Digitized by the Internet Archive 
 
 in 2007 with funding from 
 
 Microsoft Corporation 
 
 http://www.archive.org/details/chemistrreligionOOcookrich 
 
Religion and Chemistry 
 
 A RE-STATEMENT OF AN OLD ARGUMENT 
 
 JOSIAH PARSONS COOKE 
 
 Erving Professor of Chemistry and Mineralogy in Harvard University 
 
 |-f 
 
 A NEWLY REVISED EDITION 
 
 Duo si^nt <^a^ in ccgnit^i&iem Dei dvLtiat Creatura et Scriptura 
 
 y1 
 
 'x'i 
 
 St. Augustine 
 
 NEW YORK 
 CHARLES SCRIBNER'S SONS 
 
 743 AND 745 Broadway 
 1880 
 

 Copyright, 1864, by 
 PETER G. TAYLOR 
 
 Copyright, 1880, by 
 JOSIAH P. COOKE 
 
 PRES9 OF J. i. LITTLE & CO., 
 H03. 10 TO 20 ASTOR PLACE, NEW VORK. 
 
THE FIRST EDITION OF THIS BOOK WAS DEDICATED 
 TO A GREATLY BELOVED FATHER. 
 
 THIS ONE IS CONSECRATED BY THE MEMORIES 
 
 OF HIS LONG AND HONORABLE LIFE, 
 
 PEACEFULLY CLOSED. 
 
PREFACE. 
 
 The conditions under which this work was first 
 published are stated in the preface to the first 
 edition, reprinted below. Although the book has 
 been long out of print, the author has not been able 
 to revise it for a new edition until now, and returning 
 to this work of his youth, after twenty years of active 
 life, he has found nothing in the tone or sentiments 
 of the book which he desired to change. Indeed, 
 larger knowledge has only served to confirm the gen- 
 eral convictions therein expressed. But, of necessity, 
 the discovery of new facts and changes in scientific 
 theories have required alterations of phraseology in 
 many places, and more experience has led to greater 
 caution in the statement of conclusions. It was the 
 author's first intention to re-write the whole book on 
 a different plan, and in retaining the popular style of 
 the first edition he has yielded to the judgment of 
 friends who thought that the book would be more 
 useful in its early, fresh form. The discussion of the 
 
VI PREFACE. 
 
 principles of crystallography in the first edition has 
 been omitted in the revision, because found too 
 abstruse for popular reading ; but the place has been 
 more than supplied by the new matter which has 
 been added. The work is solely a popular expo- 
 sition of the subjects on which it treats, and this 
 design has precluded a fuller discussion of many 
 points, as well as that precision of statement which 
 might be expected in a more formal essay. By 
 vote, recorded in their proceedings of March 6, 1875, 
 the Directors of the Brooklyn Institute released to 
 the author their copyright in the original work, and 
 he would here express his grateful appreciation of 
 this courtesy. 
 
 Newport, September '^o, 1880. 
 
PREFACE TO THE FIRST EDITION. 
 
 The lectures now published were first delivered 
 before the Brooklyn Institute on Sunday evenings 
 of January and February, 1861, and the larger 
 part of them were subsequently repeated, during 
 the same winter, before the Lowell Institute in 
 Boston, and before the Mechanics* Association of 
 Lowell. The progress of science since that time 
 has rendered necessary many additions, and in re- 
 vising the lectures for publication, the material 
 has been thus so greatly increased that what was 
 originally prepared and delivered as six lectures is 
 now distributed over ten. At the time when the 
 lectures were written, Mr. Darwin's book on the 
 Origin of Species, then recently published, was ex- 
 citing great attention, and was thought by many 
 to have an injurious bearing on the argument 
 for design. It was, therefore, made the chief aim 
 of these lectures to show that there is abundant 
 
Vlll PREFACE. 
 
 evidence of design in the properties of the chemi- 
 cal elements alone, and hence that the great argu- 
 ment of Natural Theology rests upon a basis which 
 no theories of organic development can shake. In 
 illustrating his subject, the author has used freely 
 all the materials at his command, and if, in any 
 case, he has failed to give due acknowledgment, it 
 has been because by long dwelling on the subject 
 the thoughts of others have become blended with 
 his own. He would here acknowledge his repeated 
 indebtedness to Professor Guyot's work on " Earth 
 and Man,'* to Professor Faraday's published Courses 
 of Elementary Lectures, and to Professor Tyn- 
 dalFs Lectures on " Heat considered as a Mode of 
 Motion." He would also express his especial obli- 
 gations to the author of " In Memoriam," in whose 
 verses he has discovered a truer appreciation of 
 the difficulties which beset the questions discussed 
 in this volume, than he has ever found in the phi- 
 losophy of the schools. 
 
 Cambridge, May 3d, 1864. 
 
CONTENTS. 
 
 CHAPTER. PAGES 
 
 I. Statement of the Case — Testimony of the 
 
 Atmosphere 1-30 
 
 II. Testimony of the Atmosphere — Concluded 31-68 
 
 III. Testimony of Oxygen 69-94 
 
 IV. Testimony of Oxygen — Concluded 95-118 
 
 V. Testimony of Water 119-162 
 
 VI. Testimony of Carbonic Dioxide .* 163-202 
 
 VII, Testimony of Nitrogen 203'-228 
 
 VIII, Argument from Special Adaptations 229-257 
 
 IX. Argument from General Plan 258-292 
 
 X. Necessary Limitations of Scientific and Re- 
 ligious Thought 293-332 
 
 ix 
 
^ L i H H A a V 
 
 UNIVKS^^^TY OF 
 
 CALmJivNlA.^ 
 
 RELIGION AND CHEMISTRY. 
 
 CHAPTER I. 
 
 STATEMENT OF THE CASE— TESTIMONY OF THE 
 ATMOSPHERE. 
 
 The time has been when the Christian .Church 
 was an active antagonist of physical science ; when 
 the whole hierarchy of Rome united to condemn its 
 results and to resist its progress ; when the immedi- 
 ate reward of great discoveries was obloquy and 
 persecution. But all this has passed. The age of 
 dogmatism has gone, and an age of general scepti- 
 cism has succeeded. The power of traditional au- 
 thority has given place to the power of ideas, and 
 physical science, which before hardly dared to assert 
 its birthright, and could even be forced to recant, on 
 its knees, its demonstrated truths, has now become 
 one of the rulers of society. By its rapid growth, 
 by its conquests over brute matter, and by its won- 
 derful revelations, it has deservedly gained the 
 highest respect of man, while by multiplying and 
 1 I 
 
THE CHURCH AND SCIENCE. 
 
 diffusing the comforts of life it has become his ac- 
 knowledged friend. Every effort is now made to 
 further its progress. Its great discoveries win the 
 applause of nations, and its fortunate students are 
 remembered when the princes and nobles of the 
 earth are forgotten. 
 
 All this is well. But unfortunately, elated by his 
 success, the stripling has been at times proud and 
 arrogant, usurping authority not his due. Forget- 
 ting his early faith, he has approached with irreverent 
 thoughts the holy temple of our religion, and, not 
 content to worship in the outer court, has dared to 
 penetrate into the very Holy of Holies, and apply 
 his material tests even to the vessels of the altar. 
 No wonder that the Church should become alarmed, 
 that many of her best men, holding fast to the 
 sacred dogmas of our religion as the only sure 
 anchor of their faith in this world, and their sole 
 ground of hope for the next, should join in a gen- 
 eral cry against the whole tendency of science and 
 its results. 
 
 But this is a great mistake. Judging of the real 
 character of physical science from the pretensions 
 of a few, and not possessing the power or opportu- 
 nity of investigating for themselves, these good men 
 are unnecessarily alarmed : the phantom they fear is 
 purely of their own creation, and, could they but 
 know the whole truth, they themselves would see 
 that to ignore the well-established results of science, 
 and to denounce its legitimate tendency, is a policy 
 as short-sighted as it is illiberal and unchristian. 
 ( Fortunately, such fearful souls constitute but a 
 
THE CHURCH AND SCIENCE. 
 
 small party in the Christian Church. There is a far 
 nobler and more courageous faith than theirs, — a 
 faith so strong in its convictions that it fears no 
 criticism, however searching, and no scientific analy- 
 sis, however rigorous it may be, — a faith which finds 
 in the Bible, not a series of dead formulas, but a 
 mass of living truth, — a faith which really believes 
 that the God of nature is the God of grace, and that 
 man was created in the image of this one and only | 
 God, — R faith which wells up from the depths of the ? 
 soul, which speaks because it believes, which believes 
 because it feels, — a faith whose sources are as hid- 
 den as those of the fountain, but whose reality is as 
 living as the verdant landscape which the fountain 
 -^-waters. 
 
 It is the men with a faith like this who are the 
 really brave Christians. They are not alarmed at the 
 apparent contradictions between science and revela- 
 tion. By the very imperfections of their own facul- 
 ties, which they so keenly appreciate, they have 
 been taught that mysteries exist ; nay, they find in 
 these very mysteries the strongest bulwarks of their 
 faith ; for they feel, with Robert Hall, that " a re-T^ 
 
 ligion without its mysteries would be a temple withj 
 
 out its God.'* They are fully assured that our minds 
 were framed after the likeness of their Divine origi- 
 nal, in order that we, creatures of the dust though 
 we are, might nevertheless in our feeble measure 
 comprehend God's workmanship and sympathize 
 with his divine thoughts ; and they reject as absurd 
 the doctrine that man, thus created an intelligent 
 and sympathizing observer of God's universe, should 
 
BRAVE CHRISTIAN FAITH. 
 
 have been permitted, in the legitimate exercise of 
 the very powers which God has given him, to build 
 up a connected system of science in direct contra- 
 diction to those higher and spiritual truths which 
 the Father has been mercifully pleased to reveal to 
 his sinning children through his prophets and his 
 Son. 
 
 In the sight of this brave Christian faith there can 
 be no essential contradiction between science and 
 revelation. On the contrary, all nature appears ra- 
 diant with the Divine Presence. 
 
 " The heavens declare the glory of God, and the7~ 
 firmament showeth his handiwork. Day unto day 
 uttereth speech, and night unto night showeth 
 ;;.vlcnowledge. There is no speech nor language where! 
 their voice is not heard. Their line is gone out! 
 through all the earth, and their words to the end of 
 the world.*' 
 ^' But although this glorious song of the Psalmist 
 has been chanted through the ages as expressing the 
 all but universal belief of thinking men, there has 
 always existed at the same time a philosophy which 
 interpreted the facts of nature in a very different 
 way, and within the last few years this philosophy 
 has become more than ever before dogmatic and 
 aggressive. For the present we waive all discus- 
 sion of the fundamental questions which material- 
 ism raises. With the increasing experience of life, 
 we cling ever more and more fondly to the belief 
 that the grand thoughts which the study of nature 
 suggests to our mind are the manifestations of a 
 Being who is not only to be venerated and feared 
 
NO NECESSARY ANTAGONISM. 5 
 
 but also whom to be reverenced and loved. We be- 
 lieve that the instructions and suggestions of nature 
 are the voices of an all-powerful Friend, who knows 
 our capabilities and infirmities ; who sympathizes in 
 our joys and our sorrows, and who can be touched 
 in our aspirations and our prayers ; a Creator whose 
 laws can not be broken, and whose behests must be 
 obeyed ; but also a Father who ever watches over 
 his children, and who was in Christ reconciling the 
 world unto himself. 
 
 f We do not, of course, expect to reach such a faith ] 
 ( as this through the study of nature alone. It comes 
 not from the observation of external phenomena, 
 but through the affections and aspirations of the 
 soul, which finds in the Christian revelation that 
 which answers to its needs and satisfies its cravings; 
 Any system of natural theology like that of Paley, 
 which looks for its evidences solely to external phe- 
 nomena, is of necessity defective and powerless. 
 If nature could rise of her own self to spiritual 
 things, there would have been no necessity for a 
 revelation. Indeed, the attempt to establish a 
 spiritual truth by the evidence of material phe- 
 nomena, is, mutatis mutandis, but a repetition of 
 the error of Aristotle and his school, who vainly 
 sought to frame a system of natural philosophy 
 independently of observation. The only satisfactory 
 evidences of the truths of Christianity, indepen- 
 dent of the historical record, are to be found in 
 its adaptation to the spiritual needs of men, and it 
 is such evidences of design alone that have persuaded 
 the world. 
 
RELIGION AND CHEMISTRY. 
 
 Nevertheless, while we cannot expect to prove the 
 fundamental principles of Christian theism by the 
 evidences of material nature, it seems to us that an 
 advantage may be gained by discussing material 
 phenomena from the theistic point of view. The 
 purely mechanical aspects of nature are now so 
 prominently presented by ingenious and powerful 
 writers that it may be a satisfaction to many thought- 
 ful Christians if it can be shown that the same facts 
 may be interpreted in a very different way, and that 
 these facts are at least as consistent with the Chris- 
 tian theory of the origin of the universe as with the 
 theory of the materialist. In this conclusion the 
 Christian philosopher may securely rest, looking for 
 the confirmation of his inherited faith to his own 
 spiritual experience, in which alone convincing evi- 
 dence can be found, according to the Master's prom- 
 ise: " If any man will do his will, he shall know 
 of the doctrine, whether it be of God, or whether I 
 speak of myself." 
 
 The illustrations of the attributes of God, which 
 may be drawn from the constitution of matter, are 
 conveniently divided into two classes, — first, those 
 which appear in the adaptation of various means to 
 a particular end, and, second, those which are to be 
 found in the unity of plan according to which the 
 whole frame of nature has been constructed. The 
 first class are exhibited by the properties of matter, 
 the second by the so-called physical laws and forces. 
 
 In following out, then, the order which seems to 
 be so obviously indicated by the nature of the case, 
 I shall ask you, in the first place, to study with me 
 
ARGUMENT FOR DESIGN. 
 
 the physical condition of our atmosphere, and the 
 properties of the various materials of which it con- 
 sists ; and I am sure we shall not fail to find in one 
 and all abundant evidence of the wisdom, goodness, 
 and power of God. Having thus made you ac- 
 quainted with some of the more important scientific 
 facts required for my argument, I shall next direct 
 your attention to those grander demonstrations of 
 God's wisdom and power which appear in the great 
 laws and forces, by which the whole material uni- 
 verse is upheld, and lastly an examination of the 
 relative limits of scientific and religious thought will 
 form an appropriate termination for the course. 
 
 The argument from special adaptations which lies 
 at the basis of most works on natural theology is 
 condensed by Dugald Stewart into two simple 
 propositions. The one is, " that everything which 
 begins to exist must have a cause ; '* the other, 
 " that a combination of means conspiring to a par- 
 ticular end implies intelligence.'* To these might 
 be added the two equally clear propositions stated 
 by Dr. Reid : first, " that design may be traced from 
 its effects ; " second, " that there are evidences of 
 design in the universe." I do not at present intend 
 to discuss the logical validity of this argument, or 
 the general value of analogical reasoning which it 
 implies. Such discussions belong particularly to the 
 province of metaphysics, and I willingly leave them 
 to abler hands. It will be my chief object in these 
 lectures to bring to your notice a few of the num- 
 berless indications of adaptation in the materials of 
 our atmosphere, assuming for the present that these 
 
S ARGUMENT FOR DESIGN. 
 
 adaptations are evidences of design, and therefore 
 evidences of the existence of a personal God, in- 
 finite in wisdom, absolute in power. When we have 
 thus become acquainted with some of the facts on 
 which the argument rests, we may then profitably 
 consider the validity of the reasoning, at least so far 
 as to weigh the objections which modern material- 
 ism has urged against it. 
 
 It must, however, be constantly borne in mind that 
 the portion of the subject with which we are to 
 deal should occupy only a very subordinate position 
 in any comprehensive scheme of natural theology. 
 We have already expressed the opinion that the 
 only conclusive evidences of the truth of Chris- 
 tianity, apart from the historical record, are those 
 based on its adaptation to the spiritual wants of 
 men, and all other facts are secondary to this great 
 central truth. But even when established on its 
 broadest basis, I would not press the arguments of 
 natural theology too far. 
 
 For myself, I believe that the facts of human 
 nature themselves all tend to prove that a divine 
 revelation is the only legitimate basis for a system 
 of religion, and that an historical faith based on a 
 supernatural revelation is the only religion possible 
 for imperfect humanity. Indeed, I am led to think 
 we find evidence of the goodness of our Heavenly 
 Father in the very circumstance that the founda- 
 tions of all knowledge have been laid in such ob- 
 scurity that no unaided human intellect can wholly 
 dispel the cloud which hides the Creator from our 
 sight,— 
 
PROVINCE OF NATURAL THEOLOGY. 9 
 
 ** To feel, although no tongue can prove, 
 That every cloud that spreads above 
 And veileth love, itself is love." 
 
 This very obscurity humbles the pride of human 
 learning, and raises its constant warning against 
 that intellectual idolatry which would substitute its 
 shallow philosophy for the simple truth as it is in 
 Jesus. The Bible once received, science can furnish 
 abundant illustrations of the attributes of the Being 
 therein revealed ; but even with all the illumination 
 which has been the immediate or secondary result of 
 Christianity, man is hopeless without its authority, 
 and I would not give the slightest shadow of sup- 
 port to that irreverent presumption which, guided 
 by what it calls the unaided light of nature, would 
 construct a system of religion out of passions, in- 
 tuitions, and I know not what absurdity. 
 
 But still it must be remembered that the Chris- 
 tian revelation does not prove the existence of 
 God ; on the contrary, it appeals to a belief in his 
 being that already exists in the mind of man. The 
 Bible opens with this assumption. The first line as- 
 serts that — 
 
 " In the beginning God created the heaven and 
 the earth.'* 
 
 And the Hebrew name of God, Jehovah {I am that! 
 am), is itself a declaration of his self-existent being. 
 
 With all men a belief in some Almighty Power 
 overshadowing their being grows up spontaneously 
 in the heart, they know not how ; but the educated 
 and the intelligent seek further to find its logical 
 grounds in the evidences of nature. 
 1* 
 
lO PROVINCE OF NATURAL THEOLOGY. 
 
 / Here, then, is the first great office of natural 
 / theology. It furnishes the logical basis on which 
 I the whole scheme of revealed religion given us in 
 the Bible rests. 
 
 I have no desire to over-estimate the importance 
 of my subject. For myself, I believe, with Paley, 
 , and the other eminent writers of the same class, that 
 \ the fundamental truths of our religion can be in- 
 ferred from the constitution of the human mind and 
 \ from the course of nature with as much certainty as 
 'analogical reasoning can ever give. But still I know 
 that the evidence is not demonstrative and not likely 
 to convince the sceptic ; for in the last analysis it 
 rests on certain assumptions which he will not ad- 
 mit. And it is in vain to urge that these assump- 
 Itions are really intuitive truths and tacitly admitted 
 by the whole human race ; for he easily replies, that 
 they are not intuitive to his mind. 
 • Nevertheless, the evidences of God in nature — in- 
 cluding, of course, the human soul — are the only 
 proof we have or can have of his existence, and they 
 are, therefore, the only logical basis of the Christian 
 revelation. Nature and revelation are parts of one 
 and the same system, and, however much our pre- 
 judices may obscure the fact, Christianity rests on 
 natural religion, and cannot be logically defended if 
 the authority of the last is denied. 
 
 But however great the value of natural theology, 
 considered as the basis on which revelation rests, 
 this is not its only or most important office. In the 
 present age of the world, it confers a still more ines- 
 timable benefit on mankind by confirming, illustrat- 
 
PROVINCE OF NATURAL THEOLOGY. II 
 
 ing, and enforcing the admitted truths of revela- 
 tion. 
 ^ If it be asked of what value are further illustra- 
 \ tions of admitted truths, I answer, that there is an 
 j important class of nominal Christians who are more 
 lopen to impressions from the study of nature than 
 jto direct appeals to the heart. It is true that the 
 great mass of mankind must be Christianized, if at 
 all, through the affections and by the hard discipline 
 of sorrow ; but there are some who, not yet tried in 
 the fiery furnace of affliction, have first felt their 
 Father's hand and recognized his love while con- 
 templating his works. I do not say that persons so 
 touched are already Christians, but I do say that 
 the first step has been taken, and that is a great deal. 
 It may require many years of sad experience and 
 many a bitter pang of disappointment before they 
 come to kneel humbly at their Saviour's feet ; but, 
 like the great Apostle, they will always look back 
 to the time when the Divine presence first visibly 
 shone before them as the turning period of their life. 
 While, therefore, I should be the first to condemn 
 that hollow naturalism which would substitute a 
 system of natural theism for the simple doctrines 
 of the Bible, I must also deprecate that prejudice 
 which prevents many clergymen, through fear of 
 this tendency of the age, from availing themselves 
 of the aid of science in enforcing the fundamental 
 truths of our religion. I assure them they thus 
 neglect a most important means of influence over 
 educated and thinking men, — a means of influence 
 always important, but never more so than in an age 
 
12 PROVINCE OF NATURAL THEOLOGY. 
 
 which is marked by its cultivation of practical sci- 
 ence, and in a country where so large a portion of 
 the active energy of the community has taken this 
 practical direction. The danger of our time is not 
 so much a philosophical scepticism as a practical 
 materialism. The fear is, not that men should 
 reason themselves into unbelief, but that, spending 
 their whole lives in developing the powers of nature, 
 they should practically worship the dead matter 
 rather than the living God. If, however, we can 
 j make such persons feel that the material is but a 
 form of the spiritual, and that in fact the spiritual is 
 nowhere more manifest than in those very laws and 
 forces which they so much idolize, we shall not 
 change, it is true, the tendency of the age, but we 
 shall ennoble and sanctify it. The whole material 
 universe will become transfigured, and nature will 
 no longer be seen as a wonderful mechanical appli- 
 cation of blind forces, but as a living embodiment of 
 the Eternal One. Nature-worship may continue, but 
 it will have lost its idolatry ; for it will be no longer 
 the machine that is worshiped, but that same Liv- 
 ing Spirit which spoke in tones of thundet* from the 
 clouds of Sinai and in accents of mercy at the bap- 
 tism of Christ. 
 r^ I know it is said that nature conceals rather than 
 ( reveals God, and in a certain sense it is undoubtedly 
 j true that He is hidden from us behind the veil of his 
 I works ; but since it is permitted to man by the exer- 
 cise of his intelligence to Hft in part this veil, it is 
 certainly the duty, as it should be the privilege, of 
 the ministers of religion to show forth the un- 
 
PROVINCE OF NATURAL THEOLOGY. 1 3 
 
 speakable glory which lies behind these material 
 forms. 
 
 But why multiply arguments when we have the 
 authority of the Great Teacher himself, who fre- 
 quently appealed to nature to illustrate and enforce 
 the divine truths which he came on earth to reveal ? 
 We have indeed the whole summary of Natural 
 Theology in His simple words : 
 
 ** Wherefore, if God so clothe the grass of the 
 field, which to-day is, and to-morrow is cast into 
 the oven, shall he not much more clothe you, O ye 
 of little faith?" 
 
 With, then, such authority as this, let us not de- 
 spise the beginnings because they are not the end, 
 or undervalue the means by which many a noble 
 soul has been led to the foot of the Cross. 
 
 Without seeking, therefore, to vindicate further 
 the claims of my subject, I will at once enter upon 
 the plan already proposed for this course of lectures, 
 and will first ask your attention to the illustrations of 
 the wisdom, goodness, and power of God, which may 
 be discovered in the constitution of our atmosphere. 
 In endeavoring to carry out this plan, I shall require 
 all your indulgence and all your kind forbearance. 
 From the very nature of the case, it will be neces- 
 sary to start from first principles, and much of the 
 way we are to travel together will be uninteresting 
 and dull. If, however, the path shall lead us to the 
 summit of that holy mountain from which we can 
 gain a clearer vision of spiritual things, we shall soon 
 forget the toil and difficulty of the ascent. We 
 have no extravagant expectations of the result. 
 
14 ADAPTATIONS TO BE STUDIED 
 
 We do not hope to convince the sceptic, or to arouse 
 the indifferent from their practical unbelief. Our 
 only hope is — and this we entertain in all humility — 
 that, by pointing out a few of the footprints of the 
 Creator which lie thickly along our daily path, we 
 may encourage some earnest student toiling forward 
 on his journey of life. May God grant to us all the 
 richest blessings of his grace ; for though man may 
 plant and water. He only giveth the increase. 
 
 The illustrations of the attributes of God pre- 
 sented to us by the atmosphere are especiafly mani- 
 fest in those adaptations of properties by which it 
 has been made to subserve the welfare and happi- 
 ness of mankind, and this is to be expected, not 
 only because these relations have been the most 
 studied, and are, therefore, the best known, but also 
 because the familiar phenomena through which our 
 intelligences are connected with the external world, 
 are the im.mediate objects of our observation and 
 cognizance. Here, however, as always in the study 
 of nature, we must be careful to avoid the error 
 of considering man as the sole end of creation, and 
 of interpreting all phenomena with reference to 
 him alone. The material universe is the manifes- 
 tation of one grand creative thought, as compre- 
 hensive in the diversity of the parts as it is grand 
 in the unity of the whole. These parts have 
 been so wondrously joined and skilfully wrought 
 together, that each is linked with each, and one 
 with all. In this divine economy nothing is want- 
 ing, nothing is superfluous, and what seems to our 
 feeble vision least important |s^ as_ess^^d|liaxom-- 
 
 ^ JL'ir ^-> V^ .iv^^>^ (^ < 
 
'y^. 
 
 WITH REFERENCE TO MAN. 1 5 
 
 p]ete the unity of the plan as our own glorious man- 
 hood : 
 
 "Nothing useless is or low, 
 
 Each thing in its place is best, 
 - And what seems but idle show 
 
 . /|.1 ^iLp Strengthens and supports the rest." 
 
 Amidst all this wonderful variety in unity, man 
 stands the culminating glory of the whole. Made 
 in the image of his Creator, and but " a little lower 
 than the angels,'* he has been intrusted with domin- 
 ion and power over all the brute matter which sur- 
 rounds him. Through the long ages of geological 
 history the earth was preparing for his dwelling, and 
 i n the e arliest forms of animal life his coming was 
 prefigured and foretold. It will be natural, there- 
 
 r, 
 
 fore, to^ consider the adaptations of the atmosphere 
 with special reference to him ; and this we may do 
 legitimately, without losing sight of the grand idea 
 which underlies the whole, and of which man is 
 only the nobler part. 
 
 The atmosphere is a vast ocean of aeriform mat- 
 ter, enveloping the earth like a mantle, and rising to 
 the height of many miles above our heads, but con- 
 stantly diminishing in density as the elevation in- 
 creases. At the height of about three miles and a 
 half (3.43) the density is only one-half as great as at 
 the level of the sea; and at the height of forty 
 miles it is less than in the exhausted receiver of the 
 best air-pumps. How much higher than this the 
 atmosphere extends, it is impossible to determine 
 with accuracy. In this ocean of air all bodies on the 
 surface of the globe are immersed. It is so subtle 
 
l6 DESCRIPTION OF THE ATMOSPHERE. 
 
 that it penetrates into the minute pores of matter, 
 and fills the cavities of all organized being. It is 
 the medium in which all vital processes both of 
 plants and animals take place, and in which all 
 human activity has its seat. Let us see now with 
 what wisdom its properties have been adapted to 
 the important ends which it is appointed to sub- 
 serve. 
 
 Consider, in the first place, the physical state of 
 the atmosphere, its very aeriform condition. This 
 air is as truly matter as the solid planks on which 
 we are treading, or the granite rocks on which this 
 building rests. It is far less dense, it is true, but 
 then it has all the essential properties of matter. It 
 fills space. It resists with an ever-increasing force 
 all attempts to condense it ; and, moreover, it has 
 weight. But how different in condition from the 
 solid rock ! — so different that to the uneducated it 
 hardly seems material ; and in our common language 
 we speak of a space which is filled only with air as 
 empty. Its particles are endowed with such perfect 
 freedom of motion, and yield so readily to the 
 slightest pressure, that we move through it without 
 feeling its presence. It is firm enough to support 
 the wings of the lark as he mounts the sky, and yet 
 so yielding as not to detain the tiniest insect in its 
 rapid flight. 
 
 The physical condition of the atmosphere will 
 still further excite our admiration, when we consider 
 the wonderful play of forces by which it is upheld. 
 It may not be known to you all that upon this mass 
 of air, outwardly so calm and passive, there are con- 
 
ITS PHYSICAL CONDITION. 1/ 
 
 stantly acting two mighty forces, — the force of grav- 
 itation and the force of heat. In virtue of the 
 force of heat the particles of the atmosphere mutu- 
 ally repel each other, and the whole mass, like a 
 bent spring, tends to break from its confinement and 
 to expand into the surrounding space ; but this it 
 cannot do, for by the power of gravitation it is held 
 with a firm grasp to the surface of the globe. Were 
 this grasp for a moment relaxed, the atmosphere 
 would dash off with explosive violence and be lost 
 in the immensity which surrounds us. How great 
 the force is which is required to restrain the expan- 
 sive tendency of the atmosphere few persons have 
 an adequate conception, because the two opposing 
 forces are so perfectly balanced that we are obliged 
 to call in the aid of experiment in order to render 
 their effects evident. So true is this, that the world 
 never even dreamed of their existence until within 
 two hundred years, and the story of the discovery is 
 one of the most remarkable in the history of induc- 
 tive philosophy. This story is well known ; but as 
 it is short, and teaches us an important truth, you 
 will pardon its repetition. 
 
 Every one who has seen a common pump is fa- 
 miliar with the fact that it is the pressure of the air 
 which causes the water to rise in the suction-pipe, 
 and this suction is one manifestation of that force 
 by which the atmosphere is held so firmly to the 
 surface of the globe. The pump, however, was used 
 long before the discovery of the pressure of the at- 
 mosphere, and its action was explained by a prin- 
 ciple which seemed perfectly satisfactory then, but 
 
1 8 NATURE ABHORS A VACUUM. 
 
 which sounds strangely enough to modern ears. 
 The principle appears first to have originated with 
 the Aristotelians, and was expressed in the phrase, 
 " Nature abhors a vacuum.'* These ancient philos- 
 ophers noticed that space was always filled with 
 some material substance, and that the moment a 
 solid body was removed air or water always rushed 
 in to fill the empty space. Hence they concluded 
 that it was a universal law of nature that space 
 could not exist unoccupied by matter, and the 
 phrase just quoted was merely their figurative ex- 
 pression of this philosophical idea. When, for ex- 
 ample, the piston of a common pump was drawn up, 
 the rise of the water was explained by declaring, 
 that, as from the nature of things a vacuum could 
 not exist, the water necessarily filled the space de- 
 serted by the piston. 
 
 This physical dogma served the purpose of natural 
 philosophy for two thousand years, and it was not 
 until the seventeenth century that men discovered 
 any limit to nature's abhorrence of a vacuum. Near 
 the middle of that century some engineers were 
 employed by the Duke of Tuscany to sink a well in 
 the neighborhood of Florence to an unusual depth. 
 They finished their work, but on adjusting the pump 
 they found to their surprise that it would not work. 
 With all their efforts the water would rise only a 
 little more than thirty feet, and by no ingenuity or 
 skill could they raise it an inch higher. More dis- 
 gusted with nature than nature was with the vacu- 
 um in their pump, they applied to Galileo, then an 
 old man, living in his villa on the brow of Fiesole. 
 
THE PUMP-MAKERS AND GALILEO 1 9 
 
 He could not aid them, but he is said to have re- 
 plied, half in jest, half in earnest, that nature did not 
 abhor a vacuum above thirty feet. Had this inci- 
 dent occurred earlier in his career, Galileo would 
 undoubtedly have added to the other jewels of his 
 crown a brighter gem than all, but now the vigor 
 of his manhood was spent ; he had done his work, 
 and, worn out by the persecution M. a bigoted priest- 
 hood, he was peacefully resting from his life's labor, 
 and calmly awaiting the close. 
 
