 they are modified effects of one and the same 
 agent, the science of nature will be at once di- 
 vested of that complexity which has hitherto 
 baffled every attempt to reduce the phenomena 
 of nature to fixed principles. 
 
 It is not my object to enter into a detailed 
 examination of the various conflicting hypotheses 
 which have been invented to explain the pheno- 
 mena of electricity ; and which, for the most 
 part, have been founded on the partial, and often 
 ill conceived experiments of a little laboratory. 
 The truth is, that all our experiments are but 
 feeble and imperfect imitations of what is per- 
 petually going on in the laboratory of nature. 
 But who has ever studied the natural history of 
 lightning, by tracing its genealogy or nascent 
 production, as connected with evaporation, and 
 all the phenomena of precipitation ? Who has 
 carefully observed the connexion between flashes 
 of lightning, and torrents of rain, hail, tornados, 
 hurricanes, &c. ? The fundamental laws of elec- 
 tricity which connect it with caloric, light, mag- 
 netism, or the sublime movements of geology 
 and meteorology, will never be deduced with 
 unerring fidelity from mere artificial experi- 
 ments. The greater part of those on electricity, 
 are calculated rather to amuse and astonish 
 children, than to edify those who are in quest of 
 useful knowledge. 
 
ELECTRICITY. 285 
 
 It may be proper to observe, before I proceed 
 further, that some of the most enlightened men 
 of the last century, supposed that the phlogiston 
 of Stahl, (which was the undiscovered latent 
 heat of Dr. Black,) was the basis of heat, light, 
 and electricity. Dr. Kirwin, who strangely con- 
 founded hydrogen with the phlogiston of Stahl, 
 supposed that electricity might be composed of 
 this substance greatly rarefied, in a state of 
 combination with elementary fire ; while M. Be- 
 nedict De Saussure regarded it as a fluid com- 
 posed of heat and some other unknown principle. 
 (Voyages dans les Alpes, torn. ii. p. 243.) The 
 Abbe Nollet, Dr. Hill, the Rev. W. Jones, and 
 some others, have maintained that heat and elec- 
 tricity were modifications of the same power ; 
 but as their opinions were not supported by 
 an extended examination of their recondite ana- 
 logies, or fundamental laws, philosophers have 
 continued to regard them as distinct imponder- 
 ables. 
 
 Atmospheric Electricity. 
 
 The most direct and compendious method of 
 ascertaining the relations of caloric and elec- 
 tricity, would be a careful history of all the phe- 
 nomena connected with the origin of lightning. 
 If it can be shewn, that the caloric of aqueous 
 
286 ATMOSPHERIC ELECTRICITY. 
 
 vapour is the basis of lightning, their radical 
 identity must follow as a necessary consequence, 
 notwithstanding the widely different properties 
 which they exhibit. The truth is, that diversity 
 of form and external appearance, is no evidence 
 of a difference in the nature and fundamental 
 constitution of things ; for it has been demon- 
 strated experimentally by numerous philoso- 
 phers, that all the varieties of electricity are 
 essentially the same. What can be more diffe- 
 rent than ice, water, and steam ? Yet they are 
 composed of the same elements, combined with 
 different proportions of caloric. What more op- 
 posite in all their properties than nitric acid 
 and the gases of which it is formed ? and so of 
 a thousand other bodies. 
 
 It was long imagined, that when Franklin 
 verified the identity of lightning and common 
 electricity, he had laid the foundation of its true 
 theory. But it is now evident that many of his 
 opinions in regard to its origin and nature, were 
 partial and erroneous. At one time he supposed 
 that it was generated in the ocean by the friction 
 of salt and water that oceanic vapour was held 
 in a state of expansion by electricity and heat 
 united, while evaporation from the land was 
 caused by heat alone. He also maintained that 
 the fusion of metals by the electric fluid was a 
 cold fusion ; whereas it is now well known that 
 lightning heats, melts, ignites, and volatilizes all 
 
ATMOSPHERIC ELECTRICITY. 287 
 
 bodies. And here it may be mentioned, that 
 after the electric fluid combines with metals 
 and other bodies, producing their liquidity and 
 vaporization, it communicates no shock, and 
 loses the power of darting through conductors 
 with instantaneous velocity that is, its pecu- 
 liar properties are changed, and merged into 
 those of ordinary caloric. 
 
 That the general reader may have a distinct 
 idea of the existing state of knowledge in regard 
 to the origin of lightning, it may not be amiss 
 to present the statements of some of the most dis- 
 tinguished recent writers on the subject. 
 
 It is observed by Mr. Daniell, that " since the 
 time of Franklin, atmospheric electricity has 
 been almost entirely neglected ;" and that on this 
 most important branch of physical science, he 
 had " nothing decisive to offer." (Meteorological 
 Essays, p. 135 and 374.) The consequence of 
 which is, that he has left unexplained many of 
 the most striking arid important phenomena of 
 meteorology, such as hurricanes, tornados, and 
 hail storms, with all those violent movements of 
 the atmosphere which accompany rapid dis- 
 charges of lightning. Dr. Arnott also states, 
 that tornados, whirlwinds, &c. are owing to 
 some chemical changes in the atmosphere not 
 fully understood. (Elements of Physics, Vol. I. 
 p. 397.) 
 
 Dr. Thomson observes, in his late work on 
 
288 ATMOSPHERIC ELECTRICITY. 
 
 Heat and Electricity, that " the formation of 
 vapour seems to be connected with electricity, 
 though in what way we have no conception, and 
 that the change of vapour into clouds is pro- 
 bably connected with electrical phenomena not 
 understood." (Page 275, and elsewhere.) He 
 adds, that " the formation of rain is still in- 
 volved in impenetrable obscurity." 
 
 It is also observed by Professor Forbes, that 
 on the noble science of atmospheric electricity, 
 almost every thing has yet to be done. (Trans- 
 actions of the British Association, Vol. I. p. 252.) 
 
 As the phenomena of lightning have been 
 universally known to be immediately implicated 
 with the production of rain, it becomes neces- 
 sary to present an outline of the leading facts 
 connected with evaporation, previous to entering 
 upon the history of atmospheric electricity. 
 
 That caloric is the true and only cause of 
 evaporation, or the formation of steam, is one 
 of those self-evident propositions which would 
 seem to require no proof. But to remove all 
 doubts upon the subject, the fact has been ex- 
 perimentally demonstrated by Dr. Dalton, to 
 whom the science of chemistry and meteorology 
 is so largely indebted. 
 
 He put a little water in a dry glass flask, with 
 a thermometer in it, when he found that a small 
 quantity of vapour was formed at 32 F. At 
 40 the amount was increased : at 50 it con- 
 
EVAPORATION AND CONDENSATION. 289 
 
 tained still more vapour ; while at 60 the quan- 
 tity was yet farther augmented. He also found 
 that when the temperature of the flask was 
 suddenly reduced from 60 to 40, a portion of 
 vapour was converted into water, and that the 
 quantity retaining the elastic form was precisely 
 the same as when the temperature^ 
 nally at 40. 
 
 The above is a simple and be^5IiUiIlfepp&SI ' Y^ 
 sentation of what is perpetually goinj 
 out the atmosphere, and in the steam 
 
 By another series of admirable experiments, 
 he ascertained that the quantity and elastic force 
 of vapour, whether formed in vacuo, or under the 
 pressure of the atmosphere, are the same, and 
 determined by temperature alone the differ- 
 ence being this, that in the latter case the pro- 
 cess goes on much more slowly, because the 
 atmosphere presents a mechanical impediment 
 to its diffusion somewhat analogous to the ob- 
 struction of water by porous sand. From which 
 he inferred that vapour is not chemically united 
 with the air, as had been formerly supposed, 
 but mechanically diffused through it, forming 
 a distinct atmosphere of its own, the elastic 
 force of which is always in proportion to tem- 
 perature. 
 
 At he found the quantity and elastic force 
 of vapour equal to the pressure -064 inch of 
 mercury that is, about -^ of an inch. At 32 
 
 u 
 
290 EVAPORATION AND CONDENSATION. 
 
 they amounted to ^ of an inch at 47, about -f- 
 of an inch, or -339 at 59, -507, or \ an inch 
 at 80, 1 inch and at 90, 1-360. He also as- 
 certained, that the elastic force of vapour at 
 212 is equal to the pressure of the whole at- 
 mosphere, or 30 inches of mercury.* 
 
 From the above experiments it follows, that 
 if the temperature of the earth were 80, from 
 the equator to the poles, the quantity of vapour 
 would be everywhere the same, and equal to 
 about -5*5- of the average weight of the whole at- 
 mosphere : but that if its temperature were 
 reduced from 80 to 59, one-half of the vapour 
 would be precipitated in the form of rain if to 
 32, f of it would be converted into snow and 
 if reduced to 0, 14 out of 15 parts of the whole 
 would descend to the earth in the form of ice, 
 in obedience to that universal law of attraction 
 by which bodies cohere, and tend towards a 
 common centre. 
 
 But as the temperature of the earth dimi- 
 
 * Dr. Promt observes, that " atmospheric air, under ordinary 
 circumstances, exerts an elastic force equal to the weight of a 
 column of mercury 30 inches high; and that at 212 aqueous 
 vapour obeys precisely the same laws, and exerts the same elastic 
 force as atmospheric air under similar circumstances." (Bridge- 
 water Treatise, Chap. V. Section 2.) But it has been shown that 
 the elastic force of atmospheric air is equal to the pressure of 
 more than 1200 atmospheres, (3000 feet of mercury.) It is 
 therefore obvious that Dr. Prout has mistaken the weight of the 
 atmosphere for its elastic force. 
 
EVAPORATION AND CONDENSATION. 291 
 
 nishes from the equator to the poles, it is ob- 
 vious that the amount of water which is cap- 
 able of existing in the atmosphere in the state 
 of transparent elastic vapour, must vary pro- 
 portionally in different latitudes. There is also 
 more vapour in the atmosphere of the ocean, 
 other things being equal, than over extensive 
 bodies of dry land. 
 
 According to the observations of Captain Sa- 
 bine and Mr. Caldcleugh, as detailed by Pro- 
 fessor Daniell, it would appear, that within the 
 tropical ocean, between the western coast of 
 Africa and the eastern coast of South America, 
 the point of deposition, or dew point, is gene- 
 rally about 4 or 5 below the existing tempera- 
 ture ; sometimes only 2 and rarely more than 
 8 ; while in the interior of large continents it 
 is often 20 or 30 below the prevalent tempera- 
 ture. As the atmosphere is in a state of nearly 
 constant circulation, it is removed from one place 
 to another before arriving at the point of satu- 
 ration, and therefore contains less vapour than 
 it is capable of sustaining at the existing tem- 
 perature. Within the torrid zone, it is perpe- 
 tually expanded by solar heat, where it rises into 
 the upper regions, whence it flows to higher 
 latitudes ; while it is removed by horizontal cur- 
 rents termed sea breezes, from the ocean to the 
 heated land. 
 
 If at the temperature of 80, the atmosphere 
 
292 EVAPORATION AND CONDENSATION. 
 
 contain an amount of vapour equal to the pres- 
 sure of only half an inch of mercury, while it 
 is capable of sustaining twice that quantity, it 
 will require a reduction of temperature below 
 59 to cause precipitation. Hence it is that the 
 atmosphere often undergoes great reductions of 
 temperature without producing rain. But when 
 the air is full of vapour the process of evaporation 
 is arrested ; which explains why a cold dry air is 
 more favourable to evaporation than warm air 
 that is already saturated, especially if the former 
 be in a state of rapid motion. 
 
 Dr. Dalton found that when boiling water 
 was exposed to a current of air that carried off 
 its vapour as fast as formed, vaporization went 
 on a third faster than in a room where the air 
 was still. Hence it is, that north-east and east 
 winds, which, in the west of Europe are generally 
 dry, and far below the point of saturation, sel- 
 dom condense the vapour of France and Eng- 
 land ; but, on the contrary, often redissolve the 
 clouds already formed, producing clear weather. 
 During summer, when the atmosphere has been 
 for some time comparatively still, it is soon 
 saturated with vapour, which is indicated by 
 heavy dews, and the formation of clouds termed 
 cumuli, when the weather becomes hot and sul- 
 try ; because the caloric which is usually carried 
 off by evaporation and winds, accumulates on 
 the surface of the earth and heats the superin- 
 
EVAPORATION AND CONDENSATION. 293 
 
 cumbent air. Such a state of things generally 
 forebodes an approaching thunder storm. 
 
 That the condensation of atmospheric vapour 
 is owing to the abstraction of its caloric by 
 colder currents of air, is evident from the fact, 
 that in the tropical ocean far from land, where the 
 trade wind blows steadily in one direction, and 
 where the temperature seldom varies more than 
 2 or 3 degrees, there is less rain than in the 
 vicinity of continents and large islands, where 
 currents of air of different temperatures fre- 
 quently meet. 
 
 In the great desert of Sahara, there is scarcely 
 any rain, because the wind blowing over it is 
 generally in the same direction ; while the va- 
 pour transported by it from the ocean is still 
 farther rarefied by the intense heat reflected from 
 the scorching sands, where there are no moun- 
 tains to condense it. There are also long 
 droughts in Egypt, Palestine, New Holland, 
 and many other parts of the world where the 
 winds blow long in one direction, without en- 
 countering colder currents. During summer, in 
 the United States, the atmosphere is often so 
 much heated, that the vapour brought from the 
 ocean by southern winds is not condensed for 
 many weeks, and sometimes two months, but is 
 farther expanded, until it becomes saturated, 
 and meets with a current from the northern 
 
294 EVAPORATION AND CONDENSATION. 
 
 points of the compass, or with mountains and 
 high lands, when thunder gusts follow. 
 
 When I come to treat of winds it will be 
 shown, that the most extensive falls of rain in 
 the middle latitudes are produced by the meet- 
 ing of immense masses of air from opposite 
 quarters of different temperatures, as during 
 the equinoctial floods and storms. When both 
 contain as much vapour as they can support at 
 their respective temperatures, the amount of pre- 
 cipitation is of course the greatest. 
 
 Corresponding with the experiments of Dalton, 
 is the well established fact, that the greatest 
 quantity of rain falls within the tropics, where 
 the average temperature is from 80 to 83 F, and 
 diminishes on to the regions of lowest mean 
 temperature, where it is about 0. Hence it is 
 that the largest rivers in the world are found in 
 the tropical regions, as the Amazon, La Plata, 
 and Orinoko of S. America ; and the Indus, 
 the Ganges, the Nile, the Tigris, &c. of the 
 eastern continent. The summer temperature of 
 the Mississippi Valley is also tropical, and it is 
 well known that much more rain falls during 
 summer than winter in the middle latitudes. 
 
 The following table exhibits a general view 
 of the relative depths of rain in different lati- 
 tudes : 
 
EVAPORATION AND CONDENSATION. 295 
 
 Lat. N. 
 
 Granada 12 126 inches. 
 
 CapeFran9ois 19-46' 120 
 
 Calcutta 22 81 
 
 N. Orleans 30 63 
 
 Philadelphia 39'57' 42 
 
 Rome 41 39 
 
 England (Dalton's mean) 50 31 
 
 Petersburg 59 . . . 13 
 
 The above results are greatly modified by a 
 variety of circumstances, such as prevalent 
 winds, the relative positions of land and sea, 
 mountain ranges, &c. For example, the trade 
 wind which blows constantly from east to west 
 over the atlantic ocean within the tropics, de- 
 posits a far greater amount of rain on the eastern 
 slope of South America, than on its western 
 coast. But in the middle latitudes of the northern 
 hemisphere, where the prevalent wind is from the 
 opposite direction, the case is reversed. Hence 
 the greater amount of rain which falls on the 
 western coasts of Europe and N. America, than 
 in the interior of those continents, being wafted 
 from the Atlantic and Pacific oceans. There is 
 also more rain in mountainous regions than on 
 extensive plains. It has been ascertained, that 
 about double the quantity of rain falls on Mount 
 St. Bernard, that falls at Geneva ; and that the 
 mean annual amount of twenty places in the 
 lower valleys at the base of the Alps, is 58.5 
 inches, according to M. Schow. 
 
296 EVAPORATION AND CONDENSATION. 
 
 There is nothing more admirable in the great 
 drama of Nature than the process of evaporation 
 and condensation, by which all the lakes, rivers, 
 and fountains of the earth are elevated from the 
 ocean ; transported over continents and islands ; 
 attracted by mountains ; precipitated by polar 
 currents ; and distributed in fertilizing showers 
 to cheer the thirsty lands. Vapour is condensed 
 by cold and lofty mountains, for the same reason 
 that it collects in drops on the sides of bottles 
 filled with cold water on a summer's day. 
 
 Notwithstanding the greater amount of evapo- 
 ration and rain in the tropical than higher lati- 
 tudes, the atmosphere is more transparent, and 
 there are more clear days in the equatorial 
 regions ; and more during summer than winter 
 in temperate climates. 
 
 According to the estimate of La Cotte, which 
 may be regarded as an approximation to the 
 truth, the average number of rainy days between 
 Lat. 12 and 60 N. are in the following ratios : 
 
 N. 
 
 From Lat. 12 to 43 78 days 
 
 43 to 46 103 
 
 46 to 50 134 
 
 50 to 60 160 
 
 It is therefore evident that the transparency of 
 the atmosphere, other things being equal, is in 
 proportion to temperature, which diminishes 
 from the equator to the poles. It is also known 
 
EVAPORATION AND CONDENSATION. 297 
 
 to decrease from below upwards.* Hence it is, 
 that the lower atmosphere is transparent, even 
 when the sky is overcast with clouds,! the ele- 
 vation of which is in proportion to temperature 
 that is, the plains of condensation are higher 
 within the tropical than middle latitudes ; while 
 in the latter their elevations vary with the season. 
 From the observations of Mr. Crosthwaite it 
 
 * It was supposed by Leslie and Dalton, that the diminution of 
 temperature in the atmosphere, on ascending above the earth's 
 surface, was owing to its increased capacity for heat, caused by 
 augmented rarefaction from diminished pressure. But this is not 
 the only cause ; for it is well known, that large portions of Asia, 
 Africa, and South America, are from eight to ten thousand feet 
 above the level of the ocean ; whereas their average temperature is 
 much higher than that of isolated mountains of equal elevation 
 in the same latitudes. Mount Lebanon is not much higher than 
 the Plateau of Mexico ; yet the former is covered with snow 
 nine months in the year, while there is perpetual spring on 
 the Table lands of Mexico, about the same latitude and eleva- 
 tion. The truth is, that the greater warmth of the lower 
 atmosphere over extensive plains, than that of mountains, is 
 owing to the obstruction of the sun's rays by the earth's surface. 
 The stratum of air in contact with the earth becomes heated and 
 rises, when the next stratum is heated and rises, until the whole 
 atmosphere becomes warmed to a considerable height. Hence 
 it is, that the plain of perpetual congelation varies in height in 
 different parts of the world in nearly the same latitudes. 
 
 f The dryness of the atmosphere is in proportion to the eleva- 
 tion of its temperature above the dew point, which decreases from 
 the surface of the earth to the region of clouds. This explains why 
 rain often ceases about mid-day, when the clouds are redissolved 
 by the increasing power of the sun ; and why the lower atmos- 
 phere is so often obscured in England by a misty rain after sun- 
 set during winter. 
 
298 LIGHTNING AND RAIN. 
 
 would appear, that the under surface of dense 
 clouds in the north of England, does not exceed 
 1300 yards during winter, nor 2000 yards in 
 summer.* 
 
 To pursue this subject through all the compli- 
 cated phenomena of meteorology, would far ex- 
 ceed the scope of the present inquiry, the prin- 
 cipal object of which is to trace the origin and 
 history of atmospheric electricity. 
 
 The cardinal facts which connect the pheno- 
 mena of lightning with the theory of rain, may 
 be reduced to the following propositions : 
 
 1. In the torrid zone, where evaporation and 
 rain are most copious, the amount of lightning 
 is greatest. There is also far more during sum- 
 mer than winter in the middle latitudes, and 
 scarcely any in the polar regions. 
 
 2. In those parts of the world where there is 
 no rain, there is no lightning, as at Lima in 
 Peru ; nor is there any in Egypt, Palestine, and 
 other parts of the world during the prevalence of 
 dry weather. It therefore follows, 
 
 3. That where there is no condensation of 
 aqueous vapour, there is no lightning. 
 
 The most superficial observers of nature have 
 been impressed with the immediate connexion 
 between lightning, intense heat, and rapid preci- 
 pitations of rain. By a careful analysis of the 
 phenomena it becomes self-evident, that if caloric 
 
 * Dalton's Meteorological Essays, p. 136. 
 
LIGHTNING AND RAIN. 299 
 
 be the true and only cause of evaporation, its 
 condensation and precipitation can be effected 
 only by the evolution of the same agent. During 
 winter, the quantity and elastic force of vapour 
 in the atmosphere are comparatively low in the 
 middle latitudes, where it is condensed gradu- 
 ally on meeting with colder air. During spring, 
 evaporation augments with increase of tempera- 
 ture, when masses of warm and cold air often 
 meet, causing frequent showers of rain, and 
 sometimes hail ; still without much thunder and 
 lightning. But during summer, when the tem- 
 perature becomes tropical, and the atmosphere 
 saturated with highly elastic vapour, we have 
 tremendous explosions of thunder and lightning, 
 with rapid precipitations of rain and hail. Cor- 
 responding with the temperature of the torrid 
 zone, and the amount of evaporation, thunder 
 storms occur almost daily during the rainy 
 season, on the coasts of India and S. America. 
 
 One of the most prominent errors in regard to 
 the natural history of lightning, is the prevalent 
 notion that it collects around the surface of clouds, 
 as if they were solid insulated conductors ; and 
 that when it becomes accumulated to a certain 
 extent, it darts from one to another. Nothing 
 could be more in opposition to all analogy and 
 experience. Clouds are only banks or strata of 
 moisture, while it is universally known that elec- 
 tricity cannot be accumulated in a moist atmo- 
 sphere, that it is diffused and dissipated by 
 
300 LIGHTNING AND RAIN. 
 
 moisture, and thus prevented from being col- 
 lected in a Leyden battery. It is accumulated in 
 transparent aqueous vapour, as I shall proceed to 
 shew by the most decisive facts, and by the ex- 
 periments of different philosophers, from which 
 it darts through the neighbouring clouds in such 
 a manner as to present the appearance of pro- 
 ceeding from them ; while it is an optical illusion 
 that may be corrected by a philosophical exami- 
 nation, in short, that a large body of transpa- 
 rent elastic vapour from the tropics, may be 
 compared to an immense Leyden battery, filled 
 with an igneous fluid which is discharged in the 
 concentrated form of lightning on approaching 
 mountains or currents of cold air. 
 
 When the inquiry is divested of all extraneous 
 and hypothetical considerations, it may be re- 
 duced to the following conditions. 
 
 If it can be shewn, that transparent elastic va- 
 pour is the vehicle of atmospheric electricity, and 
 that it is rapidly condensed during discharges of 
 lightning, it will necessarily follow, that the 
 caloric of such vapour is given out in the con- 
 centrated form of electricity during a thunder 
 storm. 
 
 In reply to this reasoning it may be objected, 
 that heavy rains are often unattended with 
 lightning. To which I answer without fear of 
 contradiction, that the formation of clouds and 
 precipitation of rain are far more rapid during 
 thunder storms than when there is no lightning. 
 
DE LUC AND MURPHY. 301 
 
 It is stated by Humboldt and others, that within 
 the tropics during the rainy season, the first in- 
 dication of an approaching storm is generally a 
 light wind, with a few scudding clouds, but that 
 when it begins to lighten, the whole sky is sud- 
 denly obscured by dense clouds that immedi- 
 ately descend in torrents of rain. 
 
 That atmospheric electricity is a constituent 
 of aqueous vapour, will appear from the descrip- 
 tion of a thunder storm among the Alps, as re- 
 corded by the celebrated De Luc. He states 
 that it commenced with abundant discharges of 
 electricity from dry transparent air, which con- 
 tained neither vapours nor the electric fluid, but 
 the constituents of both, and that clouds were 
 suddenly formed around the summit of the Buet, 
 during each explosion. In other words, that si- 
 multaneous with the discharges of lightning from 
 dry transparent air, was the sudden formation of 
 clouds, and precipitation of rain. 
 
 From another portion of De Luc's work, en- 
 titled, Idces sur la Meteor ologie, it is obvious that 
 he mistook transparent aqueous vapour for " dry 
 air." He supposed that clouds were formed by 
 the union of oxygen and hydrogen gases by the 
 agency of electricity, as water is generated by 
 passing an electric spark through them.* 
 
 * This hypothesis has been revived by Mr. Murphy of Cam- 
 bridge, in a recent work on Electricity, the professed object of 
 which is to reduce the science to mathematical laws. Had this 
 ingenious author traced the history of rain from the first process 
 
302 SENECA AND THE STOICS. 
 
 According to Seneca, the ancient stoics taught 
 a similar doctrine " that air was converted into 
 fire and water," during a thunder storm : (Na- 
 tural Questions, Book ii.) from which it would 
 appear, that they were ignorant of the process 
 of evaporation, by which water is expanded into 
 elastic vapour like air ; or that they confounded 
 the one with the other. 
 
 In the 22nd chapter of the same book, in 
 which Seneca gives his own opinion, he main- 
 tains that^Ve and lightning are the same, because 
 the latter produces the same effects as fire, such 
 as the heating and melting of metals, the com- 
 bustion of forests, &c. ; but that in lightning, fire 
 was greatly condensed. 
 
 But to return from this digression, if it be 
 true that caloric is the cause of evaporation, (as 
 proved by De Luc himself,) and if transparent 
 vapour be suddenly condensed into clouds and 
 rain, with a rapidity proportional to the amount of 
 lightning, the conclusion is inevitable, that solar 
 
 of evaporation, he would probably not have maintained that 
 heavy showers of rain which accompany lightning, may be pro- 
 duced from the combination of oxygen and hydrogen by elec- 
 tricity, after it had been demonstrated by Dalton that vapour 
 or steam is composed of water and caloric, and that its con- 
 densation is owing to the evolution of caloric, whether attended 
 with lightning or not. The supposition of Dr. Darwin was more 
 consistent, who maintained that electricity was the cause of 
 evaporation, because discharges of lightning are attended with 
 rapid precipitations of rain. 
 
OBSERVATIONS OF THE AUTHOR. 303 
 
 caloric is the real basis of lightning ; for it would 
 be a violation of all the rules of philosophizing, 
 to maintain that water is converted into vapour 
 by one agent, and again reduced to water with- 
 out the evolution of the same agent. No so- 
 phistry can evade this simple but rigorous logic. 
 That the rapid precipitation of rain during a 
 thunder storm, is in proportion to the amount of 
 lightning, is attested by all experience and ob- 
 servation. Hence it is that during the fiery 
 tempests of the tropical regions, termed hur- 
 ricanes, more rain is precipitated in a few 
 hours, than during as many months in colder 
 latitudes. 
 
 It may be said that lightning is sometimes 
 unattended with rain : to which I answer, that 
 vivid flashes never occur immediately over head, 
 without a precipitation of rain or hail. This is 
 the most convincing proof, that the caloric of 
 vapour is given out in the condensed form of 
 lightning ; and is that kind of evidence from 
 which there is no appeal, being the spontaneous 
 declaration of nature herself, made in the most 
 sublime and ostensible manner. 
 
 On the 2nd of June, 1 833, the author had an 
 opportunity of observing for himself, that light- 
 ning proceeds from transparent vapour, and not 
 from clouds already formed, as many persons sup- 
 pose. This beautiful display, which was wit- 
 nessed by hundreds of individuals with admira- 
 
304 DE SAUSSURE, READ, AND POUILLET. 
 
 tion, occurred at New York, about 7 P. M. after 
 a showery day. The wind was from the south, 
 while the western sky was of a brassy hue, 
 through which the descending sun was perfectly 
 visible. In this state of the atmosphere, a vivid 
 streak of lightning was seen to dart from it, 
 when clouds were immediately formed that inter- 
 cepted the solar rays, as if an immense black 
 curtain had been drawn across the western sky, 
 and attended with copious precipitations of rain. 
 Several showers were thus produced by succes- 
 sive flashes of lightning ; and during their in- 
 termissions, the sky became partially transpa- 
 rent, but of a brassy hue as at first. 
 
 Such facts afford more decisive information in 
 regard to the nature of lightning, than volumes 
 of mere speculation ; or than thousands of arti- 
 ficial experiments ; for they completely establish 
 the important fact that elastic vapour and not 
 clouds is the proximate source of atmospheric 
 electricity. Nevertheless, I shall prove by the 
 experiments of De Saussure, Read, and Pouillet, 
 that electricity may be disengaged from all 
 vapours generated by the agency of caloric, 
 whether by natural or artificial means, or by 
 combustion that it rises from the earth in a 
 latent state of combination with aqueous vapour, 
 which it maintains in the elastic form, whence 
 it may be withdrawn by conductors, and tested 
 by the electrometer. 
 
BECCAR1A, FRANKLIN, AND VOLTA. 305 
 
 Scarcely one of the older writers on meteo- 
 rology, clearly understood the simple process of 
 evaporation. Beccaria supposed that the earth 
 was full of electric matter, which rises to the 
 upper regions of the atmosphere, carrying with 
 it water in the form of vapour. (Priestley's Hist. 
 of Electr. p. 340.) 
 
 Franklin also supposed, that vapour was ele- 
 vated from the sea, by the united agency of heat 
 and electricity. But it is now well established, 
 that caloric is the vaporizing agent all over the 
 world that wherever there is heat and water in 
 sufficient quantity, vapour is produced, whether 
 from the ocean, fresh water lakes and rivers, or 
 from the surface of the dry land and that other 
 things being equal, its amount, like that of light- 
 ning, is determined by temperature. Had Frank- 
 lin clearly understood the process of evaporation, 
 and traced the connexion between discharges of 
 lightning and precipitation, he would probably 
 have added to his discovery of the identity of 
 lightning and common electricity, the still more 
 important fact, that caloric and electricity are 
 different manifestations of the same potent ele- 
 ment. 
 
 The celebrated Volta adopted the opinion of 
 Franklin, with some slight variation. He sup- 
 posed that all bodies contained electricity, a 
 portion of which was evolved whenever they un- 
 derwent a change of state ; that when water was 
 
 x 
 
306 LAVOISIER AND LAPLACE. 
 
 converted into vapour by the agency of solar 
 heat, it acquired a greater capacity for electricity, 
 which it absorbed and carried into the atmos- 
 phere during the process of evaporation ; that it 
 was liberated whenever the vapour was con- 
 densed by cold, and thus accumulated in the 
 upper regions of the air ;* that when clouds are 
 formed, which are good conductors of electricity, 
 they become a medium by which electricity is 
 conveyed back to the earth in a tranquil manner, 
 or in the form of lightning, according as it is 
 more or less abundant. (Journal de Physique, 
 Aoiit. 1783.) 
 
 The experiments of Lavoisier and Laplace, 
 published in the Memoirs of the French Academy 
 in 1781, were intended to prove that electricity 
 is disengaged during the process of evaporation : 
 but their results were vitiated by the agency of 
 
 * Seneca informs us that Anaxagoras taught that lightning 
 descended from the setherial regions, and was collected in clouds, 
 from which it was discharged after being greatly accumulated. 
 The same hypothesis has been recently brought forward as new 
 by Dr. Hare, with this difference, that he supposes the earth to 
 constitute another great reservoir of the electric fluid, and that 
 the atmosphere is situated between two oceans of electricity; 
 while the clouds formed in the non-conducting air, operate as. 
 moveable insulated conductors. He further supposes, that thunder 
 storms are more frequent during warm than cold weather, in 
 consequence of the greater elevation to which the clouds then 
 attain, and their consequent approximation to the celestial ocean 
 of electricity. (Theoretical suggestions respecting the causes of 
 the tornado, or water-spout, &c. by Robert Hare, M.D. of Phi- 
 ladelphia.) 
 
DE SAUSSURE AND READ. 307 
 
 chemical action, which accompanied the process 
 of evaporation in most of their experiments. 
 Besides, they did not extend their researches to 
 the connexion of atmospheric electricity with 
 the phenomena of meteorology : they have there- 
 fore been very little attended to by philosophers. 
 
 Lavoisier and Laplace found, that when water 
 was poured by drops into an iron vessel healed, 
 while the vessel communicated with an electro- 
 scope, it gave signs of positive electricity ; that 
 when dilute sulphuric or nitric acid was poured 
 upon iron filings, electricity was evolved ; also, 
 during the action of dilute sulphuric acid on 
 chalk, and during the combustion of charcoal. 
 Their experiments tend to shew the relation be- 
 tween chemical action and the evolution of elec- 
 tricity ; but throw very little light on the con- 
 nexion of electricity with evaporation. 
 
 The most decisive results are those of De 
 Saussure and Mr. Read, who performed many 
 hundred experiments with the greatest care, for 
 the purpose of ascertaining the source of atmos- 
 pheric electricity ; the result of which led them 
 to the conclusion, that a perpetual circulation 
 of the electric fluid is kept up by means of 
 evaporation and condensation. 
 
 De Saussure found that when water, spirit of 
 wine, and aether, were made to boil in silver, or 
 white porcelain vessels heated, and suspended 
 by silk cords, negative electricity wa obtained ; 
 
308 EXPERIMENTS OF DE SAUSSURE. 
 
 but when a piece of red hot iron was thrown into 
 a vessel containing a small quantity of water, 
 positive electricity was strongly developed. He 
 supposed that the vast quantities of electricity 
 discharged from volcanos, was generated by the 
 action of so great a heat on waters that find their 
 way to those immense furnaces. In all such 
 cases, it is disengaged chiefly by chemical action, 
 as will be noticed when I come to treat of voltaic 
 electricity and volcanic forces. 
 
 The following experiments of De Saussure 
 shew, that aqueous vapour, however produced, 
 contains electricity. He caused water to boil in 
 a coffee-pot, by placing it on an insulated 
 chauffer (heater), when the coffee-pot was elec- 
 trified minus, during the condensation of the 
 vapour. He varied the experiment, by causing 
 the vapour of boiling water to pass into the cap 
 of an insulated alembic, to which he applied 
 snow, causing a condensation of the vapour con- 
 tained within it, when the apparatus became 
 electrified minus, or negative. The same effect 
 was produced in a more remarkable manner, by 
 applying a mixture of common salt and snow as 
 a refrigerent. He observes, that in all such cases, 
 electricity is disengaged from the vapour, and 
 conducted to the metallic vessel during the pro- 
 cess of condensation. (Voyages dans les Alpes, 
 tome ii. 251.) 
 
 De Saussure adds, that the electric fluid is 
 
THOMSON AND DE SAUSSURE. 309 
 
 generated during the conversion of water into 
 vapour by heat ; that it combines with vapour, 
 and contributes to its formation : "II monte 
 invisible et inactif, cache dans le sein de ces 
 vapeurs ; mais deployant ensuite son energie 
 lorsque ces vapeurs ont chang de forme, il 
 redescend actif, anim6 de sa force penetrante 
 et expansive." (Voyages dans les Alpes, Tom. 
 II. p. 244.) But it is quite evident that his ideas 
 were vague and unsettled in regard to the ori- 
 gin of atmospheric electricity : for he observes 
 in another volume of the same work, that it 
 seemed to be produced by the friction of clouds 
 against the air ; by the action of the solar rays ; 
 or by these two causes united. (Vol. i. p. 241 .) 
 
 Dr. Thomson has expressed nearly the same 
 opinion in his late work on heat and electricity, 
 " that atmospheric electricity may result from 
 the friction of two currents of dry air moving 
 different ways." (page 441.) 
 
 De Saussure supposed that there were two 
 kinds of vapour ; the one vesicular* and visible, 
 which contained electricity ; while transparent 
 elastic vapour was combined with, and sustained 
 by, the expansive agency of heat alone, (sans le 
 secours d'aucun autre agent.) (Vol. ii. p. 259.) 
 
 * The vesicular theory originated with Derham, who supposed 
 that vapour was composed of hollow sphericles of water filled 
 with highly attenuated air, which Mr. Leslie terms a " fanciful 
 notion, countenanced by certain dubious optical appearances." 
 
310 TRANSFORMATION^ OF CALORIC. 
 
 But I have shewn, from the observations of De 
 Luc on the Alps, and from my own atN. York, that 
 lightning is disengaged rapidly from transparent 
 vapour, by which the latter is condensed into rain. 
 The observations and experiments of De Saus- 
 sure are highly valuable ; while his theoretical 
 views are often inconsistent. He supposed that 
 electricity was destroyed by explosions of thunder ; 
 that is to say, it is generated by evaporation, and 
 destroyed by condensation. But I have already 
 shewn, that such phenomena result from changes 
 of state : and it will be seen hereafter, that there 
 are no assignable limits to the metamorphoses of 
 this subtile agent. They are as diversified as the 
 multitudinous forms of external nature. Though 
 invisible per se, it is everywhere busy in all the 
 transmutations of matter. The fabled Proteus 
 of old, is but a feeble representation of the rapid 
 changes through which it passes now silently 
 bearing the waters of the ocean aloft into the 
 atmosphere in a state of transparent aetherial 
 vapour now darting in vivid corruscations from 
 its aerial palaces on high leaping upon the 
 mountains, and cleaving rocks asunder resound- 
 ing through the heavens with its great music, 
 and sprinkling the earth- with genial showers of 
 fruitful rain. Though constantly changing, it is 
 never destroyed, but is always the same powerful 
 agent by which Infinite Wisdom seems to direct 
 and govern the stupendous frame of the universe. 
 
GENERAL REFLECTIONS. 311 
 
 Who can refrain from sentiments of profound 
 admiration of its God-like energy, and the won- 
 derful manner in which it produces an endless 
 succession of the most diversified effects ? 
 
 There is not a more striking evidence of bene- 
 ficent design in the whole mechanism of creation, 
 than the rapid evolution of heat from atmos- 
 pheric vapour, in the concentrated form of light- 
 ning, during hot and sultry weather. Were it 
 given out in the diffused form, it would cause 
 an inconvenient augmentation of temperature. 
 Besides, were it evolved gradually, as during 
 winter, the number of rainy days would be so 
 far increased, as greatly to interfere with the 
 operations of agriculture. On the other hand, 
 being given out in the form of sensible heat 
 during the formation of clouds, rain, and snow, 
 in the higher latitudes, it moderates the exces- 
 sive cold which would otherwise prevail during 
 winter. 
 
 It was observed by a distinguished writer of 
 the present day, "that the delight with which 
 speculative minds contemplate universal truths, 
 does not so much spring from perceiving that 
 some general principle holds good, and reap- 
 pears in a great number of instances very nearly, 
 or perfectly resembling one another, as from 
 discovering the occult presence or efficacy of 
 some such principle in a multiplicity of cases 
 which have few points, or perhaps no other point 
 
312 EXPERIMENTS OF READ AND POUILLET. 
 
 of resemblance besides this one of their obedi- 
 ence to some abstract law." (Isaac Taylor, Sa- 
 turday Evening, p. 131.) 
 
 When men shall thoroughly comprehend the 
 agency of caloric in all the diversified forms of 
 electricity, and how they are resolvable into one 
 general principle, innumerable new truths, the 
 existence of which has not been suspected, will 
 gradually open to view, until the vast and com- 
 plicated machinery of nature shall be fully un- 
 folded, and reduced to an intelligible theory. 
 
 I cannot dismiss this subject without noticing 
 the recent experiments of M. Pouillet, in con- 
 nexion with those of Mr. Read, which were per- 
 formed fifty years ago; because their conclu- 
 sions are in direct opposition to each other. Mr. 
 Read maintained that electricity is given out 
 by aqueous vapour, (the constituents of which 
 are oxygen, hydrogen, and caloric,) and by the 
 vapours that are exhaled from burning sub- 
 stances,* while M. Pouillet contends that elec- 
 tricity is never developed by evaporation, unless 
 attended with chemical action. 
 
 It was before stated, that De Saussure ob- 
 tained electricity during the evaporation of water, 
 from silver and porcelain vessels, where no che- 
 mical action can be supposed to have existed. 
 
 * Mr. Read considered combustion as a species of evaporation, 
 by which solid and fluid bodies were converted more or less 
 rapidly into the gaseous state. 
 
EXPERIMENTS OF READ AND POUILLET. 313 
 
 Mr. Read insulated a large hollow tin cone, with 
 many yards of small wire coiled up within it, 
 one end of which extended from the apex of 
 the cone, which was open, and was connected 
 with a sensible electrometer. Under this cone 
 was placed a vessel of water, the vapour from 
 which, on rising, was condensed and collected 
 by the cone and wire, when positive electricity 
 was produced, (which De Saussure could not 
 obtain without chemical action.) The same result 
 was obtained by burning different substances 
 under the cone. He maintained that the elec- 
 tricity which he derived from the atmosphere in 
 different degrees, at all seasons and times of the 
 day, was elicited from its vapour. He observed 
 that during the formation of thick fogs, elec- 
 tricity was abundant ; but scarce during their 
 solution and dispersion. (Spontaneous Electri- 
 city, p. 15.) He also found that his lightning 
 rod was less charged with electricity while im- 
 mediately under a cloud, than when at some 
 distance from it ; and that it acquired more 
 electricity before the rain commenced than 
 afterwards a fact which was also observed by 
 Beccaria. 
 
 These beautiful and important experiments 
 will enable us to comprehend those of M. Pouil- 
 let, which he seems not to have rightly under- 
 stood himself. He placed a cylindrical piece 
 of charcoal in a vertical position, the top of 
 
314 EXPERIMENTS OF POUILLET. 
 
 which was 2^ or 3 inches below a plate of brass 
 that was connected with the condenser. When 
 the upper part of the charcoal was ignited, a 
 current of carbonic acid arose and came in 
 contact with the brass plate, by which the con- 
 denser was positively electrified in a few mi- 
 nutes. By placing the inferior end of the char- 
 coal on the condenser, and igniting the upper 
 end, the condenser was charged with negative 
 electricity. From these experiments Pouillet 
 concluded, that during the combination of oxy- 
 gen with carbon, it gave out positive electricity, 
 while the carbon gave out negative electricity. 
 
 During some of his experiments, both positive 
 and negative electricity were evolved by the com- 
 bustion of charcoal and hydrogen ; from which 
 it would seem to follow, that positive and nega- 
 tive electricity are only plus and minus condi- 
 tions of the same agent ; although this seems 
 not to have been suspected by Pouillet. The 
 following experiments are among the most in- 
 structive which have been recorded by the French 
 philosopher. He caused hydrogen gas to flow out 
 of a glass tube. When it was ignited, a vertical 
 flame was produced, nearly half an inch in 
 breadth, and three inches in height. A coil of 
 platinum wire was employed to conduct the 
 electricity from the flame to the condenser. 
 When the coil was large enough to inclose the 
 flame, and to be about four inches from its 
 
EXPERIMENTS OF POUILLET. 315 
 
 external surface, positive electricity was indi- 
 cated, as in the experiments of Mr. Read, which 
 became more and more intense as the distance 
 diminished, until the coil touched the flame, 
 when nearly all signs of electricity disappeared. 
 Hence it was concluded, that around the flame 
 of hydrogen gas, there is a sort of atmosphere 
 at least 4 inches in thickness, which is always 
 charged with positive electricity. 
 
 Now, it is obvious that aqueous vapour is pro- 
 duced during the combustion of hydrogen gas, 
 constituting an atmosphere above and around the 
 flame ; which vapour gives out positive electricity 
 as proved by Mr. Read. It is also evident, that 
 in the immediate vicinity of the flame, the va- 
 pour cannot be condensed by the platinum coil ; 
 and therefore cannot give out much, if any, 
 electricity. It is for the same reason, that the 
 vapour of the atmosphere gives out but little 
 electricity during the heat of a clear day, which 
 increases in the evening. When Pouillet placed 
 a small coil of platinum wire in the centre of the 
 flame, so that it was enveloped on all sides, and 
 made to communicate with a condenser, the 
 instrument was electrified negatively. This is 
 a thermo-electric phenomenon which has very 
 little connexion with atmospheric electricity, as 
 will be seen hereafter. He found that during 
 the combustion of alcohol, aether, wax, oils, fat, 
 and many vegetable bodies, the same phenomena 
 
316 POUILLET, DE SAUSSURE, AND HARRIS. 
 
 were exhibited as in the experiments with burn- 
 ing hydrogen. (An. de Chim. et de Phys.XXXV. 
 401, et XXX VI. 5.) 
 
 The principal error of M. Pouillet, was in 
 supposing that electricity is never produced by 
 evaporation, unless attended with more or less 
 chemical action that when water was evapo- 
 rated from platinum cups, no electricity was 
 evolved. In addition to the evidence of De 
 Saussure, are the recent experiments of Mr. 
 Harris, who has found that the evaporation of 
 pure water from platinum vessels is attended 
 with a distinct evolution of electricity so that 
 the doctrine of Pouillet cannot be admitted, that 
 atmospheric electricity is wholly supplied by 
 chemical action and the growth of vegetation. It 
 is impossible to conceive that the vast amount 
 of lightning disengaged from aqueous vapour, 
 could be generated by chemical action, which is 
 far more energetic upon the dry land than in the 
 ocean, from which the vapour is obtained : nor 
 can it be maintained that the process by which 
 water is separated from the ocean brine is che- 
 mical ; for I have shown, that it is a mechanical 
 force, which is proportional to temperature. (See 
 Chap. iii. Book 1. and the subsequent examina- 
 tion of the two electric fluids.) 
 
 From the brief history thus presented of at- 
 mospheric electricity, it must be obvious to the 
 ^intelligent reader, that the knowledge hitherto 
 derived from experimental researches, has been 
 
OPINIONS OF LUCRETIUS. 317 
 
 extremely vague and imperfect, and that its re- 
 lations to the caloric of evaporation have scarcely 
 been inquired into. On the other hand, it is 
 equally evident, that if we analyse the pheno- 
 mena of evaporation and condensation, as they 
 are constantly going on before all eyes, we obtain 
 a simple and satisfactory solution of the problem. 
 The fact which was announced by Dalton, that 
 caloric is the only cause of evaporation, taken in 
 connexion with another fact, that aqueous vapour 
 is condensed into rain or hail, ivith a rapidity pro- 
 portional to the amount of lightning, are decisive 
 in regard to the convertibility of caloric into 
 electricity, which, as will be seen hereafter, com- 
 pletely explains the phenomena of hurricanes, 
 tornados, &c. 
 
 The ideas of the ancient Greek philosophers, 
 which were derived from observation without ex- 
 periments, were more in accordance with nature 
 and reason than the hypotheses of modern times. 
 It was maintained by Lucretius, who gives the 
 doctrines of Epicurus, that lightning consisted of 
 fire alone, and that it was derived from the sun. 
 He represents the igneous particles of fluid as 
 rushing to a focus, by which concentration they 
 acquire the power of instantaneously fusing me- 
 tals.* (De Natura Rerum, Lib. vi. 108.) That 
 
 * He further states, that it is by the meeting of warm and cold 
 air that they are elicited. It is not very obvious how this subtile 
 matter becomes concentrated into a ball of fire on quitting a mass 
 of vapour ; but such is the fact. It is equally difficult to explain 
 
318 OPINION OF BACON. 
 
 this subtile agent is greatly concentrated on quit- 
 ting a mass of vapour in the form of light- 
 ning, is proved by the fact, that a single spark 
 or flash, causes a precipitation of rain over se- 
 veral thousand acres and that it is a material 
 agent, is demonstrated by its mechanical force 
 in rending rocks, buildings, ships, trees, &c. as 
 effectually as if it were a ball of iron discharged 
 from a cannon. 
 
 Lord Bacon supposed, that the greatest heat 
 in nature was that of lightning, from its instan- 
 taneous power of fusing metals, and of igniting 
 other combustibles. As an additional proof that 
 it is a concentrated exhibition of the igneous 
 principle, it may be observed, that when solar 
 caloric is greatly concentrated by a large burn- 
 ing-glass, it fuses, ignites, and volatilizes the 
 hardest gems in a few moments, thus approxi- 
 mating the character of lightning. But since 
 
 how the electricity of a Leyden battery is condensed on present- 
 ing a metallic knob. Perhaps it is owing to all its particles 
 being attracted to the centre of the knob or that the igneous 
 matter of vapour is attracted to the centre of whatever object 
 excites it. It is worthy of notice, that when a metallic point is 
 presented to the knob of a Leyden bottle charged with electricity, 
 the igneous fluid is drawn off gradually, and no visible spark is 
 produced : but when a larger mass of matter is presented, as a 
 knob of brass, or the knuckle, it is all withdrawn at once. Thus 
 mountains, clouds, buildings, &c. attract a large portion of the 
 electric fluid at the same moment, producing a concentrated 
 spark many hundred thousand times larger than one from a 
 Leyden jar. 
 
SIR JOHN HERSCHEL. 
 
 the time of Bacon, philosophers have discovered, 
 that electricity can produce all the above effects 
 without being a material fluid others, that it 
 proceeds from the earth to the clouds, and not 
 from atmospheric vapour to the earth while 
 others again resolve all its mechanical and heat- 
 ing properties into undulations of the " unknown 
 aether." 
 
 When I come to treat of Voltaic phenomena, 
 it will be seen that the power of electricity to 
 produce a shock, and the velocity with which it 
 passes through conductors, are modified by the 
 various modes of its disengagement from ponder- 
 able matter. 
 
 With his well known sagacity, Sir John Her- 
 schel has laid down some admirable rules for 
 the purpose of facilitating our research, among a 
 great mass of assembled facts, for their common 
 cause. They are substantially the following : 
 
 1 . Invariable connexion of the cause and effect, 
 unless prevented by some counteracting cause. 
 
 2. Invariable negation of the effect, with ab- 
 sence of the cause, unless some other cause be 
 capable of producing the same effect. 
 
 3. Increase or diminution of the effect, with 
 the increased or diminished intensity of the 
 cause in cases which admit of increase and di- 
 minution. 
 
 4. Proportionality of the effect to its cause in 
 all cases of direct unimpeded action. 
 
320 SIR JOHN HERSCHEL. 
 
 5. Reversal of the effect with that of the cause. 
 He adds, that we are not to deny the existence 
 of a cause in favour of which we have a unani- 
 mous agreement of strong analogies, though it 
 may not be apparent how such a cause produces 
 the effect. (Discourse on the Study of Natural 
 Philosophy, section 145 and 148.) 
 
 The above general rules apply with great 
 force to the connexion between temperature and 
 the phenomena of lightning. 
 
 1. It has been shewn, in accordance with the 
 first rule, that a certain range of solar tempera- 
 ture is indispensable to the existence of lightning, 
 which are therefore invariably connected together 
 as antecedent and consequence, or cause and effect. 
 
 2. It has also been shewn, in conformity with 
 the second rule, that in the absence of condensa- 
 tion and precipitation of vapour there is no light- 
 ning : 
 
 3. That other things being equal, the amount 
 of evaporation, condensation, and lightning, are 
 increased and diminished with the augmentation 
 and decrease of temperature. 
 
 4. That the quantity and splendour of this 
 wonderful meteor are proportional to the accumu- 
 lation and intensity of solar heat, from the equator 
 to the poles and 
 
 5. That the effect is reversed on passing from 
 the regions of perpetual cold to the torrid zone, 
 and from winter to summer. 
 
SIR JOHN HERSCHEL. 321 
 
 In reference to the 3rd and 4th rules it may 
 be observed, that the quantity of precipitation 
 and lightning are greatly diminished, cceteris pa- 
 ribus, by uniformity of temperature, as in the 
 tropical portions of the sea far from land, and 
 other parts of the world where the winds blow 
 long in one direction ; whereas changes of tem- 
 perature are indispensable to the condensation 
 of atmospheric vapour, and to the evolution of 
 its caloric in the concentrated form of lightning. 
 
 CHAPTER II. 
 
 Theory of Winds. 
 
 Of all the subdivisions of General Philosophy, there is none 
 so little entitled to the name of science as Meteorology. 
 
 MASON GOOD. 
 
 THAT the reader may comprehend more fully 
 the connexion between caloric, evaporation, and 
 atmospheric electricity, it becomes necessary to 
 present a cursory view of atmospheric currents 
 generally. 
 
 The unequal distribution of solar caloric over 
 the earth's surface, together with its annual and 
 diurnal revolutions, determine the periodical 
 movements of the atmosphere which surrounds it. 
 
 Y 
 
322 THEORY OF WINDS. 
 
 It has been long known, that there are three 
 great currents of the aerial ocean, by which it is 
 kept in a state of perpetual circulation : one from 
 the polar regions towards the equator, which is 
 an under current ; another from the equator to 
 the poles, which is an upper current ; and a 
 third, called the great equatorial current, or trade 
 wind, which blows from east to west around the 
 globe for about 30 on each side of the equator ; 
 thus sweeping over the whole extent of the tro- 
 pical regions, which are upwards of 3000 miles 
 in width. 
 
 There is another general wind, which blows 
 from west to east in the middle and higher lati- 
 tudes, about two-thirds of the year in the 
 northern hemisphere ; while in the middle lati- 
 tudes of the southern hemisphere, where there is 
 little or no land, it is said to be nearly as uniform 
 as the trade wind. Dr. Hadley, and after him 
 Dr. Franklin, attributed these general currents 
 to the following causes. " The air between the 
 tropics, being constantly heated and rarefied by 
 the vertical sun, rises, when its place is supplied 
 by air from the higher and polar latitudes, which, 
 coming from parts that had less diurnal motion, 
 and not suddenly acquiring the swifter motion 
 of the equatorial regions, becomes an east wind ; 
 the earth moving from west to east, and slipping 
 under the air*" (See Franklin's Works, vol. iii. 
 p. 236.) 
 
THEORY OF WINDS. 323 
 
 These general views have been greatly ex- 
 tended by Dr. Dalton and Mr. Daniel!. The 
 first of these philosophers observes, that the diur- 
 nal motion of the earth at the equator is 1040 miles 
 per hour, and diminishes gradually on to the 
 poles, where it is nothing. (Meteorological Es- 
 says, page 88.) And Mr. Daniell has demon- 
 strated in the most conclusive manner, that from 
 the greater density of the polar atmosphere than 
 the equatorial, its height is proportionably less ; 
 so that the expanded air between the tropics 
 must rise and flow towards the poles as an upper 
 current. Before rising, it has acquired the tro- 
 pical motion of the earth from west to east, 
 which it retains, until descending in higher lati- 
 tudes, where the earth's diurnal motion is less, 
 it mixes with the lower air, and gives it a west- 
 erly direction. 
 
 The force and direction of the trade winds are 
 influenced by the proximity of islands and con- 
 tinents. Along the western side of Africa, their 
 direction is reversed. To the distance seaward 
 of about 300 miles, they blow towards the heated 
 land : they are reversed in a similar manner in 
 the Pacific, west of South America. When the 
 sun is in the northern tropic, they extend several 
 degrees farther north than during our winter ; 
 and when the sun is south of the equator, they 
 prevail farther south. 
 - There is a tract corresponding with the iso- 
 
324 THEORY OF WINDS. 
 
 thermal division of the globe, which, as will be 
 seen hereafter, is the magnetic equator, where 
 the great polar currents from the north and 
 south meet and neutralize each other. They are 
 characterized by a constant succession of irre- 
 gular winds and calms, with storms of thunder, 
 lightning, and rain : they are termed by seamen 
 the swamps, or rainy latitudes; and are ex- 
 tremely sultry, owing to the immense quantities 
 of caloric given out during the condensation of 
 so much aqueous vapour. 
 
 During winter, in the northern hemisphere, 
 the polar latitudes being deprived of the sun's 
 rays, while the tropical parallels are heated, we 
 have a predominance of northerly winds, the 
 dense polar air pressing towards the tropics, to 
 restore the equilibrium ; while the greater ve- 
 locity of the middle and tropical than that of the 
 northern latitudes, causes a deflection of the 
 polar currents to the south-west and west, making 
 north-east and east winds, which almost uni- 
 formly succeed to north winds, and continue 
 blowing until an equilibrium is established be- 
 tween the higher and middle latitudes. In the 
 mean time, under the influence of the solar 
 beams, the land soon becomes more heated than 
 the ocean, even south of it, which causes a south 
 wind until the equilibrium is restored between 
 the sea and land atmosphere. 
 
 During summer, in the United States, south- 
 
THEORY OF WINDS. 325 
 
 westerly winds predominate, and north-easterly 
 winds during winter, especially if the winter be 
 excessively rigorous. The same thing is true of 
 India, China, and Arabia. They are heated 
 during summer, and the atmosphere over them is 
 rarefied, which causes the air to flow in upon 
 them from the tropical seas, when it is deflected 
 to the east, by passing from latitudes that move 
 rapidly, to those which move more slowly. This 
 is what seamen term the south-west monsoon. 
 
 When the sun is south of the equator, the air 
 moves from the northern land, which is cooled 
 down, towards the equator, that has a swifter 
 motion, thus causing the ntirth-east monsoon, 
 which corresponds with the north-east wind of 
 the North American cold season. It was sup- 
 posed by Volney, that the prevailing south-west 
 wind of the Mississippi valley was a recoil of the 
 tropical trade wind, deflected by the Andes of 
 Mexico ; but the fact which he states, of its 
 crossing the Alleghany Mountains, and advancing 
 north-eastward, as far as Montreal and Quebec, 
 is sufficient to prove, that it must be owing to a 
 cause far more extensive and general in its ope- 
 ration than mountain ranges. 
 
 During summer in North America, the land 
 is greatly heated, and the air presses from the 
 Atlantic ocean, especially during the day, caus- 
 ing a sea breeze ; when from the south, it is 
 changed into a south-west wind, by passing from 
 
326 THEORY OF WINDS. 
 
 latitudes that revolve at the rate of 8 or 9 hundred 
 miles per hour, to those which move only 6 or 7 
 hundred miles per hour.* The south west and 
 north east are the prevalent winds in the United 
 States and the west of Europe. In Great Britain 
 they blow about 300 days in the year. 
 
 It has been observed in the United States of 
 America, that regular winds generally follow the 
 sun, exhibiting a tolerably uniform succession of 
 circuits from left to right, and blowing from all 
 points of the compass within a few days. For 
 example, the ordinary succession of winds is, 
 first, from the north ; next, from the north-east, 
 then from the east ; south-east ; south ; south- 
 west ; west ; north-west, and so on, in pretty 
 regular succession, and rarely, if ever, perform- 
 ing an entire circuit in the opposite direction. 
 As the greater portion of the United States is 
 more heated by the sun than the ocean, even 
 south of them, (because the surface is stationary,) 
 and for a longer time, the wind blows from the 
 south-west a greater number of days than from 
 any other quarter. At the same time, it is worthy 
 of notice, that during extremely cold winters, the 
 
 * It is the meeting of this wind, charged with aqueous vapour 
 from the ocean, with the colder north and north-east currents, 
 which causes vast precipitations of rain in the United States, 
 during the latter part of summer and beginning of autumn, 
 attended with the most fearful displays of thunder and lightning, 
 when extensive hurricanes sweep the Gulf of Mexico and the 
 southern portions of the Union. 
 