 But the key which the incident had furnished was 
 not lost. It passed into able hands, and it was the 
 fortune of Torricelli, Galileo's best pupil, to unlock 
 the secret. This young Italian philosopher, whose 
 clear, intellect had been trained in the mechanical 
 philosophy of his great master, saw at once that a 
 column of water thirty-three feet high, and no higher, 
 could not be sustained in a cylindrical tube by a 
 mere metaphysical abstraction. 
 
 This effect, he said, must be the result of some 
 mechanical force equivalent to the weight of the 
 mass of water sustained. It was not difficult to 
 prove the correctness of this reasoning, for it was 
 evident that if a column of water was sustained at 
 the height of thirty-three feet in the suction-pipe of a 
 pump by a constant force, the same force could only 
 sustain a column of a heavier liquid at a proportion- 
 ally less height. So Torricelli tried mercury, a 
 liquid thirteen and a half times heavier than water, 
 and the result was as he had anticipated. The force 
 which raised the column of water thirty-three feet 
 could only raise a column of mercury to the height 
 
20 EXPERIMENT OF TORRICELLI. 
 
 of thirty inches, which is thirteen and a half times 
 less than thirty-three feet. Torricelli did not, how- 
 ever, make this experiment with a pump, but with 
 an apparatus of his own, much simpler, and equally 
 effective. 
 
 He took a long glass tube, open at one end, filled 
 it with mercury, and, having closed the opening with 
 his thumb, inverted the tube, and plunged the open 
 end in a basin of mercury ; on removing his thumb, 
 the mercury, instead of remaining in the tube, and 
 thus satisfying nature's abhorrence of a vacuum, fell, 
 as he expected, and, after a few oscillations, came 
 to rest at a height of about thirty inches above the 
 level of the mercury in the basin. The correctness 
 of his induction having been thus verified, Torricelli 
 at once concluded that it must be the pressure of the 
 air which sustained both the water in the pump and 
 the mercury in his tube. 
 
 This experiment excited a great sensation in Eu- 
 rope ; but, as might naturally have been expected, 
 the old physical dogma was not easily laid aside, 
 and Torricelli did not live to see his opinion gener- 
 ally received. It was left to the celebrated Blaise 
 Pascal to convince the world that Torricelli was 
 right, and this he did by one of those master-strokes 
 of genius which at once silence controversy. 
 
 " If,'* said Pascal, " it be really the weight of the 
 atmosphere under which we live that supports the 
 column of mercury in Torricelli's tube, we shall find, 
 by transporting this tube upward in the atmos- 
 phere, that in proportion as it leaves below it more 
 and more of the air, and has consequently less and 
 
DEMONSTRATION OF PASCAL. 21 
 
 less above it, there will be a less column sustained 
 in the tube, inasmuch as the weight of the air above 
 the tube, which is declared by Torricelli to be the 
 force which sustains it, will be diminished by the in- 
 creased elevation of the tube." 
 
 Accordingly Pascal carried the tube to the top of 
 a church-steeple in Paris, and observed that the 
 mercury fell slightly ; but not satisfied with this re- 
 sult, he wrote to his brother-in-law, who lived near 
 the high mountain of Puy de Dome, in Auvergne, 
 to make the experiment there, where the result 
 would be more decisive. 
 
 '* You see," he writes, "that if it happens that the 
 height of the mercury at the top of the hill be less 
 than at the bottom (which I have many reasons to 
 believe, though all those who have thought about it 
 are of a different opinion), it will follow that the 
 weight and pressure of the air are the sole cause of 
 this suspension, and not the horror of a vacuum ; 
 since it is very certain that there is more air to 
 weigh on it at the bottom than at the top ; while 
 we cannot say that nature abhors a vacuum at the 
 foot of a mountain more than on its summit." M. 
 Perrier, Pascal's correspondent, made the observa- 
 tion as he desired, and found a difference of about 
 three inches, "which," as he replies, "ravished us 
 with admiration and astonishment." 
 
 Thus it was that man first learned to recognize 
 the existence of that power, which retains the at- 
 mosphere on the surface of the globe, and the his- 
 tory of the discovery should humble our intellectual 
 pride and teach us to hold our knowledge with rev- 
 
22 THE OLD DOGMA 
 
 erence and humility. This old scientific dogma of 
 the seventeenth century never fails to excite a 
 smile, and we are inclined to wonder how man could 
 ever have believed what now appears so absurd ; 
 but if, like an antiquary, we imbue our minds with 
 the spirit of that age, it will be seen, not only that 
 the dogma was not essentially absurd, but also that 
 the philosophical idea,^clothed in those quaint 
 terms, appeared to the scientific men of the period 
 as truly a legitimate induction from observed facts 
 as the law of gravitation seems to us. And the in- 
 duction was legitimate ; but since the known facts 
 did not cover the whole ground, they gave only a 
 very partial truth. The Grand Duke's pump was the 
 first failing case, and proved, not that the old prin- 
 ciple was absolutely false, but only that its applica- 
 tion was very limited. 
 
 Thanks to Galileo, Torricelli, Pascal, and New- 
 ton — noble line of genius — nature's abhorrence of a 
 vacuum gave place to the law of gravitation, and 
 two centuries of unparalleled scientific activity have 
 only served to confirm the truth, and extend the 
 domain of Newton's grand generalization ; but even 
 after this signal triumph, who now feels fully assured 
 that the law of gravitation may not find its failing 
 case? and when, two centuries hence, the future 
 historian comes to write the history of inductive 
 philosophy, who can feel certain that Aristotle's 
 dogma and Newton's law may not both be conde- 
 scendingly noticed among the partial truths which 
 served the purposes of science in its infancy and 
 childhood ? 
 
A PARTIAL TRUTH. 23 
 
 Let me not be understood to imply a belief that 
 man cannot attain to any absolute scientific truth, 
 for I believe that he can, "a^nSTl feel that every 
 great generalization brings him a step nearer to the 
 promised goal ; but I wish here at the outset most 
 strongly to impress the distinction between the un- 
 doubted facts of science, and the laws and princi- 
 ples which have grown up around them, and by 
 which they have been embodied in our systems of 
 philosophy, — the distinction, in a word, between the 
 observed phenomena of nature, and man*s interpre- 
 tation of the phenomena. 
 
 This distinction, so obvious when stated, is too 
 often forgotten, and is necessarily overlooked in our 
 scientific text-books. It is the sole aim of these 
 elementary treatises to teach the present state of 
 knowledge, and they would fail in their object if 
 they attempted by a critical analysis to separate the 
 phenomena from the laws or systems by which alone 
 the facts of nature are correlated and rendered in- 
 telligible. But although while studying science it- 
 self, we may for the time waive the distinction be- 
 tween fact and theory, the moment we come to com- 
 pare the results of science with the eternal verities 
 of religion, the distinction here enforced becomes of 
 paramount importance, and it must be our chief aim 
 to separate that which is absolute and eternal truth 
 from that which, even in its highest development, is 
 the result of human thought, and, like all things 
 human, subject to limitations and liable to change. 
 
 Had this distinction been always borne in mind, 
 the controversies between the philosophers and the 
 
24 FACT AND THEORY. 
 
 churchmen would have been less bitter and more 
 fruitful in truth ; the philosophers would have been 
 willing to waive their theories, and the churchmen 
 would have been led to respect the results of sci- 
 ence, and conform their theology to the indisputable 
 truths which God has been pleased to reveal through 
 nature no less plainly than in his written word ; and 
 if the trite anecdote of Galileo and the pump- 
 makers serve to impress the distinction on our 
 minds, this digression will not have been made in 
 vain. 
 
 You must all have recognized in Torricelli's tube 
 our modern barometer. By means of this well- 
 known instrument we can readily estimate the press- 
 ure of the atmosphere, and determine the amount 
 in our human standards of measurement. It can be 
 readily proved that the pressure of the atmosphere 
 is about fifteen pounds on every square inch of the 
 earth^s surface, and if, starting from this well-known 
 fact, you calculate the amount of pressure on any 
 extended surface, you will be astonished at the re- 
 sult. For example, the pressure exerted by the at- 
 mosphere on the area on which this building stands 
 is much greater than the whole weight of the build- 
 ing itself. The pressure on a man of ordinary stat- 
 ure is about sixteen tons ; that on one square mile 
 of surface is equal to over twenty-six million tons. 
 
 How great, then, must be the pressure on the 
 whole surface of the globe, or, what is the same 
 thing, how great is the intensity of that ever-acting 
 power, which holds the atmosphere in its appointed 
 place ! It would not be difficult to calculate the 
 
PRESSURE OF THE ATMOSPHERE. 2$ 
 
 amount and to express it in numbers; but these 
 numbers would convey to you no definite idea, for 
 our minds are incapable of forming an adequate con- 
 ception of such immensity. The attempt to grasp 
 it only exposes our weakness, and yet this force, 
 immense as it is, is so delicately balanced by the 
 sweet influences of the sunbeam, that it does not so 
 much as shake the aspen-leaf or break the gossa- 
 mer. If we believe no more than this, that the 
 world was once created by God, what must be the 
 power and wisdom of a being who could appoint 
 these mighty forces and adjust them with such per- 
 fect precision ! . But if we also believe that these 
 forces are direct emanations of Divine Power, — that 
 it is God himself who with his own right hand holds 
 the atmosphere in its place, and appoints its 
 bounds, — then all nature assumes a more glorious 
 aspect, and we feel that we are indeed surrounded 
 by the Divine Presence. Yet this force, which we 
 find so far beyond our powers of conception, is but 
 a secondary phase of that immeasurably greater 
 power which brings forth Mazzaroth in his sea- 
 son, and guides Arcturus with his sons. How fu- 
 tile all attempts to measure Divine power ! We 
 select some one of the feeble forces acting around 
 us, and succeed in reducing its value to our human 
 standards of comparison, and expressing this value 
 in numbers ; but the numbers, when obtained, are 
 beyond our grasp, and we find that we have merely 
 mounted to a little higher platform, from which we 
 discover numberless other forces immeasurably 
 greater than the first. Something, however, has 
 3 
 
26 IDEA OF THE INFINITE. 
 
 been gained. We have attained to the idea of the 
 infinite ; and to thoroughly apprehend the existence 
 of the infinite, is to take the first step toward recog- 
 nizing the existence of a God. 
 
 I know it will be said that man cannot compre- 
 hend the infinite, and if by this statement it is only 
 meant to affirm the declaration of the Bible, that 
 man cannot "find out the Almighty unto perfec- 
 tion," not even the most visionary dreamer would 
 question the position. But there is a class of 
 philosophers at the present day who think to enforce 
 the authority of revelation by maintaining the doc- 
 trine that man can know absolutely nothing of the 
 infinite, — nothing more than he now knows of the 
 facts or principles of science to be hereafter discov- 
 ered ; that, indeed, the very term infinite implies a 
 negation of all cognizable qualities. 
 
 To me, this position seems fatal to. the very cause 
 it is intended to defend, and surrenders all the ap- 
 proaches of the citadel to the infidel. For if there 
 is in man no possibility of apprehending the infinite, 
 even to the smallest degree, I can see nothing to 
 which revelation can appeal. He has then no power 
 to distinguish between the Divine and the human. 
 
 But it is riot so. Revelation implies, and all ex- 
 perience shows, that man can recognize the pres- 
 ence of the infinite by attributes as clear and unmis-' 
 takable as those which mark the presence of the 
 finite matter around him. He may not be able to 
 comprehend a single attribute of the infinite in its 
 essence; but as the mathematician, dealing with 
 infinitesimal quantities, which he cannot fully un- 
 
IDEA OF THE INFINITE. 2/ 
 
 derstand, arrives at truths of the material world 
 with all the certainty of demonstration, so the men- 
 tal philosopher may attain to moral truths in regard 
 to the Infinite Being, although the very terms he 
 employs may be veiled in impenetrable mystery. 
 
 And what is the true human conception of the 
 infinite? It is not merely something which we feel 
 to be very great indeed, but it is something which 
 we feel surpasses our utmost conceptions of the 
 great, — something which, let us account it as great 
 as we please, yet, wherever the inability of our 
 mental power fixes the limit of our conception, will 
 still be felt to be greater than the greatest. We 
 cannot gaze into the heavens without awe ; we can- 
 not examine the wonders of the dew-drop without 
 reverence ; we cannot look into our own souls 
 without trembling. It is the same invisible Pres- 
 ence everywhere, and however long false philosophy > 
 may conceal the vision, or material cares and pleas- :^ ^ 
 ures blind the senses, when man once recognizes o^^ ^^^ 
 its existence he instinctively worships and adores. ^^ 
 
 The far-reaching relations of the adaptations we '^ 
 are now studying become evident when we con- 
 sider that the density of the atmosphere is one of 
 the conditions of organic life on the surface of the 
 globe. By density is meant, I need not state, the 
 quantity of matter which the atmosphere contains 
 in a given volume ; for example, in a cubic yard. 
 This quantity is capable of exact measurement, and 
 although to a certain extent variable, it is constant 
 in the same place, under the same conditions of 
 temperature and pressure. 
 
o 
 
 28 DENSITY OF THE ATMOSPHERE. 
 
 In this latitude, at the level of the sea, one cubic 
 yard of the atmosphere, when dry and under the . 
 normal conditions of temperature and pressure, con- 
 tains about two pounds of air, and this weight is the 
 measure of its density. Now we find that the or- 
 garkization of plants and animals, including man, has 
 been adjusted to the density of the air, and illus- 
 trations of this adaptation will be met with as we 
 proceed. But accepting the fact for the present as 
 universally conceded, let us consider the conditions 
 on which this adaptation of the air to our physical 
 organization rests. 
 
 The density of the atmosphere may be said to de- 
 pend upon four conditions : first, on the inherent 
 nature of the substance which we call air itself; sec- 
 ondly, on the intensity of gravity ; thirdly, on the 
 total quantity of air on the globe ; and, lastly, on 
 the temperature. The influence of the first condi- 
 tion is not understood, but that of the last three we 
 can readily trace. If the intensity of the force of 
 gravity at the surface of the earth were to change, 
 other circumstances remaining the same, the density 
 of the atmosphere would change in the same pro- 
 portion. Thus, for example, if the intensity of 
 gravity on the earth were as great as it is on the 
 surface of the sun, the density of the atmosphere 
 would be twenty-eight times as great as at present ; 
 or if this intensity were reduced to that which exists 
 on the surface of the moon, the density would be 
 diminished to one-sixth of the existing density. 
 
 But, assuming that the intensity of the force of 
 gravity on the surface of the earth remained con- 
 
DENSITY OF THE ATMOSPHERE. 29 
 
 stant, precisely the same effect would result from 
 any variation in the total quantity of the atmos- 
 phere. Were the whole amount of air on the earth 
 increased or diminished, the density of the atmos- 
 phere at its surface would also be increased or di- 
 minished in the same proportion. Still further, as- 
 suming that, while the intensity of gravity and the 
 mass of the atmosphere remained fixed, the tem- 
 perature were changed, then also the density of the 
 atmosphere would vary, and by a quantity which 
 can be easily determined. By accurate experiments 
 it has been ascertained that an elevation of tem- 
 perature equivalent to about five hundred degrees 
 of our Fahrenheit thermometer would reduce the 
 density to one-half ; and, on the other hand, that a 
 reduction of temperature would increase the density 
 in the same proportion. 
 
 Consider next what these relations imply. Re- 
 flect that the intensity of the force of gravity de- 
 pends upon the mass of the earth. Remember that 
 the mean temperature depends upon the distance 
 of the earth from the sun, and you will see that not 
 only the actual size of the earth, but also its dis- 
 tance from the sun, and the quantity of air on its 
 surface, were all necessary conditions in order that 
 the atmosphere should have its present density, and 
 thus become the fit abode for the actual families of 
 organic beings. If any one of these conditions had 
 been different, the same result would not have been 
 attained, and man, as he exists, could not have lived 
 on this globe. 
 
 It must then have been He ** who hath meted out 
 
 \ 
 
30 UNITY OF THE DESIGN. 
 
 heaven with the span, and comprehended the dust of 
 the earth in a measure, and weighed the mountains 
 in scales, and the hills in a balance," who " formed 
 man of the dust of the ground, and breathed into 
 his nostrils the breath of life." 
 
 The unity of the design implies the oneness of 
 the designer, and although the adaptations just con- 
 sidered may not exclude every possible atheistic 
 theory of cosmogony, yet they show conclusively 
 that, if there is design anywhere, there is design 
 everywhere ; if there is design in the least, there is 
 design also in the greatest, and design in the atom 
 may thus confirm the evidence of design in man. 
 
f L 1 R 11 A I ; \ 
 
 tJNIVKHHITV OF 
 
 CALlFOilXIA. 
 
 CHAPTER II. 
 
 TESTIMONY OF THE ATMOSPHERE. — Concluded. 
 
 During a recent journey in Switzerland, at the 
 close of a delightful summer's day, in the early part 
 of July, I arrived at Interlachen, in company with 
 a number of fellow-travellers. We had been saiHng 
 on the beautiful lake of Brienz, and some minutes 
 before we reached our destination the sun had set, 
 and the mountains had already cast their long shad- 
 ows across the lake. Early in the kfternoon the 
 clouds had settled on the nearer hills, and we had 
 been disappointed at not obtaining a view of the 
 distant summits of the Bernese Oberland ; but sud- 
 denly, as the boat neared the shore, the magnificent 
 peak of the Jungfrau appeared from behind the veil 
 of clouds, clothed in her white mantle of everlasting 
 snow, and bathed with a flood of rosy light. The 
 effect thus heightened by the contrast was grand 
 beyond description, and as beautiful as it was 
 grand. It seemed like a vision of the Heavenly 
 Kingdom, — as if the glory of God had rested on the 
 mountain. The scene completely filled the soul, 
 and the heart overflowed with gratitude for the 
 blessing it enjoyed. It was felt to be one of the 
 
 31 
 
32 THE ATMOSPHERE AND LIGHT. 
 
 great privileges of a lifetime, and his would have 
 been a dull understanding, and a duller heart, which 
 did not recognize the Giver in the gift. The view 
 so riveted the attention that we hardly noticed our 
 arrival, and as we walked to the hotel we watched 
 the successive shades of crimson and purple as they 
 flitted up the mountain, until the last blended in 
 the gray of the twilight. 
 
 It may not be permitted to many to behold the 
 Jungfrau blushing before her retiring lord, but all 
 have witnessed the same effect on even a grander 
 scale, when the white clouds, piled up on the west- 
 ern horizon like vast mountain chains, become, at 
 evening, resplendent with the rays of the setting 
 sun ; and many have watched their varying tints of 
 gold and purple, until at last their ghostly forms 
 vanished in the dusk of the evening, and the stars 
 came out to take up with their measured twinkling 
 the silent song of praise. Perhaps, also, there may 
 be some who, after anxious watching through the 
 night, have felt their hearts strengthened and their 
 hopes revived when the blush of morning reassured 
 them of their Father's providence, and all nature 
 smiled in the floods of returning light. 
 
 All these glorious visions, all this beauty, and all 
 the pure emotions of our hearts which they excite, 
 we owe, my friends, to the skill with which the 
 physical qualities of the atmosphere have been ad- 
 justed to the wants of our physical and moral na- 
 tures, and they all thus become the silent witnesses 
 not only of the wisdom, but also of the goodness of 
 our God. 
 
TRANSPARENCY. 33 
 
 We have already, in the first lecture, discussed 
 some of the adaptations of the physical condition of 
 the atmosphere to the purposes which it subserves 
 on the globe, and I wish this evening to develop 
 still further the same subject, by considering a few 
 additional examples ; and first I will ask your atten- 
 tion to those evidences of design which are to be 
 found in the f-elations of the atmosphere to light and 
 heat. Here, however, I am met by a difficulty. In 
 order to explain fully these relations it would be 
 necessary to develop from first principles the sci- 
 ences of optics and thermotics, and to do this in a 
 popular manner would require several lectures. 
 These sciences furnish some of the most wonderful 
 evidences of design which are to be found in nature, 
 and I have no doubt will be given their appropriate 
 place in this series of lectures. Without, therefore, 
 attempting any detailed explanations, I will merely 
 bring before you a few facts, drawn from these de- 
 partments of knowledge, which illustrate the adapta- 
 tions of the atmosphere to its appointed ends. 
 
 The atmosphere, although very much more per- 
 vious to light than any kind of solid or liquid mat- 
 ter, is far from being perfectly transparent. Indeed, 
 the reverse is sufficiently evident from our daily ex- 
 perience. Every one has noticed that distant ob- 
 jects appear less distinct in proportion as they are 
 removed, their colors become fainter, the contrast 
 between light and shade less marked, and that they 
 seem as if covered with a pale blue veil. This effect, 
 always noticed on distant mountains, is owing to a 
 partial absorption of the light while passing through 
 2* 
 
34 DIFFUSION OF LIGHT. 
 
 the atmosphere ; for, were the passage of the rays 
 wholly unimpeded, all objects, although reduced in 
 size in proportion to their distance, would appear 
 equally distinct, and their colors equally brilliant. 
 
 The transparency of the atmosphere differs very 
 greatly under different circumstances, but it has 
 been estimated that, under the most favorable con- 
 ditions, at least thirty per cent, of all the light com- 
 ing from the heavenly bodies is absorbed before 
 reaching the surface of the earth, and in our latitude, 
 at this season, even when the sun is on the meridian 
 and the sky clear, fully one-half of his rays are thus 
 spent. Do not suppose, however, that all the light 
 so expended is lost. Quite the contrary, for every 
 particle of the atmosphere, illuminated by the sun- 
 beam, becomes itself a new centre of emission, radi- 
 ating the light in every direction. 
 
 This diffusion of the sun's rays is the cause of that 
 wonderful effect which we term daylight. I say 
 wonderful effect, for, although so familiar, it is one 
 of the most remarkable results of skilful adaptation 
 and infinite wisdom. The very daylight which 
 streams in at the open windows of our houses, filling 
 them with cheerfulness, and penetrating to their in- 
 most recesses, which enlivens the whole landscape, 
 and which bars and bolts cannot wholly exclude 
 even from the prisoner's dungeon, is another evi- 
 dence of the adaptation of the atmosphere to the 
 constitution of man. Indeed, the atmosphere is as 
 much an essential condition of our seeing as of our 
 breathing, and the immeasurable pleasure which we 
 derive from our sense of vision depends upon its 
 
DIFFUSION OF LIGHT. 35 
 
 adaptation to the organization of the eye. Were it 
 not for the diffusive effect of the atmosphere on the 
 sun's Hght, the contrast between light and shadows 
 would be so greatly increased that, while objects di- 
 rectly illuminated by the sun would shine so brill- 
 iantly as to dazzle the eyes, all surrounding objects 
 would be in darkness, and the interior of our dwell- 
 ings would be as dark as night. Our eyes, as little 
 fitted to such conditions as our lungs, would be 
 blinded by the sudden alternations, and distinct vision 
 would be impossible. This is not a matter of theory, 
 for similar effects are observed on the summits of 
 lofty mountains, where the air is much rarer than at 
 the sea level. On the top of Mont Blanc the sky 
 has a blackish hue, and the stars are seen at midday; 
 the glare of the direct light is insupportable to the 
 eye, and even the reflection from the snow blisters 
 the unprotected skin, while at the same time the 
 contrast between light and shade, unnaturally in- 
 creased, gives to all near objects a peculiar and 
 ghastly aspect. We have here, it is true, a very 
 great diminution in the density of the air ; but when 
 you reflect upon what delicate contrasts of light and 
 shade the beauty of a landscape depends, — the 
 clearness of the foreground, the gray of the middle 
 distance, and the tender purple of the distant hills 
 all blending into one harmonious whole, — you can 
 appreciate how slight a change would disturb the 
 result, and deprive the sense of beauty of its purest 
 enjoyment. 
 
 I have thus far spoken only of the influence of the 
 atmosphere in softening the intensity of the rays of 
 
36 COLOR OF THE SKY. 
 
 light, and in diffusing their action ; but the atmos- 
 phere has also, under certain conditions, the power 
 of decomposing the sun's rays, and thus producing, 
 not only those displays of gorgeous tints which we 
 witness in the sunset clouds, but also the pure blue 
 which colors the dome of heaven. 
 
 In regard to the precise means which are em- 
 ployed by nature to produce these results, scientific 
 men are not agreed. It has been proved that the 
 blue color of the sky is seen by reflected light, and 
 it is probable that the color is caused by repeated 
 reflections of the sun's rays from the surfaces of the 
 innumerable small water-bubbles which are con- 
 stantly floating in the atmosphere. You have all 
 noticed the blue color of the soap-bubble shortly 
 before it breaks. This color is caused by the action 
 of the very thin film of water in decomposing the 
 light reflected from its surface, and it is supposed to 
 be an action of the same sort, only very much in- 
 creased by repeated reflections, which gives to the 
 sky its azure hue. 
 
 While the blue color of the sky appears to result 
 from changes in the white light of the sun caused by 
 reflection, it is equally probable that the sunset tints 
 arise from changes in the same white light caused 
 by an unequal absorption of its different colored 
 rays during their transmission through the atmos- 
 phere. Here, again, the vapor in the air is sup- 
 posed to be the active agent ; and the theory is, 
 that the tints are produced while the vapor is con- 
 densing into clouds, — a change which naturally 
 occurs at sunset. But this is a mere theory, and 
 
SUNSET TINTS. 3/ 
 
 our whole knowledge on these subjects is very im- 
 perfect. 
 
 So far, however, as our present argument is con- 
 cerned, it is not essential that we should understand 
 exactly how these glorious results are obtained. 
 It is enough that we are constantly enjoying their 
 beauty, and that we know they are owing to the 
 peculiar constitution of the atmosphere. When fu- 
 ture discoveries shall bring to light the methods, 
 at present secret, by which nature gilds the sunset 
 clouds and covers our beautiful dwelling-place with 
 its canopy of blue, we shall unquestionably find 
 fresh evidences of God's wisdom ; but even now, 
 when ignorant, perhaps, of these hidden causes, 
 we have that which is far more excellent, the 
 most conclusive evidence of His goodness and love. 
 Our Father has not only adapted the atmosphere 
 to the wants of our bodies, and made it condu- 
 cive to our physical enjoyment, but He has also made 
 it the scene of the highest beauty, — a beauty which 
 satisfies the longings of our souls and calls forth 
 their noblest and purest aspirations. Man, sinful 
 as he is, cannot look up into the pure blue of 
 heaven without a sense of reproach, and the feeling 
 that it is a fit emblem of the kingdom of purity 
 and peace. And when the setting sun lights up 
 the evening altar in the West, who "can repress 
 the rising prayer of devotion, and hesitate to be- 
 lieve, with the child, that his Heavenly Father is 
 smiling behind the clouds ? There is a depth to the 
 beauty of nature which man cannot fathom. Poetry 
 cannot describe it, and the highest art only displays 
 
38 WAVE THEORY. 
 
 its weakness when it attempts to copy it. The 
 savage feels that it is immeasurably above him, and 
 worships it. The artist seeks to attain it, but the 
 more he strives, the more it surpasses his power, 
 and he dies disappointed, unless, happily, he finds 
 that the perfect ideal has been realized only in 
 Christ, and thus through nature is led up to na- 
 ture's God. Yes ! the beauty of nature is in the 
 Infinite Presence it conceals, and, unconsciously 
 though it may be, it is the spirit, not the matter, 
 which the artist loves. 
 
 Such are some of the evidences of design which 
 we discover in the relations of the atmosphere to 
 light. Let us now examine some of its relations to 
 heat, which v/e shall find not less instructive. It 
 was formerly supposed that the rays of heat, al- 
 though accompanying the luminous rays in the sun- 
 beam, were essentially different from those of light. 
 But it is now almost universally believed that the 
 rays of heat differ from those of light only, at most, 
 as one color differs from another, and that even the 
 same rays, which, falling on the retina of the eye, 
 excite the sensation of light, when falling on the 
 nerves of feeling may excite heat. But what, you 
 may ask, is the difference between the different 
 colors? The subject is somewhat abstruse, but if 
 you will follow me attentively for a few minutes I 
 will try to make it intelligible. 
 
 Every one who has dropped a stone into the 
 water of a still lake has noticed the system of waves 
 which, with its ever-increasing circles, spreads in 
 every direction from the stone ; but all may not 
 
WAVES OF SOUND. 39 
 
 know that when two stones are struck together in 
 the air a similar system of aerial waves spreads, in 
 ever-widening spheres, through the atmosphere, and 
 that it is these waves breaking on the tympanum of 
 our ears, like the waves of water on a sand-beach, 
 which produce the sensation we call sound. Two 
 stones thus struck together give rise to waves of 
 unequal size, following one another at irregular 
 intervals ; and such waves produce an unpleasant 
 sensation on our auditory nerves, which we call 
 noise. But if, instead of striking together two 
 stones, we set in vibration the string of a piano- 
 forte or the reed of an organ-pipe, we excite a sys- 
 tem of waves, all of equal size, and succeeding one 
 another with perfect regularity, and these breaking 
 on the ear produce by their regular beats what we 
 call a musical note. If the waves follow one another 
 with such rapidity that one hundred and twenty- 
 eight break on the tympanum every second, the 
 note has a fixed pitch, called in music " C natural." 
 If the waves come faster than this, the pitch is 
 higher, and if less rapidly the pitch is lower. What 
 we are all familiar with as a pitch of a musical note 
 depends, then, on the rapidity with which the waves 
 of sound strike the ear, and may evidently be meas- 
 ured by the number of waves breaking on the tym- 
 panum in a second. 
 
 Our ears are so constituted that they can hear a 
 musical note only when within certain fixed limits 
 of pitch, differing to a slight extent with different 
 individuals. The deepest bass note, which can be 
 heard, as such, by a good ear, is produced by about 
 
40 WAVES OF SOUND. 
 
 eight waves in a second. If the waves strike less 
 rapidly than this, they are perceived as distinct 
 beats, and beginning at this note the musical scale 
 ascends to a note caused by twenty-four thousand 
 waves a second, which is the highest note percepti- 
 ble by human sense. The range of a piano gener- 
 ally extends from a note produced by sixteen waves 
 in a second, to one caused by one thousand and 
 twenty-four waves in a second, as is shown by the 
 accompanying table. 
 
 DIMENSIONS OF WAVES OF SOUND. 
 
 Tsint^ Length of waves Number of waves 
 
 IMotes. ° - striking the ear 
 
 in feet. in one second. 
 
 C— 3 70 16 
 
 C— 2 35 32 
 
 C— I 17.5 64 
 
 Q 8.75 128 
 
 Q 4.375 256 
 
 C3 2.178 512 
 
 C4 1.093 1,024 
 
 Name of Note, C, D/ E, F^ G^ A^ B^ Q 
 
 Number of Waves, I28 I44 160 I/Of I92 2 1 3| 24O '256 
 
 Ratio of each number) ._ 9 g 4 3 g 2.5. ^ 
 
 to that of Note C, j ^ "8 4 "3 "0- 3 8 2 
 
 Sounds of the highest pitch, like the cry of some 
 insects, become disagreeable, and by some persons 
 cannot even be distinguished. It is quite possible 
 to produce a sound, which, though painfully shrill 
 to one person, shall be entirely unheard by another. 
 
WAVES OF LIGHT. 4I 
 
 Professor Tyndall, in his very interesting work on 
 the glaciers of the Alps, relates an instructive anec- 
 dote of this sort, which I give in his own lan- 
 guage. 
 