THEORY OF WINDS. 327 
 
 wind has continued from a month to six weeks 
 from the northern points of the compass.* 
 
 In addition to the above winds, opposite cur* 
 rents frequently meet in the higher atmosphere, 
 which are not observed at the earth's surface, and 
 thus cause precipitations of rain. A striking 
 proof of this was witnessed on the 4th of July, 
 
 * According to observations made at sixteen different military 
 posts in the United States, from lat. 35 to the northern extre- 
 mity of the Republic, including those of Sir Edward Parry, in 
 the Polar regions, winds prevail from the south-west, west, and 
 north-west, nearly two-thirds of the year; or in the ratio of 
 15830 to 8785, while the northerly winds are to the southerly 
 as 1190 to 1231. In the southern portion of the Union below 
 35, eastern winds predominate over western in the ratio of 3102 
 to 1717 ; from which it would seem that they are subject to the 
 general influence that governs the regular trade winds of the 
 tropics. In the same section of country, northern winds are to 
 southern in the ratio of 508 to 721. 
 
 As Cincinnati, lat. 39 06', affords a tolerable specimen of 
 the Ohio valley generally, it may be stated that western winds 
 prevail over eastern in the ratio of 631 to 325 ; while at New 
 York, lat. 41, they are as 580 to 279. They are also nearly in 
 the same proportions throughout the Atlantic Ocean, between 
 North America and Western Europe. (See Darby's View of the 
 United States.) 
 
 Mr. Daniell states, that upon an average of ten years, westerly 
 winds exceed easterly in the ratio of 225 to 140 in Great Britain ; 
 while northerly winds are to southerly, as 192 to 173. (Me- 
 teorological Essays, p. 114.) During spring, the prevalent wind 
 is from the dry, cold, north-eastern regions of Russia, Sweden, 
 and Denmark. Throughout the Mediterranean, Egypt, Palestine, 
 and the south of Europe generally, the wind blows nine months 
 in the year from the northern points of the compass ; because 
 situated between the cold regions of Arctic Europe and Asia, 
 and the burning plains of Africa, where the temperature is 
 100 to 115 F. in the shade. 
 
328 THEORY OF WINDS. 
 
 1834, at New York. When Robertson, the aero- 
 naut, ascended in a balloon from Castle Garden, 
 the wind was from the east, which carried him 
 westward across the Hudson river. At an ele- 
 vation of about 4000 feet above the earth he 
 disappeared in a mist or cloud, when he met 
 with a counter current from the west, that brought 
 him back over the city, and landed him ten 
 miles to the eastward on Long Island. It was 
 quite evident that the canopy of clouds, which 
 overspread the city and country in the afternoon, 
 was condensed by the colder upper current from 
 the west. 
 
 From the 7th until the 10th of July (1834,) the 
 heat was excessive, ranging from 86 to 96 F. 
 in the shade, while the wind was from the south- 
 east. On the 10th, about noon, the wind pre- 
 vailed from the west, condensing the vapour of 
 the heated air into floods of rain, attended with 
 violent thunder and lightning. It is thus that 
 a land wind, which usually brings fair weather, 
 causes precipitation, by meeting with a southern 
 wind saturated with aqueous vapour. It is highly 
 probable, that at all times when rain attends a 
 southern wind, and when the land temperature 
 exceeds that of the sea, precipitation is owing to 
 the prevalence of a colder upper current from 
 an opposite direction. 
 
 What can be more impressive and sublime than 
 those great movements of the atmosphere, by 
 which the waters of the ocean are wafted over 
 
THEORY OF WINDS. 329 
 
 continents and islands ; pestilential vapours dis- 
 persed ; the face of nature refreshed, and adorned 
 with living robes of surpassing beauty? By 
 sinking into the earth, they acquire the properties 
 of the various mineral beds through which they 
 pass, and again bubble up in fountains of deli- 
 cious water for the sustenance of animal and 
 vegetable life.* 
 
 If the whole earth were of uniform surface and 
 elevation, its temperature would be the same in 
 given latitudes and seasons, and the currents of 
 the atmosphere would present a succession of 
 
 * By the agency of warm southerly winds immense masses 
 of aqueous vapour are transported from the ocean over North 
 America, to the higher latitudes, where, meeting with a body of 
 air from the frozen regions, it is condensed into cold rains, or 
 extensive falls of snow, according to the season of the year; 
 while the northern atmosphere is thus warmed by the disengage- 
 ment of caloric from southern vapour. 
 
 If southern winds prevail for a long time from the ocean during 
 autumn, until the atmosphere is saturated with vapour over a 
 large portion of the northern hemisphere, without meeting with a 
 mass of northern air to condense it, the commencement of winter is 
 marked by an extensive fall of snow, from a foot to eighteen 
 inches, or even three feet in depth, over which the polar winds 
 pass without being warmed, to the lower latitudes, causing 
 excessive winters. This is one reason why during some winters 
 in the United States the temperature occasionally falls from 30 
 to 40 lower than during others. After such a fall of snow the 
 wind has prevailed, for six weeks together, from the northern 
 points of the compass, as in the winter of 1779 and 80, and 
 about the same length of time during the winter of 1834 and 
 35, when the mercury fell from 20 to 40, from latitude 
 35 to 43. I shall have more to say on this subject in another 
 place. 
 
330 THEORY OF WINDS. 
 
 regular movements. There would be no sudden 
 mixing of winds from opposite quarters, and no 
 lightning nor rapid precipitations of rain, be- 
 cause there would be a regular gradation of tem- 
 perature and density of the atmosphere from the 
 equator to the poles ; but, as the surface of the 
 earth is diversified by land and water, moun- 
 tains and valleys, hills and plains, unequal tem- 
 peratures in the same latitudes and seasons result, 
 causing all those irregular movements in the 
 atmosphere termed variable winds ; and which 
 can never be predicted with unerring certainty 
 until all these modifying circumstances are clas- 
 sified and reduced to general laws. 
 
 Theory of Hurricanes, Hail Storms, Water 
 Spouts, and Tornados. 
 
 Having shewn in the preceding chapter, that 
 lightning is always attended with the condensa- 
 tion of atmospheric vapour, I shall proceed to 
 prove that no violent squall, hurricane, tornado, 
 or water-spout, ever occurs without the sudden con- 
 densation of aqueous vapour; and that caloric in the 
 concentrated form of lightning, is the active spirit 
 of the storm and tempest, which governs all their 
 powerful movements. 
 
 The Typhon, or ru</>wv of the Greek philoso- 
 phers, was a hurricane accompanied with vivid 
 
THEORY OF HURRICANES, ETC. 331 
 
 flashes of lightning, which they called fire, 
 while the tornado was described by the Romans 
 as vortex igne factus, and was identical with 
 the prester, from 7rp?0w, inftammo, meaning a 
 fiery whirlwind. It is evident on the slightest 
 reflection, that violent winds which spring up 
 suddenly, and often immediately after a calm,* 
 cannot possibly be owing directly to the rarefy- 
 ing influence of solar heat, like regular winds, 
 the velocity of which rarely exceeds twenty or 
 thirty miles per hour ; while the tornado moves 
 at the rate of from one hundred to one hundred 
 and twenty miles per hour. It is during the 
 rainy season, that the tropical regions are visited 
 by those dreadful hurricanes, or fiery tempests 
 which tear up trees by their roots, destroying 
 every thing in their resistless course and when 
 rain is precipitated in floods with a rapidity pro- 
 portional to the amount of lightning. Those of 
 the East Indian seas occur during the shifting of 
 the monsoons, and are obviously owing to the 
 condensation of vapour, caused by the meeting 
 of extensive masses of air from opposite quar- 
 ters of different temperatures. The equinoctial 
 storms that sweep over the West Indies, the 
 
 * We often see against some storm 
 
 A silence in the heavens, the rack stand still, 
 The bold winds speechless, and the orb below 
 As hush as death : anon the dreadful thunder 
 Doth rend the region. Hamlet. 
 
332 THEORY OF HURRICANES, ETC. 
 
 gulf of Mexico, and the southern portions of the 
 United States, are also produced in the same 
 way, and are attended by extraordinary floods 
 of rain, with fearful displays of thunder and 
 lightning. An eye witness of the tremendous 
 hurricane which desolated the island of Barba- 
 does on the 10th of August, 1831, informed the 
 author, that it began about ten o'clock at night, 
 with torrents of rain and broad sheets of fire in 
 rapid succession, which threatened to overwhelm 
 the inhabitants in a flood, or sweep them away 
 in a tempest of flame. 
 
 On the other hand, in the tropical portions of 
 the wide Pacific, where the temperature is uni- 
 form, and the winds blow steadily in the same 
 direction, there is but little thunder, lightning, 
 and rain, and no hurricanes. The same is true 
 of the equatorial parts of the Atlantic, which are 
 far from land. It is stated by Capper, in his 
 account of winds and monsoons, that a hurri- 
 cane was never known to occur at St. Helena, 
 situated as it is, nearly midway between Africa 
 and South America. It is near the continents 
 of Asia, Africa, and America, or in the vicinity 
 of large islands, where immense masses of va- 
 pour from the sea, meet with mountains and cold 
 masses of air from the land, that hurricanes of 
 wind, lightning, and rain, are most powerful and 
 frequent, as in the Bay of Bengal, on the coast 
 of Madagascar, Mauritius, &c. In short, there 
 
THEORY OF HURRICANES, ETC. 33.3 
 
 never was a hurricane, tornado, or gale, in any 
 part of the world during the existence of per- 
 fectly dry weather. It is therefore evident, that 
 lightning, and all violent winds, are immediately 
 connected with the rapid condensation of aqueous 
 vapour or steam, which owes its existence to the 
 expansive agency of solar caloric. Even the 
 winter gales so fatal to shipping on the coasts of 
 Great Britain and France, are always attended 
 with copious precipitations of rain or snow, and 
 sometimes with lightning. 
 
 This may be readily understood when it is 
 remembered, that all the water which falls on 
 the earth, existed previously in the atmosphere 
 in the form of steam, that its volume is from 
 1300 to 1500 times that of water, at ordinary 
 temperatures, (and about i 720 times greater at 
 212.) All this steam is confined chiefly to the 
 lower regions of the air, and must necessarily 
 augment its volume in proportion to the quan- 
 tity diffused through it the consequences of 
 which are, that immense vacuums are produced 
 by its condensation, and a violent rush of the 
 surrounding air from different quarters, until an 
 equilibrium is restored. 
 
 Perhaps there is no part of the world, where 
 thunder storms are so frequent as in the Bay of 
 Mexico, and on the borders of the Gulf Stream. 
 It has been said, that of all the vessels in the 
 world, which are annually destroyed by light- 
 
334 THEORY OF HURRICANES, ETC. 
 
 ning, two-thirds have been lost on the tract of 
 the Gulf Stream. 
 
 We may readily comprehend all this when 
 we reflect, that the Gulf Stream is a portion of 
 the great equatorial current, (caused by the trade 
 wind,) which is obstructed by South America, 
 and deflected into the Bay of Mexico, where its 
 temperature is from 70 to 80, according to the 
 season. With its tropical temperature it issues 
 from the Bay of Mexico through the Florida 
 Channel, advancing along the southern coast of 
 the United States, north-eastward to the Banks 
 of Newfoundland, and thence to the western coast 
 of Ireland, until it is lost. For the distance of 
 1500 or 2000 miles its temperature is from 10 to 
 20 higher than that of the ocean on its northern 
 extremity ; the consequence of which is, exten- 
 sive evaporation. The vapour thus formed is 
 perpetually meeting with bodies of cold air, by 
 which it is condensed, causing a succession of 
 vacuums, local storms, water-spouts, &c.* We 
 are informed by seamen, who navigate the At- 
 
 * As many as sixteen water-spouts were seen at the same time 
 by Captain Lawrence on the borders of the Gulf Stream, in 
 Lat. 32 48', when off Charleston, on a voyage from New Orleans 
 to New York in 1834. They are all formed by the sudden con- 
 densation of aqueous vapour, caused by the meeting of opposite 
 currents of air that deflect each other, producing a funnel-shaped 
 cloud, that descends in torrents of fresh, and not salt water, as 
 has been generally supposed. In short, they are what Franklin 
 termed them, whirlwinds at sea. 
 
THEORY OF HURRICANES, ETC. 335 
 
 lantic between the United States and England, 
 that while one vessel encounters a thunder-storm, 
 others enjoy mild breezes within thirty or forty 
 miles of the same place. 
 
 The same general agency, modified by the 
 relative position of land and water, oceanic cur- 
 rents, mountains and valleys, operates to a greater 
 or less extent over all the earth. Off Cape Hat- 
 terass, which is washed by the Gulf Stream, 
 there is a constant succession of gales r which are 
 obviously caused by the mingling of warm and 
 cold air, as seamen always observe a sensible 
 change of temperature on passing the Cape. The 
 same cause renders the Cape of Good Hope a 
 theatre of perpetual war of conflicting tempests, 
 occasioned by the difference of temperature be- 
 tween the great equatorial current, as it doubles 
 the Cape, and the colder water of the Southern 
 Ocean. 
 
 There can be no doubt, that the amount of ca- 
 loric discharged in the form of lightning, during 
 extensive hurricanes, is in proportion to the 
 amount of condensation ; but its intensity or con- 
 centration is often less than during ordinary 
 thunder-storms ; because, during the former, the 
 electric fluid is attracted by a more extensive 
 mass of cloud, and is thus diffused. This also 
 explains why it is that the violence of lightning 
 and thunder usually abate after precipitation 
 becomes general. The electric matter, being 
 
3.30 MISCELLANEOUS PHENOMENA. 
 
 constantly drawn from the transparent aqueous 
 vapour by the extended surface of falling cloud, 
 prevents it from accumulating into a large ball 
 of fire or thunder-bolt, in the same way that a 
 damp atmosphere prevents us from charging the 
 Ley den battery of a common electrical machine. 
 The streaked and forked appearance of ordi- 
 nary lightning are optical illusions, which result 
 from the rapid passage of the electric spark 
 through the air, which makes an impression on 
 the optic nerve that remains during its passage, 
 in the same way that a burning stick when re- 
 volved, presents the appearance of a continuous 
 circle of fire. The fork is owing to a division of 
 the original spark or ball into two or more sparks, 
 which diverge from each other. The zigzag ap- 
 pearance is owing to frequent slight deflections 
 of the spark, as it moves through strata of air, of 
 different densities. Whenever an electric explo- 
 sion takes place near to the spectator, it always 
 presents the appearance of a ball of fire, at- 
 tended by a simultaneous report, like that of 
 artillery. The reason that the report is usually 
 heard many seconds after the flash is seen, is 
 owing to its distance from the point of observa- 
 tion, and to the slowness with which vibrations 
 are propagated through the atmosphere : while 
 its rumbling or prolonged existence is owing to 
 the space over which it passes. The report 
 itself is probably caused by a sudden collapse of 
 
SUMMER GUSTS. 337 
 
 the air as it fills the vacuum produced by the 
 passage of the electric bolt through it ; or by its 
 violent collision against the air, causing a tremour 
 of the atmosphere to the distance of many miles, 
 which is communicated to buildings and other 
 solid bodies. It is likewise probable that the 
 luminosity of the spark is owing to a sudden 
 combustion of air or vapour by so intense a heat. 
 
 It was first observed by Dr. Franklin, that the 
 cold summer gusts of the middle latitudes, gene- 
 rally come from the west ; from which he con- 
 cluded, that they were caused by a descent of 
 cold air from the upper current of the atmos- 
 phere, on its passage from the equatorial to the 
 polar latitudes. That this is chiefly the cause 
 of our prevalent west winds, during about two- 
 thirds of the year in the middle latitudes, is ob- 
 vious from what was stated, page 322. 
 
 That this is also the true mode of accounting 
 for many of our thunder storms, would appear 
 reasonable from the following considerations. 
 They occur during the most sultry weather, and 
 hottest time of the day; generally the afternoon, 
 when the lower atmosphere is greatly rarefied, 
 so as to favour a descent of cold air from above, 
 which rapidly condenses the transparent vapour 
 of the lower atmosphere into floods of rain, that 
 are often attended with hail, and always with a 
 great reduction of temperature. In this way 
 clouds are often formed suddenly, the whole sky 
 
338 BREAKING OF CLOUDS. 
 
 becoming obscured by dense black vapour, ac- 
 companied with thunder and lightning, violent 
 winds, and copious precipitations of rain. Dur- 
 ing such storms, more vapour is condensed into 
 rain in twenty or thirty minutes, than usually 
 falls during a whole day, or even a week, when 
 there is no lightning. All the phenomena par- 
 take of the violence which characterizes the 
 electric fluid when greatly accumulated. 
 
 Lord Bacon observes in his Natural History of 
 Winds, that " tornados are caused by the sud- 
 den breaking of clouds ," by which he meant those 
 rapid precipitations of rain that accompany 
 lightning and thunder. He also observes, that 
 " when it lightens in a clear sky, winds and rain 
 are at hand from the quarter where it lightens : 
 but if it lightens in different quarters, there will 
 follow cruel and horrid tempests." He might 
 have added, that they have already begun in 
 the places where the lightning is seen. 
 
 Hail Storms. 
 
 On the subject of hail storms, which are inti- 
 mately related to whirlwinds, water-spouts, &c. 
 much learning and ingenuity have been ex- 
 pended since the days of Franklin, without any 
 satisfactory explanation of their cause. 
 
 The celebrated Volta, supposed that they were 
 
HAIL STORMS. 339 
 
 produced by " a highly electrical condition of 
 the atmosphere that the frozen masses were 
 kept in a state of reciprocating motion between 
 two clouds, oppositely charged with electricity, 
 until the mass rendered the force of gravity pre- 
 dominant ; or until the electric tension of the 
 cloud was exhausted by mutual reaction." In 
 his report on the present state of Meteorology, 
 Professor Forbes observes, that no better solution 
 has yet been offered to the world. (Transactions 
 of Jhe British Association, vol. i. 1832.) 
 
 The leading facts connected with hail storms 
 are the following : 
 
 1 . They are generally confined to the middle 
 latitudes, where masses of cold air, from the 
 polar regions, meet with warmer air from the 
 tropical latitudes, loaded with aqueous vapour. 
 When such currents encounter each other at the 
 usual height of spring and summer clouds, the 
 vapour of the warm air is condensed into cold 
 rains, or showers of small hail, but without much 
 lightning or violent wind : whereas all the most 
 destructive hail storms are accompanied with 
 tremendous flashes of lightning, and often with 
 fearful whirlwinds, or tornados. 
 
 2. They occur chiefly during warm weather 
 in the United States, when the lower atmosphere 
 is* full of vapour, and heated for several hundred 
 miles to the temperature of 80, and sometimes 
 90 F. 
 
340 HAIL STORMS. 
 
 3. They usually run in veins of limited extent, 
 and are most frequent in level districts, especi- 
 ally such as are hemmed in by mountains, as in 
 the South of France, where they are very de- 
 structive to the crops. 
 
 4. They are often attended with the sudden 
 precipitation of immense quantities of ice, that 
 descends in large globular masses ; and always 
 with a great reduction of temperature. 
 
 Several of the above facts are exceedingly 
 difficult to explain, without admitting the hypo- 
 thesis of Franklin in regard to the cause of 
 thunder gusts, that is, a sudden descent of cold 
 air from the upper regions, by which the vapour 
 of the lower atmosphere is rapidly condensed 
 and congealed into globules of ice. 
 
 In opposition to this view of the subject, it is 
 maintained by Dr. Thomson, that the upper air 
 cannot descend without undergoing condensa- 
 tion, and giving out a portion of its latent caloric, 
 which he thinks would prevent it from cooling 
 the atmosphere. (Treatise on Heat and Elec- 
 tricity, p. 129.) Whatever may be the just weight 
 of this objection, the fact is certain, that aqueous 
 vapour is suddenly and rapidly congealed by 
 very cold air ; by which the temperature of the 
 lower atmosphere is often reduced from 80 or 
 90 down to 40 F. within a few minutes, during 
 extensive and violent hail storms. 
 
HAIL STORMS. 341 
 
 It is also certain, that a vacuum must be 
 formed in the lower atmosphere proportional to 
 the volume of vapour thus suddenly condensed ; 
 the extent of which may be estimated from the 
 vast quantities of hail that are occasionally pre- 
 cipitated in a few minutes, amounting to a depth 
 of nine inches in as many minutes, according to 
 M. Pouillet. The formation of such vacuums is 
 always attended by a rush of air from opposite 
 quarters, creating a gyratory or whirling motion, 
 the force of which is in proportion to the extent 
 of the vacuum and the rapidity of its formation. 
 That the reader may perceive the more readily 
 how intimate is the connexion between lightning, 
 the condensation of vapour, hail storms, and 
 whirlwinds, it may be proper to present a brief 
 account of a few thunder storms which occurred 
 recently in Great Britain : 
 
 On the I Oth of August, 1 835, Durham was visited 
 by a violent whirlwind, accompanied with inces- 
 sant lightning and thunder. At 7 o'clock, p. M. a 
 most vivid flash of lightning struck the Cathe- 
 dral, and hurled down an immense mass of stone, 
 that killed two of a party of students, who at the 
 moment fled from the interior of the Cathedral. 
 
 " On the same day Chesterfield was visited 
 by a violent storm of thunder, lightning, rain, 
 and hail. A large ball of fire fell in the Com- 
 mercial-inn yard, where there was an accumula- 
 
342 LIGHTNING, RAIN, HAIL, 
 
 tion of water, splashing it in all directions into 
 spray, which for a moment seemed to be enve- 
 loped in flames. 
 
 " Many such storms occurred about the same 
 time in different parts of England, Scotland, and 
 Ireland. On the 10th of June, about 3 o'clock, 
 there was a storm of lightning, thunder, and 
 hail, at Dumfries, and at Ardach on the fol- 
 lowing day, there was a violent thunder storm, 
 where the hail was two feet in depth in some 
 places, and remained on the ground for twenty- 
 four hours. 
 
 " At Sheffield, during a thunder storm, the 
 electric fluid entered the works of Mr. Ellin, and 
 struck a pile of ivory handled knives, the blades 
 of which were fused into one mass, and splitting 
 off the hafts in a singular manner. Twelve 
 individuals were thrown down, who imagined 
 that the boiler of a steam engine in the room had 
 bursted.* 
 
 " On the 6th of June, forty-two head of cattle 
 
 * It is related in some of the older books on Natural Philo- 
 sophy, that Erfurt, a small city of Germany, was struck by 
 lightning during a storm, in forty-two different places. Seven 
 persons were killed, and three houses set on fire, which were 
 quenched by the rain, that fell in torrents. 
 
 On the 15th of August, 1836, twenty-eight houses were set on 
 fire by lightning in the town of Grundelbruch : while at Villexon, 
 nineteen dwellings were consumed about the same time, during^ 
 thunder storm, attended with hail and a tornado. (Galignani's 
 Messenger.) 
 
AND VIOLENT WINDS. 343 
 
 were killed by lightning in one field, at Johns- 
 town, near Tuller. Some had their heads and 
 horns burnt, and some their shoulders. On the 
 lands of Mr. Lynham, at the hill of Talloght, 
 eighteen cattle, twenty-three sheep, and a goat 
 were also killed by lightning." (Bell's Weekly 
 Messenger, June 14, 1835.) 
 
 Tornados of the United States. 
 
 It was observed by Lord Bacon, that " all tor- 
 nados or great whirlwinds have a manifest pre- 
 cipitous motion, or darting downwards more than 
 other winds, so that they seem to fall like tor- 
 rents, and run as it were in channels." 
 
 Such tornados are remarkably frequent in the 
 United States during hot sultry weather, and 
 are attended with the most striking displays of 
 electrical phenomena; always with rapid con- 
 densations of vapour, and often with enormous 
 quantities of ice. They generally run in narrow 
 veins from 100 yards to half a mile wide ; while 
 the equinoctial hurricanes of the Southern states, 
 like those of the tropics, sweep over a vast extent 
 of surface, and are rarely if ever accompanied 
 with hail. The tornado is sometimes attended 
 by a rapid succession of lightning ; at other 
 times it presents the appearance of an inverted 
 fiery pyramid, from which is heard a continuous 
 
344 TORNADOS WITH HAIL 
 
 roll or deep roar of thunder, like that of a heavy 
 unremitted cannonade, the sound of which is 
 greatly modified and obscured by the noise of 
 the raging wind, crashing of buildings, falling 
 timber, &c. 
 
 The whirlwind which destroyed a large por- 
 tion of New Brunswick, in the state of New 
 Jersey, on the 19th of June, 1835, presented 
 many of the above phenomena. Those who 
 witnessed its commencement, observed the for- 
 mation of several inverted cones of dense black 
 vapour, which descended from the upper regions. 
 Dr. Lewis Beck describes one of these " as re- 
 sembling in appearance the eruption of a volcano, 
 which produced the impression, at a distance, that 
 some large building had been set on fire by light- 
 ning, a vivid flash or two of which had preceded 
 the formation of the cones. But in a few minutes 
 the dense column was dissipated, when another 
 black and well defined cone was formed, which 
 remained stationary for a short time, and then 
 gave place to the eruptory appearance and gy- 
 ratory movement that characterized the other. 
 The first occurred about three miles west of New 
 Brunswick. But when the second movement 
 commenced, a dense black cloud overshadowed 
 the city. Slight, but distinct explosions were 
 heard from the column in rapid succession, like 
 the bluffing of sails. Volumes of smoke and 
 flame were thought to be issuing forth, and 
 
IN THE UNITED STATES. 345 
 
 rolling over in various directions, when the idea 
 of an extensive and rapid conflagration was sug- 
 gested. The alarm bells were rung, and the 
 firemen repaired to their engines. But while all 
 eyes were directed to the black and dreadful 
 column that was approaching, no one could fix 
 upon the exact spot to which efforts should be 
 directed. This uncertainty was soon removed 
 by the desolating progress of the whirlwind 
 through the city, prostrating houses, and waft- 
 ing heavy beams of timber to a great distance." 
 Like most tornados, it was attended with hail, as 
 well as rain. The width of its tract varied from 
 100 feet to 200 yards, in the neighbourhood of 
 New Brunswick ; while three miles eastward it 
 was half a mile wide. A writer in the New 
 York Times states, that on the banks of the 
 Rariton, for 1000 yards, vegetation was scathed, 
 as if a flame had passed quickly over it. 
 
 Many other similar storms desolated different 
 portions of the Union about the same time. 
 " Late in June, Lynchburg, in Virginia, was vi- 
 sited by a tremendous whirlwind and tempest of 
 hail, which was preceded for several minutes by 
 a monotonous rumbling sound, resembling the 
 bass tones of distant thunder ; or the deep roll 
 of the muffled drum ; and reminding us of the 
 ominous notes which precede an earthquake." 
 (Lynchburg Virginian.) Dense black clouds are 
 described as pouring forth immense masses of 
 
34(> A TORNADO WITH SNOW. 
 
 ice, and so darkening the air, that houses within 
 a few paces were totally invisible. 
 
 During the summer of 1834, which was un- 
 usually sultry, tornados and hail storms of li- 
 mited extent, visited almost every state in the 
 Union, from Maine to Louisiana ; several of them 
 attended with great loss of lives and property. 
 In most cases, they pursued a course from west 
 to east. 
 
 About the 20th of March, 1832, a tornado oc- 
 curred in the southern portion of Tennessee, lat. 
 35 N. which differed in some respects from any 
 of the preceding. 
 
 After several remarkably warm days for the 
 season, accompanied with a southerly wind, a 
 tornado came on suddenly, without the slightest 
 warning, about seven o'clock, P.M. It excited 
 great astonishment, as the whole day had been 
 warm, serene, and clear, with the exception of 
 a slight haziness, up to the moment when the 
 crashing noise of falling timber announced the 
 approaching storm from the west. The tempe- 
 rature was immediately reduced from about 70, 
 to several degrees below 32 F. and attended 
 with a rapid fall of snow, which continued for 
 several hours; but the tornado blew with vio- 
 lence only about ten minutes. The next morn- 
 ing, the wind was cold and north westerly, and 
 continued northerly for two days. 
 
 This storm seems to have been owing to the 
 
GREAT COLDNESS IN CUBA. 347 
 
 prevalence of a cold upper current from the 
 north, which met and mingled with the warm 
 southern air, and suddenly congealed its vapour 
 into snow. It had not the local character of the 
 summer tornado ; for it was followed by great 
 cold over a large extent of country. 
 
 I shall close this imperfect history of thunder 
 storms with the account of an extraordinary and 
 sudden coldness which occurred in the island of 
 Cuba, on the 24th of May, 1809, that was evi- 
 dently caused by a descent of air from the upper 
 regions. 
 
 Cornelius Roberts, a sugar and coffee planter, 
 who resided forty years on the island, informed 
 the author, " that after a hurricane had been 
 blowing from the south east and south, from the 
 22nd, until eleven o'clock, A.M. of the 24th, a 
 calm followed for an hour, when the wind pre- 
 vailed from the north west. At the same time* 
 the atmosphere became extremely dark, like 
 night, accompanied with a roaring in the air, 
 tremour of the earth, and intense cold. Every- 
 thing green was killed, and became black, as if 
 a fire had passed over the country for several 
 miles in breadth, and about sixty miles in 
 length :" which proves that a mass of air may 
 descend from above and refrigerate the lower 
 atmosphere of the tropical regions, as in the 
 middle latitudes, though such a phenomenon is 
 extremely rare. 
 
348 
 
 CHAPTER III. 
 
 Barometer. 
 