 " I once crossed a Swiss mountain in company 
 with a friend ; a donkey was in advance of us, and 
 the dull tramp of the animal was plainly heard by 
 my companion ; but to me this sound was almost 
 masked by the shrill chirruping of innumerable in- 
 sects, which thronged the adjacent grass ; my friend 
 heard nothing of this, it lay quite beyond his range 
 of hearing.** 
 
 There may, therefore, be innumerable sounds in 
 nature to which our ears are perfectly deaf, although 
 they are the sweetest melody to more refined senses. 
 Nay, more, the very air around us may be resound- 
 ing with the hallelujahs of the heavenly host, when / 
 our dull ears hear nothing but the feeble accents of i 
 _pur broken prayers. ^ 
 
 We have been studying, my friends, the nature 
 of sound, in order to comprehend more readily the 
 nature of light and heat, for the phenomena in- 
 cluded under these names are produced, like the 
 phenomena of sound, by waves ; not, however, by 
 waves in the air, but by waves in a medium which 
 is as much more subtile than air as air is more sub- 
 tile than water, — indeed, a medium so exceedingly 
 thin that it eludes all our powers of chemical anal- 
 ysis ; but which, as we assume, pervades all space, 
 and this, too, whether the space be filled or not, at 
 the same time, by other forms of matter. We call 
 this medium '* ether,'* and through it the waves of 
 
42 CAUSE OF COLOR. 
 
 light speed with an inconceivable rapidity. Sound 
 travels i,ioo feet in a second, but a wave of light 
 spans 187,000 miles in the same time, and starting 
 from the sun on its journey of unnumbered years, 
 to Sirius or Arcturus, leaves the whole solar system 
 behind in a single hour. 
 
 Yet great as is the difference of velocity, the 
 analogy between sound on the one side, and light or 
 heat on the other, is complete. Every luminifer- 
 ous body, like this candle-flame, excites in the ten- 
 uous ether a system of waves, which spread, in 
 ever- enlarging spheres, with the immense veloc- 
 ity just described ; and it is these little billows 
 which, passing through the humors of the eye, and 
 breaking on the retina, produce the sensation we 
 call light, or, falling on the skin, excite the less deli- 
 cate nerves of feeling, and cause the sensation of 
 heat. 
 
 Moreover, the difference between colors is of pre- 
 cisely the same kind as the difference between 
 notes. Red, yellow, green, blue, violet, etc., are 
 names we give to sensations caused by waves of 
 ether breaking at regular intervals on the retina. 
 Color corresponds to pitch, and — what may seem to 
 you incredible — we are able to calculate from actual 
 measurements the number of waves of ether which 
 must break on the retina in a second in order to 
 produce the sensation of a given color. Here are 
 some of the numbers, and, extravagant as they 
 appear, they are the sober results of science, and 
 have been as accurately determined as the magni- 
 tudes and distances of astronomy. 
 
CAUSE OF COLOR. 43 
 
 ^^1^^^ Number of waves* Number of waves in a second. 
 
 v.oiors. jj^ ^^ inch. 
 
 Red 39?ooo 447 i^iHio^ million. 
 
 Orange 42,000 506 
 
 Yellow 44,000 535 
 
 Green 47,000 577 
 
 Blue 51,000 022 
 
 Indigo 54?ooo 658 
 
 Violet 57,000 699 
 
 It is actually true, that when we are receiving the 
 sensation of red there are no less than 477 million 
 millions of ether waves breaking on the retina of 
 our eyes every second. And more than this, we 
 have measured the length of these waves, and we 
 know that the length of a wave of red light from 
 crest to crest is -j^^oo ^^ ^^ i^^h. By examining the 
 table you will also discover that the sensation of 
 red, as compared with other colors, results from the 
 smallest number of waves, and that these waves are 
 comparatively large. On the other hand, the sensa- 
 tion of violet is caused by the largest number of 
 waves, which, however, are proportionally small in 
 size. The red light, therefore, corresponds to low, 
 
 * A given wave-length corresponds to each point on the line of the 
 solar spectrum, to be described further on. The numbers given in the 
 table are to be regarded merely as the mean values for each color, 
 measured at points on the spectrum, marked by certain prominent 
 dark lines called Frauenhofer's lines. The solar spectrum, as seen 
 with a powerful spectroscope, is crossed by thousands of these lines, 
 which have a fixed position, and therefore serve to mark definite points 
 on this otherwise continuous band of blending colors. 
 
44 THE SOLAR SPECTRUM. 
 
 and the violet to high notes of music, and between 
 these extremes there exists every gradation of pitch 
 which is here manifested in color. 
 
 Waves of all the dimensions given in the table, to- 
 gether with waves of every possible length between 
 certain extremes, — which are far wider than those 
 indicated above, — move together in the sunbeam, 
 and their combined impression produces the sensa- 
 tion of white light. We have a very simple way of 
 analyzing the sunbeam and separating its different 
 color-producing waves. The method consists in 
 passing the sunbeam through a glass prism. The 
 prism has the power of bending the beam from its 
 rectilinear direction ; but it does not change the di- 
 rection of the motion of all the waves to the same 
 extent. The longer waves, which give the sensation 
 of red, are bent from their course much less than the 
 shorter waves, which produce the sensation of vio- 
 let, while waves of an intermediate length take a 
 course between the two. Hence, after emerging 
 from the prism the directions of the different waves 
 diverge, and if we receive the beam of light thus 
 analyzed, on a screen, the various color-producing 
 waves strike the screen at different points of a con- 
 tinuous line. A more or less narrow band on the 
 screen will thus be illuminated with lights of different 
 colors in the following order — Red, Orange, Yellow, 
 Green, Blue, Indigo, Violet — and this beautiful phe- 
 nomenon is familiar to almost every one under the 
 name of the solar spectrum. 
 
 Here, where we have the whole scale of colors 
 spread out before us, the analogy of light to sound 
 
COLOR AND MUSICAL NOTES. 45 
 
 becomes still more evident. As there are persons 
 who cannot hear the shrill sound of some insects, so 
 there are many who cannot see certain colors of the 
 spectrum, and as there are unquestionably innumer- 
 able sounds in nature which are inaudible to our 
 ears, so there are innumerable waves in the ether 
 which are powerless to produce the sensation of 
 light. Moreover, singular as it may seem, we have 
 more palpable evidence of the existence of these 
 non-luminiferous waves than we can obtain in the 
 case of sound. There are waves in the ether far 
 smaller, and undulating far more rapidly, than those 
 which produce violet light ; so small that they do 
 not even jar the nerves of the retina, but which, 
 nevertheless, breaking on the prepared plate of the 
 photographer, leave there an impression which, de- 
 veloped by his skill, becomes a beautiful copy of na- 
 ture or of art. On the other hand, there are waves 
 in this same ether so large that the delicate retina 
 cannot vibrate in unison with their rough beats, but 
 which, nevertheless, breaking on the surface of the 
 skin, disturb the coarser nerves of feeling, and pro- 
 duce the glow of heat. Most of the waves which im- 
 press the optic nerve will also affect the nerves of 
 feeling ; but the reverse is not true, for many of the 
 waves which produce the sensation of heat are far 
 too large, and undulate too slowly, to set in vibra- 
 tion the retina of the eye. 
 
 I hope that I have been able to make clear two 
 points, — first, that light and heat are forms of mo- 
 tion ; second, that the differences in the phenomena 
 which have been referred to these two agents are 
 
46 THE ATMOSPHERE AND HEAT. 
 
 simply different sensations or different effects'^ pro- 
 duced by the same wave-motion. It would be 
 highly interesting, in this connection, to examine the 
 wonderfully delicate adjustments and to follow out 
 the peculiarly intricate motions which concur to pro- 
 duce the phenomena of light and heat ; for they are 
 in themselves most striking illustrations of the wis- 
 dom of the Creator. But this w^ould lead us too far 
 from our proposed plan, and I must content myself 
 with the few facts already given, which were neces- 
 sary to illustrate the relations of the atmosphere to 
 the thermal conditions of our globe. 
 
 From the principles stated, it is evident that the 
 atrnosph^erejiiust act in diffusing heat, just aswejiai^^ 
 seen that it acts^ in diffusing light. Indeed, this ef- 
 fect is one of the thousand conditions on which the 
 existence of organic life depends. Were it not for 
 the influence of the atmosphere, the greatest ex- 
 tremes of temperature would be produced by the 
 alternation of day and night, and even were the 
 
 * The effects of expansion, melting, evaporation, the permanent 
 elasticity of gases and vapors, and many other phenomena, formerly 
 referred to the action of a peculiar agent called heat, are now sup- 
 posed to be the result of the motion which the ether-waves commu- 
 nicate to the material particles of the bodies on which they strike 
 or through which they are transmitted. To understand this, we must 
 remember that the molecules, even of the densest solids, are supposed 
 to be separated from each other by comparatively large spaces filled 
 with ether, through which the waves of heat and light may move more 
 or less freely, just as the waves of air pass between the branches in a 
 forest. Moreover, as the waves of air impart motion to the branches of 
 the trees, and afterwards are kept in motion by the waving boughs, 
 so also the material particles of a body may set in motion the waves 
 of ether, or receive motion from them in return. 
 
DIFFUSION OF HEAT. 4/ 
 
 density of the atmosphere reduced only one-half, the 
 variation would be so great as to render the exist- 
 ence of the higher forms of organic life impossible, 
 except, perhaps, in the more favored regions of the 
 earth. 
 
 But not only does the atmosphere diffuse the heat 
 of the sun's rays, it also acts, and even more effectu- 
 ally, in retaining on the surface the heat which the 
 earth is constantly receiving from that great central 
 luminary. The atmosphere has been compared to a 
 mantle, and the comparison is just ; for, like a huge 
 cloak, it envelops the earth in its folds, and protects 
 it from the chill of the celestial spaces through 
 which we are rushing with such frightful velocity. 
 In order to understand how a thin and transparent 
 medium like air can thus act to keep the earth warm, 
 we must recur to some of the facts established above. 
 
 As the ether-waves, breaking on the eye more or 
 less rapidly, produce the different sensations of color, 
 so when breaking on the skin they occasion analogous 
 differences in the sensation of heat, which, although 
 not so accurately distinguished, because the sense is 
 less delicate, nevertheless are as real as the differ- 
 ence between a low and sweet musical note, and one 
 that is high and shrill. There are waves of heat 
 which break upon our nerves of feeling like the shrill 
 cry of the cricket on the ear, and seem to penetrate 
 to the very brain, while there are others which fall 
 like the low tones of an organ, diffusing throughout 
 the system a genial glow. Such, for example, is the 
 difference between the heat from a hard-coal fire 
 and that from a steam radiator. The waves of the 
 
48 THE ATMOSPHERE A CLOAK. 
 
 first sort, from their small size and rapid motion, can 
 readily pass through glass and other transparent 
 media, when the large waves with their slow motion 
 are in a great measure stopped. 
 
 Now it is found that the sunbeam is chiefly made 
 up of waves of the first class, which are therefore 
 able readily to penetrate the atmosphere and warm 
 the surface of the earth. The earth thus warmed 
 becomes itself a hot body, surrounded by an in- 
 tensely cold space, and, like anvotherhot body, tends 
 to lose its heat by radiation. /jBut the waves of heat 
 which the earth^ sets in motion are of the second 
 class, long and slow undulations, and these are in 
 great measure arrested by the atmosphere; indeed, as 
 experiments have proved, they are chiefly absorbed 
 by the lower strata,f in which we live and move. 
 
 Thus it is that the atmosphere keeps us warm ; 
 and if you desire further proof of the correctness 
 of these experimental deductions, ascend any high 
 mountain, and, as the thickness of the aerial cover- 
 ing above you is diminished by the elevation, you 
 will find that the chill increases, vegetation slowly 
 disappears, and before long you will reach a region 
 of eternal snow and ice. It is true that there are 
 other causes acting to lower the temperature at high 
 
 * The pitch, if we may so speak, and penetrating power of the 
 heat-waves depend on the temperature of the body by which they are 
 set in motion, and in proportion as the temperature rises the pitch is 
 higher and the penetrating power greater. 
 
 f Professor Tyndall has shown that this effect is due almost entirely 
 to the aqueous vapor in the atmosphere, which is present in greatest 
 quantity in the strata nearest to the earth. 
 
A TRAP TO CATCH THE SUNBEAM. 49 
 
 elevations, but the one just noticed is by far the 
 most important, as well as the primary cause. The 
 effect of the atmosphere is precisely similar to that 
 of the glass panes of a hot-house. The glass, like 
 the atmosphere, allows the rapidly undulating waves 
 of the sun to pass,* but almost "entirely arrests the 
 large and slowly undulating billows which radiate 
 from the vegetation within. They are each, in fact, 
 a trap to catch the sunbeam. 
 
 The atmosphere not only thus acts in diffusing the 
 sun's rays, and retaining the heat which they bring 
 to us, but it also subserves an equally important 
 end in distributing their genial warmth over the 
 whole surface of the earth, thus moderating the 
 climate of the temperate zone, and mitigating the 
 intense heat of the tropics. Air, like all gases, is 
 expanded by heat, and thus rendered specifically 
 lighter, and on this simple principle all our methods 
 of warming and ventilating are based. When now 
 it is remembered that the atmosphere under the 
 tropics must become more intensely heated by the 
 vertical rays of the sun than it is in the temperate 
 zones, the result will be obvious. The heated air. 
 rises, and the cold adr rushes in from the North and 
 South to take its place. Thus, two general currents 
 are excited in the aerial ocean of each hemisphere, 
 one on the surface of the earth, tending towards the 
 
 * In the sunbeam, as it passes through space, there are undoubt- 
 edly waves of low pitch in abundance, but these are almost entirely 
 arrested by the atmosphere before reaching the surface of the earth. 
 It has been estimated that of the heat the earth receives from the sun 
 about one-third is thus absorbed. 
 3 
 
50 DISTRIBUTION OF HEAT. 
 
 equator, and another, higher in the atmosphere, 
 tending towards the poles. These currents, how- 
 ever, do not blow due North or South ; for many 
 causes combine to turn them from their primitive 
 directions. 
 
 In the first place, the rotation of the globe on its 
 axis imparts to objects on the surface a motion from 
 West to East, varying in velocity from nothing, at 
 the poles, to the speed of a cannon-ball, at the 
 equator. In consequence of this, a mass of air 
 moving towards the equator is constantly arriving 
 at a point on the surface of the earth, which is 
 moving towards the East more rapidly than the 
 point it has just left ; and as, in virtue of the law of 
 inertia, the moving mass cannot accommodate itself 
 instantaneously to the increased velocity, it is left a 
 little behind, — that is, a little to the West, at every 
 step. Hence, the lower or polar currents bend 
 more and more towards the West as they approach 
 the equator, acquiring in the northern hemisphere a 
 south-westerly, and in the southern hemisphere a 
 north-westerly direction ; and the currents of the 
 two hemispheres, meeting at the equator, combine 
 to produce the great trade-wind, which, in the Pa- 
 cific Ocean, blows constantly from the East to the 
 West, and would blow regularly in this direction all 
 round the globe if the continents did not intervene 
 to disturb its course at various points. 
 
 The effect of the earth's rotation on the current 
 of warm air which flows from the equator in the 
 upper atmosphere, must evidently be the reverse of 
 that just described, bending it constantly to the 
 
TRADE- WINDS. 5 1 
 
 East, and giving to it in the northern hemisphere a 
 north-westerly, and in the southern hemisphere a 
 south-easterly, direction. But the upper and lower 
 currents do not long retain this relative position ; 
 for, as the first comes northward, it gradually sinks, 
 and, long before reaching this latitude, touches the 
 surface of the earth. Then, of course, it comes in 
 collision with the current from the North, and here 
 a strife for the mastery ensues. Sometimes the one 
 and sometimes the other prevails, and this alternat- 
 ing ascendency is one of the chief causes which ren- 
 der the winds of temperate climates so irregular. 
 
 Again, the unequal heating effect of the sun*s 
 rays on the earth, as compared with the sea, com- 
 bined with the irregular distribution of land and 
 water over the surface of the globe, tends to com- 
 plicate still further the motion of the aerial currents. 
 For reasons which will hereafter appear, the land is 
 more quickly heated by the sun*s rays than the sea, 
 when under the same conditions, and, on the other 
 hand, as soon as the sun is withdrawn, it cools more 
 rapidly. Hence, on an island in a warm climate we 
 generally have, during the daytime, a current of 
 heated air rising from the surface of the earth, and 
 a current of cooler air flowing in on all sides from 
 the ocean to take its place, while after sunset the 
 land soon cools below the temperature of the sur- 
 rounding ocean, and the current is reversed. Thus 
 is produced the daily alternation of land and sea 
 breezes, so familiar to every one who has visited the 
 tropics, where the phenomena are most strongly 
 marked. 
 
52 MONSOONS. 
 
 Quite a similar reciprocal action between the con- 
 tinents and the great ocean is caused by the alter- 
 nation of seasons, and of this the monsoons of the 
 Indian Ocean are a remarkable illustration. This 
 mediterranean ocean, shut off from the influence of 
 the general trade-winds by the great continental 
 masses which surround it, has a system of aerial 
 currents, peculiar to itself, blowing six months of 
 the year in one direction and six months in the 
 other. These are set in motion by the unequal 
 heating of the continents of Asia and Africa during 
 the extreme seasons. In the months of December, 
 January, and February, the part of Africa south of 
 the equator is exposed to the vertical rays of a 
 summer's sun, while the countries of southern Asia 
 are feeling the comparative cold of their winter. 
 The natural consequence is, that a stream of cold air 
 rushes across the Indian Ocean to feed the intensely- 
 heated current which is rising over the burning 
 plains of Africa, and produces a strong north-east- 
 erly breeze, which is the winter monsoon of India. 
 When, however, the sun comes north of the equa- 
 tor, all these conditions are reversed. The ocean 
 air now rushes to the more heated plains of India, 
 and tlie summer monsoon sets in, which blows from 
 the south-west, the change from one to the other 
 being always attended by variable winds and furi- 
 ous storms. Lastly, the position of mountain chains 
 and the configuration of the continents, which break 
 and turn the winds, or open to them a freer chan- 
 nel, have an important influence in determining the 
 direction of the aerial currents on the earth. 
 
AERIAL CURRENTS. S3 
 
 But we have not time for further details ; they are 
 given in all works on physical geography,^ and the 
 student of natural theology will find that subject rich 
 in illustrations of God's wisdom and power. We 
 have already become sufficiently acquainted with the 
 general plan to understand how the atmosphere acts 
 in equalizing the climate of the globe. The aerial 
 currents which come to us from the South bring 
 with them the heat of the tropics, and distribute it 
 over the temperate zone. As they blow from the 
 south-west, they naturally exert the greatest heating 
 power on the western coasts of the continents, and 
 this is one great cause of the well-known fact that 
 the climate of western Europe is so much milder 
 than our own, and the climate of California and 
 Oregon so much warmer than that of the corre- 
 sponding latitudes on the eastern coast of Asia. 
 Moreover, the sea-breezes on islands and along sea- 
 coasts, the monsoons of the Indian Ocean, and 
 other local currents, all combine, as our theory 
 shows, to produce the same general result, cooling 
 such regions of the earth as from any cause have 
 become overheated, and transferring the warmth to 
 places where it is more needed. Just as the heat 
 of burning fuel is diffused over a whole building 
 from the furnace by the currents of air it sets in 
 motion, so the sun's heat is diffused over the earth 
 from the tropics by the great terrestrial currents we 
 have so briefly described. Indeed, as already stated, 
 in all our methods of heating, we merely apply, on 
 
 * See Earth and Man, by Professor Arnold Guyot. 
 
54 CAPACITY FOR HEAT. 
 
 a small scale, the same general principles which are 
 at work around us in the atmosphere. 
 
 But, although the heat of the sun might set in mo- 
 tion these aerial currents, they would have but little 
 effect in warming our northern climate, were it not 
 that the air has been endowed with a certain capac- 
 ity for holding heat. All substances possess this 
 capacity to a greater or less degree, but the differ- 
 ences between them are very large. Thus the 
 amount of heat required to warm a pound of water 
 is ten times greater than would be required to raise 
 the temperature of a pound of iron, and thirty times 
 greater than would be required to raise the temper- 
 ature of a pound of mercury to an equal extent. 
 Hence, under the same conditions, a pound of water 
 may be said to contain ten times as much heat as a 
 pound of iron, and thirty times as much as a pound 
 of mercury ; or, again, in other words, the capacity 
 of water for heat is ten times greater than that of 
 iron, and thirty times greater than that of mercury. 
 The capacity of air for heat is, weight for weight, 
 about twice as great as that of iron, and although 
 only one-fifth as great as the capacity of water, it is 
 yet greater than that of most other substances. . The 
 point, however, to which I wish to direct your atten- 
 tion, is the fact that this capacity is exactly adjusted 
 to the office which the air has been appointed to filL 
 Were the capacity of the air less, the hot air from 
 the tropics would bring to us proportionally less 
 heat ; were it greater, the reverse would be the case ; 
 and in either event, the distribution of temperature 
 on the earth would be changed. To what extent 
 
THE ATMOSPHERE AND ELECTRICITY. 55 
 
 such a change would affect the general welfare of 
 man, it is impossible to determine ; but when we 
 consider how far the history of man has been influ- 
 enced by climate, it will appear that the present dis- 
 tribution of the human race — the existence, for ex- 
 ample, of a large and influential city in this place — 
 may be said to depend on the adjustment of the 
 capacity of the atmosphere for heat ; and yet it de- 
 pends no less on ten thousand other conditions, 
 many of them far more important than this. How 
 truly, then, it may be said, that even here on earth 
 we live in '^ a city which hath foundations, whose 
 builder and maker is God '* ! 
 
 Such are a few of the more obvious marks of de- 
 sign, which may be discovered by studying the 
 relations of the atmosphere to light and heat. I 
 might here close one division of my subject ; but I 
 should fail to give you an adequate idea of the 
 wonderful play of physical forces in the atmosphere, 
 were I to leave out of view that mighty agent which 
 charges the artillery of heaven and feeds the flam- 
 ing torches in the northern sky. It is true that the 
 atmospheric relations of electricity are very imper- 
 fectly understood, and the important ends which it 
 undoubtedly subserves in the economy of nature 
 almost entirely unknown. We cannot, therefore, 
 expect them to furnish us with many additional 
 illustrations of the Divine attributes ; but since elec- 
 trical phenomena play so conspicuous a part in the 
 atmosphere, and must have been included in its 
 plan, they certainly should not be overlooked if we 
 
56 THEORY OF ELECTRICITY. 
 
 would gain a general idea, however imperfect, of the 
 whole design. 
 
 Of all the assumed agents of nature there is hardly- 
 one which is so little understood, and yet has been 
 so carefully studied, as electricity. To the unedu- 
 cated it affords the convenient explanation of most 
 obscure phenomena, while with men of science it 
 is the object of much laborious investigation and 
 careful theorizing. The study of its phenomena 
 has been fruitful in the discovery of facts ; but it 
 has as yet led to but few general principles, and has 
 furnished only a meagre explanation of those grand 
 displays of nature in which it seems to be such an 
 important agent. 
 
 In regard to the nature of electricity, we are en- 
 tirely ignorant. The phenomena of light and heat* 
 admit, to say the least, of an intelligible explana- 
 tion, and can be referred to a dynamical origin ; 
 but in the case of electricity we are obliged to be 
 content with collecting facts, and must await the 
 further progress of science to reveal the now hidden 
 cause. I am well aware that electricity has been re- 
 garded as a very rare and subtile " fluid,'* and that this 
 theory has not only afforded a plausible explanation 
 of most of the phenomena of statical electricity, but 
 also that the numerical results based upon it have 
 been most remarkably verified by experiment. Yet 
 nevertheless, although the theory may still be used 
 as a convenient frame in which to exhibit the facts, 
 there are but few investigators of the present day 
 
 *See Tyndall's " Heat Considered as a Mode of Motion." 
 
FUNDAMENTAL FACTS. 57 
 
 who would claim for it more than a very partial 
 foundation in truth, and most would reject it alto- 
 gether as utterly untenable. 
 
 The fundamental facts of electricity were known 
 to the ancients, and are familiar to every one. If a 
 stick of sealing-wax or a glass tube be rubbed with 
 a warm silk handkerchief, it becomes, as we say, 
 electrified, and in this condition has the power of 
 attracting pieces of paper or any light particles of 
 matter. When the scientific men of the last cen- 
 tury came to examine these phenomena more care- 
 fully, they found that the handkerchief was also 
 electrified, and thrown into a state differing from 
 that of the glass in the one case, and that of the re- 
 sin in the other, very much as the north pole of a 
 magnet differs from its south pole. They found, also, 
 that the resin was electrified oppositely to the glass, 
 and they hence concluded that there were two kinds 
 of electricity, which they distinguished by the names 
 resinous and vitreous, or positive and negative. 
 They also discovered that this agent could readily 
 be drawn off from electrified bodies by the metals, 
 but only with difficulty, if at all, by such materials 
 as india-rubber, glass, resin, or silk, and they were 
 hence led to divide substances into conductors and 
 non-conductors of electricity. A good conductor, 
 when insulated by non-conductors, was found to re- 
 tain for a short time the electricity it had received 
 from the electrified glass or resin, although the 
 charge was soon dissipated by the surrounding air, 
 especially when moist. By bringing in the aid of 
 machinery, and thus increasing the surface of fric- 
 3* 
 
S8 FUNDAMENTAL FACTS. 
 
 tion, it was found possible to enhance very greatly 
 the effects obtained with a glass tube ; and this was 
 the origin of the electrical machine. This familiar 
 instrument is merely a mechanical contrivance for 
 rubbing together glass and silk, with two insulated 
 metallic conductors for receiving the two kinds of 
 electricity thus generated. If the hand or a metallic 
 knob was brought near the prime conductor of the 
 machine when highly electrified, it was found that a 
 luminous discharge followed, which was termed an 
 electrical spark ; and it was found possible by means 
 of a glass vessel, coated inside and outside with some 
 metallic leaf, called a Leyden jar, to accumulate the 
 two electricities in such large quantities that, when 
 allowed to flow together, the discharge was capable 
 of producing violent mechanical action, similar to 
 that of lightning, although on a vastly reduced scale. 
 It was also discovered that electricity passes readily 
 through the greatly rarefied atmosphere in the re- 
 ceiver of an air-pump, causing a luminous effect sim- 
 ilar to the aurora borealis. Lastly, it was observed 
 that electricity readily escapes into the atmosphere 
 from a pointed conductor, and, conversely, that a 
 heavy charge can be silently and harmlessly drawn 
 from an electrified body by holding near it the point 
 of a needle. By attaching a pointed conductor to 
 a boy*s kite, Franklin succeeded in drawing an elec- 
 tric spark from a thunder-cloud, and having thus 
 established the identity between atmospheric and 
 frictional electricity, he erected the pointed rod, 
 which protects our dwellings against the lightning s 
 stroke. 
 
FUNDAMENTAL FACTS. 59 
 
 More recently it has been discovered that friction 
 is by no means the only source of electricity, and it 
 seems probable that no change^ either chemical or 
 physical, takes place in nature without some mani- 
 festation of this agent. It was at first supposed 
 that there were several kinds of electricity, which 
 w^ere named thermo-electricity, magneto-electricity, 
 voltaic electricity, and animal electricity, according 
 to the nature of the process in which the electrical 
 action was developed ; but it is now universally 
 conceded that all are only different manifestations 
 of the same agent, and most investigators believe 
 that electricity will in time be shown to be a form 
 of molecular motion analogous to that which pro- 
 duces the phenomena of hght and heat, although it 
 has not as yet been found possible to frame a com- 
 prehensive and intelligible theory based upon this 
 hypothesis. Again, it has been found that friction 
 is a far more general source of electricity than was 
 at first believed. In fact, electrical phenomena ap- 
 pear to be a constant result of friction, whatever 
 may be the nature of the substances rubbed. Thus 
 it is developed by blowing air over glass, and the 
 hydro-electric machine, one of the most effective 
 means of generating electricity we possess, owes 
 its surprising energy to the friction of globules of 
 water against the sides of the vent-cock of a steam- 
 boiler."^ 
 
 When, now, we consider that the air is always 
 
 * This machine consists simply of a small steam-boiler insulated on 
 glass pillars, having a peculiarly-constructed vent-cock and provided 
 with suitable metallic conductors for receiving the electricity. The 
 
6o ATMOSPHERIC ELECTRICITY. 
 
 rubbing over the surface of the earth, at times with 
 great rapidity, we shall not be surprised to learn 
 that both bodies are constantly in an electrified 
 condition, the earth being generally charged nega- 
 tively, and the atmosphere positively. Even in fair 
 weather it is always possible to detect the presence 
 of free electricity in the atmosphere ; and during a 
 storm, when clouds filled with drops of water are 
 hurried over the surface, grinding against the hills 
 and the trees, or against each other, the atmos- 
 phere becomes a vast hydro-electric machine, whose 
 sparks are the lightning, and the noise of whose 
 discharges the thunder. Again, the various chemi- 
 cal and physical changes which are going on around 
 us, — such as the vital processes of animals and 
 plants, the combustion of fuel, volcanic action, the 
 evaporation of water, — all undoubtedly add to the 
 electrical excitement of the atmosphere, and more 
 or less modify the result. It is not important for 
 us, however, to study the action of each one of 
 these causes ; for we have, probably, in the friction 
 of moist air driven by the winds, the chief source of 
 atmospheric electricity ; and when we consider the 
 amount of friction which must attend the rapid 
 motion of storm-clouds, or of a tori^ado through the 
 atmosphere, the wonder is, not that an occasional 
 thunderbolt should kindle a conflagration, or even 
 cause a death, but that every storm does not lay 
 waste the earth along its fiery track. Moreover, 
 
 steam, as it escapes under high pressure, becomes filled with globules of 
 water which rub against the sides of the vent-tube, and this is so 
 shaped as to facilitate their formation. 
 
PROTECTION AGAINST LIGHTNING. 6l 
 
 when we appreciate the vastness of the scale on 
 which the electrical machine of nature is constructed, 
 the thunder-storm ceases to surprise us, and only 
 calls our attention to those beneficent provisions by 
 which we and our race are saved by a constant 
 miracle from the fate of the cities of the plain. 
 That the atmospheric electricity was designed to 
 subserve many important and beneficent ends, the 
 whole analogy of nature compels us to believe ; but 
 while our present ignorance conceals them from our 
 sight, we may still discover evidence of God's good- 
 ness and wisdom in those simple provisions by which 
 the atmosphere is preserved from violent or frequent 
 electrical excitements, and its charge drawn down 
 harmlessly to the earth. 
 