 IT has been long known that the fluctuations of 
 the barometer are intimately connected with all 
 the phenomena of meteorology ; that during 
 winter, in the middle and higher latitudes, its 
 depressions are followed with rain, snow, and 
 tempestuous weather ; while its rising is accom- 
 panied with cold, frosty, and dry weather ; and 
 that during summer its falling forebodes storms 
 of thunder, lightning, and rain, which are often 
 attended with violent hurricanes ; while its rising 
 indicates clear and serene weather. Yet the 
 theory of its variations has never been clearly 
 reduced to the simplicity of established prin- 
 ciples. Without stopping to examine the relative 
 merits of those who have devoted their attention 
 to this difficult and important problem, it may 
 be observed without injustice to any, that we 
 are chiefly indebted to the labours of Dr. Dalton 
 for the true mode of investigating it. 
 
 The most important facts connected with the 
 barometer may be reduced to the following pro- 
 positions : 
 
 1 . The mean height of the mercurial column at 
 
BAROMETER. 349 
 
 the level of the sea, is the same all over the earth, 
 amounting to the average of about thirty inches. 
 
 2. The density or specific gravity of the atmos- 
 phere, increases gradually from the equator to the 
 regions of loivest mean temperature, corresponding 
 with the decrease of temperature ; the consequence 
 of which is, that the height of the atmosphere must 
 diminish from the equator to the poles. 
 
 3. Within, the tropics, the temperature is always 
 nearly the same : the range of the barometer is also 
 small, varying from two lines to a quarter of an 
 inch. 
 
 4. The range of temperature augments from the 
 equator to the regions of maximum cold : the vari- 
 ation of the barometer augments in a corresponding 
 ratio, amounting to about three inches in the 
 coldest latitudes. 
 
 The range of temperature is much greater in 
 North America than in the same latitudes of 
 Europe, as will appear from the following facts. 
 During the winter of 1831 and 32, the thermome- 
 ter fell to -- 20 at Florence, in the State of Ala- 
 bamo, lat. 35 N. and 40 at Plattsburg, lat. 
 44, where it sometimes rises to 95, and even 
 100 during summer, making its extreme annual 
 range from 130 to 140 F.* The diurnal variation 
 
 * It is however but seldom, that the temperature falls below 
 in the States, south of Philadelphia and New York ; so that 
 the usual annual range of temperature does not much exceed 
 that of England, which is about 80, according to Mr. Daniell ; 
 
.350 BAROMETER. 
 
 is also very great, as the thermometer often rises 
 to 90 in September and October, during the 
 hottest part of the day, and falls below 32 at 
 night, making the daily range of temperature 
 60 F. 
 
 Still more extraordinary are the changes from 
 heat to cold in those extensive regions of North 
 America beyond the limits of the United States, 
 which have been explored by Scoresby, Parry, 
 Franklin, Ross, and other British navigators. 
 We are informed by Captain Back, that on the 
 17th of January, 1834, the thermometer stood 
 70 F. at 6 A. M. on the Great Slave Lake, 
 lat. 62 46' ; but rose to 45 in the afternoon of the 
 same day, making a diurnal range of 1 15. He 
 also states, that on the preceding day, the tem- 
 perature rose to 52 ; while the long summer days 
 were often oppressively warm. Hence it is, that 
 as we approach the polar regions, we find the 
 winds so irregular and variable, coinciding with 
 
 that is, from 11 to 90. Hence it is, that the mean range of 
 the barometer is about the same in Great Britain that it is in the 
 middle States of America, as observed by Dr. Dalton forty years 
 ago. Perhaps there is no part of the world where the fluctua- 
 tions of temperature are more frequent than in England; the 
 reason of which is obvious from its insular and geographical 
 position, being situated about midway between the burning 
 plains of Africa to the south, and the frozen regions of the 
 north ; while on the east and north east it is influenced by Sweden, 
 Poland, Russia, and the cold elevated plains of Tartary ; and 
 by the Atlantic ocean on the west ; all of which contribute their 
 share successively in forming the climate of Britain. 
 
BAROMETER. 351 
 
 the frequent changes in the density of the atmos- 
 phere, and consequent fluctuations of the baro- 
 meter. 
 
 5. Corresponding with the foregoing facts, the 
 barometer rises to the greatest height during cold 
 northerly winds in the middle latitudes, and falls 
 during warm southerly winds. That is, a mass 
 of air from the torrid zone is specifically lighter 
 than one from the polar regions, and must cause 
 a proportional fall of the mercurial column, until 
 the equilibrium is restored. 
 
 But in addition to the immediate agency of 
 temperature in modifying the specific gravity of 
 the atmosphere, the amount of aqueous vapour 
 diffused through it exerts a material influence. 
 It has been already shewn, that the quantity of 
 vapour in the atmosphere, c&teris paribus, is 
 proportional to temperature, the greater part of 
 which is confined to its lower strata, (within 
 two or three miles of the earth's surface) ; and 
 that at the temperature of 80 F., it is capable of 
 containing an amount of vapour equal to the 
 pressure of an inch of mercury, or ^th of its 
 whole weight. If, then, we take the estimate of 
 Gay Lussac, that the specific gravity of aqueous 
 vapour is less than that of air at the same tem- 
 perature, in the ratio of six to ten, it is evident, 
 that the specific gravity of the atmosphere must 
 be diminished in proportion to the quantity of 
 vapour diffused through it. Hence it is, that 
 
352 BAROMETER. 
 
 warm southerly winds, which have been ex- 
 panded by heat and saturated with vapour, cause 
 the barometer to fall. It also follows, that as 
 rains are supplied chiefly by warm southerly 
 winds, in the middle and higher latitudes of the 
 northern hemisphere, the sinking of the baro- 
 meter must be an indication of falling weather : 
 and as it has been shewn, that all violent winds, 
 such as hurricanes, tornados, &c. are owing to 
 the rapid condensation of aqueous vapour, the 
 falling of the barometer must also forebode tem- 
 pestuous weather. It is equally evident, that cur- 
 rents of cold air raise the barometer, not only 
 because of their greater specific gravity, but 
 because they condense the steam of warm air. 
 Hence it is, that for two or three days before 
 storms of thunder and lightning, wind and rain, 
 during the prevalence of warm southerly winds, 
 the barometer falls ; but rises during cool and 
 serene dry weather.* 
 
 * From several passages in Mr. Daniell's work, on the atmos- 
 phere, it would seem that he referred the sinking of the baro- 
 meter to the evolution of caloric from aqueous vapour during its 
 condensation, by which the atmosphere is expanded where it 
 takes place. (See page 126, &c.) But it has been shown, that 
 within the tropics, where the amount of condensation is greatest, 
 the fluctuation of the barometer is very small ; while it is obvious 
 from the foregoing facts and observations, that the barometer is 
 depressed by the accumulation of aqueous vapour in the atmos- 
 phere, and elevated by its condensation. 
 
 Dr. Dalton ascertained by a series of observations continued 
 for five years at Kendal, in the north of England, that the 
 barometer fell below twenty-nine inches during forty days ; only 
 
BAROMETER. 353 
 
 (). The range of the barometer is greater during 
 winter than summer in the middle latitudes. 
 
 The reason of which is, that the advancement 
 of the sun towards the pole, brings the tempera- 
 ture of the higher latitudes to nearly an equality 
 over forty or fifty parallels, and almost to the same 
 state as within the tropics, as observed by Dr. 
 Dalton : whereas during winter, the warm and 
 rarefied air of the tropical regions is often en- 
 countered by widely extended currents of cold 
 dense air from the polar latitudes ; the conse- 
 quence of which is, that the barometer will rise 
 or fall at the same time, over a great extent of 
 
 two of which were fair ; but that when it stood above its mean 
 monthly height, there was but little rain, and generally fair 
 weather. 
 
 He also found, that the heaviest rains fell when the barometer 
 was about 29'47, and not when at a minimum, as- might have 
 been expected, d priori. His explanation of this fact is simple 
 and satisfactory. He observes, that " when the barometer is 
 above the mean high extreme for the season of the year, the air 
 must, relatively speaking, be extremely dry or cold, or both. If 
 extremely dry, it is in a state for absorbing vapour ; and if ex- 
 tremely cold, no further degree of cold can be expected, and 
 therefore in neither case can there be any considerable precipita- 
 tion. On the contrary, when the barometer is very low for the 
 season, the air must relatively be extremely warm, or extremely 
 moist, or both ; if extremely warm, it is in a similar state to dry 
 air for imbibing vapour ; and if extremely moist, there must be a 
 degree of cold introduced to precipitate the vapour, which cold, 
 at the same time, raises the barometer. From which it follows, 
 that no very heavy and continued rains can be expected to 
 happen whilst the barometer remains about the lowest extreme.'* 
 (Meteorological Essays, p. 143.) 
 
 A A 
 
354 BAROMETER. 
 
 country, according as the warm and vapoury, or 
 cold and dry currents of air predominate, and 
 will be greatest when the extremes of tempera- 
 ture in the opposing currents are at a maximum. 
 
 7. The regular elevations and depressions of the 
 barometer, termed its horary oscillations, follow 
 the daily fluctuations of temperature. 
 
 According to the observations of Mr. Daniell, 
 the daily average height of the barometer at 
 London, is *010 inch higher at night than the 
 afternoon, and -005 inch higher in the morn- 
 ing than at night; it is therefore -015 inch 
 higher in the morning than the afternoon. (Es- 
 say on the Climate of London.) The daily varia- 
 tion is still greater in the interior of N. America, 
 lat. 41 25' at the rocky mountains, where Col- 
 onel Long found the mean height of the baro- 
 meter, in March, 28-713 inches in the morning 
 28 609 at noon and 28-630 at night. 
 
 From the observations of Captain Sabine, and 
 others, it would seem that the diurnal variation 
 of the barometer is greatest at the equator, where 
 the power of the sun's heat is a maximum, and 
 diminishes on approaching the Polar circles, as 
 shown in the following Table, given by Mr. 
 Daniell : 
 
 At St. Thomas, lat. 0-24' the diurnal variation was -074 inch. 
 
 Trinidad . . 10'39 -063 do. 
 
 Jamaica . . 17*56 -058 do. 
 
 Paris, . . 48-50 -028 do. 
 
BAROMETER. 355 
 
 Finally, all the variations of the barometer 
 are greater at the level of the sea than in high 
 situations, corresponding with the greater fluc- 
 tuations of temperature of the lower atmosphere. 
 
 Deiv and Frost. 
 
 After the setting of the sun, the surface of the 
 earth is cooled down by radiation from 12 to 15 
 F. below the temperature of the superincumbent 
 atmosphere, when it abstracts caloric from the 
 stratum of transparent aqueous vapour immedi- 
 ately over it, by which it coalesces into dew, or 
 crystallizes into frost, according to the tempera- 
 ture of the surface. 
 
 If the atmosphere be full of vapour, there is 
 a large deposition of dew during summer, on 
 perfectly clear nights : but during spring and 
 autumn, instead of heavy dews, we have large 
 white frosts, that are generally followed in two 
 or three days by rain ; of which they are regarded 
 by the people as a sure indication. As a ge- 
 neral rule, the quantity of dew is in proportion 
 to the amount of invisible vapour in the air ; and 
 to the difference between the temperature of 
 day and night. It is profuse in hot climates, and 
 more abundant on continents than islands, cce- 
 teris paribus: while on the ocean, far from land, 
 there is little or no dew ; because the difference 
 between the temperature of day and night at sea is 
 
356 THEORY OF DEW. 
 
 only two or three degrees. In the United States 
 of America, the difference is sometimes 00 F. 
 the consequence of which is copious depositions 
 of dew, resembling the effects of a shower of 
 rain. They are also copious in England, during 
 the prevalence of warm winds from the ocean. 
 
 All other things being equal, a greater amount 
 of dew is condensed between midnight and sun- 
 rise, than between sun-set and midnight, accord- 
 ing to the observations and experiments of Dr. 
 Wells obviously because the surface of the 
 earth is then colder, from the loss of caloric by 
 radiation. Dew, then, is not condensed and 
 precipitated like rain by the coldness of the 
 atmosphere ; but by the coldness of the earth's 
 surface, which is proved by the well known fact 
 that dew and frost are formed on the under sur- 
 face of planks, &c. as well as the upper. 
 
 It has been long known, that little or no dew 
 is formed under a cloudy canopy ; but that it 
 is abundant during clear nights. Dr. Wells 
 referred this circumstance to the obstruction of 
 caloric radiated from the earth's surface by 
 clouds. It is extremely probable, however, from 
 his own statement of facts, that he mistook a 
 mere concomitant for the real cause of the phe- 
 nomenon. He informs us, that when clouds 
 begin to form during the night, the surface of 
 the earth rises several degrees, and that dew 
 formed during clear intervals, often evaporated 
 again when the sky becomes thickly overcast ; 
 
THEORY OF DEW. 357 
 
 from which it would appear, that the caloric 
 evolved from aqueous vapour during its con- 
 densation into clouds, warms the atmosphere 
 and prevents the surface of the earth from being 
 cooled to the dew point. Admitting that a por- 
 tion of the caloric radiated from the surface of 
 the earth, is reflected back, instead of being 
 absorbed by clouds, it is insufficient to produce 
 so decided a change of temperature. During 
 clear and serene nights, when no caloric is given 
 out to the atmosphere by the condensation of 
 vapour, the earth is cooled down by radiation, 
 because it receives nothing to compensate for 
 the loss of What is given off; so that the trans- 
 parent aqueous vapour of the lower strata of the 
 atmosphere, is condensed into dew. There is 
 no dew on windy nights, for the same reason 
 that evaporation is accelerated by wind : or that 
 a renewal of water and agitation promote the 
 solution of salts. 
 
 It was before stated, that caloric is radiated 
 more copiously from rough surfaces than from 
 such as are smooth. In accordance with that 
 general fact, we find that dew is formed more 
 copiously on swansdown, wool, cotton, raw silk, 
 flax, tine shavings of wood, &c. than upon 
 compact pieces of the same materials. It 
 forms more copiously on rough metals than on 
 polished ones ; doubtless because the former pre- 
 sent a more extended radiating surface. See 
 Theory of Radiation. Book II. Chap. I. 
 
358 
 
 Mists and Fogs. 
 
 The formation of all fogs is owing to a partial 
 condensation of aqueous vapour, caused by the 
 abstraction of caloric from colder bodies often 
 by the mixture of air of different temperatures 
 near the earth's surface. For example, during 
 autumn, the temperature of the Mississippi, 
 Ohio, and other great rivers, is nearly the same 
 during night and day ; while that of the land is 
 greatly reduced at night by radiation, especially 
 towards morning, when it is at the extreme of 
 reduction. Under such circumstances, the in- 
 termixture of the land atmosphere at the tem- 
 perature of 35 or 40 F. with that of the water, 
 which is from 50 to 60, produces a fog or mist. 
 The same effect is produced on the eastern coast 
 of the United States during autumn. The land 
 is cooled down by radiation at night, while the 
 temperature of the ocean and the air over it 
 remains nearly the same. During this state of 
 things, whether the wind blows from the sea or 
 land, a mixture of warm and cold air produces 
 fogs. 
 
 Over the banks of Newfoundland, where the 
 warm air from the gulf stream is intermixed with 
 that of the cold water and icebergs of the north, 
 they prevail throughout the year. Nova Scotia 
 is, proverbially, the region of fogs. The dark 
 and thick fogs of England occur during the 
 latter part of autumn and winter, owing to the 
 
MISTS AND FOGS. 359 
 
 more rapid cooling of the land by radiation, 
 than of the surrounding ocean. 
 
 The frost rime of the Polar seas is produced 
 in the same manner as fogs, but by the agency 
 of a lower temperature. 
 
 During summer, mountains are generally 
 covered with fog in the morning, when the 
 weather is serene and clear. Being cooled 
 down at night by radiation below the dew point, 
 they abstract caloric from the transparent aque- 
 ous vapour that is always mixed with the atmos- 
 phere in greater or less quantity, by which it is 
 condensed into huge volumes of mist or fog, that 
 envelope the mountains with giant folds of ma- 
 jestic drapery ; and which are not redissolved by 
 the solar rays before 9 or 10 o'clock in the morn- 
 ing. The greater quantity of rain and snow which 
 fall on mountains than on plains, is also owing 
 to their greater coldness as before explained. 
 
 Indian Summer. 
 
 In all parts of the United States, there is an 
 autumnal period of most delightful weather, 
 which usually commences late in October, and 
 continues with occasional intermissions through 
 the greater part of November some seasons 
 in the Mississippi valley, until Christmas. It is 
 generally attended with a southerly wind, which, 
 being warm, is filled with transparent aqueous 
 
360 INDIAN SUMMER. 
 
 vapour. But as the earth becomes gradually 
 cooler on the approach of winter, by radiating 
 more caloric than it receives from the sun, the 
 air over it is also cooled down ; the transparent 
 vapour is slightly condensed into a fine hazy 
 mist, that reflects and refracts the solar rays in 
 such a manner as to produce the most rich and 
 softened lustre of the bluish purple and golden 
 air; which continues until there is a change of 
 wind sometimes, for three weeks in succession. 
 As the Indian summer is generally a dry season, 
 and as the mountains and prairies are frequently 
 on fire during such weather, the hazy appear- 
 ance of the atmosphere has been attributed by 
 many persons to the vapour of burning sub- 
 stances diffused through the air. But this cause 
 is altogether too limited in its operation to ac- 
 count for the prevalence of Indian summer 
 throughout the greater part of the American 
 continent ; and often many hundred miles from 
 burning prairies. The conflagrations that occur 
 during this season are local and transitory ; 
 while the gradual cooling down of the earth, 
 during the prevalence of warm southerly breezes, 
 is all sufficient to account for the phenomenon. 
 The same cause produces in England the most 
 dense and gloomy fogs, during the same beautiful 
 season in America. This is readily understood, 
 when we reflect that England is surrounded by 
 the ocean, that its atmosphere is much nearer 
 
INDIAN SUMMER. 361 
 
 to the point of saturation by aqueous vapour, 
 than that of a large continent and, therefore, 
 that the same, or even a less reduction of tem- 
 perature must occasion denser fogs and darker 
 days in Great Britain and other insular coun- 
 tries of the higher latitudes, than in continental 
 regions. 
 
 The Indian summer of the United States is 
 closed by the commencement and predominance 
 of northerly winds, which condense the aqueous 
 vapour that has been borne from the ocean by 
 southern breezes, causing dark cloudy weather, 
 and general rains or snows, according to the 
 latitude and elevation ; after which, the reign of 
 winter is established and the air becomes dry, 
 clear, and cold, except in the neighbourhood of 
 the lakes, or of the ocean, where it partakes of 
 an insular character. 
 
 Aurora Borealis. 
 
 Before concluding this general and imperfect 
 survey of the agency of caloric in meteorological 
 phenomena, it may not be improper to notice 
 the leading facts connected with the aurora bo- 
 realis and australis, or the northern lights, as 
 they are commonly called on this side of the 
 equator. 
 
 It has been already shewn, that the atmosphere 
 
362 AURORA BOREALIS. 
 
 and all gaseous bodies owe their volume and 
 elastic force to the agency of an igneous aether 
 which surrounds their atoms and that after 
 being greatly accumulated in aqueous vapour, 
 it is given out in the form of lightning on the 
 meeting of warm and cold currents of air. We 
 have also seen, that the great aerial ocean is in a 
 state of perpetual circulation, from the poles to 
 the equator by under currents ; and from the 
 equator to the poles by upper currents ; and that 
 the density of the atmosphere increases as we 
 advance from the tropics, to the points of lowest 
 mean temperature : from which it follows, that ca- 
 loric must be evolved by the tropical atmosphere 
 as it passes from a rarer to a denser state. It is 
 equally certain, that the tropical air must carry 
 with it a considerable proportion of aqueous va- 
 pour, that must be condensed into fogs or clouds, 
 rain or snow ; which accounts for a very common 
 attendant of the aurora, viz. a low black cloud, 
 apparently beyond it, and near to the horizon. 
 
 M. Hansteen, who has travelled much in the 
 north of Europe and Asia, observes, " that while 
 the aurorae are streaming, the sky becomes 
 opaque or misty." He further states, that " it is 
 a matter of common observation in the arctic 
 regions, confirmed by long experience, that the 
 aurora is usually followed by intense cold, espe- 
 cially after a mild day ;" doubtless, for the same 
 reason, that warm and sultry weather in the 
 
AURORA BOREALIS. 363 
 
 middle latitudes is rendered cool by a thunder 
 storm ; viz. by the mixture of cold with warm 
 air. 
 
 M. Hansteen has given a singular explanation 
 of the aurora, which shews how vague and inde- 
 finite the views of philosophers still are in regard 
 to the origin and nature of this beautiful meteor. 
 He observes, that " it is probably the result of a 
 struggle of powers put in activity by the vari- 
 ously constituted substances composing the mass 
 of the earth, which we may one day, perhaps, 
 learn to know." He thinks, that " it produces 
 the arctic fogs, by decomposing the aqueous 
 vapour of the polar atmosphere." (Edin. Phil. 
 Journal, vol. 12.) 
 
 It has been asked, why the aurora are not 
 continually formed, as the atmosphere is con- 
 stantly flowing from the tropical to the higher 
 latitudes? We might as well be asked, why 
 there is not perpetual thunder and lightning 
 while the atmosphere is moving from the sea 
 over the land, charged with aqueous vapour. 
 The condensations which occur in both cases are 
 local and temporary, and depend on the relative 
 temperatures of different aerial masses. When 
 the upper current of rarefied air from the tropics, 
 charged with vapour, comes in contact with the 
 cold air of the polar regions, it gives out a large 
 portion of caloric or electric matter, where, not 
 being compressed as in the lower atmosphere, it 
 
364 AURORA BOREALIS. 
 
 expands like the electric spark in an exhausted 
 glass tube, into broad bands, or zones and co- 
 lumns; filling the sky with halos and crowns of 
 lambent light, or undulating corruscations. It 
 is highly probable, that the aurora is given off, 
 during the condensation of the upper equatorial 
 currents with the vapours which they contain, 
 in a mode similar to the evolution of silent 
 lightning on a summer's evening, which is ge- 
 nerally many miles off, and is seen through 
 numerous strata of atmospheric air, producing a 
 diffused or lambent phosphorescence, that re- 
 sembles the aurora much more than it does 
 lightning which is near at hand. 
 
 Sometimes the whole northern hemisphere pre- 
 sents that kind of luminosity which announces 
 the dawn of morning in the east. At other 
 times the aurorse seem stationary during changes 
 of temperature from heat to cold. They often 
 present the appearance of a bank of light, (re- 
 sembling the effect of a distant conflagration,) 
 resting on, or flanked by a low dark cloud, which 
 is occasionally illuminated by broad flashes. 
 Captain Bonny castle, of Toronto, in Upper Ca- 
 nada, observes, that during the formation of all 
 remarkable aurorae, dark volumes of vapour sud- 
 denly appeared within the space comprehended 
 by the arch. (Silliman's Journal, vol. xxx. p. 
 132.) Sometimes, though rarely, the aurora 
 presents the appearance of a wide arch extending 
 
AURORA BOREALIS. 365 
 
 across the firmament, which breaks up into 
 columns or streamers that extend towards the 
 zenith. 
 
 Various conjectures have been offered in re- 
 gard to the height at which the aurorae are 
 formed, nearly all of which have been founded 
 on imaginary data. For example, some philo- 
 sophers have supposed that they must be formed 
 at a great elevation, because they have been 
 seen at the same time in very distant countries, 
 as England and America. But it would be quite 
 as reasonable to conclude, that ordinary light- 
 ning is given off at a great elevation, because it 
 lightened at the same time in England and 
 America. There is no rational ground for sup- 
 posing, that the aurorae are formed above our 
 atmosphere ; and probably never beyond a few 
 miles, while there is every reason to believe, 
 that they may be formed in hundreds of places 
 over different parts of the earth at the same time. 
 
 It was the opinion of Franklin, Parry, Ross, 
 Hood, and Dr. Richardson, that the auroras of 
 the arctic regions were frequently not higher 
 than ordinary clouds and Dr. Richardson 
 thinks that they are always attended with the 
 formation of clouds, or of that kind of haziness 
 which causes a halo around the moon a very 
 important fact, which would seem to establish 
 their connexion with the condensation of aque- 
 ous vapour, as suggested by Dr. Franklin. 
 
366 AURORA BOREALIS. 
 
 They are most probably in the upper regions 
 of the atmosphere, what thunder storms are near 
 to the surface of the earth.* The aurora? are 
 seldom, if ever, seen between the tropics, be- 
 cause the upper atmosphere is not condensed 
 there, being of uniform temperature. Even near 
 
 * Most of the appearances presented by the aurorae have been 
 imitated by artificial means. Dr. Priestley inserted with cement, 
 into the top of a tall receiver, a wire not very acutely pointed. 
 He then exhausted the receiver, and presented the knob of the 
 wire to the conductor, when every spark passed through the 
 vacuum in a broad stream of light, which often divides into a 
 variety of beautiful rivulets, that are continually changing their 
 course, uniting and dividing again in the most pleasing manner : 
 thus representing in miniature what has been called the streamers 
 of the aurora. When the wire is electrified minus, or negatively, 
 instead of streams of fire, there is a uniform luminous appear- 
 ance like a white cloud, or like the milky way in a star light 
 night, which remains for a considerable time, representing the 
 apparently stationary and diffused light of the aurora. (Priestley's 
 History of Electricity, p. 524.) 
 
 We can assign no limits to the various phenomena which the 
 electric fluid may exhibit under different circumstances. The me- 
 dium in which it is formed, in the upper regions of the atmosphere, 
 is doubtless greatly rarefied ; perhaps equal to that of a receiver 
 which has been rarefied 100 times. It would seem, however, 
 that the aurora sometimes reaches the surface of the earth. It 
 is related by Bergman, that persons travelling over the high 
 mountains of Norway, have been enveloped in it ; and Captain 
 Ross states, that he has witnessed it very near to the surface of 
 the earth ; and that it has caused the deflection of his compass 
 needle as much as thirty and forty degrees. M. Hansteen also 
 found that when the aurorse were vivid, the horizontal needle was 
 restless, quivered, and varied from three to five degrees from its 
 ordinary place. 
 
AURORA BOREALIS. 367 
 
 the earth's surface, there is comparatively little 
 lightning where the temperature is uniform, as 
 over the tropical ocean, and where the wind blows 
 uniformly in the same direction. 
 
 It is highly probable, that the electric fluid 
 is nearly all given out, before the upper current 
 reaches the centre of maximum cold ; which ex- 
 plains why the aurora is less brilliant at Mel- 
 ville Island, than at Bear Lake, the Shetlands, 
 Orkneys, and many other places in lower lati- 
 tudes. It also explains why in the coldest 
 regions, as at Port Bowen, Winter Island, &c. 
 the magnetic needle is less often disturbed by it 
 than in lower latitudes ; and why in the former 
 places, it was almost always seen by the British 
 navigators southward of them.* 
 
 Another important fact, that shows the in- 
 timate connexion between the aurorae and the 
 change of temperature which the equatorial air 
 undergoes, is, that the northern lights are more 
 numerous and brilliant during the coldness of 
 winter, when the upper currents from the tro- 
 pics, in their passage to the Polar regions are 
 greatly condensed ; and that they are then 
 
 * It is stated by Captain Scoresby, that the aurora was dis- 
 covered more frequently south than north of Spitzbergen and 
 by Sir Edward Parry, that it was generally seen south of Mel- 
 ville Island from which we may conclude, that the upper cur- 
 rent of the atmosphere has acquired nearly its maximum density, 
 and deposited nearly all its vapour, before arriving at the limits 
 of greatest cold. 
 
368 AURORA BOREALIS. 
 
 formed in much lower latitudes than during 
 summer. 
 
 It is also an important corroboration of this 
 theory, that they are seen in lower latitudes in 
 the middle and eastern portions of America and 
 Europe, than on their western coasts ; while the 
 former are known to be much colder than the 
 latter in the same latitudes; which is owing to 
 the prevalence of west winds, that blow from 
 the Pacific and Atlantic oceans, and thus tem- 
 per the middle latitudes of western coasts, by 
 giving them an oceanic or insular climate.* 
 
 The northern lights are seen much oftener 
 in Vermont, which is a cold mountainous state, 
 between latitude 42 and 44 IV . than in France 
 or England; though they are much farther 
 north. This is evidently owing to the excessive 
 
 * The effect is increased by the condensation of aqueous va- 
 pour which is brought from the ocean by westerly winds, and 
 which gives out caloric during its condensation and precipitation 
 on the western coasts. Hence, the greater amount of rain which 
 falls on the western coasts of N. America and Europe, than on the 
 interior and eastern portions. Hence also, the dryness of west 
 winds in the United States, east of the rocky mountains, which 
 deposit their vapour on the western slope, before reaching the 
 interior. In the great Mississippi valley, the east wind is dry, 
 while in the Atlantic States it is often moist during winter and 
 spring. On moving westward, it deposits most of its vapour on 
 the eastern slope of the Alleghany mountains. These facts 
 enable us to understand why in the vast regions drained by the 
 Mississippi, west winds are dry; while in Britain and France 
 they are wet, and east winds dry. 
 
AURORA ROREALIS. 309 
 
 coldness of winter in Vermont. General Martin 
 Field has recorded, in the American Journal of 
 Science, that, during the year 1830-31, the winter 
 of which was excessively rigorous, the aurora 
 was perceived on fifty-six nights ; and that 
 during ten years previously, it was observed 
 eighteen nights on an average, annually, at 
 Fayetteville in the above State. Besides which, 
 it must have existed during many cloudy nights, 
 when it was invisible. 
 
 The arched appearance of the aurora is an 
 optical illusion, produced by the limits of vision, 
 according to the laws of perspective ; for the 
 same reason that the sky presents a vaulted 
 appearance or, that clouds present the appear- 
 ance of a canopy, while in reality they are sus- 
 pended in horizontal strata. The different ap- 
 parent heights of the aurora are owing to their 
 various distances from the points of observation. 
 When the lower atmosphere between the ob- 
 server and the lights is hazy, they appear 
 irised or rose-coloured ; probably for the same 
 reason that the sun rises and sets red, when the 
 lower air is filled with vapours. 
 
 Siberia, Lapland, and the Norwegian Alps, 
 are distinguished by the frequent display of this 
 beautiful and mysterious phenomenon, which I 
 have thus endeavoured to explain in accord- 
 ance with the best established principles of 
 Meteorology. After all, it is quite probable, 
 
 B B 
 
370 AURORA BOREALIS. 
 
 that some very important facts have been over- 
 looked, which, if known and rightly considered, 
 might place the whole subject in a new light. 
 It is to be hoped, that fifty years hence, we shall 
 have fifty accurate observers of natural pheno- 
 mena for one at the present time. 
 
 Very little is known of the aurorse in the 
 southern hemisphere, except what has been 
 observed by Captains Cook and Weddel, who 
 relate that they have been frequently seen south 
 of Van Dieman's Land, and off Cape Horn, 
 where the cold is excessive.* 
 
 * From a general view of the foregoing chapters, it must be 
 obvious : 
 
 1. That all the phenomena of evaporation and rain, lightning 
 and winds, hurricanes and tornados, fluctuations of the baro- 
 meter, and formation of the aurorae, are immediately connected 
 with the theory of caloric, and those fundamental laws which 
 govern its distribution over our planet: 
 
 2. That the aurora is a thermo-electric phenomenon, pro- 
 duced during the condensation of vapour contained in the equa- 
 torial upper current of the atmosphere, on its passage to the 
 polar latitudes, in a mode analogous to the evolution of lightning 
 from the more elastic vapour of the lower and denser atmosphere, 
 on mixing with colder currents, as during thunder storms. 
 
 In opposition to this theory, it is maintained by Dr. Faraday 
 and others, that " the electric equilibrium of the atmosphere is 
 preserved by the aurora conveying electricity from the poles to 
 the equator." Can it be possible that the vast amount of light- 
 ning perpetually disengaged within the tropics, and during sum- 
 mer in the middle latitudes, is thus obtained ? With sentiments 
 of unaffected and profound humility, the preceding facts are 
 offered as an answer to this query. 
 
CHAPTER IV. 
 
 
 
 Galvanic Electricity. 
 
 THE first discovery connected with this branch 
 of physical science is found in a German work, 
 published in 1767, by Sultzer, entitled The Ge- 
 neral Theory of Pleasures. He observed, that if 
 two metals be applied, one above, and the other 
 below the tongue, and brought in contact, a 
 peculiar taste was perceived, attended with a 
 gentle flash of light; but that if applied sepa- 
 rately, no such effects were produced. 
 
 It was next discovered accidentally by Gal- 
 vani, a distinguished professor of anatomy at 
 Bologna, that on touching the crural nerve of a 
 recently killed frog, which lay on a table, near 
 the conductor of an electrical machine in action, 
 with the point of a scalpel, all its muscles were 
 thrown into convulsions, as if seized with te- 
 tanus. By repeating the experiment on diffe- 
 rent animals, he found that the effect was most 
 remarkable in those which are cold blooded, 
 and have white muscles. He ascertained after- 
 wards, that when the nerves and muscles of 
 such animals were armed with small pieces of 
 
372 GALVANIC ELECTRICITY. 
 
 different metals, similar phenomena were pro- 
 duced on bringing the metals in contact. 
 
 From these obscure results, Galvani arrived 
 at the conclusion, that there is a peculiar species 
 of electricity residing in all animals, which is 
 secreted by the brain, and conducted to different, 
 parts of the body by the nerves, causing animal 
 motion, secretion, &c. He supposed that this 
 fluid is conducted from nerves to muscles by the 
 metallic arc, as the electricity of a Leyden bat- 
 tery is conducted from it by means of a common, 
 discharger. 
 
 In opposition to the views of Galvani, it was 
 maintained by the celebrated Volta, professor of 
 natural philosophy at Pavia, that the pheno- 
 mena were due to the agency of common elec- 
 tricity, which he supposed was accumulated by 
 the contact of different metals. 
 
 Finding that when sticks of zinc and copper, 
 zinc and silver, &c. were made to touch at one 
 of their extremities, and the other brought in 
 contact with the spine and muscles of a newly 
 killed frog, excited convulsions, it occurred to 
 Volta, that by a repetition of circles, or series, 
 composed of two different metals and moistened 
 cloth, he might greatly increase the electrical 
 effects. This led to the construction of the well 
 known pile, and the couronne de tasses, which 
 have been modified into different forms of the 
 battery. In reply to the hypothesis of Volta, 
 
GALVANIC ELECTRICITY. 373 
 
 that the convulsions of the frog were owing to 
 the agency of common electricity, and generated 
 by the contact of different metals, Galvani ob- 
 jected that he had succeeded in producing con- 
 vulsions by means of a single metal. And it 
 was further shown by Aldini, a nephew of Gal- 
 vani, that by bringing a portion of a warm 
 blooded animal in contact with a cold blooded 
 
 . 
 
 one, as the nerve and muscles of a frog with the 
 bloody flesh of a newly decapitated ox, ener- 
 getic contractions were produced. When he 
 held a prepared frog in his hand, moistened with 
 a solution of salt, and applied the crural nerves 
 of the animal to the tip of his tongue, convul- 
 sions were also excited* from which he in- 
 ferred, with Galvani, that there is a peculiar 
 electricity in animal bodies which does not 
 require the contact of metals for its develope- 
 ment. It is somewhat surprising that he was 
 never led to suspect, from these curious experi- 
 ments, the identity of animal heat with the 
 cause of muscular contraction and still more 
 remarkable, that neither Galvani nor Yolta ever 
 suspected the connexion of the phenomena with 
 chemical action. 
 
 The agency of caloric in exciting convulsions 
 
 * The experiments were successfully repeated before a Com- 
 mittee of the National Institute of France, and afterwards at the 
 Anatomical Theatre in London, Great Windmill Street. 
 
374 GALVANIC ELECTRICITY. 
 
 in recently killed fish, was strikingly demon- 
 strated by some experiments of Mr. Clift, who 
 found, that four hours after the head of a carp 
 had been cut off, and its heart taken out, (the 
 fish being considered as perfectly dead,) when 
 put in hot water, it leaped out of the vessel with 
 a degree of vigour equal to the struggles of a 
 living fish. (Phil. Transactions for 1815.) 
 
 A similar fact was observed by Lord Bacon, 
 who relates that he saw, with his own eyes, the 
 heart of a criminal taken out of his body some 
 time after execution, and thrown into the fire, 
 when it leaped up several times to a considerable 
 height. Without commenting on these facts, 
 which belong to another portion of the present 
 work, it may be observed that they demonstrate 
 the agency of heat in animal motion, at least as 
 clearly as that of electricity, even admitting 
 (what has never been proved,) that electricity 
 could exist independent of caloric. 
 
 The first philosopher who referred the phe- 
 nomena observed by Sultzer, Galvani, and Volta, 
 to chemical action, was Fabroni, in a paper 
 communicated to the Academy of Florence, in 
 1792. He had often observed that fluid mer- 
 cury retained its lustre for a long time when 
 alone ; but that when amalgamated with other 
 metals, it speedily tarnished by oxidation ; and 
 that similar effects were produced on some alloys 
 of tin. He had remarked in the Museum of 
 
GALVANIC ELECTRICITY. 375 
 
 Cortona, inscriptions engraved on plates of pure 
 lead in a perfect state of preservation ; while in 
 the Gallery of Florence, he found that medals 
 composed of lead and tin, or lead and some 
 other metal, were entirely reduced to a white 
 powder, though carefully wrapped up in paper, 
 and preserved from the atmosphere in drawers. 
 He had further noticed, when in England, that 
 the iron nails then employed in fastening to- 
 gether the copper sheathing of ships, caused so 
 much corrosion of the copper, that the holes made 
 by them were sometimes larger than the heads 
 of the nails all of which he referred to chemical 
 action produced by the mutual contact of different 
 metals exposed to moisture, atmospheric air, &c. 
 That this was the case in the experiment of 
 Sultzer, he thought was proved by the fact, that 
 when the tongue was wiped dry, scarcely any 
 perceptible sensation was excited. 
 
 In another set of experiments, Fabroni put 
 different metals in vessels filled with water, two 
 and two, in contact, when he found that the 
 most ox id able metal was visibly oxidized at the 
 moment of contact. A month afterwards, the 
 connected metals had acquired so strong a 
 degree of cohesion as to require a considerable 
 force to separate them. Not only were the 
 metals oxidized, but covered over with small 
 crystals of various forms, which had been de- 
 posited from a state of solution. (Traite de 
 
.'370 GALVANIC ELECTRICITY. 
 
 TElectricite et du Magnetisme, par M. Becque- 
 rel, vol. i. p. 88.) 
 
 The above passages are sufficient to show that 
 Fabroni clearly recognized the necessity of che- 
 mical action in all galvanic phenomena, and 
 that his views were much more accurate than 
 those of his contemporaries. Still it must be 
 acknowledged, that he never explained why two 
 metals in contact oxidize more rapidly than 
 when isolated and that no satisfactory account 
 has yet been given of the primary source of 
 galvanic action by his successors the conse- 
 quence of which is, that the theory of the pile, 
 like that of universal chemistry, is still involved 
 in profound obscurity. 
 
 This much, however, is certain, that all the 
 different elements of ponderable matter have 
 various degrees of attraction for caloric ; and 
 that during all chemical combinations, there is 
 a transition of caloric from one to the other. 
 
 When treating of freezing mixtures, it was 
 shown that when chloride of sodium, chloride 
 of lime, potass, and many other salts are brought 
 in contact with ice, there is a rapid abstraction 
 of caloric from the ice to the salts, by which 
 both are dissolved and chemically united that 
 when lead, tin, and bismuth are brought in 
 contact, they dissolve at a much lower tempera- 
 ture than when isolated, and thus unite che- 
 mically into an alloy. For the same reason, 
 
GALVANIC ELECTRICITY. 377 
 
 many other metals, rocks, and gems are ren- 
 dered more fusible, and combine more readily 
 with each other by the addition of what has 
 been termed a flux. Clay is more fusible when 
 mixed with fluor spar, and quartz with lime, 
 than when separately exposed to the action of 
 heat. 
 
 Whatever may be the true explanation of 
 these phenomena, it is evident that caloric is 
 essential to oxidation, solution, and to all che- 
 mical combinations, whether of gases and li- 
 quids with each other, and with solids; or of 
 solids with each other. It therefore follows, that 
 if chemical action be indispensable to the dis- 
 engagement of galvanic electricity, caloric must 
 be the primary source of all the resulting phe- 
 nomena. Passing over the long and idle con- 
 troversy between the partisans of Volta, (who 
 maintained that galvanic electricity results from 
 the contact of different bodies ; and those of 
 Fabroni, who contend that it is wholly the result 
 of chemical action,) it may be sufficient to state, 
 that the combined researches of nearly all the 
 most distinguished philosophers of modern times 
 demonstrate, that there can be no galvanic 
 action without chemical decomposition. 
 
 For a long time it was supposed by Sir H. 
 Davy that contact was necessary to its com- 
 mencement, and that it was kept up by che- 
 mical action. But from the experiments of Wol- 
 laston, Gautheraut, Delarive, Avogadro, Parrot, 
 
378 GALVANIC ELECTRICITY. 
 
 Becquerel, and Faraday, the question may now 
 be regarded as decided. Davy himself observes 
 in the Bakerian Lecture, read before the Royal 
 Society on the 8th of June 1826, that there is 
 no instance of electro-motion, (by which he meant 
 galvanic action,) without chemical decomposi- 
 tion. He also states, that when oxidizing liquids 
 are employed in maintaining the action of the 
 battery, the more oxidable metal always afforded 
 positive electricity in relation to a less oxidable 
 one that potassium, which is the most oxidable 
 of all the metals, is positive in relation to all 
 others; and so of its amalgams that barium 
 and its amalgams are positive in relation to an 
 amalgam of zinc, which is positive in relation 
 to pure zinc, zinc to cadmium, the latter to tin, 
 tin to iron, and iron to bismuth. 
 
 Corresponding with the above results are 
 those of Delarive, who found that the direction 
 of a galvanic current is not determined by me- 
 tallic contact, nor by the nature of the metals 
 relatively to each other, but by their chemical 
 relation to the exciting liquid that of two metals 
 composing a voltaic circle, the one which is most 
 energetically attacked is positive with respect 
 to the other. Thus, when tin and copper are 
 placed in acid solutions, the former, which is 
 most actively corroded, gives a positive current 
 through the liquid to the copper: but if put into 
 a solution of ammonia, which acts most on the 
 
GALVANIC ELECTRICITY. 379 
 
 copper, the direction of the current is reversed. 
 Copper is positive in relation to lead in nitric 
 acid, which oxidizes the former most rapidly ; 
 whereas, in dilute nitric acid, by which the lead is 
 most speedily dissolved, the lead is positive. He 
 found that even two plates of copper, when im- 
 mersed in solutions of the same acid, but of 
 different strength, form a voltaic circle, the plate 
 on which chemical action is most energetic, 
 giving a current of positive electricity to the 
 other and that a compound circle might be 
 formed solely of zinc plates and one acid, pro- 
 vided the same side of each plate be more 
 rapidly oxidized than the other. 
 
 The following experiments are decisive against 
 the theory of Volta. M. Delarive ascertained 
 that when zinc and copper plates were brought 
 in contact in an atmosphere of hydrogen or 
 nitrogen, wholly deprived of oxygen, moisture, 
 and other bodies, no electricity was evolved ; 
 and when he purposely increased chemical action 
 by exposing the zinc to acid fumes, or by substi- 
 tuting for zinc a more oxidable metal, such as 
 potassium, the electrical effects observed, on 
 contact with copper, were greatly augmented, 
 the amount being in proportion to the chemical 
 action. (Ann. de Chim. et de Phys. XXXVIII. 
 et IX.) 
 
 The above facts have an important bearing on 
 the general theory of electricity ; for they seem 
 
380 GALVANIC ELECTRICITY. 
 
 to prove that what are termed positive arid ne- 
 gative electricity, are only plus and minus con- 
 ditions of one and the same sethereal element : 
 consequently, that the oxygen, chlorine, fluorine, 
 iodine, and bromine of acids, salts, &e. are at- 
 tracted by the minus or negative pole of the 
 battery ; and hydrogen, metals, and alkalies to 
 the positive pole, because in their natural state, 
 these two classes of bodies are combined with 
 different proportions of thermo-electric aether. 
 But as I have before shewn, (p. 204 and 5,) that 
 bodies are neither essentially positive nor nega- 
 tive, but vary according to circumstances, and 
 that those which belong to the electro-positive 
 class, unite with each other, as well as with 
 those that belong to the opposite class, it is evi- 
 dent that chemical attraction is not wholly the 
 result of electric polarity, as maintained by 
 Davy. 
 
 It has been often said, that the energy of the 
 voltaic battery is in proportion to the conducting 
 power of the liquid that acts on the plates. The 
 absurdity of this hypothesis will appear in a 
 striking point of view, when it is remembered, 
 that of all liquids mercury is the best conductor, 
 yet when employed between the plates of a 
 battery, no electricity whatever is disengaged. 
 The simple matter of fact is, that the quantity 
 of electricity evolved is proportional to the rapi- 
 dity with which the intervening liquid is decom- 
 
GALVANIC ELECTRICITY. 381 
 
 posed by the metallic plates ; and that when the 
 chemical action ceases, the disengagement of 
 electricity also ceases.* 
 
 * From the experiments of Hitter, Davy, and others, it would 
 appear that two different metals are not requisite to the disen- 
 gagement of the galvanic fluid, but to its concentration. Sir 
 Humphrey Davy formed galvanic series of a single plate of zinc, 
 one side of which was exposed to an acid, and the other side to 
 water also by a single metal acted upon one side by an acid, 
 and on the other side by hydro-sulphurets. (Philosophical 
 Transactions for 1821.) 
 
 It has been further shewn by M. Becquerel, that electricity is 
 evolved whenever metals are immersed in acid solutions that act 
 chemically on them. The same effect was produced during the 
 combination of acids and alkalies, when nitrate of iron acts on 
 leaves of platinum foil ; or nitro-muriatic acid upon gold ; and 
 even on mixing a concentrated acid solution with a diluted solu- 
 tion of the same acid. (Ann. de Chem. et de Phys. xxxv. 120.) 
 
 From such experiments it has been inferred, that electricity is 
 disengaged during all chemical actions. But it is certain that 
 all chemical combinations and decompositions are attended with 
 changes of temperature that is, by the absorption or evolution 
 of caloric. The disengagement of electricity during the action 
 of the strong acids on metals, alkalies, &c. has been deduced 
 from the fact, that when the two ends of a multiplying wire are 
 made to communicate with the combining bodies, the magnetic 
 needle is deflected, as it is during the passage of a current of 
 voltaic electricity through it. But the same effect is produced 
 when one end of the multiplying wire is made to communicate 
 with melted silver, and the other end with a portion of the same 
 metal in the solid state ; or when the two extremities of the mul- 
 tiplier are made to communicate with different parts of other 
 metals when of different temperatures from which it would 
 appear that the magnetic phenomena are independent of chemi- 
 cal action, and result from the transition of caloric through the 
 multiplying wire, as will be proved further on. 
 
38-2 
 
 Theory of Galvanic, or Voltaic Electricity. 
 
 ON the first introduction of the Voltaic pile 
 into Paris, Napoleon was so strongly impressed 
 with its importance, that he offered 60,000 fr. 
 to the individual, of whatever nation, who should 
 make 'a decided advancement in the knowledge 
 of its theory, as Franklin did in common elec- 
 tricity. Had this extraordinary man devoted 
 himself to the task, it is probable that he would 
 have gained the prize. He proposed several 
 interesting points of inquiry in regard to the 
 theory of its action. He wished that experi- 
 ments should be made on the pile at very dif- 
 ferent temperatures, for the purpose of ascer- 
 taining whether caloric created any remarkable 
 difference in its power of producing electricity. 
 On witnessing the transport of the elements of 
 salts to its respective poles, he is represented to 
 have said to his physician Corvisart, " Docteur, 
 voila 1'image de la vie." (Traite de 1'Electr. 
 et du Magnetisme, vol. i. p. 108, par M. Bec- 
 querel.) 
 
 It sometimes happens, that new discoveries 
 retard the general progress of science for a time, 
 by withdrawing the attention of philosophers 
 from a general and comprehensive survey of na- 
 ture, to that of some obscure and petty province. 
 
 The brilliant discoveries of Galvani, Volta 
 
GALVANIC, OR VOLTAIC ELECTRICITY. 383 
 
 and Davy, directed the inquiries of men to the 
 chemical and physiological properties of electri- 
 city, to the neglect of the still more obvious 
 agency of caloric. Had philosophers studied the 
 cause of solution, combustion, fermentation, and 
 ordinary decomposition, with half the attention 
 bestowed on Electro-Chemistry, they would have 
 discovered that caloric is indispensable to the 
 chemical union of oxygen with combustibles ; 
 of salts with water ; metals with acids, and with 
 each other ; in short, that without caloric, there 
 is no chemical attraction. 
 
 This would have led them to investigate the 
 relations of caloric and electricity, one of the 
 most important problems in physics, from its 
 intimate relation to the whole constitution of 
 nature. If they be only modifications of one 
 and the same universal element, we cannot 
 expect fully to comprehend the most simple 
 phenomena of attraction and repulsion, without 
 understanding its general laws. 
 
 When treating of chemical solution, it was 
 demonstrated that metals are dissolved by the 
 caloric of the strong acids, and combined chemi- 
 cally with them, as certainly, as that salts are 
 dissolved by the caloric of water, and thus chemi- 
 cally combined with it. 
 
 If then there be not two causes of chemical 
 attraction, it is evident, that the same agent 
 
384 THEORY OF GALVANIC, 
 
 which causes sulphuric acid to combine with 
 copper, making a transparent solution of copper, 
 causes the same acid to combine with the plates 
 of the voltaic battery, by which they are oxi- 
 dized and dissolved, when a portion of the latent 
 caloric of the acid is given out in the concen- 
 trated form of electricity, conducted from the 
 plates by the connecting wires, and thence to 
 the extremities of the battery. 
 
 I have already shown that sulphuric acid is 
 composed of oxygen, sulphur and caloric that 
 nitric acid is composed of oxygen, nitrogen and 
 caloric and so of other compounds. When solu- 
 tions of nitric, sulphuric, or hydro-chloric acids 
 are poured upon metals, there is a rapid transition 
 of caloric from the acids to the metals, by which 
 they are made to combine chemically, with 
 great diminution of volume, and evolution of 
 heat. When they are poured on copper and 
 zinc filings, they are decomposed, and the metals 
 oxidized still more rapidly. But when the 
 same metals are arranged in the form of a gal- 
 vanic battery, and immersed in the same solu- 
 tions, electricity is evolved : from which it would 
 seem to follow, that the latent caloric of acids 
 is given out in the form of calorific or electric 
 power, according to the mode of its disen- 
 gagement. 
 
 Another fact of fundamental importance to a 
 
OR VOLTAIC ELECTRICITY. 385 
 
 right understanding of the nature of voltaic 
 electricity, and its relation to caloric is, that its 
 character is modified by the size and number of 
 plates composing the battery. For example, 
 when it is composed of a few large plates of 
 zinc and copper, an imponderable fluid is 
 evolved, possessing all the properties of highly 
 concentrated caloric, which fuses and ignites 
 the hardest gems and densest metals submitted 
 to its action ; while it is destitute of nearly all 
 the properties by which common electricity 
 is characterized. The largest battery of this 
 description ever constructed, was that of Mr. 
 Children, which was composed of twenty plates 
 of zinc and copper, six feet long, and thirty-two 
 inches broad. When immersed in a strong acid 
 solution, it melted, ignited, and fused a large 
 platinum wire, six feet in length ; but communi- 
 cated little or no shock to the system; would not 
 charge a Ley den jar ; produced no sensible effect 
 on the electrometer ; and, unlike common electri- 
 city, was conducted slowly by metals, minerals, 
 fluids, fyc.* 
 
 When the battery is composed of two exten- 
 sive coils of zinc and copper ; or of many plates, 
 
 * The large battery of the Royal Institution, employed by Sir 
 H. Davy, which consisted of 2000 pairs of 4 inch plates, melted 
 platinum, quartz, the sapphire, magnesia, and lime, like wax, 
 both in vacuo and in the atmosphere; while charcoal, plumbago, 
 and the diamond were rapidly dissipated in the form of vapour. 
 
 > C 
 
386 THEORY OF GALVANIC, 
 
 so arranged as to constitute only a single pair 
 of zinc and copper plates of enormous dimen- 
 sions, as in Dr. Hare's calorimotors, the calorific 
 effects are still more remarkable. 
 
 On the other hand, when the battery is com- 
 posed of a large number of metallic plates of 
 small size, and immersed in the same solutions, 
 electricity is evolved, which affects the electrome- 
 ter, communicates a shock, and passes through 
 conductors with a speed approaching that of 
 lightning. * 
 
 These striking facts led Dr. Hare to suppose 
 that both caloric and electricity are developed 
 during all galvanic operations; and that they 
 
 * When the battery is composed of a few large plates, and 
 immersed in an acid solution, caloric is evolved until the acid is 
 decomposed, or until the metallic plates are consumed. But if 
 the battery be composed of a large number of small plates of the 
 same metals, and immersed in the same acid, electricity is pro- 
 duced, until the plates or acid are consumed by oxidation ; 
 which demonstrates the identity of caloric and electricity beyond 
 the possibility of a doubt ; for it would be a perversion of com- 
 mon sense to suppose, that by merely changing the size and 
 number of the plates, a radically different fluid could be evolved, 
 while the metals, and solutions in which they are immersed, are 
 the same. Shall I be asked for clearer proofs that the latent 
 caloric of acids is the basis of electricity ? We might as well be 
 asked to prove that the sun is the fountain of light and heat ; or 
 that rain accompanies lightning, 
 
 It is generally known that the most powerful batteries are 
 composed of bodies which act with the greatest energy upon 
 each other, such as zinc, copper, and nitric acid; and that such 
 as undergo no chemical changes exhibit no electrical effects, 
 such as gold, silver, and water. 
 
OR VOLTAIC ELECTRICITY. 367 
 
 are combined with each other by what he calls 
 " the reciprocal attraction of imponderables." 
 He supposed that when two or more large 
 plates were employed, caloric predominated; 
 but that when a large number of small plates 
 were used, electricity predominated. One thing 
 is certain, that the character of the galvanic 
 fluid is modified by every variation in the size 
 and number of the plates composing the battery. 
 But if we suppose that caloric is combined with 
 galvanic electricity, because it fuses and ignites 
 metals, or other bodies, we shall be forced to 
 admit that it is also a constituent portion of 
 common electricity, for it fuses and ignites 
 bodies like voltaic electricity. He further sup- 
 poses, that " electricity fuses and ignites metals, 
 &c. by combining with their latent caloric ; thus 
 augmenting its repulsive agency, and causing it 
 to overcome their cohesion." But he omits the 
 important fact, that electricity also increases their 
 temperature, and that its former properties are 
 changed and merged into those of caloric, as it 
 fuses and ignites bodies. 
 
 The unavoidable conclusion from the above 
 facts is, that caloric and electricity are only 
 different forms of the same elementary agent, 
 varied by the numerous modes of its separation 
 from ponderable matter : or, that there are two 
 distinct and universal agents combined with 
 ponderable matter, and with each other, "by the 
 
388 THEORY OF GALVANIC, 
 
 reciprocal attraction of imponderables," as main- 
 tained by Dr. Hare. It need scarcely be ob- 
 served, that there has never been the slightest 
 evidence adduced that such an attraction exists 
 between caloric and electricity, admitting them 
 to be distinct fluids ; while it is contrary to the 
 simplicity which characterizes all the operations 
 of nature to suppose the existence of two uni- 
 versal agents, endowed with the same funda- 
 mental properties. There cannot be two uni- 
 versal principles of action in nature; because 
 if they were different they would interfere with 
 each other, and produce discord and if they 
 were alike they would produce like results, which 
 amounts to the same thing as if they were radi- 
 cally identical.* If every apparent difference 
 between caloric and electricity be taken as an 
 argument against their identity, it would be easy 
 to prove that there are more than one hundred 
 electricities. There is a far greater difference 
 between the voltaic fluid disengaged by Chil- 
 dren's battery, and that from a common elec- 
 trical machine, than between the former and 
 the caloric evolved by ordinary combustion- 
 while the deflagration of steel wires in oxygen 
 
 * Sir Isaac Newton thought it " inconceivable that two aethers 
 could be diffused through all nature, one of which acts upon the 
 other, and by consequence is reacted upon, without retarding, 
 shattering, dispersing, and confounding one another's motion/' 
 (Optics, p. 339.) 
 
OR VOLTAIC ELECTRICITY. 389 
 
 gas, and the detonation of gunpowder, are more 
 like an electric explosion than any thing else. 
 
 The ordinary process of combustion by which 
 heat is evolved, consists in the combination of 
 oxygen with other elements. The galvanic fluid 
 is decomposed by the same process : while it 
 would be contrary to all the rules of a sound 
 induction, to suppose that two or more distinct 
 ethereal agents could be disengaged from the 
 same elements. If we reject this simple mode 
 of reasoning, we shall be compelled to admit 
 the existence of as many electricities as there 
 are modes of separating it from ponderable 
 matter, which would be absurd. It is far more 
 consistent with facts and the harmonious sim- 
 plicity of nature to suppose that one agent pro- 
 duces all the diversified powers and activities of 
 matter that it exhibits different properties and 
 appearances under different circumstances, ac- 
 cording to its diffusion, concentration, compres- 
 sion, &c. and to the mode of its combination 
 with different substances, in a solid, liquid gas- 
 eous, or imponderable state, as in the matter of 
 light. 
 
 We have already seen, that a certain tempe- 
 rature is indispensable to combustion, fermenta- 
 tion, putrefaction, and to every process of oxida- 
 tion, however slow, as the rusting of metals, 
 that when atmospheric oxygen is thus made 
 to combine with metals, its volume is dimi- 
 
390 THEORY OF GALVANIC, 
 
 nished, and a portion of its latent caloric libe- 
 rated, in the form of radiant matter, by which 
 the process of oxidation is kept up. I have 
 also proved, that when metals are exposed to the 
 action of strong acids, there is a transition of 
 caloric from the acids to the metals, by which 
 the latter are dissolved and chemically combined 
 with the menstruum ; that caloric is the cause of 
 all attraction between fluids and solids ; that 
 the solvent power of water, acids, &c. is greatly 
 augmented by heat ; and that when metals are 
 dissolved in the strong acids, caloric is given out 
 in great abundance, as in ordinary combustion. 
 So nearly does the operation of a voltaic battery 
 resemble combustion, that more or less heat is 
 always disengaged by its action. When the acid 
 solution is strong, and chemical action energetic, 
 the whole apparatus becomes warm ; viz. a por- 
 tion of the latent caloric of the acid is conducted 
 from the plates to the connecting wire in the 
 form of electricity ; while another portion is libe- 
 rated in the diffused form of sensible heat, as 
 when water and acids are poured upon burnt lime. 
 That the caloric of liquids is the cause of their 
 chemical action on the plates of the battery, is 
 proved by the fact, that when the apparatus is 
 supplied with hot solutions of the strong acids, 
 its energy is greatly augmented, and the metallic 
 plates rapidly dissolved ; in other words, the 
 battery is very soon burnt out. 
 