 Since the atmosphere is, at best, a very poor con- 
 ductor, the electricity developed by the processes 
 just considered tends to accumulate ; and under pe- 
 culiar conditions the clouds may become so highly 
 charged, that at length the pent-up power acquires 
 sufficient force to break through all barriers, and 
 the lightning dashes to the earth, crashing, rending, 
 and burning on its way. To guard his roof from its 
 destructive action, man erects the lightning-rod, 
 whose bristling points quietly drain the clouds, or, 
 failing to do this, receive the charge, and bear it 
 harmlessly to the earth. But ages before Franklin 
 pointed the first rod to the storm, the Merciful Par- 
 ent of mankind had surrounded the dwellings of 
 his children with a protection far more effectual than 
 this; for, since jdie creation of organic life, every 
 pointed leaf, every twig, and every blade of grass 
 
62 PROTECTION AGAINST LIGHTNING. 
 
 has been silently disarming the clouds of their de- 
 structive weapon. It is difficult to improve upon 
 nature, and man constantly finds that in his best 
 inventions he hasTieen anticipated from eternity by 
 an Inventor greater than himself. So, not long after 
 Franklin had discovered the efficacy of metallic points 
 in dissipating charges of electricity, and had applied 
 the principle in constructing the lightning-rod, it was 
 found that a common blade of grass, sharpened by 
 nature's exquisite workmanship, was three times as 
 effectual to the end in view as the finest cambric 
 needle, and a single twig far more efficient than the 
 metallic point of the best-constructed rod. When, 
 now, you reflect how many thousands of these vege- 
 table points every large tree directs to the sky, and 
 consider what must be the efficacy of a single forest 
 with its innumerable twigs, or of a single meadow 
 with its countless blades of grass ; when you remem- 
 ber that these are only subsidiary to those vast light- 
 ning-conductors the mountain-chains, whose craggy 
 summits pierce the clouds themselves ; and still fur- 
 ther, when you learn that rain-drops and snow- 
 flakes also have been made good conductors, so that 
 during storms a natural bridge for the lightning 
 reaches across from the clouds to the earth, you 
 will see how abundant the protection is, and with 
 what care Providence has guarded us from the de- 
 structive agent. It is only under unusual circum- 
 stances, when electricity is developed more rapidly 
 than it can be dissipated through these numberless 
 channels, that a violent discharge takes place, and 
 if then it tears, burns, or kills, it also reveals the 
 
MARKS OF DESIGN. 63 
 
 Merciful Hand which constantly spares. Moreover, 
 through this servant of his pleasure, God is con- 
 stantly educating and elevating his creatures. In 
 the wild coruscations of the lightning, and in the 
 reverberating roll of the thunder. Nature exhibits 
 one of her grandest aspects, and when, through the 
 cold, dry air of the polar region the electric charges 
 shoot down to the earth in tremulous flashes, we 
 see her lighting up those grand displays of northern 
 fire which enliven the long night of the arctic win- 
 ter, or in this more favored climate excite the admi- 
 ration of all.*^ 
 
 I must here conclude this very imperfect sketch 
 of the physical adaptations of the atmosphere to the 
 ends it subserves on the earth. We studied in the 
 first place its aeriform condition, and found that its 
 density not only formed an essential part of the 
 scheme of organic nature, but also was closely related 
 to the dimensions of the solar system. In this Lec- 
 ture we have studied the relations of the atmosphere 
 to light, heat, and electricity ; and although we have 
 been able only to glance at some of the more prom- 
 inent features in these wonderful displays of . crea- 
 tive energy, we have found, wherever we turned, 
 abundant illustrations of the wisdom, power, and 
 goodness of our God. I trust that you have been 
 impressed by the vastness, the complexity, and yet 
 
 * I am indebted for many of the above illustrations to an admirable 
 paper on atmospheric electricity, in the American Almanac for 1854, 
 by my friend and colleague Prof. Joseph Lovering. 
 
64 MARKS OF DESIGN. 
 
 the simplicity and harmony of the whole design, for 
 these are the chief points which I have endeavored 
 to set forth. But oh how imperfect any conception 
 which I can give you must be ! This atmosphere is 
 sustained in the proper working of all its parts only 
 by the exact balancing of a thousand conditions. 
 Attempt to make yourself acquainted with these 
 conditions, and, disregarding those which you re- 
 cognize at once as surpassing human intelligence, 
 study only such as are thoroughly understood and 
 universally admitted to have been primary con- 
 ditions in the plan of nature before the atmosphere 
 could exist as it is. This is not an impossible task. 
 It would require years of study and it would lead 
 you into every department of physical science, but 
 the result would well repay your labor. You would 
 find it easy to follow out any one line of the con- 
 ditions, until it became lost in the obscurity of the 
 unknown ; but to form an adequate conception of the 
 simultaneous working of all the conditions in their 
 varied bearings, or even of two or three of them, you 
 would soon discover to be a hopeless task. The com- 
 plication of this wonderful machinery so far tran- 
 scends man's insight, that to understand its com- 
 bined action is simply impossible. But although thus 
 made keenly sensible of the limits of human thought, 
 you would be filled with gratitude for the high priv- 
 ilege enjoyed of studying the divine mechanism, even 
 though you understood its workings only obscurely 
 and in part. 
 
 ^aley has compared the mechanism of nature to 
 a wStch, and, so far as the argument for design is 
 
MARKS OF DESIGN. 65 
 
 concerned, the analogy is perfect. We must never 
 forget, however, that there is an essential difference 
 between the scheme of nature and the most compli- 
 cated human mechanism. I have seen a carpet- 
 loom weaving a pattern composed of twelve differ- 
 ent colors, and, as I watched the shuttles of various 
 colored yarns which were selected by the hands of 
 the machine with unerring certainty, and thrown 
 through the warp, it seemed as if the very iron were 
 endowed with intelligence, and the impression was 
 one of wonder and bewilderment. To comprehend 
 such complexity appeared impossible ; but the more 
 I studied the details of the machine, the more 
 thoroughly I understood the mode of its action, 
 until at last the wonder vanished; and although 
 not ceasing to admire the skill of the inventor, I felt 
 that I had comprehended the whole, and could even 
 conceive of the mental process by which such a 
 wonderful combination of means had been thought 
 out and adjusted to produce the desired end. The 
 artist was ingenious, but the machine was still 
 human. 
 
 How different it is with the mechanism of na- 
 ture ! Here, also, it is true, the more we study, 
 the more we understand the workmanship ; but 
 then we never reach the limit. The more our 
 powers of thought and observation are developed, 
 and the more our experience is enlarged, the more 
 the field of possible knowledge expands before us. 
 The larger our attainments, the less we seem to 
 know. 
 
 We still recognize the unmistakable marks of in- 
 
(£ MARKS OF DESIGN. 
 
 telligence in the design, but it is no longer a fathom- 
 able intelligence ; we feel that it is infinitely above 
 us : in a word, we feel that it is God. Would that 
 my feeble language might convey to you the full 
 power of this impression ; for until one has become 
 conscious of the infinite beauty and skill with which 
 the numberless parts of nature have been fashioned 
 and adjusted, one cannot appreciate the force of 
 the conviction which the impression gives. We 
 may make ourselves familiar with the dimensions of 
 Mont Blanc ; we may read the most glowing descrip- 
 tions of this " monarch of mountains," heightened 
 by all the arts of eloquence or of poetry ; we may 
 cross the ocean and travel to the beautiful valley of 
 Chamouni at its base ; we may even climb its side, 
 study its glaciers, and cross its fields of snow : but 
 we can form no adequate conception of its gran- 
 deur, until, ascending one of the lofty mountain- 
 peaks which surround it, we see its summit still 
 towering above our heads, apparently higher than 
 before. So it is in the study of nature. No de- 
 scription can convey an adequate conception of the 
 impression which it leaves upon the mind. It is not 
 until the student, after long study, has become thor- 
 oughly acquainted with some one portion, however 
 limited, of its wonderful economy, that he begins to 
 appreciate the perfection of its parts, the infinite 
 skill with which all have been adjusted, and the true 
 grandeur of the w^hole. 
 
 By most men these heights of knowledge are un- 
 attainable. Why, then, should we hesitate to receive 
 the evidence of a philosopher like Newton, who. 
 
MARKS OF DESIGN. 6/ 
 
 after spending a long life in the investigation of 
 nature, and with a success unparalleled in the history 
 of science, uttered this memorable sentiment shortly 
 before his death : ^^^ I do^or~1mow whM I rhay 
 pear to the world ; but to myself I seem to have 
 been only like a boy playing on the sea-shore, and 
 devoting myself now and then to finding a smoother 
 pebble or a prettier shell than ordinary, while the 
 great ocean of truth lay all undiscovered before me." j 
 I know this sentiment has been so many times re- 
 peated as to seem trite, but, coming from whom it 
 does, it cannot be too often quoted. It is the testi- 
 mony of the foremost master of science to its great- 
 est and sublimest truth. 
 
 We can all recognize the marks of design in na- 
 ture, and when we add to this evidence of our senses 
 the testimony of a man like Newton, who assures us 
 that the more our powers are enlarged, and the 
 wider our knowledge becomes, the grander and 
 vaster the design will appear, until it surpasses all 
 our powers of thought or imagination, we begin to 
 feel the full depth of the truth I have been endeav- 
 oring to enforce. If our minds are incapable of 
 comprehending the plan, who could have been equal 
 to the design ? " Whence, then, cometh wisdom, 
 and where is the place of understanding, seeing it 
 is hid from the eyes of all living, and kept close 
 fromthefowlsof the air? "^ ^ ^ God understandeth 
 the way thereof, and he knoweth the place thereof. 
 For he looketh to the ends of the earth, and seeth 
 under the whole heaven, to make the weight for 
 the winds ^ * -^ and a way for the lightning of 
 
68 MARKS OF DESIGN. 
 
 the thunder. Then did he see it and declare it; 
 he prepared it, yea, and searched it out. And 
 unto man he said, Behold the fear of the Lord, 
 that is wisdom, and to depart from evil is under- 
 standing," 
 
CHAPTER III. 
 
 TESTIMONY OF OXYGEN. 
 
 Were we to limit our regards to those physical 
 qualities of the atmosphere which we studied in the 
 first two chapters, we should overlook the most won- 
 derful adaptations in its divine economy. These 
 properties belong to the atmosphere, in great meas- 
 ure at least, in virtue of its aeriform condition, and, 
 so far as we know, an atmosphere composed of 
 other gases, and still having the same density, would 
 soften the intensity of the light, and diffuse the 
 genial influences of the sun's heat, as well as air. 
 Not so, however, with the chemical qualities of the 
 atmosphere, which we are next to consider. These 
 belong to the atmosphere solely as air, and could not 
 have been obtained with any other known materials. 
 
 When a chemist wishes to investigate the nature 
 of a new substance, his first step is to analyze it. 
 Let us, therefore, as a preliminary to our present in- 
 quiry, ascertain what is the composition of this 
 aeriform matter we call air. The air has been ana- 
 lyzed hundreds of times in every latitude and in 
 every climate ; and the result has been uniformly 
 that which is given in the following table : — 
 
 69 
 
70 COMPOSITION OF THE ATMOSPHERE. 
 
 Composition of the Atmosphere, 
 
 * 
 
 Oxygen 20.61 
 
 Nitrogen 77.95 
 
 Carbonic Dioxide 04 
 
 Aqueous Vapor (average) 1.40 
 
 Nitric Acid, \ 
 
 Ammonia, r traces. 
 
 Carburetted Hydrogen, ) 
 
 100.00 
 
 Composition in Tons. 
 
 Oxygen 1,233,010 billions of tons. 
 
 Nitrogen 3,994,593 '* " 
 
 Carbonic Dioxide 5,287 " " 
 
 Aqueous Vapor 54,460 " " 
 
 Besides oxygen and nitrogen gases, which, as you 
 will notice, are the chief constituents, there are al- 
 ways present in the atmosphere the vapor of water, 
 carbonic dioxide, and ammonia gas ; and if we add 
 to these uniform constituents the various exhalations 
 constantly arising from the earth, we shall have as 
 accurate an idea of the composition of the air as 
 chemistry can give. While, however, the propor- 
 tions of oxygen and nitrogen are almost absolutely 
 constant, those of the other ingredients are very 
 fluctuating, and the total quantity exceedingly small, 
 never amounting in all, exclusive of aqueous vapor, 
 to more than one part in a thousand, unless in some 
 confined locality, and under very unusual circum- 
 
 * Miller's Elements of Chemistry. 
 
THE ATMOSPHERE A MIXTURE. /I 
 
 stances. Do not, however, measure the importance 
 of these variable, and in a degree accidental, constit- 
 uents by their amount, for, although present in such 
 small quantities, they are not less essential in the 
 atmosphere than the two gases which make up al- 
 most its entire mass. 
 
 Moreover, we must carefully avoid the error of 
 considering air as a distinct substance, like water 
 or coal. On the contrary, it is merely a mechanical 
 mixture of its constituent gases, and is in no sense 
 a definite chemical compound. Indeed, we may 
 regard the globe as surrounded by at least three 
 separate atmospheres, — one of oxygen, one of nitro- 
 gen, and one of aqueous vapor, — all existing simul- 
 taneously in the same space, yet each entirely dis- 
 tinct from the other two, and only very slightly 
 influenced by their presence. To each of these 
 atmospheres the Author of nature has assigned 
 separate and different functions. They are like so 
 many servants in a household, each with a distinct 
 set of duties, which are discharged with a fidelity 
 and diligence unknown to any earthly service. Let 
 us consider what those duties are, and see how 
 skilfully each is adapted to the offices which it is 
 designed to fill. 
 
 Were all the other constituents of the air re- 
 moved, the earth would still be surrounded by an 
 atmosphere of oxygen, having about one-fifth of 
 the density, and exerting at the surface of the 
 globe about one-fifth of the pressure, of the pres- 
 ent atmosphere. In studying the chemical rela- 
 tions of air, let us begin with some of the more 
 
72 PERMANENT AERIFORM CONDITION. 
 
 important functions of this remarkable substance, 
 and these will fully occupy us during this and the 
 succeeding chapter. 
 
 It is easy to prepare oxygen in a pure state. It 
 is then a perfectly colorless and transparent gas, 
 and so persistently does it retain its aeriform con- 
 dition that it cannot be reduced to the liquid state 
 by pressure alone. A German chemist, Natterer, 
 submitted this gas to a pressure of over forty-five 
 thousand pounds, or twenty tons on a square inch, 
 but he did not succeed in changing its condition. 
 More recently, by the combined action of great 
 pressure and the most intense cold which can be 
 artificially produced, all the gases formerly called 
 permanent have been liquefied, and oxygen among 
 the number. But this remarkable result, while it 
 shows conclusively that the so-called permanent 
 gases differed from other forms of aeriform matter 
 in degree only, and not in kind, also brings into 
 prominence the extreme qualities of these constitu- 
 ents of our atmosphere. Most aeriform substances 
 may be reduced to liquids by pressure under a very 
 moderate reduction of temperature ;"^ but oxygen 
 
 * For every aeriform substance there is a fixed temperature above 
 which the gas cannot be reduced to a liquid" by any pressure, how- 
 ever great ; but below which this change can be produced if the 
 mechanical force is sufficient. This fixed temperature is called ** the 
 critical point," and the pressure required to condense a gas becomes 
 less and less as the temperature is reduced below this point, which 
 differs very greatly with different substances. The critical point of 
 many of the known gases is above the ordinary temperature of the air, 
 and a,U such gases may be reduced to liquids simply by mechanical 
 
PERMANENT AERIFORM CONDITION. 73 
 
 and nitrogen retain their aeriform condition under 
 the widest variations of temperature which exist 
 on the earth. 
 
 The importance of this fact will be seen at once 
 on comparing the condition of the oxygen and 
 nitrogeiTm The atmosphere with that of the aqueous 
 vapor. A fall of temperature of only a few degrees 
 will generally condense a portion of the vapor, and, 
 small as is its relative amount, the resulting rain is 
 at times poured down upon the earth in deluging 
 floods ; and if you consider what must have been 
 the destructive results had the whole mass of the 
 atmosphere been liable to a similar fluctuation, even 
 under extreme conditions, you will discover in the 
 permanency of oxygen a most obvious adaptation 
 of its properties to the thermal condition of our 
 globe. 
 
 The permanently aeriform state of oxygen will 
 appear still more remarkable when we consider how 
 largely it enters into the composition of the solid 
 crust of the earth. Oxygen belongs to that class 
 
 pressure. The critical point of carbonic dioxide gas is about 88°, and 
 as this temperature is within the limits of the variations in our cli- 
 mate, carbonic dioxide furnishes the most convenient illustration of 
 the principle we are discussing. For example, in some specimens of 
 granite rock we find cavities which are filled with liquid carbonic di- 
 oxide if the temperature is below 87° — as can readily be seen by ex- 
 amining with a microscope the thin sections prepared for this purpose 
 — but when the temperature rises above 87° the liquid at once disap- 
 pears, to condense again, however, as soon as the temperature falls. 
 The critical points of oxygen and nitrogen are not exactly known, 
 but must be more than 150® below the zero of Fahrenheit, and hence 
 chemists did not succeed in condensing these gases to liquids until 
 they submitted them to extreme cold as well as to great pressure. 
 4 
 
74 PERMANENT AERIFORM CONDITION. 
 
 of substances which the chemists call elements, 
 because they have never succeeded in resolving 
 them into simpler parts, and of all the elements 
 it is by far the most widely diffused. As we have 
 already seen, one-fifth of the volume of the atmos- 
 phere consists of this gas ; but this is a small amount 
 compared with that which enters into the com- 
 position of most substances. You may be surprised 
 at the statement, but it is nevertheless true, that 
 between one-half and one-third of the crust of this 
 globe and of the bodies of its inhabitants consists 
 of oxygen. No less than eight-ninths of all water is 
 formed of the same gas. It makes up three-fourths 
 of our own bodies, not less than four-fifths of every 
 plant, and at least one-half of the solid rocks. Re- 
 membering now that twenty tons of pressure on a 
 square inch are not sufficient to reduce oxygen to a 
 liquid condition, consider what must be the strength 
 of that force which holds it thus imprisoned. In a 
 tumbler of water there are no less than six cubic 
 feet of oxygen gas, condensed to a liquid condi- 
 tion, and held there by the continuous action of 
 a force which can be measured only by hundreds of 
 tons of pressure. We call the force chemical af- 
 finity; but who shall measure its power? Who but 
 He who could make with such a subtile material 
 the rocks, with which he " laid the foundations of 
 the earth," and the waters which roll over its sur- 
 face? 
 
 Oxygen gas, like all other forms of aeriform 
 matter, tends to expand, and can be prevented 
 from obeying this natural tendency only by en- 
 
DENSITY OF OXYGEN. 75 
 
 closing it in an air-tight receiver. As it exists in 
 our glass jars, under the ordinary conditions of 
 temperature and pressure, one cubic foot of oxy- 
 gen weighs 590.8 grains, although in its more ex- 
 panded state, as it exists in the atmosphere at the 
 surface of the globe, it has but one-fifth of this 
 density. One cubic foot of nitrogen gas weighs, 
 under the same circumstances, 517.5 grains; but 
 although there is such a decided difference between 
 the specific gravities of the two gases, yet so per- 
 fectly are they mixed together throughout the whole 
 extent of the atmosphere, that analysis has been un- 
 able to detect more than a very slight difference in 
 composition between the air brought from the sum- 
 mits of the Alps and that from the deepest mine 
 in Cornwall. Why, you may ask, do not these gases 
 obey the well-known laws of hydrostatics, the heav- 
 ier oxygen sinking to the surface of the earth, and 
 the lighter nitrogen floating above it ? Simply 
 because gases, unlike the other forms of matter, 
 have the property of '* diffusing " through each other, 
 and existing together in the same space. The pres- 
 ence of one gas does not prevent the entrance of 
 another into the space which it occupies, and if two 
 open jars, containing different gases, are placed 
 together, mouth to mouth, each gas will expand 
 until it fills the whole volume of both receivers. 
 Moreover, the greater the difference between the 
 densities of the gases, and the greater consequent 
 disposition to separate, the stronger is their ten- 
 dency to mix together. This process is known as 
 " diffusion," and plays a very important part in the 
 
^6 DIFFUSION. 
 
 plan of creation. Were no such law in operation the 
 two gases composing air would have separated par- 
 tially, and the atmosphere have become unfitted for 
 many of its important functions. Take, for example, 
 the function of transmitting sound. 
 
 As the air is now constituted, there is a constancy 
 of pitch, however far sound travels. Any tone once 
 generated remains the same tone until it dies away. 
 Its degree of loudness alters in proportion to the 
 distance of the listener, but the pitch is constant. 
 Were it not, however, for this law of diffusion, — 
 were the atmosphere not perfectly homogeneous, 
 and the gases of which it consists even partially 
 separated, — there would have been a very different 
 result. The constancy of pitch could no longer 
 have been depended upon. The sound as it travelled 
 would vary its pitch with the ever-varying medium 
 through which it passed, and would arrive at the ear 
 with a tone entirely different from that with which 
 it started. Nor would it require any great differ- 
 ence in the medium to produce a sensible result and 
 to confuse all those delicate differences of pitch on 
 which the whole art of music depends. Whenever, 
 therefore, you may be next enjoying the grand Pas- 
 toral Symphony of Beethoven or the Requiem of 
 Mozart, recall the careful adjustment of forces by 
 which alone these magnificent creations of genius 
 were rendered possible, and you cannot fail to re- 
 cognize in this simple law of nature the same hand 
 that first strung the lyre and made the soul of man 
 responsive to its seven notes. 
 
 Returning again to the qualities of oxygen, let us 
 
PASSIVE AND ACTIVE CONDITION. JJ 
 
 notice, in the next place, that it is entirely destitute 
 either of odor or of taste. This fact is a matter of 
 common experience ; for as oxygen exists in a free 
 state in the atmosphere, it would there manifest 
 these properties did they exist : and reflect how 
 essential these negative qualities are to our comfort 
 and well-being. Moreover, in its ordinary con- 
 dition, oxygen seems entirely devoid of any active 
 properties. It does not affect the most delicatg and 
 evanescent vegetable dyes, which the weakest chem- 
 ical agents will either alter or destroy. And con- 
 sider the oxygen as it exists in the air. How bland 
 and seemingly inactive it is there ? Reflect that it 
 bathes the most delicate animal organisms, that it 
 pervades the minutest air-passages of the lungs, — 
 remember that it is in contact with all matter, — 
 and every substance will seem to bear evidence to 
 the fact that oxygen in the state of gas possesses no 
 active properties, and is incapable of manifesting 
 any strong chemical force. And yet, if you infer 
 that oxygen always appears in the passive con- 
 dition, and is under all circumstances incapable of 
 violent action, you will be entirely deceived ; for so 
 far from being one of the weakest, it is the strong- 
 est of the chemical elements, and beneath this 
 apparent mildness there is concealed an energy so 
 violent, that, when once thoroughly aroused, noth- 
 ing can withstand it. A single spark of fire will 
 change the whole character of this element, and 
 what was before inert and passive becomes in an 
 instant violent and irrepressible. The gentle breeze 
 which was waving the corn and fanning the brows- 
 
78 NATURE OF FIRE. 
 
 ing herds, becomes the next moment a consuming 
 fire, before which the works of man melt away into 
 air. 
 
 And here I must correct an erroneous, although 
 very common impression, that there is something 
 substantial in fire. This is one of those ideas, origi- 
 nating in an illusion of the senses, which we have 
 inherited from a more ignorant age, and which our 
 modern science cannot wholly dispel from the popu- 
 lar mind. Fire was formerly regarded as one of the 
 elementary forms of matter, and all burning was 
 supposed to consist in the escape of this principle of 
 fire, previously pent up in the combustible substance. 
 In support of this doctrine the old philosophers con- 
 fidently pointed at flame as the visible manifestation 
 of the escaping fire-element ; and, childish as this 
 doctrine may seem, it was the prevalent belief of the 
 world for at least two thousand years. 
 
 The last phase which this doctrine assumed was 
 the phlogiston theory of the last century. In the 
 hands of Bergmann and Stahl, the vague ideas of 
 the time received a more material form, and were 
 embodied in a philosophical system. They termed 
 the principle of fire phlogiston, and burning, or the 
 escape of fire, dephlogistication, and their ingenious 
 system did not a little to retard the progress of 
 truth. The philosophers of that age either took no 
 account of the increase of weight which results from 
 burning, or attempted to explain the few instances 
 in which the fact was forced upon their attention by 
 the fanciful notion of Aristotle — that the essence of 
 fire was specifically light. Hence, they reasoned, 
 
THEORY OF PHLOGISTON. 79 
 
 phlogiston buoys up all bodies into which it enters, 
 and after its escape in the process of burning, the 
 burnt material must weigh more than before. It 
 was not until 1783 that the true theory of combus- 
 tion was discovered, and from this discovery mod- 
 ern chemistry dates. The fortunate discoverer was 
 Lavoisier. He proved, by simply weighing the prod- 
 lucts of combustion, that burning, instead of being 
 a loss of phlogiston, is a union of the burning sub- 
 stance with the oxygen of the air, and this theory 
 is now one of the best established principles of 
 science. 
 
 Burning is merely chemical change, and all com- 
 bustion with which we are familiar in common life 
 is a chemical combination of the burning substance, 
 whether it be coal, wood, oil, or gas, with the oxygen 
 of the air. Combustion is simply a process of chem- 
 ical combination, and the light and heat which are 
 evolved in the process are only the concomitants of 
 the chemical change. Why those mysterious in- 
 fluences of light and heat are radiated from the coal 
 which is combining with oxygen in our grates, we 
 may understand better hereafter ; but this much we 
 already know, — the sensations of light and heat are 
 caused by waves of an ethereal medium breaking 
 upon the extremities of the delicate nerves of our 
 human organism ; and such waves are set in motion 
 during the chemical change which we call combus- 
 tion. What the chemist mostly studies, however, is 
 the change itself, and to this we will for the present 
 confine our attention. 
 
 The chief products of ordinary combustion, that is, 
 
80 WEIGHT OF THE SMOKE. 
 
 the compounds of oxygen with the elements of coal, 
 wood, and illuminating gas, are only two in number, 
 carbonjc dioxide ^as and aqueous vapor. These 
 products, as is well known, are perfectly colorless and 
 transparent aeriform substances, wholly without odor 
 or taste, and entirely devoid of every active quality. 
 For this reason they escape without observation from 
 the burning wood, ascend our chimneys, and by the 
 force of diffusion are spread throughout the atmos- 
 phere ; but if, as may readily be done by chemical 
 means, we collect the neglected smoke and weigh 
 it, we shall find that it weighs much more than the 
 burnt wood, and, as more careful experiments will 
 show, its weight is exactly equal to that of the wood 
 added to that of the oxygen of the air consumed 
 during the burning. 
 
 Moreover, this smoke, though so long unno- 
 ticed by man, was not overlooked by the Author 
 of nature. It is a part of his grand and benefi- 
 cent design in the scheme of organic nature. No 
 sooner do the products of that wood burning on 
 the hearth escape into the free expanse of the outer 
 air, than a new cycle of changes begins. The car- 
 bonic dioxide and the aqueous vapor, after roving 
 at liberty for a time, are absorbed_by the leaves of 
 some jwide-spreading tree, smiling in the sunshine, 
 andln the tiny laboratory of their green cells are 
 worked up by those wonderful agents, the sun-rays, 
 into new wood, absorbing from the sun afresh supply 
 of power, which is destined, perhaps, to shed warmth 
 and light around the fireside of a future generation. 
 
 But let us not anticipate our subject. In a future 
 
FIRE, HOW SUSTAINED. 8 1 
 
 chapter we shall discuss this wonderful cycle of 
 changes at some length. At present I wish to 
 direct your attention to the remarkable contrast 
 of qualities presented by the element oxygen in its 
 active and passive conditions. How is this com- 
 plete inversion of properties to be explained ? 
 There is a cloud of mystery hanging over the sub- 
 ject, which the progress of knowledge has not as yet 
 entirely dispelled ;"^ but, so far as the cause is known, 
 I will endeavor to make it intelligible. The difference 
 in the action of oxygen in these two conditions de- 
 pends on temperature. At the ordinary tempera- 
 ture of the air its chemical affinities are dormant, 
 and, although endowed with forces which are irre- 
 sistible when in action, it awaits the necessary con- 
 ditions to call them forth. One of the grandest 
 works of ancient art which have come down to us is 
 the colossal statue of the Farnese Hercules. The 
 hero of ancient mythology is represented in an erect 
 form, leaning on his club, and ready for action ; but 
 for the moment every one of the well-developed 
 muscles of his ponderous frame is fully relaxed, and 
 the figure is a perfect ideal of repose, yet a wonder- 
 ful embodiment of power. Here in this antique we 
 have most perfectly typified the passive condition 
 of oxygen, the hero of the chemical elements. Raise 
 now the temperature to a red heat, and in a moment 
 all is changed. The dormant energies of its mighty 
 
 ■^During the past four years the study of thermo-chemistry has 
 given us the first clue toward a solution of this problem ; but as yet 
 the results do not admit of a concise and popular statement. 
 
 4* 
 
A 
 
 S2 FIRE, HOW SUSTAINED. 
 
 powers are aroused, and it rashes into combination 
 with all combustible matter, surrounded by those 
 glorious manifestations of light and heat which every 
 conflagration presents. 
 
 In order to evoke the latent forces in the oxygen 
 of the atmosphere, it is not necessary, however, to 
 raise the temperature of any considerable portion 
 either of the gas or of the combustible. There is 
 a provision in nature by which chemical combina- 
 tion, once started at any portion of the combustible 
 mass, is sustained until the whole is consumed. (All 
 chemical combination is attended by the evolution 
 ^ of heaty and in the combination of oxygen with 
 most combustible substances the amount of heat 
 thus generated is so great, that by the burning of 
 one portion sufficient heat is evolved to raise the 
 temperature of a second portion to the point of 
 ignition, and thus the process is continued. Con- 
 sider, for example, what takes place in the burning 
 of a jet of gas. We start the combustion by bringing 
 the flame of a lighted match over the orifice of the 
 burner. By this the temperature of the gas and 
 that of the air surrounding it are raised to a red- 
 heat, and chemical combination at once ensues. 
 But the chemical union, as just stated, is attended 
 with the evolution of great heat, which, before it is 
 dissipated, raises to the point of ignition the tem- 
 perature of the next portion of gas issuing from 
 the burner. This, combining in its turn with oxy- 
 gen, generates a fresh quantity of heat, and thus 
 keeps up the combustion so long as the gas is sup- 
 plied. What I have shown to be true of a gas- 
 
POINT OF IGNITION. 83 
 
 burner is equally true of all ordinary combustion, 
 and so a single spark may be sufficient to light up a 
 conflagration which will reduce to ashes a whole 
 village or involve a city in ruin. 
 
 Thus it appears that burning is chemical combi- 
 nation with oxygen, that this union is attended with 
 the evolution of heat, and that a high temperature 
 is the condition under which oxygen manifests its 
 latent power. But, you may say, these facts do not 
 explain the difference between the two states of 
 oxygen, they merely give the conditions under which 
 these states are manifested ; and this is true. Why 
 it is that at one temperature oxygen is so completely 
 passive, and at another temperature, a few hundred 
 degrees higher, so highly active, we cannot fully ex- 
 plain ; but the facts are undisputed. 
 
 The temperature at which oxygen assumes its 
 active condition is called the point of ignition. Al- 
 though fixed for each substance, it differs very 
 greatly with the different kinds of combustible mat- 
 ter, being determined, apparently, by their relative 
 affinities for the great fire-element. Thus phos- 
 phorus ignites at a temperature less than that of 
 boiling water, sulphur at about 500*^, wood only at a 
 full red-heat, anthracite coal at a white-heat, while 
 iron requires the highest heat of a blacksmith's forge. 
 Beginning with a phosphorus match, which can be 
 ignited by friction, and using the more combustible 
 materials as kindlings, we can readily attain in our 
 furnaces the highest temperature required, and thus 
 the energies of this powerful agent are fully at the 
 command of man. But notice at the same time 
 
84 FIR HOW RESTRAINED. 
 
 that the^ point of ignition of wood, coal, and com- 
 mon combustibles, has been placed sufficiently above 
 the ordinary temperature of the air to insure the 
 general safety of our combustible dwellings ; and 
 when we consider how liable they are, even now, to 
 accidents from fire, we shall appreciate the care 
 which has been taken by our Heavenly Father to 
 guard us against this terrible danger. 
 