OR VOLTAIC ELECTRICITY. 391 
 
 It is stated by Singer, Donne, and others, that 
 the energy of De Luc and Zamboni's columns* 
 is greatly augmented by an elevated tempe- 
 rature, and diminished by a reduction of tempe- 
 rature ; that they are more active during summer 
 than winter ; and in a warm than a cold room. 
 Dr. Jaegar found, that after the dry pile had 
 lost its energy, it was restored by a temperature 
 of from 104 to 140 F. That the energy of this 
 pile is owing to chemical action, like every other 
 form of the battery, is proved by the oxidation 
 which it undergoes, and by the total loss of its 
 power when perfectly dry. 
 
 When isolated plates of zinc and copper are 
 immersed in dilute nitric acid, they are oxidized 
 and dissolved, when caloric is liberated as during 
 combustion; but when they are connected by 
 means of a metallic wire, galvanic electricity is 
 evolved. There can scarcely be a doubt that if 
 the caloric evolved by ordinary combustion could 
 be concentrated and conducted off like the gal- 
 vanic fluid, it would exhibit electrical pheno- 
 mena. Pouillet has actually shown that elec- 
 tricity is disengaged during nearly all combus- 
 tions, though in a slight degree, as had been 
 
 * The first is formed of disks of writing paper, interposed be- 
 tween thin leaves of zinc and silver; while that of Zamboni was 
 composed of paper disks gilt or silvered on one side, and the 
 other side covered with a layer of black oxide of manganese 
 mixed with honey. 
 
392 THEORY OF GALVANIC, 
 
 proved long ago by Lavoisier and Laplace, De 
 Saussure, and by Mr. Read. Were it not for the 
 caloric contained in nitric acid, it would not dis- 
 solve zinc and copper filings. For the same 
 reason, it would not combine with the plates of the 
 battery ; nor would it enter into chemical combi- 
 nation with any other substances. The battery 
 owes all its energy to chemical action, as cer- 
 tainly as that combustion is a chemical action. 
 Can common sense admit that caloric causes at- 
 mospheric oxygen to combine with combustibles, 
 and that some other agent causes the oxygen 
 of acids to combine with the plates of a voltaic 
 battery ? The supposition is wholly unphiloso- 
 phical, and is contradicted by all the analogies 
 of nature. Combustion is a chemical process to 
 all intents and purposes, and is produced by the 
 same agent which causes all other chemical 
 actions. Another important general fact, showing 
 the intimate relation between combustion and 
 galvanic action, is, that the action of the pile, 
 like that of combustion, is far more energetic 
 in oxygen gas than in atmospheric air ; and 
 ceases in vacuo, in nitrogen, and other gases that 
 do not act chemically on it. 
 
 If we compare the effects of galvanic elec- 
 tricity with those of caloric evolved by ordinary 
 combustion, we find that they are the same. 
 When voltaic electricity fuses, ignites, and vola- 
 tilizes, metals, gems, and all other combustibles, 
 
OR VOLTAIC ELECTRICITY. 393 
 
 does it not produce the same effect as that of an 
 oxy-hydrogen blow pipe ? or the concentrated 
 heat of a forge ? and if it produce the same 
 effects, must it not be the same agent? Can 
 electricity render bodies hot, and yet not be an 
 igneous fluid ? When charcoal is submitted to 
 the action of a galvanic current under water, it 
 is ignited, and decomposes the water as when 
 heated by ordinary combustion : and if an iron 
 wire, connecting the extremities of a battery in 
 action, be made to pass through water, it be- 
 comes hot and boils. When the wire is thus 
 heated, it attracts oxygen from water, as when 
 rendered red hot by other means. Like caloric, 
 electricity causes oxygen and hydrogen to com- 
 bine to form water, and again causes its decom- 
 position. 
 
 If then it be an established axiom in philo- 
 sophy, that the same effects should be ascribed 
 to the same cause, caloric and electricity must 
 be essentially the same agent. 
 
 The recent experiments of Dr. Faraday have 
 furnished many important facts, which show the 
 intimate relation between combustion and the 
 evolution of electricity by galvanic action. 
 
 It is very well known, that oxygen is not 
 indispensable to combustion ; that during the 
 rapid combination of chlorine, fluorine, iodine, 
 &c. with carbon, hydrogen, sulphur, phospho- 
 rus, and the metals, caloric is evolved in the 
 
394 THEORY OF GALVANIC, 
 
 form of radiant heat, as in ordinary combustion ; 
 in short, that caloric is evolved during nearly all 
 rapid chemical combinations. By following up 
 the experiments of Sir H. Davy, Dr. Faraday 
 has shown, that when chlorides, iodides, fluor- 
 ides, oxides, cyanides, nitrate of potass, chlorate 
 of potass, sulphate of soda, and various other 
 compounds were fused by heat, and interposed 
 between the plates of copper and platinum of 
 a voltaic battery, electricity was evolved as when 
 acids were employed ; and in some cases much 
 more freely. He adds, " there are hundreds of 
 bodies which evolve electricity in the same man- 
 ner, when in a state of fusion ; but that when 
 they became solid, the decomposition and the 
 electric currents ceased." He thinks that soli- 
 dification prevents decomposition, &c. " merely 
 by chaining the particles to their places, under 
 the influence of aggregation." (Experimental 
 Researches in Electricity, 4th Series.) Had this 
 distinguished experimenter recognized the agent 
 by which particles are aggregated and chained 
 together, he would have found that it is the alpha 
 and omega of chemical action, without which 
 there could be no voltaic electricity, and that 
 it is the source of all electro-chemical combina- 
 tions and decompositions. 
 
 But there are certain minute philosophers, 
 who maintain that the slightest difference be- 
 tween any two agents destroys their identity. 
 
OR VOLTAIC ELECTRICITY. 395 
 
 If such objections to the unity of caloric and 
 electricity were well founded, we should be 
 compelled to admit the existence of more than 
 a hundred species of electricity ; for it differs 
 with every modification of the process by which 
 it is produced, from thermo-electricity of the 
 lowest tension, to that of the Ley den battery, 
 which darts through metals and the living body 
 with the speed of lightning. 
 
 It is known, that the different forms of vol- 
 taic electricity pass with different degrees of 
 velocity through the same conductors ; and that 
 in this respect there is an almost infinite variety in 
 the properties which it presents. Yet these dif- 
 ferences have not prevented Wollaston, Faraday, 
 and many of the most distinguished philosophers 
 of the continent, from maintaining the identity 
 of electricity under every variety of form and 
 appearance which it exhibits, from that of Chil- 
 dren's battery, to De Luc and Zamboni's pile 
 and from a flash of lightning to the magnetic 
 spark, or the shock of a torpedo. Surely there 
 is a far greater difference between the electri- 
 city developed by a common machine and Chil- 
 dren's battery, than between the latter and solar 
 heat concentrated by means of a large burning 
 glass. It was shown by Mr. Parker of Fleet 
 street, that the most intense heat of a burning 
 glass three feet in diameter, though sufficient to 
 fuse and volatilize gems and metals in a few 
 
396 VOLTAIC ELECTRICITY. 
 
 seconds, passed through water without heating 
 it like electricity and that when it was made to 
 strike upon the finger, it produced little or no 
 sensation of heat, but that of a sharp cutting 
 instrument. 
 
 Analogies between Voltaic Action , and Subter- 
 ranean Chemical Forces. 
 
 FROM a general view of the foregoing facts and 
 observations, it would appear, that the galvanic 
 or voltaic pile affords a miniature representa- 
 tion of nearly all the chemical changes perpe- 
 tually going on throughout nature ; while it 
 exhibits the relations of caloric and electricity 
 in all their multiform states, in the most instruc- 
 tive manner. There is also a striking resem- 
 blance between the phenomena of galvanic heat 
 and that developed by volcanic agency ; not 
 only in the chemical mode of their production, 
 but in the effects they afterwards exhibit. In 
 both cases the radiating power of the igneous 
 aether evolved is exceedingly small, compared 
 with its power of fusing rocks, metals, gems, &c. 
 while they are both attended with thermotic and 
 electrical phenomena. A large voltaic battery, 
 capable of producing a current sufficiently 
 powerful to fuse and ignite the most obdurate 
 bodies, excites no sensation of warmth beyond 
 
VOLTAIC ACTION. 397 
 
 the apparatus. It is stated by M. Pouillet 
 Scrope, on the authority of Dolomieu, corrobo- 
 rated by his own observations, that very little 
 heat is radiated from a mass of red hot lava 
 that at the distance of a few feet, the thermo- 
 meter is scarcely affected by it, which induced 
 Dolomieu to suppose that its fluidity was due to 
 some other cause than caloric. (Scrope on Vol- 
 canos, p. 20.) 
 
 The reason why incandescent lava does not 
 radiate heat like coal, wood, &c. when in a state 
 of ignition, is doubtless owing chiefly to the 
 greater attraction of metallic and rocky masses 
 for caloric, than combinations of animal and 
 vegetable matter, as explained under the head of 
 radiation. 
 
 It has been long known, that the most intense 
 electrical phenomena are displayed during vol- 
 canic eruptions. If it be inquired why persons 
 near to a mass of incandescent lava experience 
 no electric shock, it may be answered, that no 
 shock is received from a voltaic battery of large 
 plates ; nor should we be able to discover that 
 any electricity was evolved were it not con- 
 ducted off by the connecting wires to the ex- 
 tremities of the pile : even then, it exhibits 
 chiefly the phenomena of concentrated caloric, 
 and but slight indications of electricity. 
 
 Mr. Scrope has given a highly graphic de- 
 scription of the electrical action that accom- 
 
398 VOLTAIC ACTION, AND 
 
 panied an eruption of Vesuvius that he wit- 
 nessed in October, 1 822 ; and which resembled 
 the awful displays of lightning that attended 
 its eruption in 89, when Pompeii and Hercu- 
 laneum were overwhelmed with lava ; and by 
 which his father lost his life. " From every 
 part of the immense cloud of ashes that hung 
 suspended over the mountain, flashes of forked 
 lightning darted continually. They proceeded 
 in greatest number from the edges of the cloud. 
 They did not consist, as in the case of a thunder 
 storm, of a single zigzag streak of light, but a 
 great many confiscations of this kind appeared 
 suddenly darting in every direction, from a cen- 
 tral point, forming a group of brilliant rays, 
 resembling the thunder bolts placed by the 
 ancient artists in the hands of the cloud com- 
 pelling Jove." (Scrope on Volcanos, p. 81.) 
 
 It is also related by Sir William Hamilton, 
 that the eruptions of Vesuvius in 1767, 79, and 
 94, were attended with the most tremendous exhi- 
 bitions of lightning ; and the two latter with 
 extremely loud explosions of thunder. Zigzag 
 lightning darted incessantly from the enormous 
 black clouds that hung over the crater, resem- 
 bling in all respects that of ordinary thunder 
 storms ; and accompanied by heavy showers of 
 rain, with whirlwinds, like those which attend 
 water spouts. Sometimes balls of fire issued 
 from the black cloud, which burst into serpen- 
 
SUBTERRANEAN CHEMICAL FORCES. 399 
 
 tine streams of fire. He thought that the vio- 
 lence of the subterranean action might be known 
 from the height to which the vapour and smoke 
 ascended, and by the amount offerilli, or vol- 
 canic lightning. (Philosophical Transactions of 
 the Royal Society, for 1795.) 
 
 Dr. Daubeny further relates, on the authority 
 of M. Monticelli, and other persons who wit- 
 nessed the eruption of Vesuvius in August, 1834, 
 that from a current of lava which overwhelmed 
 one hundred and fifty houses, and covered about 
 five hundred acres of ground, there arose a black 
 cloud, from which emanated very vivid flashes 
 of lightning, sometimes followed by thunder, but 
 not always. (Philosophical Transactions, 1835.) 
 
 It is also related in the American Journal of 
 Science, that on the 20th of January, 1835, Ni- 
 caragua, in central America, was visited by a 
 tremendous earthquake, and followed by an 
 eruption of the volcano of Cosiguina, by which 
 the atmosphere was filled to a great height and 
 distance with phosphoric sand, smoke, and va- 
 pour, from which issued perpetual flashes of 
 lightning throughout the night of the 20th, and 
 the whole of the next day. On the 23rd, 
 towards morning, tremendous loud thunder claps 
 were heard in succession, like the firing of the 
 largest cannon, from which it was supposed by 
 the inhabitants at the Port of Balize, on the 
 Bay of Honduras, that a naval action was going 
 
400 VOLTAIC ACTION, AND 
 
 on ; or that a ship was in distress. It is stated 
 that during this earthquake, the country was 
 convulsed for more than a thousand miles. 
 
 It is here worthy of special notice, that nearly 
 all the volcanos of our planet that are situated 
 on dry land, amounting to about two hundred, 
 have been found in the vicinity of the ocean ; 
 while it is probable, from the vast number of 
 volcanic islands, that there are at least three 
 times as many beneath the sea. 
 
 It is well known to modern geologists, that 
 submarine eruptions are exceedingly frequent. 
 On the 12th of June, 1811, immense volumes 
 of smoke were observed to arise from the sea, 
 near the island of St. Michael, one of the Azores, 
 by Captain Tillard of the Sabrina, from which 
 issued at intervals, for several days, the most 
 vivid flashes of lightning, and sometimes a con- 
 tinual blaze. During these eruptions an island 
 was formed, about a mile in circumference, and 
 two hundred and eighty feet high, which Cap- 
 tain Tillard visited, in company with several of 
 his officers, on the 4th of July, when he named 
 it Sabrina, after his ship. By the middle of 
 October, it had disappeared, leaving a dangerous 
 shoal. 
 
 During an earthquake on the 9th of July, 
 1757, eighteen small islands emerged from the 
 sea, near the N. west corner of St. George, 
 another of the Azores ; which also disappeared 
 in a few months. 
 
SUBTERRANEAN CHEMICAL FORCES. 401 
 
 The destruction of the town of Conception in 
 Chili, by an immense wave of the sea, twenty- 
 eight feet in height, which rolled over it, must 
 have been caused by a submarine volcano, as we 
 are informed by Mr. Caldcleugh, that two erup- 
 tions of dense smoke were observed to issue 
 from the sea, with violent ebullition, and the 
 evolution of large quantities of gas. 
 
 About the same time, flame and smoke burst 
 from the sea, near the island of Juan Fernandez, 
 over which the waves rolled to a great height, as 
 at Conception.* (Phil. Trans. 1835.) 
 
 But to return ; it has been shown that the vol- 
 taic fluid, whether thermal or electrical, is dis- 
 engaged from nearly all bodies when in a liquid 
 state from water, acids, saline solutions, from 
 oxides, chlorides, iodides, &c. when in a state of 
 fusion, during their chemical decomposition by 
 the plates of a battery. The resemblance of 
 this process to that of subterranean chemical 
 action is somewhat remarkable. For example, 
 the products of volcanic eruptions render it 
 almost certain, that subterranean caloric is dis- 
 engaged from sea water, which finds its way to 
 the interior through fissures and submarine cra- 
 ters, where its oxygen combines with sulphur, 
 metals, &c. as the oxygen of acids unites with 
 
 * It is singular enough that, while this sheet was in the press, 
 news arrived from South America, that the Island of Selkirk had 
 sunk beneath the ocean. 
 
 D D 
 
402 VOLTAIC ACTION, AND 
 
 the plates of a common battery.* That volcanos 
 are in some way abundantly supplied with sea 
 water, is evident from the vast quantities of 
 steam discharged during their eruptions, which 
 contains chloride of sodium, hydro-chloric acid, 
 chloride of copper, iron, &c. as well as from their 
 geographical positions near the sea. In short, the 
 earth may be regarded as a huge galvanic pile, 
 kept in a state of perpetual subterranean che- 
 mical action by the waters of the ocean, as our 
 little batteries are maintained in action by vari- 
 ous solutions. 
 
 When the plates of a common battery are 
 completely oxidized, chemical action ceases : 
 so when all the materials within a given range 
 of subterranean territory become saturated with 
 oxygen, sulphur, chlorine, &c. chemical action 
 ceases, and the volcanic forces become quiescent, 
 to be renewed elsewhere for indefinite periods of 
 time, until exhausted or burnt out like the plates 
 of a voltaic battery. 
 
 In North America, they have been nearly 
 
 * The hydrogen of water may unite with sulphur, making sul- 
 phuretted hydrogen ; while the union of oxygen with sulphur, 
 makes sulphurous acid, which combines with lime, and drives 
 off carbonic acid, a common product of hot springs and vol- 
 canos. The nitrogen of atmospheric air which is admitted 
 through craters, and is mixed in greater or less quantity with 
 all water, combines with hydrogen, forming ammonia. In fine, 
 there is no limit to the play of affinities that take place in this 
 grand laboratory, under the agency of so intense a heat. 
 
SUBTERRANEAN CHEMICAL FORCES. 403 
 
 extinct since the elevation of the rocky and 
 Alleghany mountains above the ancient sea that 
 once covered the northern hemisphere : while in 
 South America, and on the eastern continent, 
 volcanos are numerous, but confined chiefly to 
 the borders of the ocean. The only feeble re- 
 mains of subterranean chemical action in North 
 America are its warm springs, which convey off 
 whatever heat is generated below the surface, in 
 a tranquil manner. 
 
 The same observations apply to the greater 
 part of Europe and Asia, The Alps, the Appe- 
 nines, the Himalayas, and many other moun- 
 tain ranges of the old world, afford no evidence 
 of existing subterranean combustion, except the 
 numerous warm springs that issue from their 
 sides. Were it not for this continual discharge 
 of heat, it is probable that they might still be 
 convulsed at long intervals by volcanic explo- 
 sions, or by earthquakes, which are owing to 
 the confinement of volcanic steam by superin- 
 cumbent pressure. Warm springs may there- 
 fore be regarded as " safety valves of the globe," 
 still more emphatically than volcanos. It is very 
 well known that when the great Geyser of Ice- 
 land is obstructed by throwing stones into its 
 funnel, its temperature rises rapidly, which is 
 soon followed by eruptions of steam and water 
 to a great height. It is equally certain, that if 
 the obstruction were equal to the pressure of 
 
404 VOLTAIC ACTION, AND 
 
 two or three thousand feet of rocks or lava, 
 earthquakes would follow. 
 
 It was before stated, that the rapidity with 
 which acid, alkaline, and other solutions are 
 decomposed by the plates of the battery, is aug- 
 mented by increasing their temperature, that 
 the amount of chemical action, like that of 
 evaporation and rain, is greatest on the surface 
 of the earth within the tropics, cceteris paribus; 
 and diminishes as we approach the regions of 
 perpetual frost. 
 
 The same thing would seem to be true of 
 subterranean chemical action : which points out 
 the agency of solar heat in the production of 
 volcanos, and connects the whole theory of geo- 
 logical dynamics with that of solution, combus- 
 tion, and of universal chemistry. It is a re- 
 markable fact, which has never been explained 
 by geologists, that the highest mountains of the 
 earth are within the torrid zone, where they rise 
 to an elevation of from four to five miles above 
 the ocean level ; while in the middle latitudes 
 they do not exceed the height of fifteen or six- 
 teen thousand feet ; and not more than five or 
 six thousand feet beyond the polar circles, al- 
 though they are nearer to the centre of the globe 
 than any other part of its surface. The islands 
 of the Pacific and Atlantic oceans are also far 
 more numerous within the tropical than the 
 higher latitudes ; while it is certain that nearly 
 
SUBTERRANEAN CHEMICAL FORCES. 405 
 
 all of them have been elevated by submarine 
 volcanos. 
 
 All the chemical and geological operations of 
 our planet would seem to be in proportion to the 
 energy of solar radiation. Within the tropical 
 regions, the aggregate quantity of earthy and 
 metallic matter conveyed from the interior of the 
 earth in a state of chemical solution by springs, 
 is immense. The amount of evaporation and 
 rain being great, the rivers are large, and rapidly 
 destroy rocks, hills, and mountains, by mechani- 
 cal agency, which are transported to lakes and 
 seas, that are rapidly filled up by fluviatile de- 
 posits of sand, gravel, clay, pebbles, boulders, 
 &c. forming new lands. The waters of the ocean, 
 that find their way to the interior are warm, and 
 rapidly oxidize its metals and other minerals, by 
 which a corresponding amount of heat is disen- 
 gaged. 
 
 Thus it is evident that all the phenomena of 
 meteorology, chemistry, and geology, are re- 
 solvable into the agency of caloric, or thermo- 
 electric power. If rocks and hills are dissolved 
 by running water, and transported to lakes and 
 seas, caloric is the universal solvent. And here 
 must end for ever the long and idle controversy 
 between the Plutonian and Wernerian geolo- 
 gists. If caloric be indispensable to fluidity and 
 solution, it is as necessary to the formation of 
 sedimentary rocks as to the generation of granite, 
 
406 VOLTAIC ACTION, AND 
 
 basalt, and other volcanic products, which are 
 composed chiefly of metallic oxides, such as 
 those of silicium, calcium, aluminum, iron, pot- 
 assium, and sodium, the oxygen of which is 
 derived mostly from sea water. 
 
 There is something great and sublime in the 
 simplicity of the idea, that the same familiar 
 power which " warms in the sun," and clothes the 
 world with enchanting beauty, raises mountains 
 from the ocean, and keeps the whole stupendous 
 fabric of the universe in a state of perpetual 
 motion and circulation. 
 
 It was supposed by some of the older geolo- 
 gists, that in the earlier periods of the world, 
 there were no volcanos by others, that they 
 were far more active than at present while 
 Descartes, Leibnitz, Buffon, Fourier, and a mul- 
 titude of more modern philosophers, have main- 
 tained that the earth originally existed in a state 
 of fusion or incandescence throughout ; and that 
 it has been gradually cooling down ever since. 
 To those who believe in the uniformity of 
 nature's laws, it is needless to insist, that 
 none of these opinions have any foundation 
 in fact ; and that they are discountenanced by 
 all analogy. We are rather authorized to be- 
 lieve that the amount of chemical action going 
 on throughout the earth is the same in all given 
 periods of time, and in proportion to the amount 
 of matter. But if volcanic agency were due to a 
 
SUBTERRANEAN CHEMICAL FORCES. 407 
 
 central fire, it is difficult to comprehend why the 
 tropical mountains should be from five to six 
 times higher than those of the polar regions, 
 why volcanos are confined chiefly to the vicinity 
 of the ocean, why they should discharge enor- 
 mous quantities of steam saturated with muriatic 
 salts, why they should continue in action at 
 intervals for unknown periods of time, and then 
 become extinct, why volcanic islands are more 
 numerous in the tropical than higher latitudes, 
 and why hot springs should not be equally dis- 
 tributed all over the earth. 
 
 The facts collected by M. Cordier and others, 
 proving that the temperature of the earth in- 
 creases as we descend below the surface, have 
 been regarded by many geologists, as conclu- 
 sive evidence that earthquakes and volcanos are 
 caused by a central fire. It is true, that in 
 many parts of the world, the temperature of 
 rocky strata, and of the water that issues from 
 them, is higher at the bottom of deep mines than 
 at the surface, varying greatly however in dif- 
 ferent places. Mr. Fox found that in the Dal- 
 coath copper mine, in Cornwall, at the depth of 
 two hundred and thirty fathoms, a thermometer 
 placed in a hole in the rock, stood at 76 F., and 
 at 82 in water, ten fathoms deeper ; the mean 
 annual temperature of the surface being 50. 
 But the same gentleman states that about two 
 million gallons of water are daily pumped from 
 
408 VOLTAIC ACTION, AND 
 
 the Fold ice mine, at the temperature of from 90 
 to 100 ; while the mine is only one hundred and 
 seventy-six fathoms deep. It is therefore evi- 
 dent that the temperature is not proportional to 
 depth. 
 
 On the other hand, when we reflect that water 
 is continually acting upon metals, causing their 
 oxidation, and that chemical action is the grand 
 process by which latent heat is disengaged, we 
 need be at no loss to account for its accumulation 
 at great depths beneath the surface, where metals 
 are abundant. 
 
 It is impossible to know with certainty how 
 far the waters of the ocean penetrate beneath 
 the surface probably not beyond the depth of 
 a few miles ; nor is there any good reason to 
 suppose that there is much chemical action at 
 greater depths, owing to the superincumbent 
 pressure ; while it is known that on the surface 
 of the earth there is very little chemical action 
 without moisture. This much however is cer- 
 tain, that so far as we can trace back the history 
 of our planet, it has been composed as at pre- 
 sent, of mountains and valleys, seas and plains, 
 and stocked with plants and animals that have 
 successively arisen and passed away, leaving 
 their fossil remains as a record of their former 
 existence. We have the most indubitable proofs, 
 that our mountains of granite, gneiss, basalt, &c. 
 were formed during long geological epochs, by 
 successive volcanic movements, and contempo- 
 
SUBTERRANEAN CHEMICAL FORCES. 409 
 
 raneous with the deposition of our stratified 
 rocks ; while there is not the slightest evidence 
 that ever the earth was in a state of liquid fusion 
 throughout. According to the estimate of Mr. 
 Lyell, there are about two thousand volcanic 
 eruptions every century, which in six thousand 
 years would make 120 thousand. 
 
 If then it be admitted, that an equal amount 
 of caloric is removed by thousands of hot 
 springs, it is evident that such an enormous 
 loss, if not compensated by the waters of the 
 ocean, (which receive their temperature from the 
 sun,) would cause a sensible diminution of the 
 internal heat of the globe, and consequently, "of 
 its volume. But it is acknowledged by Fourier, 
 Laplace, and Arago, that the temperature of the 
 earth has not varied the -3-5-0 th of a degree in two 
 thousand years. This conclusion was deduced 
 from the fact, that the length of the day has not 
 diminished perceptibly since the time of Anaxa- 
 goras, which it is maintained must have been the 
 case, had any diminution of the earth's volume 
 taken place. 
 
 With the exception of Mr. Lyell and Dr. 
 Daubeny, nearly all geologists of the present 
 day have embraced the hypothesis of a central 
 fire, maintaining that the superficial crust of 
 the earth is supported by a mass of incandescent 
 lava. Baron Fourier supposed, (for he certainly 
 never proved it,) that the earth was originally 
 projected in a state of fusion or of incande- 
 
410 VOLTAIC ACTION, AND 
 
 scence, into the planetary space, the tempera- 
 ture of which he estimates at about 58 F. 
 due to radiation from the sun and fixed stars. 
 
 By a long and laborious series of mathema- 
 tical investigation, he arrived at the conclusion 
 " that the earth once heated to any temperature 
 whatever, and thus plunged into a colder me- 
 dium than itself, would cool no more in 1,280,000 
 years, than a globe of a foot in diameter com- 
 posed of the like materials, and placed in the 
 same circumstances would in a second of time, 
 -that is to say, in this immense time, no appre- 
 ciable variation would take place." (Ann. de 
 Chim. et de Phys., October, 1834.) 
 
 The absurdity of supposing that " all the 
 caloric of the earth below the invariable stra- 
 tum (which does not extend much beyond one 
 hundred feet below the surface,) comes from a 
 central fire," is too obvious to require a serious 
 refutation. 
 
 If there have been two thousand volcanic erup- 
 tions every century, according to the estimate 
 of Mr. Lyell, it would give 25,600,000 eruptions 
 in 1,280,000 years: yet the temperature of the 
 globe has not sensibly diminished in that time 
 according to the estimate of Fourier. But if 
 25,600,000 volcanic eruptions, together with 
 several thousand times as many hot springs, 
 had proceeded from a central fire, the reduction 
 of the earth's temperature must have been enor- 
 mous. It is therefore evident, that the whole 
 
REVOLUTIONS OF CLIMATE. 411 
 
 theory is not only hypothetical, but incompetent 
 to explain the phenomena. 
 
 There is nothing so remarkable in the natural 
 history of our planet, as the great revolutions of 
 climate and organic life which it has undergone 
 during the countless ages of the past. The most 
 fertile imagination never conceived anything so 
 wonderful as the varied scenes which the surface 
 of the earth has exhibited during different epochs, 
 before it was inhabited by man, or any of the 
 higher orders of animals. The rationale of these 
 mutations is by far the most comprehensive and 
 important problem in geology ; for it involves the 
 whole theory of organic life, and its immediate 
 relation to the vast science of physical astronomy. 
 The leading facts hitherto discovered, may be 
 reduced to the following general propositions : 
 
 1. That throughout the northern hemisphere, 
 from the shores of the Mediterranean to the north 
 of Europe and Asia, and from the southern 
 United States to Melville Island, in lat. 75 N. 
 the transition, secondary, and tertiary formations 
 are filled with the fossil remains of plants and 
 animals, which could have existed only in a uni- 
 formly warm climate, analogous to that of our 
 present tropics : 
 
 2. That at different epochs, the land and sea 
 were inhabited by totally different orders, genera, 
 and species of organized beings, which succes- 
 sively arose, flourished for a time, and then 
 gradually passed away, leaving only their pet- 
 
412 REVOLUTIONS OF ORGANIC LIFE. 
 
 rified remains as a lasting record of their exist- 
 ence : 
 
 3. That the more ancient the formations, the 
 more simple are the organisms they contain, and 
 the more unlike any which now inhabit the 
 earth ,* until we arrive at the newer secondary, 
 in which have been found a few birds and mar- 
 supial remains : 
 
 4. That during the uniformly elavated tem- 
 perature which prevailed in the middle and 
 higher latitudes, there was a corresponding uni- 
 formity in the zoological and botanical character 
 
 * For example, from the commencement of the transition to 
 the termination of the coal formation, (supposed to represent three 
 subdivisions, or geological epochs,) the sea every where abounded 
 with encrinites, polypi, terebratulse, trilobites, orthoceratites, and 
 other testacea, with a few species of strange fishes, which seem to 
 have been the only vertebrated animals then existing. But all 
 of these passed away, (unless we suppose what has not yet been 
 proved, that they underwent a gradual change under the influ- 
 ence of a different climatic condition of the earth,) and gave place 
 to animals wholly different from any that have existed since the 
 newer secondary eras, such as the huge icthyosauri, plesiosauri, 
 pterodactyli, turtles, and other reptiles. As we advance to- 
 wards the present epoch, we find in the older tertiary formation, 
 the palseotherium, the anoplotherium, and remains of cetacea re- 
 sembling the manati. These also passed away, and were suc- 
 ceeded by a still greater variety of warm blooded animals, some 
 of which are represented by living species ; such as the elephant, 
 rhinoceros, hippopotamus, fragments of the ape, and several 
 species of the feline genus ; to which may be added, the dinothe- 
 rium, the megatherium, the gigantic mastodon, and the elasmo- 
 therium, (a strange quadruped resembling both the horse, and 
 rhinoceros, ) all of which belonged to the newer tertiary epoch, 
 and which have also long since been numbered with the myriads 
 of extinct animals. 
 
THEORY CMP MR. LVELL. 413 
 
 of the earth, from the equator to the polar 
 regions.* 
 
 In his recent excellent work on geology, Mr. 
 Lyell refers all the past revolutions of organic 
 life to changes of climate, and the latter to 
 geological causes alone ; such as the gradual 
 shifting of sea and land, brought about by the 
 agency of volcanos, earthquakes, hot springs, 
 currents and waves of the ocean, the corroding 
 action of rains, rivers, springs, and chemical 
 decomposition. But if we admit with Mr. Lyell, 
 that the greater part of the dry land now scat- 
 tered over the northern hemisphere, may have 
 been formerly confined within the tropics, and 
 the mean temperature of the whole earth thus 
 
 * For example, nearly all the fossil plants hitherto discovered 
 in the older formations consisted of ferns, coniferae, Equiseta- 
 cese, and Cycadeae ; which in all, comprised only about five 
 hundred species, that presented very little diversity of form. It 
 is even asserted by the most intelligent botanists who have care- 
 fully examined the subject, that for a long period, during which 
 the climate of the middle latitudes seems to have exceeded the 
 present temperature of the tropics, cycadese alone formed about 
 one third of the entire Flora ; whereas they now constitute only 
 one two thousandth of the whole. But in the present diversified 
 condition of the earth, as regards temperature, it contains about 
 one hundred thousand species of plants, and above five hundred 
 thousand species of animals. It would therefore appear that 
 diversity in the generic and specific character of organized bodies, 
 depends chiefly on varieties of climate and season, which differ 
 in all the higher latitudes, and owing to the influence of local 
 causes, are scarcely ever exactly alike, even in the same latitudes, 
 as will be shewn in the first chapter of Book V. This subject 
 opens a vast field of inquiry to those physiologists who may be 
 disposed to investigate the origin of organic species. 
 
414 INFLUENCE OF 
 
 elevated 20 or 30, as he maintains ; it is still 
 evident, that the polar regions would be excluded 
 from the sun several months in the year, during 
 which time, all vegetation would be arrested ; 
 for it ceases whenever the mercury sinks below 
 52, according to Humboldt. It is therefore evi- 
 dent, that such a climatic condition of the earth 
 would be wholly incompatible with the existence 
 of a tropical vegetation, which is known to require 
 a mean temperature of about 80 throughout the 
 year. 
 
 Among all the causes which modify the tem- 
 perature of our planet, the most influential by far 
 is the obliquity of the earth's axis. In reality, 
 this condition determines chiefly, the vast differ- 
 ence between the climate of the tropical, tem- 
 perate, and frigid zones, together with all the 
 varieties of season. The question therefore natu- 
 rally arises, whether all the great changes of 
 climate which the earth has undergone, may not 
 have been owing to modifications of the same 
 cause, such as variations in the inclination of 
 its axis, or even a gradual transposition of the 
 equator and poles ? In support of this natural 
 view of the subject, it may be observed, that the 
 successive generation and extinction of tropical 
 plants and animals in the higher latitudes, would 
 seem to require the repeated occurrence of such 
 astronomical changes, which in their turn, afford 
 a complete explanation of all the phenomena. 
 And that such changes are not inconsistent with 
 
ASTRONOMICAL CAUSES. 415 
 
 the laws of nature is evident from the fact, that 
 the obliquity of the ecliptic has been constantly 
 diminishing for the last 4000 years. 
 
 It has been often asserted by writers on astro- 
 nomy, that great changes in the planetary incli- 
 nations would be inconsistent with the stability of 
 thesystem, as if all the operations of the universe 
 were not maintained by unceasing changes and 
 revolutions. But as Mr. Whewell observes, 
 " the cause of perturbation has the whole extent 
 of time to work in, " there is reason to believe, 
 that in the progress of long astronomical cycles, 
 every part of the earth has successively been 
 exposed to a vertical sun, and that such changes 
 are absolutely essential to the conservation of 
 the system in its existing state. For if the equa- 
 torial protuberance of the planets be owing to 
 the greater amount of light which falls upon the 
 tropics than upon the higher latitudes, it is ob- 
 vious that they would in time lose their present 
 spherical forms, by which their rotary motions 
 would be deranged, unless prevented by a gra- 
 dual transposition of the equator to higher lati- 
 tudes, or even to the polar circles. And that 
 such a transposition has actually taken place, is 
 strongly corroborated by the high and uniform 
 temperature which prevailed throughout the 
 middle and higher latitudes of the northern he- 
 misphere when it was the abode of tropical plants 
 and animals. 
 
416 THEORY OF M. AGASSTZ. 
 
 Nor is it less obvious, that if the inclination of 
 the earth's axis should go on augmenting from 
 to 40, there would be such a general refrige- 
 ration, as would destroy nearly all the pre-exist- 
 ing organisms of the middle latitudes, where 
 the mountain valleys would be filled with ice, 
 perhaps to the level of the sea ; as in Greenland, 
 Spitzbergen, and the southern polar continent. 
 In short, there would be what has been called 
 the Glacial Period by Dr. Louis Agassiz, who 
 has traced the evident marks of moving glaciers 
 on the polished and scoriated rocks of Switzer- 
 land, the Tyrol, Germany, Scotland, Ireland, 
 England, and France. And they have since 
 been observed in the United States.* 
 
 If we extend our view to the solar system, we 
 perceive that floods of aethereal matter in the form 
 of light, are perpetually flowing from the sun, and 
 
 * I cannot, however agree with M. Agassiz, that during what 
 he calls the glacial period, the whole surface of the earth pre- 
 sented a vast field of ice, from which projected only the highest 
 mountain ridges; nor that a cold by which every living being was 
 benumbed, suddenly appeared, and destroyed the myriads of or- 
 ganisms which but a moment before had been enjoying existence; 
 because it is impossible to account for such " a catastrophe" in 
 accordance with any of the known laws of nature. For example, 
 whence came all the waters required to produce a field of ice 
 many thousand feet in thickness ? And what had become of the 
 heating power of the sun, when the earth was seized with that 
 sudden Jit of the ague ? Yet there is ample proof, that immediately 
 antecedent to the existing order of things, a climate of polar 
 severity prevailed throughout the middle latitudes of the northern 
 hemisphere, and quite sufficient to destroy nearly ail the pre- 
 existing orders of tropical plants and animals. 
 
SUBTERRANEAN CHEMICAL FORCES. 417 
 
 keeping the air, the ocean, and the earth, in a 
 state of unceasing circulation converting solids 
 into liquids, gases and vapours, which are suc- 
 cessively changed into plants and animals. The 
 atmosphere is continually wasted by oxidation r 
 combustion, and the respiration of animals. But 
 is it not as constantly reproduced by vegetable 
 and animal decomposition? and are we not 
 authorized to conclude, that if the whole at- 
 mosphere were annihilated, it would be again 
 reproduced? or that if all the waters of the 
 ocean were extinguished, they would be gra- 
 dually regenerated by igneous chemical agency? 
 Wherever there is chemical action there must 
 be liquids and gases generated.* During respi- 
 ration and putrefaction carbonic acid is gene- 
 rated, the appropriate of food of living vege- 
 tation, which returns a portion of oxygen to the 
 atmosphere under the influence of solar light. 
 During the decomposition of organic matter, a 
 portion of atmospheric oxygen combines with 
 its hydrogen, forming water, and so on through 
 all the endless ramifications of nature, we per- 
 ceive that death is only a transformation of 
 matter, by which the earth is perpetually re- 
 novated, and crowned with immortal beauty. 
 
 * Hence the improbability of the astronomical hypothesis, 
 that the moon, Vesta, and some other planets, have no atmos- 
 pheres ; or that the atmosphere of Ceres is more than 668 miles 
 high, and that of Pallas 465 miles, according to the observations 
 of Shroeter and others. 
 
 E E 
 
418 
 
 CHAPTER V. 
 
 Hypothesis of two Electric Fluids. 
 
 Is the electric fluid one and the same in all 
 bodies ? or is it a compound fluid ? Each of these 
 hypotheses have been zealously maintained since 
 the time of Dufay and Franklin. But the con- 
 troversy has consisted rather in pointing out 
 frivolous distinctions in the phenomena pro- 
 duced, than in tracing the fundamental laws by 
 which they are governed. After a patient ex- 
 amination of the facts adduced by the British 
 and Continental philosophers, I have not been 
 able to discover any decisive evidence that there 
 are two electricities. On the contrary, it might 
 as well be maintained that there are fifty, or an 
 indefinite number; for this Protean agent ex- 
 hibits an endless diversity of appearances and 
 effects under different circumstances, according 
 to the various bodies from which it is obtained, 
 the mode of its developement, &c. 
 
 It was discovered by Dufay, about a century 
 ago, that when glass, rock crystal, diamond, pre- 
 cious stones, and many other substances, were 
 
HYPOTHESIS OF TWO FLUIDS. 419 
 
 warmed and rubbed with silk or woollen cloth, 
 they repelled light bodies in their vicinity; but 
 that when resinous bodies were made electric by 
 friction in the same manner, they attracted light 
 bodies which had been electrified by excited 
 glass. Having caused a piece of gold leaf to be 
 repelled, and suspended in the air by an elec- 
 trified glass tube, and meaning to chase it about 
 the room by a stick of excited gum copal, he 
 found that, instead of being repelled by it as it 
 was by the glass tube, it was eagerly attracted. 
 From which he concluded that there were two 
 kinds of electricity, residing in two different 
 classes of bodies ; one of which he termed vitreous, 
 and the other resinous, and that bodies charged 
 with either kind repel bodies charged with the 
 same kind, but attract bodies charged with the 
 other kind. But when it was afterwards dis- 
 covered by Dufay, that all bodies acquired the 
 power of attracting and repelling the same sub- 
 stances, according to the manner in which they 
 were electrified, he frankly acknowledged that 
 vitreous and resinous electricity were only dif- 
 ferent degrees of one and the same fluid. 
 (Priestley's Hist, of Electricity, pp. 43 and 412.) 
 Yet the doctrine of two electricities has been 
 constantly imputed to Dufay by nearly all writers 
 on the subject for the last 70 years. 
 
 It is said by those who still maintain the doc- 
 trine of two fluids, that if the gold leaves of an 
 
420 HYPOTHESIS OF TWO FLUIDS. 
 
 electrometer are made to diverge by means of 
 an electrified stick of resin, they will collapse 
 on the approach of an excited glass tube ; when 
 all signs of electricity disappear as if annihi- 
 lated. Nothing could be more fallacious than 
 such experiments ; for I have often found, that 
 after the gold leaves were made to diverge by 
 excited glass, they expanded still farther on the 
 approach of excited wax, and vice versa. The 
 result is evidently modified by the degree of 
 friction employed, and by the quantity of elec- 
 tricity thus disengaged. 
 
 It was long since observed by Dr. Watson, 
 that the rubber of a common electrical machine, 
 exhibited the same electricity in all respects as 
 that which had been produced by the friction of 
 sealing wax, sulphur, rosin, &c. and afterwards 
 by Canton, Franklin, Beccaria, and Wilson, that 
 whenever two vitreous bodies were equally elec- 
 trified they repelled each other, but when 
 unequally, they attracted each other ; and that 
 the same was true of resinous bodies. Dr. 
 Franklin also found, that when glass globes 
 were excited by friction, the spark was larger and 
 longer than when a sulphurous globe was used, 
 and made a louder noise ; from which he inferred 
 that the glass contained on its surface more elec- 
 tricity than sulphur ; he therefore denominated 
 that of the glass plus or positive, and that of the 
 sulphur negative terms which are now in ge- 
 neral use. 
 
HYPOTHESIS OF TWO FLUIDS. 421 
 
 It was subsequently ascertained, that when- 
 ever two different bodies are rubbed against 
 each other, they are in different states of elec- 
 tricity that when a glass tube is rubbed with a 
 dry silk handkerchief, the former is rendered 
 positive and the latter negative ; but if an insu- 
 lated metal be brought near to the glass, the 
 latter becomes negative and the metal positive. 
 Hence it was concluded by Franklin, that during 
 the action of a common machine, electricity is 
 evolved from the rubber, and attracted by the 
 cylinder of glass, from which it is attracted by 
 the prime conductor, and thence to other con- 
 ducting bodies. When amber and the tourma- 
 line are rubbed together, the latter becomes 
 plus or positive in relation to the amber ; but 
 when the tourmaline is rubbed against the dia- 
 mond, it is minus or negative, and the diamond 
 positive and so of many hundred other bodies. 
 
 The above facts are exceedingly important, 
 and are alone sufficient to prove that positive 
 and negative are only different degrees of one 
 and the same fluid, which accumulates in va- 
 rious proportions on different bodies, according 
 to the relative degrees of their attraction for it. 
 There are no two bodies in nature which have 
 the same degrees of attraction for electricity; 
 nor are there any two bodies which exhibit the 
 same electrical state when rubbed against each 
 other. It has even been found that the same 
 
422 HYPOTHESIS OF TWO FLUIDS. 
 
 bodies exhibit positive or negative electricity 
 according to their colour, or the condition of 
 their surface that smooth glass is rendered posi- 
 tive by friction with woollen cloth, and negative 
 when made rough by grinding it with emery, 
 all other things being equal.* 
 
 It cannot be denied that the electricity of a 
 common machine is derived chiefly from the 
 rubber ; for it is well known that its quantity is 
 greatly increased by spreading over the rubber 
 an amalgam of zinc or tin, the oxidation of 
 which supplies electricity freely, as in the action 
 of a voltaic battery ; while amalgams of silver 
 and platina, which do not oxidize at ordinary 
 temperatures, are of no use. But is it not evi- 
 dent, that if the prime conductor receive its 
 electricity from the rubber, that positive and 
 negative are only different proportions of the 
 same fluid? that it accumulates and becomes 
 plus on the prime conductor, because of its 
 greater attraction for it?| and that whether 
 positive or negative, its essential properties are 
 
 * Is not the attraction of rough glass for electricity less than 
 that of smooth glass, for the same reason that caloric escapes 
 more rapidly from rough than from smooth metals ? and does it 
 not accumulate upon insulated metals in greater quantities than 
 on electrics for the same reason that the former are good con- 
 ductors? (See page 194.) 
 
 f Something analogous takes place during the action of the 
 Galvanic pile. When the battery is composed of zinc and silver, 
 
HYPOTHESIS OF TWO FLUIDS. 423 
 
 the same under all circumstances? Is it not 
 owing to the attraction of metals for electricity, 
 that during the concretion of melted sulphur, 
 chocolate, calomel, and glacial phosphoric acid 
 from a state of vapour, in insulated metallic 
 vessels, the latter become electrified plus, and 
 the former minus? 
 
 It was before stated, that the more oxidable 
 metal in the galvanic circle furnishes positive 
 electricity in relation to the less oxidible one, 
 which is in direct opposition to the theory of two 
 fluids. M. Becquerel regards it as a proof of 
 two galvanic fluids, that positive electricity per- 
 meates imperfect conductors more readily than 
 negative. But this is just what might be ex- 
 pected from the plus and minus conditions of the 
 same agent. In accordance with this view, it 
 has been found, that other things being equal, 
 the heating effect of voltaic electricity is in pro- 
 portion to its quantity, and that the heating 
 effect of positive electricity exceeds that of ne- 
 gative. 
 
 It was maintained by Winterl, Oersted, Ber- 
 zelius, and at one time by Davy, that heat and 
 light were produced by the union of positive and 
 negative electricity. After what has been al- 
 and immersed in an acid solution, the zinc is oxidized, by which 
 electricity is disengaged, and passes to the silver, which is ren- 
 dered plus ; while the zinc, like the rubber from which the elec- 
 tricity proceeds, is negative. 
 
424 HYPOTHESIS OF TWO FLUIDS. 
 
 ready offered in regard to the relations of caloric 
 and electricity, it would be useless to multiply 
 arguments against so bald an hypothesis. It 
 was afterwards shown by Sir Humphry Davy 
 himself, that both heat and light are produced 
 by either positive or negative electricity alone, 
 though he adopted the doctrine of two fluids. 
 
 The following experiments of De Saussure 
 clearly illustrate the identity of positive and ne- 
 gative, with plus and minus conditions of the 
 electric fluid. On pouring water into heated 
 iron or copper vessels when insulated, and con- 
 nected with an electrometer, rapid oxidation was 
 produced, and positive electricity evolved ; but 
 after the metal became covered over with a coat- 
 ing of oxide, less electricity was disengaged, 
 which was negative. (Voyages dans les Alpes, 
 torn. ii. p. 244.) 
 
 It is also worthy of special notice, that he pro- 
 cured electricity from the vapour of water with- 
 out any chemical decomposition (a fact which 
 has been recently controverted by Pouillet, as 
 before stated, p. 316,) that the evaporation of 
 water from heated silver and white porcelain 
 vessels was attended with a disengagement of 
 electricity, that was generally positive, but some- 
 times negative. The same thing was observed 
 on placing incandescent pure white quartz in 
 water. 
 
 The advocates of two fluids explain the phe- 
 
HYPOTHESIS OF TWO FLUIDS. 425 
 
 nomena of electrical attractions in a singularly 
 gratuitous manner. They say that when an 
 electrified glass tube, or stick of wax, is brought 
 near to light bodies, it communicates to them 
 the opposite electricity from its own ; and that 
 they are brought together by the mutual attrac- 
 tion of the two electricities for each other that 
 when they touch the excited electric, they ac- 
 quire the same kind of electricity which it has, 
 and consequently are repelled. (Thomson on 
 Heat and Electricity, p. 362.) It might as well 
 be said, that liquid metals attract the same 
 metals when solid, because they are in opposite 
 states of electricity ; or that the attraction of the 
 living body by frozen mercury is owing to the 
 combination of the former with positive, and the 
 latter with negative electricity ; and that the 
 effect is produced by the mutual affinity of the 
 two fluids : whereas I have proved that the at- 
 traction of frozen mercury, and other cold metals, 
 for the living body is in proportion to their 
 affinity for caloric, which is plus in the one, and 
 minus in the other; and that all such pheno- 
 mena are owing to the attraction of caloric and 
 electricity for ponderable matter. 
 
 The whole train of Dr. Thomson's reasoning 
 in favour of two fluids is founded on groundless 
 assumptions. 1. That there is no attraction be- 
 tween electricity and ponderable matter: 2. that 
 there is an attraction between positive and negative 
 
426 HYPOTHESIS OF TWO FLUIDS. 
 
 electricity : 3. that matter does not repel matter: 
 and, 4. that nothing but the pressure of the am- 
 bient atmosphere prevents the escape of electricity 
 from bodies. (Idem p. 424.) Feeling some doubt 
 in regard to the last position, he elsewhere 
 speaks of "the unknown cause which prevents 
 it from leaving them." (Page 431.) Dr. Thom- 
 son maintains, that " matter does not repel matter, 
 because, in the motions of the heavenly bodies, 
 no such repulsion has ever been observed," 
 from which it would seem that he denies the 
 existence of a repulsive agency in nature. Hav- 
 ing assumed the above premises, he adds, " if 
 matter does not repel matter, and if there does 
 not exist any attraction or affinity between elec- 
 tricity and matter, then the Franklinian theory 
 of positive and negative electricity cannot be 
 correct."* (Page 425, on Heat and Electricity.) 
 
 * It is somewhat remarkable, that ^Espinus, who first gave to 
 Franklin's theory a mathematical form, should have regarded it 
 as incapable of explaining the phenomena of electrical attrac- 
 tions and repulsions, without also admitting that " matter repels 
 matter." What does he mean by this ? Has it not been recog- 
 nized by all the most distinguished writers on Natural Philo- 
 sophy, from Newton to Laplace, that all matter is endowed with 
 a power of repulsion as well as attraction ? And I have proved 
 that both these effects are produced by one and the same active 
 principle, which surrounds the particles of all bodies which, in 
 certain proportions maintains their solidity, in others their liqui- 
 dity, vaporization, and gasefaction and without which there 
 could be no contraction and expansion of matter, consequently 
 no motion. 
 
HYPOTHESIS OF TWO FLUIDS. 427 
 
 In accordance with the hypothesis, that there 
 are two electric fluids which have a mutual at- 
 traction for each other, it has been maintained 
 by several writers on Natural Philosophy, that 
 when a cloud passes over a mountain, or any 
 other portion of the earth, it communicates to 
 the mountain, &c. the opposite electricity from 
 its own, when the two fluids attract each other, 
 producing a discharge of lightning. Such is the 
 mystic jargon of which this great and beautiful 
 science is composed at the present day. The 
 truth is, that, notwithstanding the many new 
 facts which have been discovered within the last 
 35 years, the theory of electricity is far more 
 unintelligible than it was left by Franklin, Can- 
 ton, Wilson, Beccaria, and Priestley; for they did 
 recognize the important fact, that all the attrac- 
 tions and repulsions produced by electricity are 
 owmg to its affinity for common matter, and 
 repulsion of its own particles. Many of its phe- 
 nomena are yet involved in profound obscurity. 
 We know not why it is, that when an insulated 
 oblong conductor is brought near to an electri- 
 fied body, the end nearest to it becomes nega- 
 tive, and the opposite end positive, while in the 
 centre there is no sign of electricity. We do not 
 comprehend clearly why a Leyden bottle cannot 
 be charged and discharged while insulated nor 
 why the electricity of a large battery, or of an 
 immense mass of aqueous vapour, becomes con- 
 
4 '28 HYPOTHESIS OF TWO FLUIDS. 
 
 centrated into a spark or ball of fire. Much 
 also remains to be done before the theory of the 
 voltaic pile is thoroughly understood. 
 
 If, however, it be true, that all the forms and 
 modifications of this mysterious agent are con- 
 vertible into caloric, the theory of both will be 
 greatly simplified, and must shortly be reduced 
 to a very few fundamental axioms. 
 
 I have proved from the most elaborate series 
 of experiments on record, performed by De 
 Saussure and Read, that all atmospheric elec- 
 tricity, even that of the most serene weather, is 
 disengaged from aqueous vapour and by the 
 experiments of Dal ton, that caloric is the true 
 and only cause of evaporation. There is also a 
 perpetual flux and reflux of the electric fluid, 
 corresponding with the diurnal variations of 
 temperature, and fluctuations of the barometer. 
 According to De Saussure, it diminishes from 
 9 or 10 o'clock m the morning until 5 or 6 
 p. M., and increases until 8, when it again de- 
 creases until sunrise, when it is almost null 
 that is, it is most abundant when the vapour of 
 the air is undergoing condensation, (for the 
 same reason that it is plus or positive during 
 the formation of clouds, and during rain or 
 snow ;) but diminishes during the heat of the 
 day, while the vapour of the air is undergoing 
 expansion, by which it is connected with the 
 whole theory of evaporation, condensation, and 
 
HYPOTHESIS OF TWO FLUIDS. 429 
 
 lightning. It is further stated by De Saussure 
 and many others, that atmospheric electricity is 
 constantly changing from positive to negative, 
 which is also quite inconsistent with the hypo- 
 thesis of two fluids.* 
 
 Theoretical Views of Caloric and Electricity. 
 
 It is only by extending our knowledge of 
 nature, that we are enabled to trace an endless 
 diversity of apparently isolated effects to some 
 principle which connects and governs them ; or 
 to distinguish an unknown cause from the indi- 
 vidual and ever varying phenomena it produces. 
 The most signal and delightful triumphs of phi- 
 losophy spring from the perception of analogies 
 that seem remote and obscure, until closely ana- 
 lyzed. From the imperfect outline which has 
 been already presented of this vast and compli- 
 cated subject, it is obvious that all the opera- 
 tions of nature are so intimately connected, that 
 we cannot make any substantial progress in the 
 discovery of general principles without ascending 
 to the primary source of all physical power. 
 
 * It is related by Van Marum, that the doctrine of two elec- 
 tric fluids became general in France from the fact, that M. Hauy 
 was ordered by Napoleon to prepare a Treatise on Natural Phi- 
 losophy for the use of the Polytechnic School, and not having 
 time for reflection, he hastily adopted Coulomb's version of the 
 two fluids. Well might Count Oxenstiern say, to his son, come 
 and see with how little wisdom the world is governed. 
 
430 THEORETICAL VIEWS OF 
 
 Until this is done, it cannot be said that even 
 the foundation of physical science has been laid 
 on a durable basis. 
 
 In a strict and philosophical sense, it must be 
 admitted, that the words heat, caloric, igneous 
 fluid, electricity, &c. convey extremely limited 
 and imperfect ideas of that all-pervading prin- 
 ciple of action which preserves this universal 
 frame of things in a state of perpetual motion 
 and transformation. According to general ac- 
 ception, the term heat or caloric points to some 
 very general and important phenomena, such as 
 the sensation of warmth, or rather temperature, 
 liquefaction, vaporization, combustion, expan- 
 sion, &c. But these are transitory and occasional 
 effects, that are produced by its union with pon- 
 derable matter in certain proportions, and by no 
 means universal under all circumstances. 
 
 The term electricity is still farther from con- 
 veying an adequate idea of an universal agent, 
 than caloric. If we admit the existence of an 
 electric fluid, sui generis, which darts through 
 conducting bodies with immeasurable velocity, 
 and communicates a shock to the living frame, 
 it will not account for the phenomena of climate. 
 It is not in the form of electricity that it warms 
 in the solar beams. We cannot trace to its ac- 
 tion the melting of winter snows and polar ice- 
 bergs, the evaporation of water from the ocean, 
 and the elastic force of the atmosphere, the 
 
CALORIC AND ELECTRICITY. 431 
 
 contraction and expansion of gaseous bodies ; 
 combustion, solution, the production of winds, 
 rain, snow, dew, mists, and fogs, with all the 
 multitudinous phenomena of chemistry, geo- 
 logy, and physiology. It is, therefore, idle to 
 regard electricity as a primum mobile, or as an 
 universal principle of action. Besides, it has 
 been proved, that when solar caloric is greatly 
 accumulated in aqueous vapour, as in the tro- 
 pical regions, and during summer in the middle 
 latitudes, it is often disengaged suddenly in the 
 form of lightning, attended with rapid precipi- 
 tations of rain, or hail, and that, without the 
 caloric of aqueous vapour, there could be no 
 lightning ; consequently, that the sun is the great 
 fountain of atmospheric electricity. The truth 
 is, that if cold be regarded as only an abstraction 
 or diminution of caloric, it follows that tempera- 
 ture is an universal attribute of this principle ; 
 and I have shown that the attractive and repul- 
 sive powers of all bodies are modified by every 
 change of temperature which they undergo. It 
 is therefore evident, that caloric is not only far 
 more diffused throughout nature than electricity, 
 but that it is a permanent source of power, which 
 is perpetually attracting and repelling the atoms 
 of ponderable matter, and maintaining their soli- 
 dity as well as fluidity. 
 
 I have shown that every form and variety of 
 voltaic electricity are the results of chemical 
 
432 THEORETICAL VIEWS OF 
 
 action, and that without caloric there could be 
 no chemical action, from which it also follows, 
 that all the electrical phenomena of the battery 
 are modified and subordinate effects of the om- 
 nipresent igneous principle. 
 
 The term tether is yet more vague and inde- 
 finite than caloric or electricity, as it does not 
 very clearly indicate any of the foregoing pro- 
 perties, unless it be extreme subtilty. It is true 
 that the Greek philosophers regarded it as an 
 igneous principle, and as the source of power; 
 but without explaining the manner in which it 
 operates. We have also seen that Sir I. Newton 
 referred cohesion, capillary attraction, solution, 
 and even universal gravity to its agency ; but 
 without recognizing the law by which it pro- 
 duces the opposite effects of attraction and re- 
 pulsion ; or the mode in which it exhibits the 
 various phenomena of heat and electricity. 
 
 This much is certain, that whatever form the 
 spirit of matter assumes, or by whatever name 
 we designate it, it is under all circumstances an 
 aethereal essence, capable of uniting and sepa- 
 rating the elements of nature, and of communi- 
 cating to organized beings the sensation of heat. 
 There cannot, therefore, be any serious objection 
 to the use of caloric as a generic term, while we 
 keep in mind, that it is an universal source of 
 physical power, and the first of second causes. 
 I have shown that nearly all the most distin- 
 
CALORIC AND ELECTRICITY. 433 
 
 guished philosophers, ancient and modern, have 
 recognized the existence of such a power. It 
 was the Ilvp KaOapaiov of Hippocrates the ^Tv^n 
 of Aristotle, or the form of forms, by which he 
 meant the cause of causes the anima mundi of 
 the Romans the archeus of Paracelsus and Van 
 Helinont the mater ia subtilis of Descartes the 
 pneumatical power of Bacon the phlogiston of 
 Beccher and Stahl the electric fluid of Frank- 
 lin, Priestley, and Beccaria the latent heat of 
 Dr. Black and the caloric of modern times. 
 