 But even this precaution would have been insuf- 
 ficient to secure safety, were it not that the active 
 energies of oxygen, even when aroused, have been 
 most carefully tempered by extreme dilution. It 
 would be easy to show by experiment that the 
 slowness of combustion depends on the fact that in 
 the atmosphere oxygen is mixed with a great mass 
 of an inert gas, and the proportions have been so 
 adjusted in the scheme of creation as generally to 
 restrain the awakened energies of the fire-element 
 within the narrow limits which man appoints ; but 
 when, through his misfortune or carelessness, it over- 
 rides these limits, and, from administering to man's 
 wants, becomes the agent of his destruction, we are 
 reminded in the awful conflagration by what a deli- 
 cate tenure we hold our earthly possessions, and 
 how small a change would be sufficient to involve 
 all organized matter in a general conflagration. 
 Remember now that fire is one of the most valuable 
 servants of mankind ; that it is the source of all 
 artificial heat and light ; that in the steam-engine it 
 is the apparent origin of that power which animates 
 the commerce and the industry of the civilized 
 world ; that under its influence iron becomes plastic, 
 
FIRE, HOW RESTRAINED. 85 
 
 and the ores give up their metallic treasures ; that 
 it is, in fine, the agent of all the arts, — and you can- 
 not wonder that in a ruder age the Romans should 
 have enthroned its presiding deity on Olympus, or 
 the Persians worshipped its supposed essence as 
 divinity itself. Looking at it again, in the light of 
 modern science, as merely the manifestation of the 
 latent power of this bland and diffusive atmosphere, 
 the truth seems almost incredible. To think that 
 this, the strongest of the chemical elements, — which, 
 although a permanent gas, forms more than one-half 
 of the solid crust of the earth, and is endowed with 
 such mighty af^nities that it is retained securely in 
 this solid state, — could have been so shorn of its en- 
 ergies as not to singe the down of the gossamer, and 
 yet so tempered that its powers may be evoked at 
 the will of man and made subservient to his wants ! 
 To me the double condition of oxygen is one of the 
 most remarkable phenomena of nature. I ponder 
 it again and again, with increasing wonder and ad- 
 miration at the skill of the infinite Designer, who i 
 has-been able to unite in the same element perfect 
 mildness and immeasurable power. It seems as if 
 the millennium of the Hebrew prophet were pre- 
 figured in the atmosphere. " The wolf also shall 
 dwell with the lamb, and the leopard shall lie down 
 with the kid, and the calf and the young lion and 
 the fatling together, and a little child shall lead 
 them.'' 
 
 If I have succeeded in making clear the relations 
 of this twofold character of oxygen to man and his 
 works, I think that you cannot fail to have been 
 
86 OXYGEN THE WORLD-BUILDER. 
 
 impressed with the evidence of design which the 
 subject affords. This evidence is seen in the facts, 
 first, that the same element is at different tempera- 
 tures endowed with such opposite and apparently 
 incompatible qualities ; secondly, that in each of its 
 conditions the properties are so skilfully adapted 
 to the functions which it is appointed to perform ; 
 thirdly, that the temperature at which it assumes 
 its active state has been so accurately adjusted to 
 the thermal conditions of the globe ; and lastly, 
 that its active energies have been so carefully 
 guarded, and placed to so great a degree under the 
 control of man. But we have not as yet one-half 
 exhausted the subject. Here, as everywhere else 
 in nature, the argument is cumulative; the more 
 we study, and the more our knowledge is enlarged, 
 the more it grows upon us ; and wherever we may 
 leave the field, we always are conscious that there 
 is a still richer harvest to be reaped beyond. 
 
 If the crust of the globe is a fair sample of the 
 whole mass, oxygen was the chief material employed 
 by the Great Architect in constructing our earth. 
 Moreover, world-building was a process of burning, 
 like those we have been studying, and the founda- 
 tions of the earth were undoubtedly laid in flames. 
 
 When we attempt to break up the various ma- 
 terials around us into simpler parts, we soon reach 
 a class of substances which cannot be further de- 
 composed. Simple inspection will show that gran- 
 ite rock, for example, is a mixture of three min- 
 erals, called feldspar, mica, and quartz. We know, 
 
OXYGEN THE WORLD-BUILDER. 8/ 
 
 also, that feldspar consists of alumina, potash, and 
 silica, that mica contains the same materials in 
 different proportions, and that quartz is silica alone. 
 Lastly, the chemists have discovered that alumina 
 is composed of aluntiniun and oxygen^ potash of po- 
 tassium and oxygen, and silica of silicon and oxygen. 
 But here we must stop ; for when you ask us of 
 what these last-named materials are made, we find 
 ourselves in the condition of the old philosopher, 
 who got on very well with his flat earth, support- 
 ing it on an elephant, and the elephant on a tor- 
 toise, until he came to seek a resting-place for the 
 tortoise ; but then his theory failed. So is it with 
 our science. These undecomposed materials are 
 the blocks on which the whole is built ; and we are 
 totally ignorant of what lies below. 
 
 We call all substances which have never yet 
 been decomposed, whatever may be their nature, 
 chemical elements, and of such some seventy are now 
 known. Setting apart oxygen as the supporter of 
 combustion, the great mass of the remaining ele- 
 ments are combustible ; that is, under certain con- 
 ditions they combine rapidly with oxygen, evolv- 
 ing light and heat. Indeed, many of the combus- 
 tible substances with which we are most familiar 
 are elements. Charcoal is an element, phosphorus 
 is an element, sulphur is an element, iron and all 
 other metals are elements, and out of such com- 
 bustible materials, together with oxygen, the world 
 is made, but chiefly out of oxygen. 
 
 When we burn charcoal in air, or in pure oxygen 
 gas, the burning is a process of world-making. The 
 
88 WORLD-BUILDING. 
 
 charcoal combines with oxygen, and the result is 
 a transparent, colorless gas, called carbonic dioxide. 
 Many may not have heard of such a substance be- 
 fore, but it is always present in the atmosphere, at 
 least in small quantities, and if we continue our 
 process of world-making a little further, we shall 
 find that it enters into the composition of some of 
 the most familiar rocks and minerals. 
 
 I have at the bottom of this closed glass tube a 
 small piece of a yellowish-white metal, looking very 
 much like a flattened shot ; and so it is, but the 
 metal is not lead, although it resembles lead very 
 closely. Like lead it is quite soft, and can be easily 
 beaten into leaves thinner than writing paper ; but 
 it is very much lighter than lead, and tarnishes so 
 rapidly in the air that we are obliged to keep it thus 
 protected. We call the metal calcium, and although 
 you may never have seen the substance before, it is 
 one of the most abundant metals in nature, yet 
 seldom seen, because of the extreme difficulty with 
 which it is extracted from its ores. When heated to 
 redness, calcium burns with a brilliant white light 
 and a scintillating flame. In burning, it combines, of 
 course, with oxygen, and the result is lime, com- 
 mon quick lime, such as is used for making mortar. 
 This is a process which in the original world-mak- 
 ing must have played a very important part, for 
 lime rocks form a large portion of the earth's crust. 
 None of these rocks, however, will slake like quick- 
 lime, and we must go a step further in our world-build- 
 ing, and bring in the agency of water, before we can 
 reach the actual condition of things. 
 
WORLD-BUILDING. 89 
 
 We have now before us two products of burning, 
 one a solid, called lime, made by uniting calcium 
 with oxygen, the other a gas, called carbonic 
 dioxide, made by uniting charcoal with oxygen. 
 Both are soluble to a certain extent in water, and 
 these clear solutions, called lime-water and soda- 
 water respectively, are even more familiar to you 
 than the substances themselves. Mix now the so- 
 lutions together. The water becomes at once very 
 turbid, and there soon settles from it a white pow- 
 der. The lime and carbonic dioxide have united, 
 and this is the result. If we collect and examine 
 the white powder we shall find that it is chalk, and 
 from the same material, spread in thick layers over 
 the ocean-bed, and subsequently hardened by the 
 mutual action of heat and water, have been formed 
 limestone, marble, and the different varieties of lime 
 rock, which are all ores of calcium. 
 
 But we may study with profit a second example 
 of world-building. I have here a small quantity of 
 another very abundant element, called silicon, but, 
 like calcium, a comparative rarity, because it is with 
 difficulty obtained pure. It resembles in many re- 
 spects carbon, and has been observed in three dif- 
 ferent states, corresponding to charcoal, graphite, 
 and diamond Like carbon, it also is combustible, 
 combining with the oxygen of the air when heated 
 to a high temperature, and forming a very hard 
 white solid, called by chemists silica, which is the 
 same thing as quartz, rock-crystal, agate, jasper, 
 calcedony, opal, etc. All these familiar minerals are 
 merely different conditions of this one material, and 
 
90 WORLD-BUILDING. 
 
 contain over one-half their weight of oxygen gas. 
 When ground to a coarse powder by the action of 
 running streams, they become sand, and the grains 
 of sand, compacted together, form sandstone and 
 similar rocks ; and you will begin to appreciate the 
 enormous amount of silicon which must have been 
 burnt up in the process of world-making, when you 
 learn that at least one-half of the solid crust of the 
 earth consists of silica in its different varieties. 
 
 Setting aside the silica for a moment, let us 
 turn to another very widely distributed element,^ 
 called aluminum. This brilliant white metal, com- 
 paring favorably even with silver in lustre, was, until 
 very recently, as great a rarity as calcium or silicon ; 
 but within a few years a process has been discovered 
 by which it can be extracted from its ore at a cost 
 sufficiently low to render the metal available in the 
 arts, and it has now come into quite general use for 
 making mathematical instruments, for jewelry, and 
 for similar purposes. It forms also, with copper, a 
 valuable alloy, which does not readily tarnish, and 
 resembles gold so closely that the two cannot be 
 distinguished by their external appearance. 
 
 Aluminum, like most of the metals, is combusti- 
 t)le, although it does not burn readily in the air, 
 unless the temperature is very high and the metal 
 finely subdivided ; but it then burns very brilliantly, 
 emitting a vivid light, and forming a compound 
 called by chemists alumina, which is melted by the- 
 intense heat to a yellowish transparent glass, and is 
 the same substance from which nature makes the 
 sapphire and the ruby, Emery also, which, on 
 account of its great hardness, is used so largely for 
 
WORLD-BUILDING. 9 1 
 
 polishing, is only a rougher form of the same ma- 
 terial. Unite now the alumina to silica, add water, 
 and we get clay. Burn the clay, and we have, ac- 
 cording to the fineness of the materials, porcelain, 
 pottery-ware, or bricks. 
 
 Taking next the element magnesium, which is also 
 a brilliant white metal, allied to zinc, you notice that 
 it takes fire even in the flame of a candle, and burns 
 with dazzling brilliancy. The result is magnesia, 
 so much used as a medicine. Unite magnesia to 
 silica, and we have, according to the proportions, 
 hornblende or augite, two minerals which abound in 
 many varieties of rock. Add water to the composi- 
 tion, and we get also serpentine or soapstone, with 
 several other allied mineral species. 
 
 I might multiply these illustrations indefinitely, 
 but I will limit myself to only one other example. 
 Here is a metallic element called potassium, so light 
 and combustible that it swims and burns on water. 
 Burning in water may seem, at first sight, very par- 
 adoxical ; but in studying chemistry we must be 
 ready to give up old prejudices. Water is almost 
 pure oxygen, containing in the same volume more 
 than one hundred times as much of the fire-element 
 as air, and all combustibles would burn in water 
 were it not that the oxygen is imprisoned in the 
 liquid by an immensely strong force. Potassium, 
 however, has such intense chemical affinities that it 
 will break through all bars and bolts in order to unite 
 with oxygen, and it therefore burns thus brilliantly 
 even in the midst of water.^ The final result is a 
 
 * The flame in this experiment is caused by the burning of the 
 hydrogen gas, which is one of the products of the chemical action. 
 
92 
 
 WORLD-BUILDING. 
 
 white solid called potash, which dissolves in the liq- 
 uid. Melt together, now, potash, lime, and silicious 
 sand, and we have glass. Un'te silica, alumina, and 
 potash, and we get feldspar ; combine them in differ- 
 ent proportions, and we have mica ; varying again 
 the proportions, we obtain garnet. Lastly, mix 
 quartz and feldspar together with mica or horn- 
 blende, in an indiscriminate jumble, and we have 
 the several varieties of granitic rocks. 
 
 Such, then, are some of the steps in the process 
 of world-building. I do not mean to imply that we 
 can reproduce all these substances in our laborato- 
 ries, although even this is true in almost every case. 
 My object is only to show what must have been in 
 general the process of nature, and to make evident 
 the fact that oxygen has been the chief world- 
 
 Oxygen, 
 
 Silicon, 
 
 Aluminum. 
 Magnesium. 
 Calcium. 
 
 K, Na, Fe, C. 
 
 S, H, CI, N. 57 others. 
 
 builder. But why call oxygen the world-builder 
 more than the other elements ? This diagram an- 
 swers the question, and it illustrates one of the most 
 
WORLD-BUILDING. 93 
 
 remarkable facts to which the study of this func- 
 tion of oxygen has led. Of the seventy known ele- 
 ments, more or less, thirteen alone make up at least 
 y%^(j of the whole known mass of the earth. Of this, 
 oxygen forms about ^, silicon about ^ ; then we 
 have aluminum, magnesium, calcium, potassium (K), 
 sodium (Na), iron (Fe), carbon (C), sulphur (S), hy- 
 drogen (H), chlorine (CI), and nitrogen (N) filling up 
 nearly the other fourth, while the remaining ele- 
 ments — including all the useful metals except iron — 
 do not constitute altogether more than j^-^. The di- 
 agram, however, only represents the relative propor- 
 tions very rudely, as the subdivisions are necessarily 
 based on very rough estimates and imperfect data. 
 
 Evidently, then, so far as our knowledge extends, 
 oxygen, silicon, and carbon, together with a few 
 metals, have been the chief building-materials em- 
 ployed by the Great Architect, and oxygen has 
 been, as it were, the universal cement by which the 
 other elements have been joined together to form 
 that grand and diversified whole we call our earth. 
 
 One more remark in regard to this subject, and I 
 will close this chapter. It is probable that there 
 was a time, anterior to the earliest geological rec- 
 ords, when the elements were in a free state; 
 when the oxygen now solidified was a gas, and 
 when, at the appointed time, the union of the 
 elements began. Then our earth was a bright, 
 burning star, radiating heat and light into space. 
 Indeed, if we accept the nebular hypothesis of 
 Laplace, the earth was formerly a part of the sun, 
 was thrown off by the centrifugal force from his 
 
94 WORLD-BUILDING. 
 
 burning mass, and, like a spark from a forge, soon 
 burnt out, although after this lapse of time the great 
 central fire is burning still. But whether Laplace be 
 right or not, this much is certain ; — the crust of the 
 earth, so far as we can examine it, is like a burnt 
 cinder, and 'the atmosphere of oxygen which sur- 
 rounds it is merely the residuum left after the gen- 
 eral conflagration, — left because there was nothing 
 more to burn. Unmeasured ages have passed away 
 since then ; the earth's crust has cooled and solidi- 
 fied ; the waters have been condensed and gathered 
 into the great ocean-basins ; the dry land has been 
 covered with verdure and peopled with all kinds of 
 four-footed beasts, winged fowls, and creeping things ; 
 the waters have been tenanted with countless forms 
 of swimming creatures; and, last of all, man has 
 come to live in this fair creation, and study the won- 
 ders of his dwelling-place. He finds on the earth's 
 burnt crust an abundant supply of combustible ma- 
 terial for all his wants. But if the world was once 
 burnt up, and the elements glowed with fervent heat, 
 how is it that these combustibles have been left un- 
 consumed ? Modern science has been able to an- 
 swer this question. It has discovered that during 
 the long geological periods a silent agency has been 
 slowly recovering a small amount of combustible 
 material from the wreck of the first conflagration. 
 The sunbeam has partly undone the work of the 
 fire, and whatever now exists on the earth unburnt, 
 wood, coal, or metal, we owe to that wonderful agent 
 the solar light. How the result has been accom- 
 plished, I propose to consider in a future chapter. 
 
f LIBRARY "^ 
 
 UNIA^EHSITY OF 
 
 ^ CALIFOKNIA. , 
 
 CHAPTER IV.- 
 TESTIMONY OF OXYGEN — Concluded. 
 
 Besides the two extreme conditions of oxygen, . 
 there exists still a third, in a measure intermediate 
 between them, but still differing essentially from 
 either, — a condition in which the element discharges 
 functions, less brilliant it is true, but not less inter- 
 esting and instructive, than those which we studied 
 in the last chapter. The phenomena in which this 
 condition of oxygen is chiefly active require, as a 
 general rule, months, or even years, for their full 
 manifestation. Moreover, they are so silent and 
 unobtrusive, as frequently to be passed unnoticed ; 
 but nevertheless, when we have become acquainted 
 with their magnitude and importance, I am sure you 
 will agree with me that they far surpass in true 
 grandeur those dazzling displays of power which the 
 fire-element manifests when fully aroused. This 
 third phase of the element can be best studied in 
 its effects, and to two of these I now ask your 
 attention. 
 
 Every one knows that, when wood or any other 
 organized structure is exposed to the moist atmos- 
 phere, it gradually decays. It first becomes rotten, 
 
 95 
 
96 DECAY. 
 
 and then slowly disappears. All may not know, 
 however, that decay consists in a slow union of the 
 organized structure with oxygen, and that the log 
 of wood which is left to rot in the forest undergoes 
 precisely the same change as one which is burnt on 
 the hearth. The sole difference is, that, while the 
 last is burned up in a few hours, the first entirely 
 disappears only after the lapse of many years. 
 Wood, like all organized vegetable structures, con- 
 sists mainly of three elements, carbon, hydrogen, 
 and oxygen. When heated on the hearth, in con- 
 tact with the air, it takes fire and burns ; that is, its 
 combustible elements combine with oxygen, the 
 carbon to form carbonic dioxide, and the hydrogen 
 to form aqueous vapor, both of which escape by the 
 chimney. But of these two ingredients of the wood, 
 hydrogen is by far the most combustible ; that is, it 
 has the greatest tendency to combine with oxygen, 
 and therefore burns first, leaving the less combus- 
 tible carbon in the form of glowing coals. If at 
 this point we take up one of these coals and quench 
 it in water, it will be found to be common black 
 charcoal ; but if left on the hearth, the coal also 
 burns, gradually smouldering away, and passing up 
 the chimney as carbonic dioxide gas. 
 
 Quite a similar succession of phenomena is pre- 
 sented in the forest during the process of decay. In 
 decay, as in burning, the oxygen of the air unites 
 with the hydrogen of the wood more rapidly than 
 with the carbon, and in consequence the rotten 
 wood becomes darker and darker, from the excess of 
 black charcoal, as the change advances. Moreover, 
 
DECAY. 97 
 
 if the supply of air is insufficient, as when the wood 
 is buried in swamps, it is finally reduced to coal, 
 which corresponds to half-burnt wood. In the open 
 air, however, the charcoal as well as the hydrogen is 
 burnt, and the log of wood is resolved, as in ordinary 
 combustion, into carbonic dioxide and water, leaving 
 only a few handfuls of earth to mark the spot where 
 it lay. This change requires years before it is fully 
 consummated, and it is not therefore wonderful that 
 its nature should not have been understood until a 
 comparatively recent period. Thanks to modern 
 chemistry, the subject is now less obscure. We may 
 not be able to trace all the steps of the process, but 
 this much we know. Decay and burning are essen- 
 tially the same chemical change. The substances 
 involved are the same, the results are the same, and 
 we have even been able to prove that the amount 
 of heat generated is the same, the only difference 
 being, that, in burning, the whole amount of heat is 
 set free in a few hours, producing phenomena of in- 
 tense ignition ; while in the process of decay the 
 same quantity, slowly evolved during perhaps a 
 century, escapes notice. 
 
 It has been observed, that, if wood be left in 
 contact with dry oxygen, it may be kept indefinitely 
 without undergoing change, — a fact sufficiently 
 proved by the mummy cases of Egypt, which in 
 that dry climate have been preserved for over three 
 thousand years ; — also, that if wood is impregnated 
 with certain salts, as in the process of Kyanizing or 
 Burnetizing, decay may be arrested, even in a damp 
 situation, for a long time. In both cases the pre- 
 5 
 
98 DECAY. 
 
 vention depends on destroying certain very unstable 
 compounds which are present in all green wood, and 
 which start the decay. These are termed by chemists 
 albuminous substances, the chief of which, vegetable 
 albumen^ is almost identical with the white of an 
 egg. The great bulk of all vegetable structures, as 
 was stated above, consists of only three elements, 
 carbon, hydrogen, and oxygen ; but these albumi- 
 nous substances — which, as a rule, are present only 
 in very small quantities — contain, in addition to the 
 three just mentioned, a fourth element, nitrogen. 
 Partly because they contain nitrogen, and partly, 
 unquestionably, in consequence of the complex man- 
 ner in which the four elements are combined, the 
 albuminous substances are vastly more unstable than 
 the great mass of vegetable matter, and in the 
 presence of moisture they soon undergo an internal 
 change, called putrefaction, or fermentation, by 
 which they are broken up into simpler compounds. 
 The precise nature of the process is not understood, 
 but nothing appears to be added to the substance, 
 unless it be water, and the change seems to consist 
 in the falling to pieces of a complex organic structure. 
 At all events, oxygen gas is not essential to the pro- 
 cess, but the oxygen of the air which happens to be 
 in contact with the fermenting substances, in some 
 mysterious way, undergoes a remarkable change. 
 It becomes endowed with active properties even at 
 the ordinary temperature, and_, with its affinities thus 
 exalted, slowly consumes the wood, together with 
 all other organic compounds present. Moreover, the 
 process, once started, sustains itself. As, in burning, 
 
DECAY. 99 
 
 the union of the combustible matter with oxygen 
 engenders sufficient heat to maintain the surround- 
 ing gas in its highly active modification, so in like 
 manner the process of decay seems to modify con- 
 tinually the neighboring oxygen, arousing its ener- 
 gies, and thus continuing the change. when once 
 begun. 
 
 While the plant is in great measure made up of 
 non-nitrogenized substances, the anirhal, on the 
 other hand, consists almost entirely of albuminous 
 compounds. The flesh, the nerves, and the bones 
 of our bodies all contain nitrogen, and, like the vege- 
 table albumen, are prone to decay ; and this change 
 is constantly going on in our living members. In a 
 most profound sense, " in the midst of life we are in 
 death.'* The materials of our bodies are being con- 
 stantly renewed, and the great mass of their struc- 
 ture changes in less than a year."^ At every motion 
 of your arm, and at every breath you draw, a portion 
 of the muscles concerned is actually burnt up in the 
 effort. During life, in some utterly mysterious man- 
 ner, beyond the range of all human science, the 
 various gases and vapors of the atmosphere, to- 
 gether with a small amount of a few earthy salts, 
 are elaborated into various organized structures. 
 They first pass into the organism of the plant, and 
 
 * The rapidity of the change has not been accurately determined. 
 Some authors state that the great mass of the body changes every 
 month, and when we consider the large quantities of water, carbonic 
 dioxide, and ammonia daily secreted, the statement^appears credible ; 
 but in the absence of direct proof we have set the limit unnecessarily 
 high in order to avoid the slightest exaggeration. 
 
ICX) DOCTRINE OF THE RESURRECTION. 
 
 thence are transferred to the body of the animal ; 
 but no sooner are they firmly built into the animal 
 tissues, than a destructive change begins, by which 
 before long they are restored to the air or the soil, 
 only to renew the same cycle of ceaseless change. 
 Life, during its whole existence, is an untiring 
 builder, the oxygen of the atmosphere a fell de- 
 stroyer; and when at last the builders cease, then 
 the spirit takes it heavenward flight, and leaves the 
 frail tenement to its appointed end. Dust returns 
 to the dust, and these mortal mists and vapors to 
 the air. 
 
 I know that there are some who entertain a vague 
 fear that these well-established facts of chemistry 
 conflict with one of the most cherished doctrines of 
 the Christian faith ; but so far from this, I find that 
 they elucidate and confirm it. I admit that they do 
 disprove that interpretation frequently given to the 
 doctrine of the resurrection, which assumes that 
 these same material atoms will form parts of our 
 celestial bodies ; but then I find that this interpre- 
 tation is as much opposed to Scripture as to science. 
 The Saviour himself, in his reply to the incredulous 
 Sadducees, severely rebuked such a material con- 
 ception of his spiritual revelation, and the great 
 Apostle to the Gentiles, in his vision of the glorified 
 body, distinctly declares that this body is not the 
 body that shall be ; but that, as the grain sown in 
 the furrow rises into the glory of the full-eared corn, 
 " so when this corruptible shall have put on incor- 
 ruption, and this mortal shall have put on immortal- 
 ity,*' our natural body, sown in dishonor and weak- 
 
DOCTRINE OF THE RESURRECTION. lOI 
 
 ness, will be raised a spiritual body, clothed in glory 
 and in power. " And as we have borne the image 
 of the earthy, we shall also bear the image of the 
 heavenly/* 
 
 The glorious doctrine of the resurrection here pre- 
 sented, modern scientific discoveries most fully con- 
 firm. They have shown that our only abiding sub- 
 stance is merely the passing shadow of our outward 
 form, that these bones and muscles are dying within 
 us every day, that our whole life is an unceasing 
 metempsychosis, and that the final death is but one 
 phase of the perpetual change. Thus the idea of a 
 spiritual body becomes not only a possible concep- 
 tion, but, more than this, it harmonizes with the 
 whole order of nature ; and now that we can better 
 trace the processes of growth in the organic world, 
 and understand more of their hidden secrets, the in- 
 spired words of Paul have acquired fresh power, and 
 convey to us a deeper meaning than they ever gave 
 to the early Fathers of the Church. It is no wonder 
 that, when men were less enlightened, the doctrine 
 should have been misinterpreted ; but now, when 
 the truth has been illuminated by the study of na- 
 ture, why longer harass the understanding and vex 
 the spirit with these material clogs? Hear again 
 the words of the Apostle : " This I say, brethren, 
 that flesh and blood cannot inherit the kingdom 
 of God ; neither doth corruption inherit in corrup- 
 tion." " For this corruptible must put on incorrup- 
 tion, and this mortal must put on immortality.'* And 
 now, turning to the glorious truth as Christ revealed 
 it and Paul preached it, how greatly is our faith 
 
I02 DOCTRINE OF THE RESURRECTION. 
 
 strengthened by these lights of nature ! All philos- 
 ophy assures us that the finite and limited can be 
 manifested only under form. 
 
 '^That each, who seems a separate whole, 
 Should move his rounds, and, fusing all 
 The skirts of self again, should fall 
 Remerging in the general Soul, 
 
 *' Is faith as vague as all un sweet : 
 Eternal form shall still divide 
 The eternal soul from all beside ; 
 And I shall know him when we meet.'' 
 
 Chemistry has shown us that it is the form alone of 
 our mortal bodies which is permanent, and that we 
 retain our personality under constant change; and 
 I lastly, in organic nature, the sprouting of the seed, 
 the breaking of the bird from the egg, the bursting 
 of the butterfly from the chrysalis, and ten thousand 
 other transmutations not less wonderful, which we 
 are daily witnessing around us, all unite their analogies 
 to elucidate and confirm the glorious and comforting 
 doctrine of a material resurrection in form. 
 
 Moreover, when we remember that our organs of 
 vision and hearing are capable of receiving impres- 
 sions either of light or sound only when the rapidity 
 of the undulations which cause them is comprised 
 within certain very narrow limits, and when we re- 
 call the facts stated in a previous chapter, that there 
 are waves of light and sound of which our dull 
 senses take no cognizance, that there is a great dif- 
 ference even in human perceptivity, and that some 
 
GHOSTLY OFFICE OF OXYGEN. I03 
 
 men, more gifted than others, can see colors or 
 hear sounds which are invisible or inaudible to the 
 great bulk of mankind, you will appreciate how 
 possible it is that there may be a world of spiritual 
 existence around us — inhabiting this same globe, 
 enjoying this same nature — of which we have no 
 perception ; that, in fact, the wonders of the New 
 Jerusalem may be in our midst, and the song of the 
 angelic hosts filling the air with celestial harmony, 
 although unheard and unseen by us. Let me 
 not be understood as implying that science has in. 
 any sense revealed to us a spiritual world, or that 
 it gives the slightest shadow of support to those 
 products of imposture, credulity, and superstition, 
 which, under the name of witchcraft, mesmerism, or 
 spiritualism, have in every age of the world de- 
 ceived so many. The only revelation man has re- 
 ceived of a spiritual existence is recorded in the 
 Bible; but modern science has rendered the concep- 
 tion of such an existence possible, and in this way has 
 removed a source of doubt. The materialist can no 
 longer say that the spiritual world is inconceivable ; 
 for these discoveries show that it may be included 
 in the very scheme of nature in which we live, and 
 thus, although science may not remove the veil, it 
 at least answers this cavil of materialism. 
 
 Returning now to the main subject, consider for 
 a moment the importance of this ghostly office of 
 oxygen in the scheme of organic nature. Reflect 
 how soon this fair world would become a great 
 charnel-house were it not for these provisions, by 
 which its youth is constantly renewed. Remember 
 
IC4 RESPIRATION. 
 
 also that this process of decay furnishes the mate- 
 rials from which young life builds her fresh and 
 blooming forms ; that, although in the midst of life 
 we are in death, it is equally true that death is only 
 a phase of life. Then these changes of outward 
 nature will assume a new aspect. It will be seen 
 that they are the beneficent provisions of infinite 
 wisdom, in themselves full of interest and beauty, 
 and only sad and melancholy as they are associated 
 with bereaved affections and disappointed hopes, or 
 with that only real death, the moral death of the 
 soul. ** O death, where is thy sting ? O grave, 
 where is thy victory? The sting of death is sin; 
 and the strength of sin is the law. But thanks be 
 to God, which giveth us the victory through our 
 Lord Jesus Christ." 
 
 I might profitably occupy several hours in de- 
 scribing the various processes of slow combustion, 
 for they are all rich in illustrations of skilful design ; 
 but I must content myself with only one other ex- 
 ample, and from the many which crowd upon me I 
 have chosen respiration, because it is so well under- 
 stood and because it is so intimately associated with 
 our own physical existence. Respiration is a true 
 example of combustion. The seat of the combustion 
 is the lungs. The substance burnt is sugar. The 
 products are carbonic dioxide gas and water. 
 
 The materials of animal food may be divided into 
 three classes : non-nitrogenized substances, such as 
 starch and sugar ; nitrogenized substances, like lean 
 meat and eggs ; and, lastly, fatty substances, like 
 butter. To these must be added a small proportion 
 
RESPIRATION. I05 
 
 of earthy salts, which, however, as they enter into 
 the composition of almost all varieties of food, do 
 not properly form a distinct class. All of the three 
 classes of food are absolutely necessary to support 
 the life of the higher animals, and especially of man, 
 and they are all contained in those articles of diet 
 which will of themselves alone sustain life. Milk 
 may be regarded as the type of animal food. 
 
 Composition of Milk* 
 
 Natural State. ^^^^^^^ 
 
 Water 87 
 
 Curd or casein a^\ 34f 
 
 Butter or fat 3 23^ 
 
 Sugar (of milk) 4f 37 
 
 Ash (nearly) f At\ '"^ 
 
 100 100 
 
 It contains, in the first place, a non-nitrogenized 
 substance, sugar; in the second place, a nitrogen- 
 ized substance, casein, which separated from milk 
 forms cheese ; and, lastly, a fatty substance, which 
 when separated by churning forms butter. 
 
 Wheaten Bread. Lean Beef. 
 
 Water 45 78 
 
 Fibrin or gluten 6 19 
 
 Fat I 3 
 
 Starch, etc 48 
 
 100 100 
 
 Bread, again ; consists of starch, a non-nitrogne- 
 ized substance ; of gluten, a nitrogenized substance, 
 
 * Johnston's Chemistry of Common Life. 
 
I06 RESPIRATION. 
 
 and it also contains about two per cent, of a peculiar 
 oil. No article of food which does not contain all 
 three of these classes of substances can alone sup- 
 port life for any length of time. A man would 
 starve to death on starch alone, on meat alone, or 
 on butter alone. The relative proportion, however, 
 in which these three classes of substances are re- 
 quired by man, depends on his outward circum- 
 stances, such as the climate, his physical activity, his 
 occupation, or his peculiar temperament, and to the 
 right balance of his food he is guided by experience. 
 
 The different classes of food serve different func- 
 tions in the body. The nitrogenized and a portion 
 of the fatty substances are used to supply the con- 
 stant waste of the tissues which results from all the 
 animal processes. They are in some unknown way 
 vitalized in the system, and converted into new 
 muscles, tendons, and nerves, which take the place 
 of those that have been used up. On the other 
 hand, the non-nitrogenized substances, such as 
 starch, are supposed to take no part in the for- 
 mation of new tissues, and to be merely the fuel 
 by which the animal heat is maintained. Let us 
 very briefly follow these substances through the 
 body, and see when and how they are burnt. 
 
 By far the greater part of our daily food consists 
 of varieties of starch or sugar. These two sub- 
 stances are almost identical in composition, and 
 starch may be converted into sugar with the great- 
 est ease. Leaving out of view the large amount of 
 water which all our food contains, we find that of 
 wheaten bread no less than 39 per cent, consists 
 
RESPIRATION. 10/ 
 
 of starch or sugar ; of potatoes fully 92 per cent, 
 is made up of the same materials, and in general 
 they form over four-fifths of the solid part of all 
 our food. These substances when taken into the 
 stomach are almost instantaneously converted by 
 the saliva and the gastric juice into the variety 
 of sugar known as grape-sugar, so called because 
 it is the sweet principle of ripe grapes. The sweet 
 principle of honey and molasses, and the incrusta- 
 tion which is so frequently seen on figs and raisins, 
 are also essentially the same substance. Grape- 
 sugar, being very soluble, dissolves in the water 
 present, and the solution is absorbed by the veins 
 which ramify on the surface of the intestinal canal, 
 into which the digested food passes from the 
 stomach. The blood, now containing sugar in so- 
 lution, returns through the liver to the right side 
 of the heart, and by this organ, which consists es- 
 sentially of two ingeniously contrived force-pumps, 
 arranged side by side, it is forced through the lungs, 
 where the sugar is brought in contact with the air. 
 Let us next examine for a moment this remarkable 
 structure. 
 
 The lungs, as is well known, consist of two large 
 organs, on either side of the chest, called the left 
 and the right lung. The right lung is divided into 
 three smaller lungs, called lobes, the left into but 
 two.. On examining any one of these lobes it will 
 be found to be made up of an immense number 
 of small membranous bags, all closely packed to- 
 gether. These small bags, called cells, connect 
 by means of the bronchial tubes and windpipe with 
 
I08 RESPIRATION. 
 
 the air, through the nose and mouth. They vary 
 in size, but on an average are about y^ of an 
 inch in diameter, and the total number of the 
 cells in the lungs has been estimated at six hun- 
 dred millions. Their walls are exceedingly -thin, 
 and the cells may therefore be easily compressed. 
 The whole mass of the lungs is also exceedingly 
 elastic, and by the action of a system of muscles 
 their volume is alternately increased and dimin- 
 ished in the process of respiration. The amount 
 of air which is thus drawn into the cells, and again 
 expelled at each inspiration, differs in different indi- 
 viduals. The average quantity in the ordinary tran- 
 quil respiration of an adult is about a pint ; but in a 
 full respiration it may be as much as two and a half 
 pints, and by an effort the lungs may be made to 
 inhale from five to seven pints. As the average in 
 health is about eighteen inspirations a minute, which 
 corresponds to about eighteen pints of air inhaled 
 and exhaled, it follows that three thousand gal- 
 lons of air pass through the lungs of an adult man 
 every day. Some estimate it as high as four thou- 
 sand gallons a day for an average man in average 
 circumstances, and as high as five thousand seven 
 hundred gallons a day for an athletic man under- 
 going severe exertion. In order that you may form 
 an idea of this quantity, I will add that four thou- 
 sand gallons of air would fill a room measuring about 
 eight and a half feet in each dimension. 
 
 Let us now turn to the blood, and examine the 
 apparatus by which it is exposed to the air in 
 the lungs. As we have already seen, the blood 
 
RESPIRATION. lOg 
 
 charged with sugar is received into the heart, from 
 whence it is pumped through a long tube, called 
 the pulmonary artery, into the lungs. This artery 
 divides again and again until it is reduced to very 
 small capillary tubes, which ramify on the surfaces 
 of the air-cells. The walls of these capillaries are 
 formed of the thinnest conceivable membrane, so 
 as to bring the blood into as close contact as pos- 
 sible with the air. Here oxygen gas is absorbed in 
 large quantities, and carbonic dioxide gas evolved. 
 The blood now holds in solution at the same time 
 oxygen gas and suga?, and, thus charged, it returns, 
 by a series of veins to the left side of the heart, 
 when by the second of the two force-pumps it is 
 again forced through the general circulation of the 
 body. In the meantime the oxygen absorbed by 
 the blood while in the lungs burns up the sugar. 
 Sugar, like wood, consists of carbon, hydrogen, and 
 oxygen.' The last two are present in the pro- 
 portions to form water, so that sugar may be 
 said to be composed of charcoal and water. Of 
 these two substances the charcoal only is combus- 
 tible. This, during the circulation of the blood, is 
 slowly burnt up by the dissolved oxygen, and 
 converted into carbonic dioxide, which remains in 
 solution until it is discharged, when the blood re- 
 turns again to the lungs, or else escapes through the 
 skin. 
 
 Thus it appears that respiration is a process of 
 combustion, in which the fuel is sugar, and the 
 smoke carbonic dioxide and aqueous vapor. I need 
 not dwell on a fact so universally known as the 
 
no RESPIRATION. 
 
 presence of carbonic dioxide in the breath. All, 
 however, may not know how large is the volume 
 of this gas which they daily exhale. It varies with 
 age, sex, food, health, and a variety of other cir- 
 cumstances. In a full-grown man the weight of 
 carbonic dioxide evolved from the lungs varies from 
 one to three pounds in twenty-four hours, which 
 is equivalent to from nine to twenty-seven cubic 
 feet. During the present lecture the amount of 
 carbonic dioxide which has been exhaled into this 
 room by the audience is equal to at least seven 
 hundred and fifty cubic feef,^ and would fill a 
 room measuring about nine feet in each direction. 
 From the quantity of carbonic dioxide gas exhaled 
 we can very readily calculate the amount of char- 
 coal burnt, which in a full-grown man will vary 
 from five to fifteen ounces in twenty-four hours. 
 Hence, the amount of charcoal which, in the form 
 of sugar, has been burnt up^ in the lungs of the 
 audience during the last hour, is equal to at least 
 fifteen pounds,^ which I have had weighed out 
 and placed on the lecture table, in order to give 
 you an idea of the quantity. Moreover, it has 
 been proved that the quantity of heat evolved by 
 a given amount of charcoal in burning is abso- 
 lutely the same, whether the combustion be rapid 
 or slow, so that the same amount of heat has been 
 generated in our bodies during the last hour by 
 the slow process of respiration as would have been 
 set free by burning this basketful of charcoal. It 
 
 * Calculated for one thousand persons. 
 
RESPIRATION. 1 1 1 
 
 is no wonder, then, that the temperature of the 
 body is always so much above that of the air, and 
 that even in the coldest climate the heat of the 
 blood is maintained as high as ninety-six degrees. 
 In regulating the temperature of his body, man 
 follows instinctively the same rules of common- 
 sense which he applies in warming his dwellings. 
 In proportion as the climate is cold, he supplies the 
 loss of heat by burning more fuel in his lungs, and 
 hence the statements of arctic voyagers, who have 
 told us that twelve pounds of tallow-candles make 
 only an average meal for an Esquimaux, are not 
 inconsistent with the deductions of science. 
 
 Respiration, then, like decay, is a process of slow 
 cojnbustion, in which the oxygen of the air attacks 
 and consumes, even at the ordinary temperature, the 
 sugar in the blood. Let us now compare with it 
 the rapid combustion of the same substance. Dur- 
 ing this lecture every robust man present has, on an 
 average, burnt up the equivalent of about one ounce 
 of sugar. This combustion has taken place so quiet- 
 ly, and has set free the requisite amount of heat so 
 gradually, that we have not been conscious of it. In 
 the blood, where the burning has been going on, sugar 
 and oxygen, as we have seen, are in close contact. 
 In this crucible I have mixed together just one ounce 
 of sugar and one and one-eighth ounces of solidified 
 oxygen, solidified by the force of chemical affinity 
 and bound up in a white salt called chlorate of pot- 
 ash. The oxygen and sugar are therefore here lying 
 side by side, as in the blood, but the conditions of 
 slow combustion which exist in the body not being 
 
112 -JIESPIRATION. 
 
 present in the crucible, they will remain in contact 
 indefinitely, until some external agency is applied. 
 The oxygen is now in its passive condition, but a 
 single drop of sulphuric acid will arouse its dormant 
 energies, and you have instantly one of the most 
 dazzling displays of combustive energy which can be 
 produced by art. The only difference between this 
 brilliant deflagration and the combustion which, 
 during the last hour, has taken place in each of our 
 bodies, is simply this : the heat which in the blood 
 has been imperceptibly evolved during an hour, was 
 here concentrated into a few moments, and there- 
 fore produced phenomena of intense ignition. All 
 the other conditions, — the material burnt, the quan- 
 tity of material employed, the products generated, 
 and the amount of heat evolved, — are in both cases 
 essentially the same. 
 
 On comparing these two phenomena together, re- 
 flect for a moment on the false estimate which we 
 are apt to make of the phenomena of nature. The 
 splendid displays of combustion arrest our attention 
 by their very brilliancy, while we overlook the silent 
 yet ceaseless processes of respiration and decay, be- 
 fore which, in importance and magnitude, the grand- 
 est conflagrations sink into insignificance. These 
 fire but the spasmodic efforts of nature ; those, the 
 appointed means by which the harmony and order 
 of creation are preserved. Those of us who have 
 merely studied the brilliant phenomena of nature 
 appreciate but imperfectly the grandeur of its forces, 
 and " those of us who limit our appreciation of the 
 powers of oxygen to the energies displayed by this 
 
RESPIRATION. II 3 
 
 element in its fully active state, form but a very in- 
 adequate idea of the aggregate results accomplished 
 by it in the economy of the world. ""^ Contemplate 
 the amount of oxygen employed in the function of 
 respiration alone. Faraday has roughly estimated 
 that the amount of oxygen required daily to supply 
 the lungs of the human race is at least one thousand 
 millions of pounds ; tbat required for the respiration 
 of the lower animals is at least twice as much as this, 
 while the always active processes of decay require 
 certainly no less than four thousand millions of 
 pounds more, making a total aggregate of seven 
 thousand millions of pounds required to carry on 
 these processes of nature alone. Compared with 
 this, the one thousand millions of pounds which, as 
 Faraday estimates, are sufficient to sustain all the 
 artificial fires lighted by man, from the camp-fire of 
 the savage to the roaring blaze of the blast-furnace 
 or the raging flames of a grand conflagration, seem 
 small indeed. 
 
 Amount of Oxygen required Daily. 
 
 * 
 
 Whole population 1,000,000,000 
 
 Animals 2,000,000,000 
 
 Combustion and fermentation. . . . 1,000,000,000 
 
 Decay and other processes 4,000,000,000 
 
 Oxygen required daily = 8,000,000,000 lbs. 
 
 * Taken from Faraday's Lectures on the Non-Metallic Elements, 
 but correcting an obvious error in reducing the pounds to tons. 
 
1 14 RESPIRATION. 
 
 Tons, 
 3,571,428 in a day. 1 
 
 1,304,642,357 in a year. 
 Whole quantity, 1,178,158,000,000,000. 
 
 How utterly inconceivable are these numbers, 
 which measure the magnitude of nature's processes, 
 — eight thousand millions of pounds of oxygen con- 
 sumed in a single day ! When reduced to tons, 
 the numbers are equally beyond our grasp, for it 
 corresponds to no less than 3,571,428 tons. If such 
 be the daily requisition of this gas, will not the oxy- 
 gen of the atmosphere be in time exhausted ? It is 
 not difficult to calculate approximately the whole 
 amount of oxygen in the atmosphere. It is equal 
 to about 1,178,158 thousand millions of tons; a sup- 
 ply which, at the present rate of consumption, would 
 last about nine hundred thousand years. We need 
 not, therefore, fear that the amount of oxygen in the 
 atmosphere will be sensibly diminished in our day or 
 generation ; but then this period, immense as it is, 
 is not to be compared with the ages of geological 
 time. The time which has elapsed since the coal 
 we are now burning was deposited in its beds is to 
 be counted by many millions of years, so that since 
 the coal epoch the oxygen of the atmosphere must 
 have been all consumed again and again. Why, 
 then, has it not all been removed from the atmos- 
 phere? Simply because, in the beautiful balance 
 of creation, there is always some recuperative pro- 
 cess for every such loss. In the case before us, it is, 
 as we have seen, the vegetation. As fast as our 
 
OZONE. 115 
 
 breath, our fires, and the process of decay around us 
 are removing the Hfe-giving oxygen, just so fast it is 
 restored by every green leaf which waves in the sun- 
 shine, and by every blade of grass which sprouts 
 under our feet. What the animal removes, the plant 
 restores. 
 
 I have before stated that, in the process of decay, 
 the oxygen of the atmosphere, which is active in 
 producing the change, is undoubtedly in a peculiarly 
 modified condition, a condition in which its affinities 
 are highly exalted even at the ordinary temperature 
 of the air; and I also stated that this active con- 
 dition of the element is apparently maintained by 
 the process of decay itself. This subject has been 
 greatly elucidated by modern discoveries. Of all the 
 known processes of slow combustion, the simplest 
 and the most active is the slow combustion of phos- 
 phorus. This familiar substance, used to tip the 
 ends of lucifer matches, if exposed to the moist air, 
 slowly combines with oxygen, shining at the same 
 time in the dark with a peculiar phosphorescent 
 light, whence the name of the substance, from two 
 Greek words, signifying light-bearer. The process 
 is therefore entirely analogous to decay and respira- 
 tion ; but since phosphorus is a chemical element, 
 the change is far simpler, and can be more readily 
 studied, and for this reason it may serve to elucidate 
 those more complex processes of nature. 
 
 Some years since. Professor Schonbein, a distin- 
 guished Swiss chemist, discovered that, while a stick 
 of phosphorus was slowly burning in a jar of moist 
 •air, a portion of the oxygen present underwent a 
 
Il6 OZONE. 
 
 most remarkable change. Without entering into 
 the details of these experiments, I will simply state 
 that, when thus modified, ordinary oxygen seems 
 entirely transformed. The great mass of the oxy- 
 gen of the air, as you will remember, is wholly 
 devoid of odor, and without action on the most de- 
 licate organic structures or the most fleeting vege- 
 table colors; but when thus treated it acquires a 
 very strong and pungent odor, rapidly rusts polished 
 metals, excites decay in organized tissues, and at 
 once bleaches the most permanent dyes. Could 
 there be a more complete inversion of properties ? 
 One of the most striking characteristics of this new 
 modification of oxygen is its peculiar odor, and 
 hence Schonbein calls it ozone, from a Greek verb 
 signifying io smell. It frequently happens that a 
 great discovery supplies the wanting links between 
 a number of obscure facts, and thus adds quite as 
 much to our knowledge by its indirect bearings as 
 by the positive additions it makes to the general 
 stock. So it has been with the discovery of ozone. 
 Every one who has used an electrical machine must 
 have noticed the peculiar smell which follows the 
 electrical discharge. This was formerly supposed to 
 be the odor of the electrical fluid itself; but as soon 
 as ozone was discovered, the odor was recognized at 
 once as belonging to this new agent, and it was soon 
 ascertained that electricity is one of the most efli- 
 cient means of modifying the oxygen of the air. 
 
 Returning now to the fact that the slow combus- 
 tion of phosphorus throws a portion of the surround- 
 ing oxygen into a peculiar condition, in which it is 
 
OZONE. 117 
 
 highly active in producing decay and other processes 
 of oxidation, — it certainly seems probable that decay 
 and respiration, which are also examples of slow 
 combustion, may act on the air in the same way. 
 Moreover, the inference that ozone is the active 
 agent in these processes is also supported by the 
 fact that it is always present, to a greater or less ex- 
 tent, in the atmosphere, although, at most, in ex- 
 ceedingly minute quantities. Ozone, being so highly 
 corrosive, cannot be present in the atmosphere in 
 perceptible quantities without producing important 
 effects, and some persons have thought not only to 
 refer to it the various processes of slow combustion, 
 but also to trace a connection between the preva- 
 lence of various contagious diseases and the excess 
 or deficiency of this agent in the air of the infected 
 district ; but these speculations are not as yet based 
 on sufficient evidence, and are not worthy of serious 
 attention. 
 
 Without, however, introducing any theories not 
 yet fully established into the line of our argument, 
 this much is clear. Oxygen gas appears in nature in 
 three conditions, or under three manifestations : — 
 first, entirely passive, as in the great mass of the 
 air; secondly, partially active, in the processes of 
 decay and respiration ; thirdly, highly active, in the 
 phenomena of combustion. In each of these condi- 
 tions its properties have been adjusted with infinite 
 skill and delicacy, on the one hand to the thermal 
 and electrical conditions of the globe, and on the 
 other, to the constitution of man and of all organic 
 nature. 
 
Il8 OZONE. 
 
 Here I must conclude my brief sketch of this 
 wonderful element. If I have succeeded in impress- 
 ing on your minds some of its more characteristic 
 qualities, if, above all, you have become aware how 
 exactly and delicately these qualities have been ad- 
 justed in the scheme of creation, and if you have 
 seen how the smallest permanent change would dis- 
 turb the result, — this is all that I could hope. It 
 might be expected that the element with which 
 creative power built up the greater part of the crust of 
 our globe, leaving only a small excess to constitute 
 its atmosphere, would furnish abundant evidence of 
 design, and how fully is this expectation realized ! 
 Would that I might present to you the evidence 
 more forcibly ! But it is possible in a popular lec- 
 ture only to touch at some of the more striking 
 points, and I have felt all the time like a school- 
 boy at play, in spring, in some garden rich in flowers, 
 snatching here and there a few of the more gaudy 
 tulips, which had fully bloomed, but leaving the 
 beautiful and delicate buds all unnoticed. But then 
 these buds of knowledge will blossom, and, when 
 the summer comes, will bear a still sweeter testi- 
 mony of goodness and of love. 
 
CHAPTER V. 
 
 TESTIMONY OF WATER. 
 
 The atmosphere, as you will remember, consists 
 mainly of two permanent and elementary gases ; 
 and having discussed the functions of its active 
 element, oxygen, it would seem natural to consider 
 next the offices of nitrogen, that most singularly 
 inert gas, which constitutes no less than four-fifths 
 of its whole mass ; but we shall understand more 
 clearly the complicated relations of this truly won- 
 derful substance, associated as it is with all the 
 higher forms of corporeal vitality, after we are 
 acquainted with two of the remarkable cycles in 
 nature, in which the water and carbonic dioxide 
 of the atmosphere play a conspicuous part. It is 
 true that these two substances are very variable 
 constituents, and make up at best only an exceed- 
 ingly small fraction of the whole mass of the air ; 
 but nevertheless, they discharge functions no less 
 important than those of oxygen and nitrogen, and 
 we shall find that they are equally rich in illustra- 
 tions of the wisdom and power of God. 
 
 I have already alluded to the fact that the most 
 striking illustrations of creative wisdom have been 
 
 119 
 
I20 GENERAL DIFFUSION OF WATER. 
 
 discovered in those substances which are the most 
 abundantly distributed through nature, and which 
 are the most intimately associated with man, and of 
 no substance is this principle more remarkably true 
 than it is of water. As you well know, water is the 
 liquid of the globe, and, if we except certain tran- 
 sient products of volcanic action, it is the only liquid 
 which exists naturally on its surface. Moreover, it 
 is in constant circulation, and, like the blood in our 
 bodies, is the medium through which nourishment 
 is conveyed to all parts of organized nature, and its 
 life sustained. We should naturally expect that a 
 substance filling so important a place in the scheme 
 of creation would furnish undoubted evidences of 
 design, and it will be my object in the present lec- 
 ture to illustrate a few of the more striking ex- 
 amples of adaptation which its qualities present, 
 beginning with the aeriform condition of water as 
 it exists in the atmosphere. 
 
 The condition of the atmosphere of aqueous va- 
 por, which surrounds the globe, differs essentially 
 from that of the more permanent gases which are 
 simultaneously present. Oxygen and nitrogen can- 
 not be reduced to liquids even by the intense cold 
 at the poles. It is very different with aqueous 
 vapor. The slightest reduction of temperature, 
 when the air is saturated with moisture, is sufficient 
 to condense a portion of the vapor to water, and to 
 shower it on the earth in drops of rain. On the 
 other hand, when the temperature rises, the heat 
 converts more water into vapor, and the aqueous 
 atmosphere is replenished. Thus it is that the 
 
THE AQUEOUS CIRCULATION. 121 
 
 atmosphere of aqueous vapor on the earth is liable 
 to very great fluctuations, from which the Creator 
 has protected the great mass of the air by endowing 
 oxygen and nitrogen with the power of retaining 
 the aeriform condition under all circumstances ; and 
 we shall find that the fluctuation in the one case is 
 as important as the stability in the other. 
 
 I stated in the last lecture that our atmosphere 
 may be regarded as made up of three partial at- 
 mospheres, simultaneously surrounding the globe, 
 and as was the case with the atmosphere of oxygen, 
 we shall best understand the fluctuations of the 
 aqueous atmosphere if we begin by eliminating, for 
 a moment, from our thoughts the other two. In 
 order to make the subject clear, it will be neces- 
 sary for me to dwell very briefly on a few well- 
 established facts in meteorology, which, although 
 not very interesting in themselves, will unfold to us 
 some of the beautiful provisions of nature by which 
 the aqueous circulation of the globe is maintained. 
 
 If there were no free oxygen or nitrogen gas, the 
 earth would still be surrounded with an atmosphere 
 of aqueous vapor, and we are able to foresee, in 
 some small measure, what the conditions of such an 
 atmosphere would be. Its density at the sea level 
 would depend chiefly on the temperature, and 
 would therefore vary very rapidly with the latitude, 
 and would be constantly changing at the same lo- 
 cality with the alternations of the climate. We are 
 able to determine approximately what the density 
 would be at any given temperature, and a few of 
 the results are included in the following table : 
 
 6 
 
122 
 
 THE AQUEOUS CIRCULATION. 
 
 Weight at the Sea Level of one Cubic Foot of Vapor. 
 
 Temperature. 
 Fahrenheit. 
 
 Weight. 
 Grains. 
 
 o° 0.78 
 
 10° I. II 
 
 20° 1.58 
 
 30° 2.21 
 
 Temperature. 
 Fahrenheit. 
 
 40 . 
 
 50°. 
 60°. 
 
 Weight. 
 Grains. 
 
 • 3.09 
 . 4.28 
 
 . 5.87 
 
 Temperature. 
 Fahrenheit. 
 
 70 . 
 
 8o^ 
 
 90 
 
 Weight. 
 Grains. 
 
 . 8.00 
 
 .10.81 
 
 .14.50 
 
 It is evident from these numbers, that a very- 
 small change of temperature would cause immense 
 fluctuation in such an atmosphere. At 0° one 
 cubic foot of the aqueous atmosphere could contain 
 only about three-fourths of a grain of vapor, while 
 at 80° it could contain fifteen times as much, and 
 hence, although under the tropics the density of our 
 assumed atmosphere would be comparatively large, 
 there would be almost a complete vacuum at the 
 poles. Into this vacuum the vapor would flow from 
 the equator, and thus in either hemisphere there 
 would result a perfect torrent of vapor rushing to- 
 wards the North or South. But it is also evident 
 that, as this current became chilled in passing 
 through the cooler climate of the temperate zone, 
 the vaporwould gradually condense to water, which, 
 falling on the land or on the ocean, would return 
 in time to the equator, ready to begin again the 
 same succession of ceaseless changes. 
 
 Although the presence of the air materially mod- 
 ifies, it does not essentially change, the aqueous cir- 
 culation. The air retards the formation of vapor, 
 but does not prevent it, and at any given tempera- 
 ture the same amount of water will evaporate into 
 
THE AQUEOUS CIRCULATION. I23 
 
 a given space, whether it be a perfect vacuum or 
 filled with air. Thus, for example, when air at 80° 
 is saturated with moisture, it contains, as before, ex- 
 actly 10.81 grains of vapor, and the table just given 
 applies equally well to the actual condition of the 
 globe, covered with its dense atmosphere of oxygen 
 and nitrogen, as to the case just assumed. There 
 is, however, a most important difference between 
 the two conditions, — a difference on which the 
 adaptation of the system of aqueous circulation in 
 the order of nature entirely rests. 
 
 Were there no air on the globe, the quantity of 
 vapor would adjust itself almost instantaneously to 
 any variation of temperature, and the maximum 
 amount possible w^ould always be present at any 
 given place. An elevation of temperature would be 
 attended by rapid evaporation, and the amount of 
 water required to fill the space would suddenly flash 
 into vapor ; while, on the other hand, a correspond- 
 ing depression of temperature would be accompa- 
 nied with an equally sudden precipitation of the 
 excess of water which the air could no longer con- 
 tain, not in genial showers or diffusive rain, but in 
 terrific torrents, of which the deluging showers of 
 the tropics can give us only a feeble conception ; for 
 the drops, falling without resistance, would be as 
 destructive in their effects as volleys of leaden shot. 
 
 In the actual condition of the atmosphere, the 
 presence of a dense medium very greatly retards 
 these changes, and although it does not alter their 
 essential nature, it moderates their action and miti- 
 gates the violence of their effects. An elevation of 
 
124 THE AQUEOUS CIRCULATION. 
 
 temperature is followed by an evaporation of water 
 into the air ; but the process is comparatively slow, 
 and it is a long time before the air is fully saturated. 
 So, also, when the air is saturated, a depression of 
 temperature is followed by the condensation of a 
 portion of the vapor into rain ; but here, again, the 
 mass of the atmosphere tempers the abruptness of 
 the transition, and allays its violence. The vapor 
 condenses first into a fine dust consisting of repellent 
 particles of water, which are so minute, and, conse-^ 
 quently, fall so slowly against the resistance of the 
 air, that they seem to float in the atmosphere ; and 
 when, in consequence, probably, of some electrical 
 discharge, these particles, losing repulsive energy, 
 unite to form drops of rain, they again are wafted 
 down so slowly through the resisting medium, and 
 alight so softly, that the " soft falling snow and the 
 diffusive rain '' have become fit emblems of the be- 
 neficence of God, as they give the strongest evi- 
 dences of his wisdom and skill. Moreover, the glori- 
 ous clouds, which add so much to the beauty of the 
 landscape, and typify in their virgin whiteness the 
 purity of heaven, are only collections of water dust 
 floating* in the upper atmosphere, and mark the 
 
 * It is well known that in a mass of air charged with aqueous vapor, 
 the tension of the vapor is added to the tension of the air, and that 
 such a mixture is lighter than a mass of dry air of the same tempera- 
 ture, whose tension equals the united tension of the gas and vapor. If, 
 now, the vapor in such a mass of air is condensed to water dust, whose 
 particles are mutually repelled by their similar electrical charges, we 
 may conceive that the electrical tension takes the place of the tension 
 of the vapor, so that the resulting cloud, as a whole, may be as light 
 as the surrounding atmosphere in which it floats. 
 
THE AQUEOUS CIRCULATION. 1 25 
 
 stage of transition between vapor and rain ; and, 
 further still, it is probable, as I stated in a previous 
 lecture, that it is these same minute liquid drops 
 which tint the morning and evening sky with their 
 gorgeous hues, and cover our earthly dwelling-place 
 with its canopy of blue. 
 
 Again, the presence of the air very greatly re- 
 tards the aqueous circulation above described, with- 
 out" altering its essential character. There is now 
 the same great difference between the density of 
 the atmosphere of vapor at different latitudes, as if 
 it were the only atmosphere on the globe, and the 
 dense vapor of the tropics tends constantly to flow 
 towards either pole ; but as it cannot move without 
 carrying with it the whole mass of the atmosphere, 
 this tendency merely increases the velocity of those 
 great aerial currents, already described in a previous 
 lecture. Still the general fact remains the same. 
 From the whole surface of the globe water is con- 
 stantly evaporating into the aqueous atmosphere 
 which surrounds it. The heated air from the tropics, 
 heavily charged with moisture, is continually mov- 
 ing towards the colder regions, both of the North 
 and of the South ; and as the current thus becomes 
 chilled, the vapor is slowly condensed, and the water 
 showered down in fertilizing rains on the land. 
 Thus it is that those beautiful provisions which we 
 see in the rain all depend on the presence of the air, 
 and result from a careful adjustment of the proper- 
 ties of aqueous vapor to the exact density of our 
 atmosphere. " Hath the rain a Father? '* Science, 
 by discovering these evidenceToT^skllTul adaptation, 
 
126 THE AQUEOUS CIRCULATIOK 
 
 has most conclusively answered this question, and 
 the answer is the same now as in the days of Job. 
 "Behold, God is great. . . . He maketh small the 
 drops of water: they pour down rain according to 
 the vapor thereof." 
 
 But what becomes of the rain ? Would that I could 
 answer this question satisfactorily. We all under- 
 stand the general theory of the aqueous circulation, 
 but the deepest philosophy and the keenest science 
 are not able to fathom its details, or to comprehend 
 in their fulness the world of wonderful adaptations 
 which the question unfolds. We all know that the 
 drops of rain percolate through the soil, and collect 
 in natural reservoirs formed between the layers of 
 rock, and that these reservoirs supply the springs. 
 The rills from numerous adjacent springs unite to 
 form a brook, which increases as it flows, until it 
 finally becomes the majestic river, rolling silently on 
 its course. Every drop of that water has been an 
 incessant wanderer since the dawn of creation, and 
 it will soon be merged again in the vast ocean, only 
 to begin anew its familiar journey. If you would 
 gain an idea of the magnitude and extent of this 
 wonderful circulation, you must bring together, in 
 imagination, all the rivers of the world, the Amazon 
 and the Orinoco, the Nile and the Ganges, the Mis- 
 sissippi and the St. Lawrence, and, adding to these 
 the ten thousands of lesser streams, endeavor to form 
 a conception of the incalculable amount of water 
 which during twenty-four hours they pour into the 
 vast basin of the world, and then remember that 
 during the same period at least four times as much 
 
THE AQUEOUS CIRCULATION. I27 
 
 water must have been raised in vapor, and scattered 
 in rain over the surface of the globe. Would you 
 form an idea of the importance of this circulation, 
 you must not limit your appreciation to its economi- 
 cal value, as a great source of power, working the 
 mills and the forges of civilized man, and building 
 up vast marts of manufacturing industry, nor must 
 you regard alone its commercial value, bearing as it 
 does on its bosom to the ocean the freights of em- 
 pires. These applications of power, however impor- 
 tant in themselves, are insignificant in extent com- 
 pared with those mighty agencies which the aque- 
 ous circulation is constantly exerting in nature. It 
 has been the great agent of geological changes : here 
 washing avv^ay continents, and there building them 
 up ; here gullying out valleys, and there smoothing 
 away inequalities of surface ; here dissolving out the 
 particles of metals from the solid rocks, and there 
 collecting them together in beds of useful ores. It 
 has covered the earth with verdure and animal life, 
 by conveying nourishment to the plant and food to 
 the animal. It sustains our own bodies, for it is a 
 portion of this very circulation which ebbs and flows 
 in our veins, and whose pulsations beat out the mo- 
 ments of our lives ; and could I bring together in one 
 picture the infinite number of beneficent ends which 
 it has been made by Providence to subserve, I am 
 sure that you would agree with me that there is not 
 in nature stronger evidence of design than in the 
 adaptations of this simple and familiar liquid. 
 