 Analogies of Caloric and Electricity. 
 
 All that we can possibly know of either ca- 
 loric or electricity, must be derived from a careful 
 study of their fundamental properties, as exhibited 
 in the various phenomena which they produce 
 under different circumstances. Any hypotheses 
 concerning their essential nature are beyond 
 the scope of this inquiry. 
 
 For the sake of those who have not sufficiently 
 directed their attention to the intimate relations 
 of caloric and electricity, it may be of import- 
 ance to bring under one general view some of 
 their most striking analogies. 
 
 It has been shewn throughout the preceding 
 portion of this work, that all the motive powers 
 of caloric are resolvable into the primary and 
 
 F F 
 
4.34 ANALOGIES OF 
 
 universal law by which it repels its own particles, 
 and is attracted by ponderable matter, with forces 
 that vary inversely as the squares of the distance. 
 
 The phenomena of electrical attractions and 
 repulsions are clearly resolvable into the same 
 law. 
 
 It would be a needless waste of time to bring 
 forward the numerous proofs, that all the forces 
 of attraction and repulsion are inversely as the 
 squares of the distance. It has been demon- 
 strated by Buffon, Laplace, Coulomb, and other 
 philosophers, that the power of all emanations, 
 such as light, caloric, and electricity in the dif- 
 fused state, are subject to the same law, like 
 that of gravity. The ringing of electric bells, 
 the dancing of pith balls under an electrified 
 tumbler, of paper images, and many other simi- 
 lar experiments, performed for the amusement 
 of popular assemblies, are reducible to the above 
 law. When light leaves of gold, copper, silver, 
 zinc, &c. are brought near to the wire that con- 
 nects the extremities of a battery in action, or to 
 insulated metals when electrified by a common 
 machine, they are attracted by them. 
 
 When treating of chemical attraction, (Book 
 II. Chap. II.), it was shown that caloric causes 
 oxygen to combine with all other elements, from 
 the slowest process of oxidation, as in the rusting 
 of metals, fermentation, &c. to the most rapid 
 combustion. Electricity produces the same 
 
CALORIC AND ELECTRICITY. 435 
 
 effects. It was first observed by Dr. Franklin, 
 that when iron or steel wires were submitted to a 
 few electrical shocks, they became covered over 
 with a coating of rust. Dr. Priestley observed 
 the same effect on other metals after which 
 Cuthbertson proved by a great variety of expe- 
 riments, that all the known metals might be 
 rapidly oxidized by common electricity, even 
 gold and platina, which are difficult to oxidize 
 by the ordinary modes of applying heat. 
 
 By the attraction of caloric for ponderable 
 matter, it combines with various solids, produces 
 their fusion, and causes them to cohere with each 
 other. By its repulsion of its own particles, it 
 decomposes oxides, chlorides, iodides, bromides, 
 alloys, and all other compounds. 
 
 The same is true of electricity, which dissolves 
 and decomposes the most refractory bodies, such 
 as the earths, alkalies, and all other metallic 
 oxides, and again causes their elements to re- 
 combine. In short, there is no combination or 
 decomposition which may not be effected by 
 caloric and electricity, when sufficiently concen- 
 trated, and in due proportions. 
 
 When treating of cohesion, it was shewn that 
 all bodies have different degrees of attraction 
 for caloric ; and that their, conducting power was 
 in proportion to that attraction, that the lightest 
 known solids give out large quantities of caloric 
 during combustion, and are bad conductors ; 
 
430 ANALOGIES OF 
 
 while metals and other dense bodies that evolve 
 much less caloric, are good conductors, and 
 that other things being equal, the conducting 
 power of metals is augmented in proportion as 
 they are deprived of caloric. 
 
 It is also known that the lightest solids, cateris 
 paribus, afford the largest amount of electricity 
 by friction, and that they are bad conductors of 
 electricity. It was further ascertained by Sir 
 H. Davy, that the conducting power of metals 
 for voltaic electricity is diminished in proportion 
 to their temperature; (Phil. Trans. 1821 :) (and I 
 have shewn that their cohesion is diminished in 
 the same ratio.) It is therefore evident, that the 
 conducting power of bodies for both caloric and 
 electricity is modified by every alteration in the 
 relative proportions of aethereal and ponderable 
 matter of which they are composed ; and that as 
 a general rule, with few exceptions, the same 
 bodies are conductors and non-conductors of 
 both.* (See Theory of Conduction.) 
 
 It was before observed, that no two series of 
 
 * It may be objected, that some bodies which are non-con- 
 ductors of electricity when solid, become conductors in the liquid 
 state. But it is doubted by Dr. Faraday whether such bodies 
 ever do conduct electricity without undergoing decomposition, 
 as he found that, whenever they act chemically on the plates of 
 a battery, electricity is disengaged. Query. Is it not more pro- 
 bable that the non-conducting power of such bodies in the solid 
 state is owing to the crystalline arrangement of their particles, as 
 in the form of ice or snow ? (See p. 190.) 
 
CALORIC AND ELECTRICITY. 437 
 
 experiments, hitherto instituted for the purpose 
 of ascertaining the relative degrees of cohesion 
 and conducting power of the different metals, 
 have presented the same results. (See p. 180.) 
 It is however certain, that copper, gold, silver, 
 platina, iron, and zinc, are the best conductors 
 of electricity, and it has been shown by M. 
 Becquerel, that potassium is of all others the 
 worst conductor. (Ann. de Chim. et de Phys. 
 xxxii. 420.) 
 
 In opposition to the simple and rational theory 
 of Franklin, that electricity repels its own par- 
 ticles, and is attracted with various degrees of 
 force by different species of ponderable matter, it 
 has been maintained by Coulomb, Poisson, and 
 other philosophers, that there is no affinity between 
 electricity and ponderable matter, and that it is 
 confined to the surface of bodies by the pressure of 
 the atmosphere. 
 
 Nothing could more clearly illustrate the ten- 
 dency of mankind to take things upon trust, and 
 without examination, than the general adoption 
 of this partial and erroneous doctrine, by nume- 
 rous modern writers on physical science. It 
 seems to have been founded chiefly on the fact ? 
 that electricity escapes from the surface of 
 bodies more readily in vacua than under the pres- 
 sure of the atmosphere. But it has been de- 
 monstrated by Morgan, Cavallo, Ampere, and 
 Sir Humphrey Davy, that electrical attractions 
 
438 ANALOGIES OF 
 
 and repulsions take place in vacua as well as 
 under the pressure of the atmosphere. See 
 Philosophical Transactions for 1822, where the 
 experiments of Davy are recorded. 
 
 It is very true, that electricity in the diffused 
 state, moves more freely over the surface of 
 bodies, than through their substance ; and that 
 atmospheric air, when perfectly dry, assists in 
 preventing its escape from other bodies, because 
 it is a bad conductor. It was before stated, that 
 an electric spark expands in an exhausted re- 
 ceiver into a diffused lambent light and Mr. 
 Harris of Plymouth, has proved, that the striking 
 distance of the spark varies inversely as the 
 density of the air through which it passes, the 
 charge being the same. But these experiments 
 afford no proof that electricity is not attracted 
 by ponderable matter. The important practical 
 application of metallic conductors, as lightning 
 rods by Franklin, was founded wholly on their 
 attraction for the electric fluid. It never entered 
 into the imagination of this eminent philosopher, 
 that flashes of lightning are determined to the 
 earth and its conductors by the pressure of the 
 atmosphere. 
 
 That electricity, when concentrated, is capable 
 of passing through the substance of bodies, was 
 proved by Jallabert of Geneva 70 years ago, 
 who found that it might be readily transmitted 
 through metals, covered over with pitch. (Priest- 
 
CALORIC AND ELECTRICITY. 43f) 
 
 ley's Hist, of Electricity, p. 127.) But the same 
 thing is fully demonstrated by the fusion of 
 metals, rocks, gems, and all other bodies by 
 lightning and other forms of electricity, and by 
 the transmission of shocks through living bodies. 
 
 Notwithstanding the mathematical demonstra- 
 tions of the Coulombian theory, it is founded on 
 hypothetical and false assumptions ; and, when 
 applied to the explanation of natural pheno- 
 mena, is evidently of no practical value. It is 
 therefore not surprising, that Sir John Leslie 
 should have observed, in his history of physical 
 science, that it deserved the Dunciad. 
 
 To trace the analogies of caloric and electri- 
 city through all their diversified effects would 
 be an endless task. They are both disengaged 
 from all bodies by friction, pressure, percussion, 
 and by chemical action ; but vary according to 
 the manner in which the operation is performed. 
 It was proved by Becquerel, that the intensity 
 of electricity evolved by pressure was in pro- 
 portion to the force employed from which it 
 would seem, that, when the particles of bodies 
 are forced nearer together suddenly, a portion of 
 their latent caloric is disengaged in the concen- 
 trated form. 
 
 The greatest of all mysteries connected with 
 electricity is the protean power, by which it 
 assumes an endless variety of forms, and thus 
 evades our inspection. We have seen that vol- 
 
440 ANALOGIES OF 
 
 taic electricity, evolved from a single pair, or 
 from a few series of large plates, with an inter- 
 posing liquid, differs greatly from that which is 
 obtained from a battery composed of the same 
 materials, but consisting of a great number of 
 smaller plates, and that the latter is equally dif- 
 ferent from the electricity of the atmosphere, or 
 that procured from a common machine. In fine, 
 that these differences are as numerous as the 
 circumstances are various under which the phe- 
 nomena take place. What then ? Shall we as- 
 sume the existence of an indefinite variety of 
 electric fluids ? Nothing could be more absurd, 
 or in opposition to the fundamental laws by 
 which they are governed. 
 
 It has been supposed, that electricity is far 
 more subtile and refined than caloric, because of 
 the ease and rapidity of its passage through 
 metals and other conductors. This also is a 
 partial view of the subject ; for caloric passes 
 freely through mica, glass, and some other trans- 
 parent bodies, which arrest the electric fluid 
 when in the concentrated form. Nor is it true 
 that glass is altogether impervious to the electric 
 fluid. Compared with lac, it may be regarded 
 as a conductor ; for electricity produces attrac- 
 tions and repulsions through glass. If a small 
 pith ball be suspended within a glass jar by a 
 fine silk thread, it will be attracted by an elec- 
 trified glass tube on the outside. It is further 
 
CALORIC AND ELECTRICITY. 441 
 
 stated by Dr. Priestley, that electricity escapes 
 through some species of glass, like water through 
 a sieve, (History of Electricity, p. 592) ; and 
 there is a medical electrician in New York, by 
 the name of Humbert, who often amuses his 
 friends by discharging a Leyden jar of immense 
 size, through the coats of the glass without frac- 
 turing it. Besides, if a metallic wire be inserted 
 into a glass receiver, exhausted of air, and con- 
 nected with an electrical machine in action, a 
 stream of electric light is seen to proceed from 
 the wire in a straight line to the plate of the air- 
 pump : but if a conductor be presented to the 
 side of the glass, the electric light is drawn to- 
 wards it, which shows that electricity is attracted 
 through glass. The same thing is true, to a cer- 
 tain extent, of sealing wax, as shown by Dufay 
 a hundred years ago ; it is therefore evident, 
 that all bodies are permeable to this subtile aether. 
 The rapid passage of electricity through con- 
 ductors, and its power of communicating a shock, 
 are the most remarkable properties which dis- 
 tinguish it from caloric. But this difference 
 vanishes when we perceive, that it is only elec- 
 tricity of a peculiar tension or concentration, that 
 exhibits these powers ; and that many of its forms 
 produce no such effects. That the passage of 
 electricity through living bodies, without pro- 
 ducing the sensation of heat, is chiefly owing to 
 its velocity, would appear from the fact, that a 
 
442 MECHANICAL AGENCIES OF 
 
 spark from a Leyden battery may be passed 
 through gunpowder without igniting it, unless 
 retarded in its progress by an imperfect con- 
 ductor, such as water, when it inflames gun- 
 powder. When electricity of high tension passes 
 without interruption through conductors, it does 
 not heat them ; whereas, if they be too small to 
 allow its free passage, or if the conductors be 
 imperfect, they are heated, fused, and volati- 
 lized. The same is true of solar caloric, when 
 concentrated by a large burning glass, which 
 passes through water and other transparent sub- 
 stances without heating them ; but if made to act 
 on bodies that obstruct its passage through them, 
 they are fused, ignited, and dispersed in the form 
 of flame. 
 
 It has been a leading object of this inquiry 
 to show how partial and erroneous is the pre- 
 vailing notion, that the agency of caloric is limited 
 to the production of temperature, liquefaction, 
 combustion, &c. It is to its power of producing 
 motion, and of maintaining the harmonious action 
 of all the elements, that we are to seek for the 
 laws which connect it with the science of uni- 
 versal nature. 
 
 I have pointed out its mechanical agency in 
 steam, by which it produces every variety of 
 motion, horizontal, vertical, and rotatory and 
 by which it has given to man a power over matter 
 superior to all the achievements of ancient or 
 
CALORIC AND ELECTRICITY. 443 
 
 modern times in gunpowder and other fulmi- 
 nating compounds in volcanic eruptions and 
 in that process of evaporation by which the rains 
 of heaven are distilled from the ocean, trans- 
 ported through the atmosphere, and deposited 
 in fertilizing showers that it holds together the 
 atoms of solids with inconceivable force, and dis- 
 aggregates them with equal force in short, that 
 it is the grand instrument of Almighty Power 
 in executing the laws of nature. 
 
 The mechanical agency of electricity is equally 
 striking, though less constantly exerted. It over- 
 comes the cohesion of all bodies, whether simple 
 or compound, and acts equally on particles or 
 masses. It transports the different elements of 
 bodies to opposite poles of the battery. Acids 
 may be conveyed through alkalies, and alkalies 
 through acids, to their respective poles without 
 neutralizing each other. It has been shewn by 
 M. Fusinieri, that electric sparks issuing from 
 the brass conductors of ordinary machines, con- 
 tain incandescent particles of zinc and copper. 
 When drawn from silver, they contain impal- 
 pable particles of silver, that may be seen with a 
 good microscope, and discovered by chemical 
 tests. When a spark issuing from a knob of 
 gold passes through a plate of silver, a circular 
 spot, or stratum of gold is seen on the surface of 
 the plate where the spark entered and emerged, 
 which soon volatilizes and disappears and when 
 
444 MECHANICAL AGENCIES OF 
 
 it issues from a ball of copper, similar phe- 
 nomena occur. The spark also acquires new 
 particles from the metal through which it passes. 
 In all such cases, the colour of the spark de- 
 pends on the nature of the metal thus ignited 
 from which Fusinieri concludes, that electric 
 light is always combined with ponderable matter; 
 and that lightning owes its luminosity and odour 
 to the combustion of such matter. (Giornale del 
 Pavia, 1825.) 
 
 Dr. Priestley relates, that when the steeple of 
 St. Bride's church in London was torn by a flash 
 of lightning, it acted as an elastic fluid ; and that 
 its effects were exactly similar to what would 
 have been produced by gunpowder pent up in 
 the same places and exploded. 
 
 It is also related by Mr. Lyell, on the autho- 
 rity of Dr. Hibbert, that at Funzie, in Fetlar, 
 one of the Shetlands, about the middle of the 
 last century, a rock of mica schist, one hundred 
 and five feet long, ten feet broad, and in some 
 places four feet thick, was torn in an instant, by 
 a flash of lightning, from its bed, and broken 
 into three large, and several smaller fragments. 
 One of these, twenty-six feet long, ten feet 
 broad, and four feet thick, was simply turned 
 over. The second, which was twenty-eight feet 
 long, seventeen broad, and five in thickness, 
 was hurled across a high point, to the distance 
 of fifty yards. Another broken mass, about 
 
CALORIC AND ELECTRICITY. 445 
 
 forty feet long, was thrown still further, in the 
 same direction, quite into the sea, while many 
 smaller fragments were scattered up and down. 
 (Principles of Geology, vol. i. p. 260.) 
 
 A similar effect of lightning was related, not 
 long since, in the German papers. It was stated 
 that an enormous rock had been removed from 
 the bed of a stream in Prussia, by boring a deep 
 hole in it, into which was inserted a bar of iron 
 twenty-eight feet long. The consequence was, 
 that soon after, during a thunder storm, the 
 lightning was directed to the bar, and the rock 
 shattered to fragments. It would be useless to 
 dwell on the mechanical effects of electricity in 
 rending rocks, trees, buildings, &c. were it not 
 that there are still numerous writers on natural 
 philosophy, who affect to doubt its materiality ; 
 and some who resolve it into undulations of the 
 unknown aether, as if it could not be bottled up 
 in a Leyden battery like water, or any other 
 material fluid, or as if it did not act upon the 
 sense of sight, hearing, feeling, smelling, and 
 even of taste, like other material agents and as 
 if undulations were capable of causing horizontal, 
 vertical, and rotatory motion. 
 
 It was shown in Book II. Chap. ii. that other 
 things being equal, the chemical effects of calo- 
 ric are uniformly in proportion to its absolute 
 quantity. 
 
 It has also been shown by Davy, Children, 
 
446 EXPERIMENTS OF 
 
 and many other modern experimenters, that 
 both the heating and chemical powers of voltaic 
 electricity are in direct proportion to its quan- 
 tity ; and that the quantity evolved is in propor- 
 tion to the amount of chemical action which cor- 
 responds with the universally acknowledged fact, 
 that the heat of combustion is in the same ratio. 
 
 Without deciding whether electricity be a ma- 
 terial agent, sui generis, or mere motion of ordi- 
 nary matter, Dr. Faraday maintains, that " the 
 atoms of matter are in some way endowed or 
 associated with electrical powers, to which they 
 owe their most striking qualities, and amongst 
 others, their mutual chemical affinity," and he 
 has endeavoured to ascertain experimentally, the 
 absolute amount of this agent, motion, or power, 
 which is associated with the particles or atoms 
 of matter. He found that " one grain of water 
 required an electric current to be continued for 
 three minutes and forty- five seconds to effect its 
 decomposition ; which current must be powerful 
 enough to retain a platina wire y^ of an inch in 
 thickness, red hot in the air, during the whole 
 time." From which he concluded, that an equal 
 quantity of electricity is employed in holding 
 the particles of one grain of water together ; and 
 that it is probably equal to a very powerful flash 
 of lightning. (Experimental Researches in Elec- 
 tricity, Sixth Series, Phil. Transactions, 1834.) 
 
 He adds, in another section, (873), that " the 
 
DR. FARADAY. 447 
 
 chemical action of a grain of water upon four 
 grains of zinc, can evolve electricity equal in 
 quantity to that of a powerful thunder storm." 
 
 If this inference were well founded, the chemi- 
 cal action of a pound of water upon four pounds 
 of zinc, would afford as much electricity as many 
 thousand thunder storms, each of which is often 
 attended with from twenty to fifty or more flashes 
 of lightning : so that if the Doctor should devise 
 a mode of disengaging it in the concentrated 
 form, and in rapid succession, his experiments 
 would rival the thunders of Jove. 
 
 But this is not the climax of modern discove- 
 ries : for if we are to credit the account of Pro- 
 fessor Ritchie, u Dr. Faraday has found from a 
 recent experiment that, by the action of electri- 
 city on a copper wire, as much light was given 
 out in the course of a few days, as could be 
 emitted from the sun in a year." (Records of 
 Science, vol. i. p. 315.) And that this miraculous 
 story was not intended as a satire, would appear 
 from the gravity with which Dr. Ritchie adduces 
 it " as a strong argument in favour of the undu- 
 latory theory of light," of which he was known 
 to be a strenuous advocate. But I must return 
 to the sober and legitimate facts of science. 
 
 Like caloric, we have found that electricity fuses 
 the most hard and refractory bodies. As an ex- 
 ample of this, we are informed by Becquerel, 
 on the authority of Dr. Fiedler, that in eastern 
 
448 ELECTRIC LIGHT. 
 
 Prussia and Silesia, large glass tubes are fre- 
 quently found in banks of sand, from twenty to 
 forty feet in length, formed by the sudden fusion 
 of silicious matter by flashes of lightning; and, 
 as might naturally be supposed, that the inner 
 surface of these fulminary tubes is smooth, while 
 the outside is rough. In regard to the mechan- 
 ical effects of lightning in rending trees, displac- 
 ing large rocks, and perforating the walls of 
 buildings, the community is generally more or 
 less informed. 
 
 Again ; like caloric, electricity expands all bodies 
 into flame or light. But Sir I. Newton, and after 
 him Sir H. Davy, defined flame as gaseous 
 matter raised to a red or white heat : from which 
 it would seem that they both regarded flame as a 
 modification of ponderable matter. And I have 
 already shewn that all bodies may be converted 
 into light, whether by heat or electricity ; and 
 that its colour varies according to the nature of 
 the ponderable matter employed;* that potas- 
 sium, strontium, lithium, boron, and some other 
 bodies, burn with a red light ; hydrochlorate of 
 calcined soda, with an orange light ; oil, tallow, 
 and resins, with a yellow light ; hydrogen 
 
 * Much additional information might be obtained on this im- 
 portant subject, by submitting all the elements of ponderable 
 matter to the agency of voltaic electricity, separately in succes- 
 sion ; and by analyzing their light with a prism, or by causing it 
 to pass through differently coloured transparent media. 
 
CAUSE OF MAGNETIC POWER. 449 
 
 and some others, blue light; arid iodine, violet 
 light, but that when different elements are 
 burnt together, the result is a compound light, 
 which may be decomposed with a prism into 
 different primitive colours like the solar rays 
 
 in short, that there is no essential difference 
 between electric light and that of ordinary com- 
 bustion, and that electricity is never luminous 
 or visible, except when in a state of combina- 
 tion with ponderable matter, as maintained by 
 Fusinieri. 
 
 Since the discovery of OErsted, that a metallic 
 wire which connects the extremities of a voltaic 
 battery in action, is capable of deflecting a mag- 
 netic needle placed near it from its ordinary 
 position ; and of Davy and Arago, that it is 
 capable of attracting iron filings during the pas- 
 sage of an electric current through it, philoso- 
 phers have seemed to suppose that the produc- 
 tion of magnetic effects was a peculiar and dis- 
 tinctive attribute of electricity. But if it were 
 established, that electricity is a distinct fluid, sui 
 generis, it is nevertheless demonstrable, that ca- 
 loric is capable of producing magnetic pheno- 
 mena in a still more remarkable and universal 
 manner and that electricity of high* tension, 
 which produces a shock, and darts through 
 metals with the greatest velocity, produces very 
 feeble and partial effects on the magnetic needle, 
 during its passage through a multiplying wire. 
 
 G G 
 
450 MAGNETIC EFFECTS OF 
 
 It was first remarked by Davy, that the mag- 
 netic influence of a voltaic current was in pro- 
 portion to the heat developed in the wire con- 
 necting the extremities of the battery. (Philoso- 
 phical Transactions, 1821.) And it is now uni- 
 versally known, that batteries composed of a few 
 large plates of zinc and copper, or even of a 
 single pair of plates, are the best adapted for 
 exhibiting magnetic phenomena in fine, that 
 the magnetic power of voltaic electricity is pro- 
 portional to the quantity evolved, and inversely 
 as its tension, or power of communicating a 
 shock that thermo-electricity which affords 
 none of the usual signs of common electricity, 
 such as diverging the gold leaves of an electro- 
 meter, and passing rapidly through conductors, 
 deflects a delicate magnetic needle. It was long 
 since observed by M. CErsted, that common 
 electricity passed too rapidly through metallic 
 wires to affect the needle an hypothesis which 
 has been confirmed by M. Colladon of Geneva, 
 who found that when the wire was covered with 
 three folds of silk, (which must have retarded the 
 velocity of the electric current through it,) the 
 needle was deflected as by a current of voltaic 
 electricity. 
 
 The most important application of (Ersted's 
 discovery was the invention of what has been 
 termed an electric multiplier, or galvanometer, by 
 M. Schweigger of Halle, which has been variously 
 modified by other philosophers. Before the in- 
 
CALORIC AND ELECTRICITY. 451 
 
 vention of this beautiful instrument, a prepared 
 frog was considered the most delicate test of gal- 
 vanic electricity. But it has been found, that 
 the multiplier is not only a far nicer test of elec- 
 tricity, but that it is also the most delicate ther- 
 moscope ever invented that -^fa part of a de- 
 gree of Fahrenheit's thermometer produces a 
 sensible movement of a small needle suspended 
 by a fibre of silk. From which it follows, that 
 magnetic phenomena are not confined to the 
 action of electricity, but also result from the 
 agency of caloric in quantities too small for mea- 
 surement by any other test. 
 
 It is therefore not a little surprising, that when 
 Dr. Faraday offered as a proof, that all the 
 varieties of electricity are essentially the same, 
 because they all produce magnetic effects, that 
 he did not recognize the identity of caloric and 
 electricity. 
 
 Guided by the general fact discovered by 
 (Ersted, that a magnetic needle placed over the 
 wire connecting the poles of a battery in action 
 has a tendency to arrange itself at right angles 
 to the conducting wire, Schweigger covered a 
 common brass wire with silk thread, for the 
 purpose of insulating it. This wire was then 
 lapped round a piece of wood, 50, 100, or 200 
 times. When its two extremities were connected 
 with the poles of a battery in action, the galvanic 
 current passes through all the windings of the 
 wire, by which the magnetic effects are multi- 
 
452 MAGNETIC EFFECTS OF 
 
 plied with every turn of the wire ; so that when 
 a magnetic needle is suspended in the middle of 
 the hank of wire, it is placed at right angles to 
 it. In this way the power of the multiplier was 
 made to detect, not only minute portions of elec- 
 tricity that could not be otherwise appreciated, 
 but the smallest changes of temperature, as be- 
 fore observed.* 
 
 By an improvement of this important instru- 
 ment, MM. Nobili and Melloni were enabled to 
 detect the heat of phosphorescent wood, dead 
 fish, living insects, and that of the different co- 
 loured rays of the solar spectrum. But it was pre- 
 viously discovered by Dr. Seebeck of Berlin, that 
 when a circuit is formed by soldering together 
 two metals, and applying the heat of a lamp to 
 one of the junctions, a needle placed within it 
 was deflected from the magnetic meridian, and 
 placed at right angles to the metals forming the 
 circuit. It was afterwards found by Dobereiner, 
 that the heat of the hand was sufficient to cause 
 a deflection of the needle, when applied to the 
 junction of the two metals and by others, that 
 the same effect was produced by applying ice, 
 aether, or any thing which alters the tempera- 
 ture in one part of the circuit from that of the 
 
 * It was also by wrapping a piece of soft iron, bent in the 
 form of a horse shoe, with insulated copper wire, and connecting 
 its extremities with the poles of a galvanic battery, that Pro- 
 fessor Moll of Utrecht was enabled to convert it into a tem- 
 porary magnet of great power. 
 
CALORIC AND ELECTRICITY. 453 
 
 rest. M. Becquerel found, that when one end 
 of the multiplying wire was heated and brought 
 in contact with the other end, the needle was 
 deflected. Hundreds of similar experiments 
 might be adduced, all of which demonstrate the 
 agency of caloric in producing magnetism, where 
 there is no sign whatever of electric tension; 
 and that the magnetic needle is a true test of 
 the smallest quantities of caloric that have ever 
 been measured. 
 
 Some of the most delicate experiments on re- 
 cord were performed by Dr. Locke of Cincinnati. 
 By interposing one quarter of a grain of anti- 
 mony between the two copper wires of a mul- 
 tiplier, and applying the warmth of his finger, 
 the needle was deflected 22. In another ex- 
 periment, one of the copper wires was laid upon 
 the other, without the interposition of any other 
 metal, and the warmth of the hand applied as 
 before, when the needle was deflected 6. The 
 same results were obtained by substituting the 
 warmth of the breath instead of that of the hand. 
 The temperature of the room in which the ex- 
 periments were made was 65. F. (American 
 Journal of Science, April, 1834.) 
 
 But the most decisive proof that caloric and 
 electricity are only modifications of one and the 
 same agent is, that they are mutually convertible 
 into each other ; and that the electric fluid ob- 
 tained from a permanent natural magnet, fuses, 
 volatilizes, and ignites charcoal, metals, and 
 
454 GENERAL CONCLUSIONS. 
 
 other solids, like ordinary caloric, as may be 
 daily witnessed at the Adelaide Gallery in Lon- 
 don. 
 
 From a general review of the foregoing chap- 
 ters, the following conclusions have been de- 
 duced : 
 
 1 . That the latent caloric of aqueous vapour is 
 the true and only basis of lightning : 
 
 2. That the latent caloric of liquids is the basis 
 of voltaic electricity in all its various forms : 
 
 3. That they are both governed by the same 
 universal law of attraction for ponderable matter, 
 and repulsion of their own particles : 
 
 4. That the essential properties of positive and 
 negative electricity are the same under all cir- 
 cumstances : 
 
 5. That when metals are made red hot by 
 electricity, whether it be disengaged from a gal- 
 vanic battery, a common machine, or from a 
 magnet, it immediately loses its peculiar power 
 of darting through conductors and producing a 
 shock, being transformed into caloric, when it 
 excites the sensation of heat, and converts solids 
 into liquids, vapours, and gases, which present 
 the same properties as if generated by the action 
 of ordinary caloric : 
 
 6. That if caloric and electricity be not modi- 
 fications of one power, and the cause of all me- 
 chanical and chemical action, the whole of mo- 
 dern science is a perfect chaos of contradictions. 
 
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