 In order that we may appreciate, in some humble 
 measure, the force of this evidence, let us consider 
 
128 ADAPTATION OF WATER. 
 
 some of the qualities of water; but, at the same 
 time, let us not forget that the strength of our 
 argument lies not so much in the fact that each 
 property has been skilfully adjusted to some spe- 
 cific end, as it does in the harmonious working of 
 all the separate details. Had man creative power, 
 the first would fall within the range of his intelli- 
 
 I gence ; but to adapt the same substance to a thou- 
 sand different ends, and to adjust each of its prop- 
 erties to a thousand different conditions, covering 
 with their complex network all the known universe, 
 implies a power nothing less than infinite, and an 
 
 I intelligence nothing lower than divine. It is evi- 
 dent, however, that we can gain a knowledge of the 
 general plan only by studying the details, and un- 
 fortunately it is to these details that our accurate 
 knowledge is almost entirely confined. We can 
 see, for example, that each property of water has 
 been designed for some specific purpose. We can 
 also recognize the evident fact, that all the proper- 
 ties work harmoniously together in the general 
 scheme of nature; but, in the present state of 
 knowledge, to trace the intimate relations of these 
 properties is frequently as impossible as it is to 
 form a clear conception of the coexistenee and har- 
 monious action of all. Yet in these very facts lies 
 the whole force of the argument from design, and it 
 is only the limitations of our knowledge and facul- 
 ties which weaken the impression on our minds. 
 But were these limitations removed, all argument 
 would become unnecessary, for then, reasoning 
 would be exchanged for vision, and in the reful- 
 
A CONSTITUENT OF ORGANIZED BEINGS. 1 29 
 
 gence of the Divine Presence we should know even 
 as we are known. 
 
 It is a familiar fact, that water is an essential con- 
 dition of organic life ; but few persons, I suspect, 
 are aware that this familiar liquid constitutes the 
 greater part of all organized beings. The physical 
 man has been described by one writer as consist- 
 ing of merely a few pounds of solid matter dis- 
 tributed through six pailfuls of water, and it is a 
 fact that no less than four-fifths of these bodies of 
 ours are made up of water. Yet this is a small 
 proportion compared with the amount which enters 
 into the structure of most of the lower animals. 
 Some of these, such as the medusae, — sunfishes, — are 
 little else than organized water. Professor Agassiz 
 obtained from one of the large sunfishes found on 
 our coast, weighing thirty pounds, only two hundred 
 and forty grains of solid matter ; and we may safely 
 say that at least nine hundred and ninety-nine parts 
 in a thousand of these singular animals consist of 
 water. Water constitutes, to almost as great an ex- 
 tent, most of the vegetable products which are articles 
 of food, as will be seen by the accompanying table. 
 
 Plums 
 
 contaii] 
 
 L 75 per cent, of water. 
 
 Potatoes 
 
 
 75 
 
 
 
 Apples 
 
 
 80 
 
 
 
 Carrots 
 
 
 ^3 
 
 
 
 Turnips 
 
 
 90 
 
 
 
 Watermelons 
 
 
 94 
 
 
 
 Cucumbers 
 
 
 97 
 
 
 
 It is evident from these facts that water is the 
 
 6* 
 
I30 A CONSTITUENT OF ORGANIZED BEINGS. 
 
 chief material of which all organized structures are 
 formed, and in studying the aqueous circulation we 
 have already become acquainted with the beautiful 
 provisions of nature by which this life-giving liquid 
 is distributed over the earth, and showered down 
 upon the meadow and forest alike. Without water 
 organic life cannot exist, and where, from any local 
 causes, the supply fails, there we find a barren wil- 
 derness ; while, on the other hand, the genial influ- 
 ences of the rain will soon make even " the desert 
 blossom as the rose." It is a remarkable fact of 
 physical geography, that the distribution of water by 
 the aqueous circulation is rendered more effective 
 by the peculiar structure of the continents, and the 
 position of the great mountain chains. 
 
 **The mountain chains," writes Professor Guyot, 
 in his excellent work Earth and Man^ " are great 
 condensers, placed here and there along the con- 
 tinents to rob the winds of their treasures, and to 
 serve as reservoirs for the rain-waters, and to dis- 
 tribute them afterwards as they are needed over the 
 surrounding plains. Their wet and cloudy summits 
 are untiringly occupied with this important work, 
 and from their sides flow numberless torrents and 
 rivers, carrying in all directions wealth and life." 
 
 Thus the mountains, whose majestic forms affect 
 so powerfully the human soul, and which have ex- 
 erted such an influence on the history of the race, 
 are also among the most beneficent means in the 
 Divine Providence by which the earth has been fer- 
 tilized and rendered a fit abode for man. Moreover, 
 these mountain chains have been evidently so dis- 
 
THE DEW. 131 
 
 tributed as to give the greatest efficiency to the 
 aqueous circulation, and to irrigate the continents 
 most effectively with their fertilizing floods. We 
 cannot, therefore, suppose that even these ridges on 
 the earth's surface, which are the lasting records of 
 ancient geological changes, were fixed by chance, 
 for they also bear traces of His intelligence who 
 seeth the end from the beginning, and every part 
 of whose works is adapted to every other. " Lord, 
 thou hast been our dwelling-place in all generations. 
 Before the mountains were brought forth, or ever 
 thou hadst formed the earth and the world, even 
 from everlasting to everlasting, thou art God." 
 
 But it is not the mountains alone which condense 
 the vapor of the atmosphere ; for, under certain 
 conditions, the level plains act in a similar way, and 
 distil the precious drops of dew upon" field and 
 meadow, distributing it among the plants with dis- 
 criminating care for the necessities of each. The 
 dew is simply another phase of the great aqueous 
 circulation, and, like the rain, it is a persuasive wit- 
 ness of the Divine Disposer, who has adjusted its 
 amount to the wants of the vegetable world. Every 
 one has noticed the deposition of moisture on a 
 pitcher of ice-cold water during a summer's day, 
 and in this familiar fact, we have at once an example 
 and an illustration of the simple provision by which, 
 during even the long droughts of summer, the plants 
 receive a partial supply of water, sufficient, at least, 
 to sustain their life until the later rains bring the 
 autumn fruits to maturity, and stimulate a more 
 vigorous growth. 
 
132 THE DEW. 
 
 The explanation of the dew upon the pitcher is 
 very simple. The layer of air in contact with its 
 cold mass is rapidly cooled, and when it can no 
 longer hold all the moisture it contains, the excess 
 is deposited in drops on the surface. Exchange 
 now the pitcher for the earth, and you have at once 
 an explanation of the proximate cause of the dew. 
 After sunset the earth, like the pitcher, cools down 
 the layer of atmosphere immediately in contact with 
 it to such a degree that the whole of the vapor can 
 no longer retain its aeriform condition. As a neces- 
 sary result, a portion is condensed and deposited 
 upon the surface, and this is what we call dew. But it 
 will be asked. What cools the earth so suddenly after 
 the setting of the sun ? For this is not so evident as 
 the cause of the coldness of the pitcher. Certainly 
 not, and the question will lead us to a study of those 
 relations in which the adaptations to be discovered 
 in this natural phenomenon are chiefly to be found. 
 
 The earth, as I stated in the second lecture, is 
 moving with immense rapidity through a space 
 whose temperature is at least 270 degrees below the 
 zero of Fahrenheit's thermometer, and, like a heated 
 cannon-ball hung in the middle of a cold room, it is 
 continually losing heat by radiation. The dense 
 atmosphere with which it is enveloped, acting, as we 
 have seen, like a blanket, protects the earth from the 
 intense cold of space to a certain extent ; but still 
 the constant loss of heat is so great, that, were the 
 sun's rays withheld for a few days, the temperature 
 of the surface-land, even in the tropics, would fall as 
 low as it is now at the poles during the long night 
 
THE DEW. 133 
 
 of the arctic winter. In the daytime the earth re- 
 ceives from the sun more heat than it loses ; but 
 when this great thermal source is temporarily with- 
 drawn, the loss of heat continuing as rapidly as be- 
 fore, the surface becomes quickly cooled, and the 
 deposition of dew follows, as just explained ; or, if 
 the temperature falls below the freezing-point, the 
 dew is changed to frost. 
 
 You must all have noticed that the most copious 
 deposition both of dew and frost takes place on clear 
 nights, and that during cloudy weather this supply 
 of moisture is entirely withheld. The reason is ob- i 
 vious. The earth loses heat by radiation, and the j 
 clouds, intercepting the rays, reflect them back to f 
 the earth. A shed or any other protection spread 
 over the ground acts in the same way, and it is well 
 known that a covering, however slight,* is sufficient 
 to protect tender plants from the blight of the early 
 frosts. Can it then be an accident, a mere result of 
 chance, that the dew is deposited most abundantly 
 where it is needed most, and that this supply of 
 moisture fails only when the clouds promise a more 
 copious draught of liquid nourishment from the rain ? 
 
 There is still another fact presented by the dew 
 which is equally suggestive. The heavens do not 
 distil their liquid treasures upon all objects alike, 
 but the dew is deposited much more abundantly 
 on the herbage, the shrubs, and the trees, which 
 need the refreshing moisture, than on fallow land, 
 the sandy plain, or the beaten road ; and here 
 again the cause has been discovered. It is evident 
 from the general theory of the subject, that the 
 
134 THE DEW. 
 
 largest amount of dew will fall on the coldest surface, 
 and it is equally obvious that, other things being 
 equal, those objects will cool most rapidly which 
 have the smallest supply of heat to lose, and which 
 radiate it with the greatest freedom. Now it has 
 been ascertained by experiment, that the facility of 
 radiating heat depends entirely on the nature of the 
 surface, and the surfaces of leaves have such a re- 
 markable power in this respect, that it would seem 
 as if they were especially designed for the purpose. 
 If next you consider how small a quantity of matter 
 the leaves contain, compared with their large radi- 
 ating surfaces, you will see that there are all the 
 conditions present of rapid cooling. When, there- 
 fore, under a clear evening sky; the rays of heat are 
 escaping from all objects into the celestial space, the 
 green foliage soon becomes colder than the barren 
 rocks or the inanimate clod, and receives, in conse- 
 quence, a greater supply of dew. 
 
 It will be remembered, as I stated in the second 
 lecture of this course, that the points of leaves have 
 the power of silently discharging the thunderbolts 
 of heaven, and that, in consequence, every tree acts 
 far more efficiently to avert the stroke of this destruc- 
 tive agent than the best constructed lightning-rod. 
 Is not, now, the force of this evidence of adaptation 
 very greatly enhanced, when we find that the sur- 
 faces of these same leaves have been endowed with 
 an equally remarkable power of radiating heat, by 
 which they are insured a daily supply of moisture 
 when they need it most ? Could the adaptation of 
 the structure of the leaf to these two entirely dis- 
 
THE DEW. 135 
 
 tinct physical conditions of the atmosphere be the 
 result of anything but intelligence ? Admitting, with 
 the modern advocates of the development theory, 
 that under the pressure of circumstances a plant 
 may change its structure so as to adapt it to the 
 external conditions, still I think no one will be so 
 bold as to maintain that there can be any brute 
 agency in vegetation endowed with such foresight 
 as to have adapted the material and structure of 
 each leaf, from the very first, to the physical condi- 
 tions of the globe, and this, moreover, for the pur- 
 pose of effecting ends so remotely connected with 
 its own organization as the discharge of electricity 
 or the radiation of heat. If this can result from 
 chance, under its modern name of natural selection, 
 then chance is but a counterfeit name of God. 
 Gideon believed that God would save* Israel, be- 
 cause the dew fell on the fleece, but not on the 
 ground, and afterwards on the ground, but not on 
 the fleece; and shall we doubt the reality of the 
 Divine Providence, before whom a similar miracle 
 is repeated every evening, with such beneficent re- 
 sults? If it be the mark of intelligence to be able 
 to fathom and comprehend this wonder of Nature, 
 can it be anything below Infinite Intelligence ^^ who 
 hath begotten the drops of dew " ? 
 
 I might, with advantage, enter more into detail in 
 regard to the laws of the distribution both of the 
 rain and of the dew, but time and space forbid. I 
 have been able only to open the subject ; yet if I 
 have succeeded in impressing you with the extent 
 of the field which these beautiful phenomena pre- 
 
136 WATER THE GREAT PURIFIER. 
 
 sent to your inquiry, it is all that I could expect. 
 We have seen that it is through these familiar chan- 
 nels that liquid nourishment is conveyed to the or- 
 ganic world, and the reservoirs supplied which feed 
 the great river-system of the globe. But we should 
 form a very imperfect idea of the resources of nature 
 were we to limit our regards of the aqueous circula- 
 tion to this important use. The life-blood of our 
 bodies, which conveys to each muscle the nourish- 
 ment it requires, when it returns again through the 
 veins, this errand well done, is no less usefully em- 
 ployed in carrying away the portions of the tissues 
 which have been worn out in the processes of life ; 
 and where from any cause this last function is not 
 faithfully discharged, and the wasted muscles are 
 allowed to remain in the system, disease and death 
 are the inevitable results. So also is it with the life- 
 liquid of nature, which in the rain and the dew car- 
 ries food to the whole organic world. When this 
 office has been fulfilled, it returns again to the ocean, 
 washing away those waste products of organic life, 
 which, if they remained, would cause pestilence 
 and death. It is true that we cannot trace all 
 the details of this cleansing process ; but you need 
 not the aid of science to assure you of the general 
 facts. Let the free flowing of the rain-water be 
 interrupted, and you well know that stagnant pools, 
 breeding pestilence, or deadly swamps, exhaling ma- 
 laria, are the immediate results. I cannot overstate 
 the importance of this function of the aqueous cir- 
 culation, or too strongly insist on the evidence of 
 wisdom which the adaptation of the properties of 
 
^ESTHETIC ASPECTS. 1 37 
 
 water to this beneficent end implies. It is the 
 great cleansing agent of the world. Wherever it 
 flows, there it purifies, and its limpid streams, clear 
 as crystal, are fit emblems of the purity of heaven. 
 Hence the significance of this liquid in all religious 
 systems. The ancient Egyptians worshipped the 
 water of the Nile, and the Hindoo idolaters of the 
 present day reverence with equal devotion the wa- 
 ter of the Ganges. Passing to Judaism, we find the 
 washing with water enjoined as a sacred duty by 
 the Hebrew law ; and lastly, in the Christian dis- 
 pensation the pure liquid has become the medium 
 of its most sacred rite, and the outward washing of 
 baptism typifies that inward " washing of regenera- 
 tion," by which alone man is saved. 
 
 Glancing now, for a single moment, at the aesthetic 
 aspects of the subject, consider what sources of 
 pleasure the varied phases of the aqueous circula- 
 tion furnish, and what an influence on the soul of 
 man they are calculated to exert. The bubbling 
 spring, the purling rill, the murmuring brook, the 
 sparkling cascade, the roaring torrent, the majesti- 
 cally flowing river, are familiar images of poetry, 
 and the occasions of mental emotions which all have 
 experienced and none can fully describe ; while the 
 mighty cataract and the ocean-storm are among the 
 sublimest aspects of nature, and inspire the beholder 
 with reverence and awe. When, now, you reflect 
 that the chords of the human soul have been so 
 strung as to vibrate in sympathy with these emo- 
 tions of the material creation, and that thus the 
 aqueous circulation has been made a means of in- 
 
138 FERTILITY OF RESOURCES. 
 
 structing and elevating the human race, can you 
 refuse to accept the evidence of wisdom and good- 
 ness which a system, so far-seeing in its design, and 
 so beneficent in its results, affords ? 
 
 The mechanism of nature differs, as we have seen, 
 from the creations of human ingenuity, in the fer- 
 tility of its resources. Man combines numerous 
 means in order to produce a single end; but in 
 nature the most varied and apparently incompatible 
 results flow from a single design. In God's works 
 the means are employed, not as we use them in the 
 poverty of our resources, but from the exuberance 
 of riches. To use the language of another : ^^ All 
 the means are ends, and all the ends are means ; *' 
 and the grand result is an harmonious system, in 
 which every part is a whole, and where the whole 
 that is known is felt to be only a very insignificant 
 part. Such is the character of the aqueous circula- 
 tion, which we are now studying, and assuredly the 
 numerous results we have already seen flowing from 
 this simple mechanism are suf^cient to mark the 
 system as Divine ; but we have not as yet exhausted 
 its resources. Indeed, we have been all the time 
 looking at only one side of the design, and there is 
 a whole set of adaptations yet unnoticed, which are 
 no less important in the scheme of organic nature 
 than the one we have chiefly considered. And when 
 we have become acquainted with these, we shall 
 find still other phases of this boundless plan pre- 
 sented to our view, and not until man ceases to 
 learn by study, or the waters cease to roll, will the 
 subject be exhausted. 
 
LATENT HEAT OF STEAM. 1 39 
 
 We have thus far only considered the agency of 
 the aqueous circulation in distributing over the earth 
 the chief constituent of all organic matter, together 
 with some of the secondary ends which the river- 
 system of the globe subserves. But there is another 
 condition of organic life no less essential than moist- 
 ure. The animal kingdom is absolutely dependent 
 on the vegetable, and plants cannot grow except 
 within a limited range of temperature. Therefore, 
 unless during at least a portion of the year the 
 amount of heat supplied is sufficient to maintain 
 the temperature of the climate within the required 
 limits, organic life cannot exist in that region. Now 
 this familiar substance, water, has been endowed 
 with most remarkable and unusual properties, by 
 which the aqueous circulation has been made a great 
 means of distributing heat, and thus of sustaining 
 organic life in vast tracts of country where otherwise 
 it could not exist ; and it is to this class of its adap- 
 tations that I wish next to call your attention. 
 
 One of the prominent inventions of modern times 
 is the method of heating large buildings by steam. 
 You must all have seen the apparatus. There is first 
 the boiler, where the steam is generated by the com- 
 bustion of fuel ; then pipes, by which it is distrib- 
 uted to the different rooms ; next the iron radiators, 
 in which the steam is condensed to water, and during 
 this change gives out heat, which is radiated from 
 the corrugated surface of the iron; and, lastly, the 
 return pipes, through which the condensed water 
 flows back to the boiler, ready to start again on the 
 same journey. Every one is familiar with these 
 
I40 HEATING BY STEAM. 
 
 external aspects of the apparatus ; but all may not 
 know that the efficiency of the method depends 
 entirely upon a remarkable quality of water, a qual- 
 ity which is not possessed to the same degree by any 
 other known liquid. Were you to test with a ther- 
 mometer the temperature of the w^ater in the boiler 
 and that of the steam rising from it, you would be 
 surprised to find, — if you were not forewarned of the 
 fact, — that they were precisely at the same point ; 
 and yet in order to change one pound of boiling 
 water into one pound of steam it is necessary to 
 burn up sufficient coal to raise the temperature of 
 ten pounds of ice-cold water to the boiling-point. 
 The coal which is burning under the boiler does not 
 raise the temperature of the water. Press the fire 
 ever so hard, you cannot increase the temperature 
 either of the water or of the steam by a single de- 
 gree. The effect of increasing the fire will be only 
 to generate steam more rapidly, for the whole of 
 the immense amount of heat set free by the burning 
 fuel is absorbed by the boiling water in changing 
 into steam. But this heat is not lost. It reaaains 
 latent^ in the steam, is carried by it into the different 
 rooms, and there, when the steam changes back 
 again into water, it is all given up, without the 
 slightest diminution, diffusing its genial warmth 
 through the house. The steam, therefore, is merely 
 the vehicle by which heat is carried over the build- 
 ing. The heat comes from the burning fuel in the 
 cellar, and originally it came from the sun ; for the 
 coals burning under the boiler are merely fagots, as 
 it were, of condensed sunbeams, gathered by the 
 
THE EARTHS STEAM HEATER. -' I4I ^> 
 
 plants of some ancient geological epoch, subse- 
 quently fossilized and preserved in the earth for our 
 use. The steam merely acts the part of a common 
 carrier; but what I wish you to notice is the fact 
 that steam is peculiarly fitted for the work, because 
 it has been made capable of holding so large a quan- 
 tity of heat. 
 
 Your attention, perhaps, has been called to the 
 efficiency and economy of this method of heating; 
 you have admired its neatness and absolute safety 
 from fire, and have been delighted with the softness of 
 the temperature which it diffuses through the rooms; 
 or, if you have examined more closely the details 
 of the apparatus, you must have been struck with 
 the ingenuity of the adjustments by which it is self- 
 regulated. Yet this is no new invention. A similar 
 apparatus, on a vastly grander scale, working with 
 far greater economy and efficiency, and provided 
 with adjustments of wonderful delicacy, which per- 
 fectly regulate its action, and which never fail and 
 never wear out, has been at work ever since the 
 dawn of the creation, and is at this moment soften- 
 ing the inclemency of our northern winter. 
 
 The general aqueous circulation is a great steam- 
 heating apparatus, with its boiler in the tropics and 
 its condensers all over the globe. The sun's rays 
 make the steam, and wherever dew, rain, or snow 
 falls, there the heat, which came originally from the 
 sun, and which has been brought from the tropics 
 concealed in the folds of the vapor, is set free to 
 warm the less favored regions of the earth. This 
 apparatus of nature, although so much simpler, and 
 
142 THE EARTH S STEAM HEATER. 
 
 working without pipes, iron boiler, or radiators, is 
 exactly the same in principle as the steam-heater, 
 which may be seen at work in almost every large 
 factor}-'. It is true that the atmospheric vapor is a 
 much better vehicle of heat than ordinary steam, and 
 it is also true that this thermal application is but 
 one of the hundred uses of the aqueous circulation ; 
 but still the general method is the same, and both 
 systems owe their efficiency to the unique property 
 with which water has been endowed. It is true that 
 other liquids in changing into vapor absorb heat, 
 but the heat stored up in these vapors is vastly less 
 than that in steam, and it must be noticed that, of 
 all created forms of matter, this familiar liquid, which 
 fills the ocean, which distils upon us in the rain, and 
 which flows in the rivers, is the only substance 
 which has been thus especially endowed. Is this an 
 accidental concurrence of circumstances? or is it, on 
 the contrary, the work of Infinite Wisdom? We 
 regard, and with reason, the beautiful invention of 
 man, by which our dwellings are warmed, as an evi- 
 dence of .intelligence ; and can we refuse to recog- 
 nize the existence of that higher Intelligence, which 
 not only adjusted the more perfect system of nature, 
 but also created the properties of water, on which 
 the efficiency of both depends ? 
 
 Having considered that peculiar quality of vapor 
 through which the aqueous circulation becomes an 
 important means of distributing the sun's heat over 
 the surface of the globe, we might next discuss more 
 at length the extent of its influence, and examine in 
 detail the ingenious system of checks and balances 
 
CAPACITY OF WATER FOR HEAT. I43 
 
 by which the action of this great heating apparatus 
 is regulated, and its constant working secured ; but 
 here, as before, having glanced at the main points, 
 I must leave it to your study to fill the unavoidable 
 blanks, and pass on to consider another special 
 property of water by which a similar result is se- 
 cured. 
 
 The amount of heat required to raise the tem- 
 perature of a pound of water, or of any other sub- 
 stance, one degree, is capable of exact measurement, 
 and the quantity has been determined experimen- 
 tally for almost every known substance. These ex- 
 periments have led to a remarkable result, to which 
 I alluded in a former lecture. It appears that, 
 when water is heated through a given number of 
 degrees, it absorbs more than twice as much heat as 
 any other substance (except one or two very closely 
 related bodies), and more than ten times as much as 
 iron and most of the metals. It is not probable 
 that many of my audience have verified this strik- 
 ing result, but you all know how long it takes to 
 boil a tea-kettle, even over a brisk fire, and have, 
 therefore, some conception of the amount of heat 
 which cold water is capable of absorbing. This 
 familiar experience shows that water has a very 
 great capacity of holding heat, and accurate ex- 
 periment has proved, as just stated, that, with the 
 exception just noticed, water contains, at the same 
 temperature, more than twice as much heat as any 
 other solid or liquid known. 
 
 The importance of this simple provision will ap- 
 pear if you reflect that it makes the ponds, the 
 
144 THE OCEANS ARE RESERVOIRS OF HEAT. 
 
 lakes, and the oceans great reservoirs of heat. It 
 not only requires a vast amount of heat to warm 
 one of these large bodies of water, but when once 
 warmed they cool very slowly. Hence the marked 
 difference between the oceanic and the continental 
 climate in the same latitude. During the summer 
 the ocean eagerly absorbs the heat of the sun's rays, 
 which are showered upon it in such profusion ; but 
 water has so great a capacity for heat, that the 
 ocean, nevertheless, does not grow very warm, and, 
 moreover, a large amount of the heat it receives is 
 carried away by the vapor which is constantly rising 
 from its surface. In winter, on the other hand, the 
 water gives up its heat to warm the colder air ; but 
 it contains such an inexhaustible supply, that the 
 loss does not materially lower its temperature. 
 There results, in consequence, a great uniformity of 
 temperature, in which the air, by its perpetual con- 
 tact with the surface of the water, necessarily shares, 
 and this uniformity extends, in a greater or less de- 
 gree, to the -climate of all islands and seaboard dis- 
 tricts. It is quite different with the surface of con- 
 tinents. There the soil becomes rapidly heated 
 under the vertical rays of a summer's sun, and, as 
 its particles are immovable, the surface-layer soon 
 rises to a high temperature ; while, on the other 
 hand, in winter it is cooled by radiation with equal 
 rapidity ; and this is the cause of those extremes of 
 heat and cold which characterize all countries of the 
 temperate zone removed from the influence of the 
 ocean. The oceanic climate is moderate, while the 
 continental climate is excessive. During the day, 
 
OCEANIC AND CONTINENTAL CLIMATES. I45 
 
 under the same circumstances, the land is warmer 
 than the sea, and colder during the night, or, taking 
 the different seasons, the land is warmer than the 
 sea in summer and colder in winter. These general 
 principles have been verified by the extensive series 
 of meteorological observations which, during the last 
 twenty-five years, have been made all over the civil- 
 ized world. You will find an excellent abstract of 
 the results in Professor Guyot's work on Earth and 
 Man, before referred to. I have time only to cite 
 a few familiar facts in illustration of my subject, 
 which I will give nearly in his words. 
 
 ** On the coast of Cornwall shrubs as delicate as 
 the laurel or the camellia are green through the 
 whole year, while under the same latitude in the 
 interior of the continents, the most hardy trees can 
 alone brave the rigor of the winter. But on the 
 other hand, the mild climate of England cannot 
 ripen the grape, although almost under the same 
 parallel grow the delicious wines of the Rhine. At 
 Astrachan, on the northern shore of the Caspian, as 
 Humboldt tells us, the grapes and fruits of every 
 kind are as beautiful and luscious as in the Canaries 
 and in Italy; the wines have all the fire of those of 
 the south of Europe, although in the same latitude, 
 at the mouth of the Loire, on the Atlantic sea-coast, 
 the vines hardly flourish at all. But while in the 
 south of France the winter is a perpetual spring, the 
 summers of the Caspian are succeeded by a winter 
 of almost polar severity." 
 
 I might multiply illustrations, but these are sufB- 
 cient to show how the remarkable property of water 
 7 
 
146 EFFECT OF OCEAN CURRENTS. 
 
 which we are considering tends to equaHze the cli- 
 mate of the globe. 
 
 This influence of water is very greatly increased 
 by the oceanic currents, which, like the winds, are 
 set in motion by the heat of the sun, and are con- 
 stantly carrying the warm waters of the tropics 
 toward the poles. One of the most remarkable of 
 these currents is the Gulf-Stream, which flows near 
 our coast, and which diffuses the warm waters of the 
 Caribbean Sea and the Gulf of Mexico over the 
 Northern Atlantic, depositing on the shores of Scot- 
 land and Norway the plants and seeds of the tropics. 
 It is solely the heat which these waters bring with 
 them from the equator that has made the island of 
 Great Britain so great a centre of commerce and civ- 
 ilization ; for it must be remembered that the latitude 
 of England is the same as that of Labrador, and, 
 were it not for the influence of this ocean current, 
 her soil would be equally desolate and barren. If 
 the configuration of our Western Continent were 
 only so slightly changed as to give a passage to the 
 equatorial current through the present Isthmus of 
 Panama — a change insignificant in comparison with 
 those which have heretofore taken place— "the 
 mountains of Wales and Scotland would become 
 again the abode of glaciers, and civilization would 
 disappear before the invasion of arctic cold." ^ So 
 also it is to the enormous mass of heated water 
 which the Gulf-Stream pours into the seas surround- 
 
 **W. Hopkins's Address before the Geological Society of Great 
 Britain. 
 
POINT OF MAXIMUM DENSITY. I47 
 
 inc^ northern Europe that Sweden and Norway owe 
 their temperate climate, while at the corresponding 
 latitudes on our own continent the land is shrouded 
 in eternal ice and snow. 
 
 But all these provisions for distributing heat 
 over the earth's surface would have been insuffi- 
 cient to maintain organic life in our northern cli- 
 mate, were it not for still another remarkable 
 property with which water has been endowed, — a 
 property even more entirely unique than either of 
 those we have studied, and one which seems to be 
 an exception to the general laws of nature. The 
 familiar cycles of organic life, both in animals and 
 plants, afe intimately associated with the succession 
 of the seasons, and this, in its turn, depends on the 
 inclination of the earth's axis to the plane of the 
 ecliptic, and on the great primary laws by which 
 this axis is constantly maintained in a position par- 
 allel to itself during the revolution of the planet 
 around the sun. To these fundamental conditions 
 in the formation of the solar system the whole con- 
 stitution of organic life on the earth has been ad- 
 justed ; and Dr. Whewell, in his excellent Bridge- 
 water Treatise, has discussed at length the evi- 
 dences of design which this circumstance affords. 
 It would be foreign to my plan, to consider these 
 evidences here; but, assuming the succession of the 
 seasons as a part of the order of creation, and as a 
 means of adapting a larger portion of the earth's 
 surface to the habitation of organized beings, it is 
 evident that the higher forms of organic life could 
 be sustained in these northern regions only by fur- 
 
148 POINT OF MAXIMUM DENSITY. 
 
 nishing to the plants and animals an adequate pro- 
 tection against the intense cold of winter, and thus 
 preserving the growth of one summer until the 
 returning sun awakened new life in the succeeding 
 spring. 
 
 The required protection has been provided by 
 making a most marked exception to the general 
 laws of expansion in the case of water. It is the 
 general law of nature that all substances are ex- 
 panded by heat and contracted by cold, and water 
 forms no exception to the general rule, except 
 within certain very narrow limits of temperature, 
 shortly to be noticed. Indeed, were it not for the 
 expansion, we could not readily either heat or cool 
 a large mass of liquid matter. All liquids are very 
 poor conductors of heat, and can be heated only by 
 bringing their particles successively in contact with 
 the source of heat. When you set a tea-kettle over 
 a fire, the first effect of the heat is to expand the 
 particles of water resting on the bottom of the 
 kettle, which, being thus rendered specifically lighter, 
 rise, and are succeeded by colder particles, which 
 are heated and rise in their turn ; and thus the cir- 
 culation is established by which all the particles are 
 successively brought in contact with the heated bot- 
 tom of the kettle, and in the course of time the 
 temperature of the whole mass is raised to the 
 boiling-point. The case is similar when you add 
 ice to a pitcher of water in order to cool it. The 
 water at the top of the pitcher, in contact with the 
 ice is, of course, cooled, and, being thus rendered 
 specifically heavier than the water below, sinks 
 
POINT OF MAXIMUM DENSITY. I49 
 
 and gives place to the warmer water, which is 
 cooled and sinks in its turn, and thus, as before, a 
 circulation is established, which continues until the 
 temperature of the whole water is reduced to 40"^. 
 But at this point the circulation is entirely arrested ; 
 for, in consequence of its singular constitution, 
 water at 39° is lighter than water at 40°, and con- 
 sequently remains at the top. And so it is as the 
 temperature sinks toward the freezing-point. The 
 colder the water, the lighter it becomes, and the 
 more persistently it remains at the surface. Hence, 
 although the upper layers of water may be readily 
 cooled to the freezing-point, yet, in consequence of 
 its poor conducting power, the great body of the 
 liquid below will remain at the temperature of 40''. 
 The coTd^^atmosphere of winter acts upon the 
 ponds and lakes exactly as the ice on the water in 
 the pitcher. They also are cooled from the surface, 
 and a circulation is established by the constant sink- 
 ing of the chilled water until the temperature falls 
 to 40°. But at this point, still eight degrees above 
 the freezing-point, the circulation stops. The sur- 
 face-water, as it cools below this temperature, re- 
 mains at the top, and in the end freezes ; but then 
 comes into play still another provision in the proper- 
 ties of water. Most substances are heavier in their 
 solid than in their liquid state ; but ice, on the con- 
 trary, is lighter than water, and therefore floats on 
 its surface. Moreover, as ice is a very poor conduc- 
 tor of heat, it serves as a protection to the lake, so 
 that at the depth of a few feet, at most, the tem- 
 perature of the water during winter is never under 
 
I50 ICE LIGHTER THAN WATER. 
 
 40°, although the atmosphere may continue for 
 weeks below zero. 
 
 If water resembled other liquids, and continued to 
 contract with cold to its freezing-point, — if this ex- 
 ception had not been made, the whole order of 
 nature would have been reversed. The circulation 
 just described would continue until the whole mass 
 of water in the lake had fallen to the freezing-point. 
 The ice would then first form at the bottom, and the 
 congelation would continue until the whole lake had 
 been changed into one mass of solid ice. Upon 
 such a mass the hottest summer would produce but 
 little effect ; for the poor conducting power would 
 then prevent its melting, and instead of ponds and 
 lakes we should have large masses of ice, which 
 during the summer would melt on the surface to the 
 depth of only a few feet. It is unnecessary to state 
 that this condition of things would be utterly incon- 
 sistent with the existence of aquatic plants or an- 
 imals, and it would be almost as fatal to organic life 
 everywhere ; for not only are all parts of the creation 
 so indissolubly bound together that, if one member 
 suffers, all the other members suffer with it, but 
 moreover, the soil itself would, to a certain extent, 
 share in the fate of the ponds. The soil is always 
 more or less saturated with water, and, under exist- 
 ing conditions in our temperate zone, the frost does 
 not penetrate to a sufHcient depth to kill the roots 
 and seeds of plants which are buried under it. But 
 were water constituted like other liquids, the soil 
 would remain frozen to the depth of many feet, and 
 the only effect of the summer's heat would be to 
 
THE FROST BLANKET. 15I 
 
 melt a few inches at the surface. It would be, per- 
 haps, possible to cultivate some hardy annuals in 
 such a climate, but this would be all. Trees and 
 shrubs could not brave the severity of the winter. 
 Thus, then, it appears that the very existence of life 
 in these temperate regions of the earth depends on 
 an apparent exception to a general law of nature, so 
 slight and limited in its extent that it can only be 
 detected by the most refined scientific observation. 
 
 Moreover, this exceptional property is united in 
 water with another quality, which greatly aids in 
 preserving vegetable life during the winter months. 
 We shudder at the thought of snow, but neverthe- 
 less it affords a most effectual protection to the soil, 
 forming as warm a covering as would the softest 
 wool. Water in all its conditions has been made a 
 very bad conductor of heat, and snow is ranked with 
 wool among the poorest of conductors. Heat, there- 
 fore, cannot readily escape from a snow-covered so]], 
 and thus its temperature is prevented from falling 
 materially below the freezing-point, however great 
 the severity of the season. Notice now, that, when 
 winter sets in and the cold increases to such a degree 
 as to endanger the tender plants. Nature promptly 
 spreads her great frost -blanket over forest, prai- 
 rie, meadow, and garden alike, so that all may slum- 
 ber on in safety until the sun returns and melts away 
 the downy covering, when the buds break forth 
 again and the trees put on a new mantle of living 
 green. 
 
 This leads me to speak of still another remarkable 
 property of the wonderful liquid we are studying ; 
 
152 HEAT OF FUSION. 
 
 for nature has provided in the constitution of water 
 a most effectual means of tempering the transition 
 of the seasons, and protecting vegetation against 
 the early frosts of autumn or the first deceptive 
 glow of returning spring. In order to freeze a liquid 
 it is necessary to remove from it a certain quantity 
 of heat called the heat of fusion, and the more of 
 this heat a liquid contains, with the more difficulty, 
 of course, it freezes, and when once frozen the less 
 readily the solid melts. Now water contains a 
 larger amount of heat of fusion than any other 
 liquid yet examined, and in this respect, therefore, 
 it is also peculiarly constituted. And mark how this 
 property tends to produce the result just noticed. 
 As the weather becomes cooler in autumn, our ponds 
 and lakes gradually give up the stores of heat which 
 they contain, until the temperature of the whole 
 mass of water is reduced to 40° ; then the surface- 
 water cools still further to the freezing-point ; but 
 before it can beconle any colder than this the water 
 must freeze, and in freezing it will set free four 
 times as much heat as it has already given out in 
 cooling from the temperature of summer (63°) to the 
 freezing-point. It is evident, therefore, that freez- 
 ing must be a slow process. Moreover, it is also a 
 warming process, and although the temperature of 
 surrounding objects can never be thus raised above 
 the freezing-point, nevertheless the immense amount 
 of heat evolved greatly tends to retard the approach 
 of severe cold, and prepares the way for the inclem- 
 ency of winter. So also, when spring comes, vege- 
 tation is not awakened by her first touch to be 
 
HEAT OF FUSION. I53 
 
 exposed to the blights of the early frosts, and before 
 the snow covering can be melted off the danger is 
 mostly passed. Again, when we consider what de- 
 vastating floods would sweep the earth were the icy 
 bonds of winter suddenly dissolved, we shall dis- 
 cover still further evidence of the wisdom of that 
 Being who has so adjusted the properties of water 
 that both frost and freshet are the exception, not 
 the rule. 
 
 I have said that water presents the only well- 
 established exception to the laws of expansion by 
 heat, and some writers on natural theology have 
 dwelt on this point as one of great importance to 
 their argument. But I cannot think they are wise ; 
 for, to say the least, they rest their argument on our 
 ignorance, and not on our knowledge. It is true 
 that in the present state of science the anomalous 
 expansion of water near the freezing-point seems to 
 be an exception'^ to the general laws of nature; but 
 hereafter this very anomaly may appear to be the 
 natural result of a more general law not yet dis- 
 covered, or, like the perturbations in the orbits of 
 the planets, may prove to be the strongest confirma- 
 tion of the very law it now seems to invalidate. 
 Moreover, I do not share in that indefinite dread of 
 natural laws which troubles so many religious minds. 
 To me the laws of nature afford the strongest evi- 
 dences of the existence of a God, and in their uni- 
 formity I see merely the constant action of an omni- 
 present Creator, who acts with perfect regularity 
 
 * The peculiarity consists in the anomalous expansion of water, not 
 in the fact that water expands in freezing, as stated by some w^riters, 
 
 7* 
 
154 NATURE OF THE EVIDENCE. 
 
 because he acts consistently and with infinite wis- 
 dom. I beHeve that all parts of nature are correlated 
 by laws, and that the wider our knowledge becomes, 
 the more universal these laws will appear. I do not, 
 therefore, regard the constitution of water as some- 
 thing apart from law, and as the evidence of a power 
 coming down, as it were, upon law to make an ex- 
 ception to it. This is making altogether too much 
 of law. God is not bound by law. He acts wisely, 
 beneficentry, and with a definite plan, and the most 
 we can claim for natural laws is, that they are our 
 imperfect human expressions of this Divine plan. 
 Moreover, that is a far nobler view of God's wisdom 
 which supposes Him to be able to harmonize special 
 adaptations with general laws. What I find so re- 
 markable in the constitution of water is, not that it 
 is an exception to the general laws of nature, but 
 that, while filling its place in the general plan, it 
 has been endowed with such extreme properties, 
 and that in each case the peculiar property has 
 special adaptations at once so complex and so impor- 
 tant. Not only has water this exceptional property 
 of expanding when other liquids contract, but, more- 
 over, of all known substances it has the greatest 
 capacity for heat ; so also, when changing into va- 
 por, it absorbs more heat than any other liquid ; 
 again, it is far lighter in the solid than in the liquid 
 state ; and lastly, it contains the largest amount of 
 heat of fusion as yet observed in any substance. 
 All this may be in harmony with general laws. I 
 have no doubt that it is ; but the existence of the 
 law does not in the least impair the significance of 
 
NATURE OF THE EVIDENCE. 155 
 
 the fact, that in each of these respects water has 
 been pecuHarly constituted. This one liquid of the 
 globe, which covers more than three-fourths of its 
 surface, which circulates through all its channels, 
 which percolates through all its pores, which consti- 
 tutes three-fourths of all organized beings, has been 
 endowed with these four pre-eminent qualities, on 
 each of which the whole order of terrestrial nature 
 may be said to depend. I cannot conceive of stronger 
 evidence of design than this ; and if these facts do 
 not prove the existence of an intelligent Creator, 
 then all nature is a deception and our own faculties 
 a lie. Yet, my friends, this is only a small part of 
 the evidence of design which science has discovered 
 in this familiar liquid. I might occupy several lec- 
 tures with this subject alone, but I have time only 
 to glance at two more striking facts. 
 
 Water is the most universal solvent known, and 
 there are but few substances which are not, to a 
 greater or less degree, dissolved by it. Those which 
 we call insoluble generally differ from the rest only 
 in degree. Thus, all lime rocks dissolve to a limited 
 extent in spring water, and the same is also true 
 of almost all mineral substances. The magnificent 
 crystals which we frequently find in the rocks are 
 formed in almost every case by a deposition of the 
 mineral substance from a state of solution in water. 
 The feeble solvent power of the water for these sub- 
 stances is made up by the large volume of the 
 solution, and the length of time occupied in the 
 process of crystallization. Many of the large crys- 
 tals which may be seen in cabinets of minerals have 
 
156 SOLVENT POWER. 
 
 been unquestionably thousands of years in formation. 
 And not only does the solvent power of water stud 
 the cavities of the rocks with gems, but it is also 
 constantly producing most important changes in 
 the rocky structures of the globe itself, here cement- 
 ing together the loose sands, and there converting 
 the soft clays into firm and solid rock. 
 
 Again, the solvent power of water extends to 
 aeriform as well as to the solid substances, so that 
 the gases composing the air pervade the lakes and 
 the oceans as well as the atmosphere. Indeed, it is 
 on the gases dissolved in the water that all the aqua- 
 tic plants and animals live, and the members of the 
 various finny tribes breathe the free oxygen dis- 
 solv^ed in the water, as we breathe the oxygen of 
 the air. Again, the process of respiration is essen- 
 tially the same with these lower animals that it is 
 with us, and the structure of their organs has been 
 adjusted to the amount of this life-sustaining ele- 
 ment which water is capable of dissolving. More- 
 over, the power which water possesses of dissolving 
 oxygen is much greater than its power of dissolving 
 nitrogen, and hence the air dissolved in the ocean 
 is proportionally much richer in oxygen than our 
 atmosphere. This is undoubtedly another quality 
 with which water has been endowed in order to 
 render the oceans, the lakes, and the rivers a fit 
 habitation for that world of organic life which mod- 
 ern zoology has revealed. That we are unable to 
 trace all its relations, is evidently owing to the im- 
 perfection of our knowledge. But here a new field 
 of study opens before us, which, when fully explored, 
 
CHEMICAL RELATIONS. 157 
 
 will undoubtedly prove as rich in the evidence of 
 design as the atmosphere itself. 
 
 It is not, however, merely as a solvent, that water 
 is an important agent in the great laboratory of the 
 world. I have already stated to what extent all 
 animal and vegetable substances are composed of 
 water, and that some, such as the jelly-fishes among 
 animals, and the gourd family among plants, may be 
 said to be living forms of water. But we should 
 entertain a very erroneous conception of the condi- 
 tion of the water in these animal and vegetable 
 structures, were we to regard it as so much dead 
 material, building up the form like the bricks in an 
 edifice. This water is in constant circulation, con- 
 veying nourishment to all the parts, and at the same 
 time removing from the system those tissues which 
 have fulfilled their functions and become effete. It 
 is being constantly decomposed, and as rapidly again 
 reformed, assuming the most protean conditions, 
 and administering to the functions of the animal 
 economy in a thousand ways. 
 
 As a constituent of inorganic matter, water is no 
 less important than it is in organized being. A sub- 
 stance so bland as water, and apparently so entirely 
 inactive, which fills the most delicate vegetable 
 cells, and penetrates the finest capillaries of the 
 body, — whose minuteness and delicacy no art can 
 approach, nor imagination scarcely conceive, — yet 
 without affecting either in the slightest degree, we 
 should suppose would be endowed with no affini- 
 ties, and capable of exerting no chemical force. 
 Yet what is the fact? In attempting to classify 
 
IS8 COMPOSITION OF WATER. 
 
 chemical compounds, I have studied with care the 
 chemical history of water, and its relations to other 
 substances, and it is still to me a perfect enigma in 
 nature. For, so far from being that inert material 
 which its bland exterior would seem to indicate, it 
 is among the most important of chemical agents, 
 forming some of the most stable compounds, and 
 surprising the chemist by the strength of its affini- 
 ties. Not only is water a common constituent of 
 most crystalline salts, and an essential ingredient of 
 many of the powerful acids which are used both 
 in the arts and in the chemist's laboratory, but it 
 makes, also, a not unimportant part of the rocky 
 crust of the globe. Besides forming the immense 
 deposits of ice which perpetually surround either 
 pole, and the glaciers which creep down the high 
 mountain slopes, we find that water enters as an 
 essential ingredient into the composition of talcose 
 and chlorite slate, gypsum, serpentine, soapstone, 
 and other rocks. Moreover, water is the medium 
 in which most chemical processes take place, and 
 throughout all geological history it has been pro- 
 ducing the most fundamental changes in the com- 
 position of the earth's crust, the extent of which 
 geologists are only of late beginning to appreciate. 
 It is now supposed that granite and similar rocks, 
 which were formerly regarded as products of igne- 
 ous fusion, have been really formed from loose 
 beds of mud and clay, through the transforming 
 power of this wonderful and powerful agent. 
 
 When, lastly, we consider the composition of 
 water, our wonder is still further increased ; for it 
 
LATENT POWER. 1 59 
 
 consists of two permanent gases, condensed by the 
 force of chemical affinity to the liquid condition. 
 With one of these, oxygen, you are already famil- 
 iar. The other is a light, combustible gas, called 
 hydrogen, fourteen and a half times lighter than 
 air, and by far the lightest form of matter known. 
 One cubic foot of water yields more than eighteen 
 hundred cubic feet of a mixture of these two gases, 
 and so persistently do they retain their aeriform 
 condition, that not even a pressure of twenty tons 
 on the square inch is sufficient to reduce them 
 to liquids. Yet, immense as this pressure seems, 
 requiring all the mechanical skill of man to apply it, 
 that force must be still greater which is constantly 
 acting in every drop of water to hold these highly 
 elastic gases in the liquid state. It is difficult to 
 estimate the magnitude of such power, as our only 
 standard of measurement is the quantity of some 
 other force, equally immeasurable, which is required 
 to balance the first. Water is easily decomposed 
 by electricity, and the amount of this agent required 
 to force apart its constituents may perhaps give you 
 some imperfect conception of the magnitude of 
 that power by which they are so securely impris- 
 oned. The statement may seem incredible, but yet 
 it has been proved by Professor Faraday, that it 
 requires more electricity to decompose a drop of 
 water than to charge a thunder-cloud. 
 
 What a revelation of power we have here ! In 
 every drop of water there is a constant striving of 
 the elements to escape; they are exerting a force 
 to break the bonds that unite them, which can be 
 
l6o SUMMING UP 
 
 measured only by the power of concentrated thun- 
 der-bolts, and yet this immense force is kept in 
 check by a force of equal power, and so exactly bal- 
 anced that not the slightest disturbance can occur. 
 When now I endeavor to estimate the value of this 
 chemical force by our human standards, and find 
 that in comparison with it all the mechanical en- 
 ergy which man can exert, even when aided by the 
 appliances of modern art, is utterly insignificant ; 
 and when I reflect that in every particle of water 
 the force is still acting, so that every rain-drop 
 which falls is a silent monitor of human weakness, 
 I am overwhelmed by that mystery in nature, which, 
 here as elsewhere, ever points upward to the Infinite, 
 and thus silently teaches that the mighty influence 
 which binds the atoms of the rain-drop is merely 
 the manifestation of His ceaseless power who hold- 
 eth '' the waters in the hollow of His hand." 
 f It is a very common mistake to suppose that 
 /the grand in nature is to be seen only in its 
 i great water-falls and its lofty mountains ; for, to 
 the intellectual eye, there is more real grandeur, 
 more evidence of omnipotence, in a single rain- 
 drop than in the rush of Niagara or in the magni- 
 tude of Mont Blanc. The more I study the evi- 
 dence of design in this simple liquid, the more I 
 find there is to learn, and I feel the utter inade- 
 quacy of any language to convey the full and com- 
 plete idea. Review, for a moment, the examples 
 of adaptation which have been so briefly noticed. 
 Remember that water is the liquid of our globe, 
 and the only liquid which exists in any abundance 
 
SUMMING UP. l6l 
 
 on its surface. The total amount of all other liquids 
 is in comparison but as *' a drop of a bucket." Con- 
 sider, next, that its specific gravity has been so ad- 
 justed t hat our ships float, and the oceans are made 
 great highways for the nations ; that it is easily con- 
 verted into vapor, and as easily condensed to fer- 
 tilizing rain and refreshing dew, which nourish the 
 growing plants, fill the springs, and keep the rivers — 
 the great arteries of the globe — in circulation ; that 
 at a comparatively low temperature it is changed 
 into highly elastic steam, which, imprisoned by man 
 in his iron boilers, has become the great civilizer of 
 the world ; that it has been so exceptionally consti- 
 tuted that the great mass cannot be cooled below 
 forty degrees, and again has been made such a poor 
 conductor of heat that, when the surface is frozen, the 
 very ice becomes a protection against the cold ; that 
 to this same liquid there has been given a very great 
 capacity for heat, and that thus it has been made 
 the means of tempering materially the climates of 
 the globe. Add to this that water has been made 
 an almost universal solvent ; that from the sub- 
 stances it holds in solution the Crustacea form their 
 shells and the coral polyps build their reefs ; that it 
 fills the cavities of the rocks with gems, and their fis- 
 sures with useful ores. In connection with this host 
 of wonderful mechanical adaptations, remember that 
 water has been made a chemical agent of great 
 energy and power ; that there have been united in 
 it the apparently incompatible qualities of bland- 
 ness and great chemical force ; that, although in the 
 laboratory of nature it corrodes the most resisting 
 
l62 SUMMING UP. 
 
 rocks, it also circulates through the leaflets of the 
 rose and the still more delicate human lungs ; that 
 it forms the greater part of all organized beings, 
 from the lichen to the oak, and from the polyp to 
 man. Reflect, now, that these are only a few of the 
 grosser qualities and functions of this remarkable 
 compound, gleaned here and there from many 
 others no less wonderful, and you will form still 
 but a very imperfect conception of the amount of 
 design which has been crowded into it. Attempt 
 to find a liquid, which, if in sufficient quantity, 
 might supply its place, and you will be still further 
 impressed by this evidence of intelligence and fore- 
 thought. Of all the materials of our globe, water 
 bears most conspicuously the stamp of the Great 
 Designer, and as in the Book of Nature it teaches 
 the most impressive lesson of His wisdom and 
 power, so in the Book of Grace it has been made a 
 token of God's eternal covenant with man, and still 
 reflects His never-fading promise from the painted 
 bow. 
 
CHAPTER VI. 
 
 TESTIMONY OF CARBONIC DIOXIDE. 
 
 When standing by some quiet mill-stream, have 
 you ever speculated on the origin of the power which 
 is animating the machinery of the great factory on 
 its banks, spinning and weaving the crude cotton 
 into miles of cloth every week? Or at Niagara, did 
 the thought ever strike you, when gazing up at 
 those floods of water which come tumbling over 
 the rocky cliffs, and plunging into the seething sea 
 at your feet, that similar floods had been pouring 
 over that ancient river-bed for countless ages with- 
 out diminishing the inexhaustible supply? Or, if 
 it has been at once your privilege and your terror 
 to witness that grandest sight of nature, a violent 
 storm at sea, have you been impressed by the un- 
 tiring might of that mysterious agent which impels 
 the raging winds and upheaves the roaring billows? 
 Whence can come all the power? and what keeps 
 in motion that wonderful aqueous circulation, which 
 we studied in the last chapter? 
 
 Although the origin of this never-ceasing motion 
 may be still concealed, we have at least traced back 
 
 163 
 
164 CIRCULATION OF CARBON. 
 
 the power to a proximate source in the great central 
 luminary of our system. It is the gentle influences 
 of the sunbeam that raise the water in vapor, and 
 it is the same solar rays that keep in motion the 
 great aerial currents, spreading the clouds over 
 the earth, and distilling their liquid treasures " to 
 satisfy the desolate and waste ground, and to cause 
 the bud of the tender herb to spring forth." In- 
 credible as it may appear, it is actually the sun 
 that weaves the cloth, that feeds the fountains of 
 Niagara, and it is his delicate rays that rule in 
 the tempest and direct the storm. But there are 
 other influences of the sunbeam still more subtle 
 than these, and there are other cycles of changes, as 
 grand as the aqueous circulation, of which the sun 
 is also the ever-active cause. 
 
 Referring to the table before given, representing 
 the composition of the atmosphere, you will notice 
 that the great aerial ocean contains more than five 
 million billions of tons of an aeriform substance 
 called carbonic dioxide. This amount, although 
 absolutely very great, is nevertheless only a small 
 fraction of the whole atmosphere, making up less 
 than a thousandth part of its total mass. A cubic 
 foot of air does not contain more than a quarter 
 of a grain of carbonic dioxide ; yet there is not 
 one of the atmospheric constituents more intimately 
 associated with organic life, or which discharges 
 more important functions. Although itself a col- 
 orless gas, carbonic dioxide consists of ordinary 
 black charcoal combined with oxygen, and these 
 elements are united by one of the strongest affini- 
 
CIRCULATION OF CARBON. 165 
 
 ties known in nature ; yet, intense as this force is, 
 the power of the sun is greater, and his rays, acting 
 on the green leaves of the plants, are constantly 
 decomposing the gas and Hberating the carbon, to 
 be incorporated into the various forms of vegetable 
 life. Here, however, it remains only for a brief 
 period ; for when the plants have finished their 
 allotted term of life, the carbon again unites with 
 oxygen, and, in the form of carbonic dioxide, is 
 restored to the atmosphere by the process of com- 
 bustion or decay. But frequently, before these 
 destructive changes complete the cycle, the car- 
 bon undergoes a further transformation, and through 
 the process of digestion becomes a part of the body 
 of the animal. Yet this transmutation, as a general 
 rule, only hastens the final result ; since the processes 
 of animal life are very rapid, and sooner or later the 
 carbon is burnt up in the body, and breathed out 
 into the atmosphere, ready to renew the same series 
 of changes. In this lecture I wish to ask your atten- 
 tion to the evidences of design which may be dis- 
 covered by studying this wonderful circulation of 
 carbon ; and we shall find that the properties both 
 of carbon and carbonic dioxide have been most 
 carefully adjusted to the part which they play in 
 the great scheme of nature. We might begin our 
 study at any link of this endless chain of phenom- 
 ena; but to bring the subject into orderly con- 
 nection with our previous trains of thought, let us 
 return to the phenomena of combustion, which we 
 considered in the third chapter, and study the de- 
 tails of this familiar process a little more closely. 
 
l66 COMPOSITION OF FUEL. 
 
 All fuel, without exception, contains charcoal, or, 
 as the chemists call it, carbon. Wood, soft coal, 
 oil, wax, similar combustibles, which burn with 
 flame, contain, besides carbon, a variable quantity 
 of hydrogen and oxygen ; but hard coal, coke, and 
 common wood charcoal are almost pure carbon. 
 The adaptations of each of these classes of combus- 
 tibles demand special notice, and let us begin by 
 studying the evidences of design which are to be 
 found in an ordinary hard-coal fire ; and while, in 
 imagination, we are preparing the fire to be lighted 
 on the grate, we may study with profit some of the 
 external properties of the coal, for even they betray 
 the master-hand of the Great Architect. 
 
 Examining closely this lump of charcoal, you will 
 notice that it retains all the delicate structure of 
 the wood from which it was prepared. Here is the 
 fibrous bark next the sap-wood, and then the annual 
 rings, all as on a stick of beech ; and if you will 
 take the pains to make a thin section of the char- 
 coal, you will find, on examining it with a mi- 
 croscope, that the minutest cells have been pre- 
 served. You know how charcoal is made. The 
 wood is exposed to a high temperature in the char- 
 coal mounds or furnaces, by which the gases which it 
 contains are driven off, while the charcoal, not being 
 volatile, remains behind. Here, then, is a remark- 
 able fact, — that, although the wood has been ex- 
 posed to a red heat in the process of carbonization, 
 yet the minutest cells have not been destroyed; and 
 it illustrates an equally remarkable quality of char- 
 coal, on which, as we shall see, its usefulness as fuel 
 
INFUSIBILITY OF CARBON. 167 
 
 very greatly depends. Carbon, in all its forms, is 
 absolutely infusible. It does not even soften at the 
 highest temperatures which can be attained by art, 
 
 -^nd it is for this reason that the charcoal retains so 
 perfectly the structure of the wood. Were carbon 
 fusible at a red heat, the charcoal would run together 
 into a shapeless mass in the mounds or furnaces 
 in which it is prepared, and did it even soften at this 
 temperature, the forms of these delicate cells could 
 never have been preserved. Viewed in connection 
 with the volatile qualities of the other elements of 
 organized beings, the extreme fixity of carbon in its 
 uncombined condition is worthy of your special 
 attention. The only other essential elements of 
 organic matter are oxygen, hydrogen, and nitrogen ; 
 and these three substances are not only gases, but 
 gases which, even at the lowest natural temperature 
 cannot be condensed to the liquid condition by press- 
 ure alone ; yet so strong is the tendency of carbon 
 to remain solid, that it condenses these gases around 
 itself in every organized substance that exists. Car- 
 bon is thus the solid substratum of organized mat- 
 ter, the/ skeleton, as it were, of every organic form. 
 How evidently, then, has the attribute of infusibility 
 been adapted to this important function which car- 
 bon has been appointed to subserve ! 
 
 Examining again this lump of charcoal which we 
 are using to kindle the fire, mark that it has a 
 black color and is perfectly opaque. These qualities 
 are so evident to the most superficial observation 
 
 ^that they are apt to pass unnoticed, and yet it is 
 these qualities of charcoal which make it so valu- 
 
1 68 BLACK COLOR AND OPACITY. 
 
 able as a basis of printing ink. All may not 
 know that printing ink is a mixture of lamp-black 
 and oil, and that the letters on a printed page 
 are formed by thin layers of black charcoal spread 
 over the white paper; and charcoal is peculiarly 
 well adapted for this use, since, however finely sub- 
 divided, it never loses its dead black color and per- 
 fect opacity. But this property of charcoal would 
 be useless to the scholar for diffusing knowledge, 
 were it not combined with qualities still more re- 
 markable, and almost unique. Carbon is not acted 
 upon by atmospheric agents, and, moreover, is abso- 
 lutely insoluble in any liquid, with the exception 
 of melted iron. The letters of the first Bible ever 
 printed are as black as they were the day they left 
 the types. They have been exposed to the action of 
 atmospheric air for four hundred years, and, were 
 carbon in the slightest degree acted upon by the 
 atmosphere, they would long since have disap- 
 peared. As it is, they will endure as long as the 
 paper on which they are printed lasts. 
 
 The almost unparalleled insolubility of charcoal is 
 a quality equally important in this relation, for, were 
 charcoal, even to a slight extent, soluble in water, 
 the books of our fathers would have been rendered 
 illegible by the dainpness to which all libraries are 
 more or less exposed ; and were carbon soluble even 
 in such liquids as alcohol, ether, or the volatile oils, 
 the printed page would not have been, as now, safe 
 from alteration, and all kinds of fraud would have 
 been easy. We justly honor the names of Guten- 
 berg and Faust, whose art has done so much to en- 
 
PERMANENCY. 
 
 lighten and civilize the globe, and we'bestoi^due i* 
 admiration on those improvements in the aro qL O >^ 
 printing, nowhere more developed than in our owry'^. / 
 land, which have made the press the great agent * // 
 of power, and elevated the moral and intellectual 
 above the physical man ; but while we pay just trib- 
 ute to the genius of these benefactors of the race, 
 let us not forget that greater Benefactor, who was 
 before them all; for in the most familiar qualities 
 of this piece of charcoal, on which the art of print- 
 ing so greatly depends, there has been displayed, 
 since the foundation of the globe, an evidence of 
 wisdom and skill before which all human ingenuity 
 sinks into insignificance. 
 
 But the most remarkable attribute of carbon does 
 not appear in this piece of charcoal ; for of all the 
 chemical elements carbon is by far the most Protean 
 in its aspects, and charcoal is but one of its many 
 manifestations. In the first place, there are the nu- 
 merous varieties of coal, including charcoal, coke, 
 lamp-black, and bone-black, all having the same gen- 
 eral properties, and most of them partaking more 
 or less of the structure of the organic tissues from 
 which they were made. But, besides these varieties, 
 which, although differing so much in their outward 
 aspect, have all essentially the same properties, there 
 are two entirely different states of carbon, differing 
 as much from each other and from common charcoal 
 as any two solids possibly could. 
 
 Are you aware that the brilliant gem you prize so 
 highly is the same chemical element as these black 
 coals? The diamond is simply crystallized carbon, 
 8 
 
170 MODIFICATIONS OF CARBON. 
 
 and although we do not' know certainly how dia- 
 monds are made in the great laboratory of nature, 
 yet there is no fact of chemistry better established 
 than this."^ To those who are not familiar with the 
 results of modern chemistry, it seems almost in- 
 credible, and even the chemist can hardly believe 
 the truth while he affirms it. It is at utter vari- 
 ance with the former doctrine of his science ; it 
 cannot be reconciled with any of his previous con- 
 ceptions, and constantly reminds him of the limi- 
 tations of his knowledge and the uncertainty of his 
 philosophy. And, turning to the more familiar as- 
 pects of the subject, how singular the fact, and how 
 typical of the universality of Christian brotherhood, 
 that He, who " hath made of one blood all nations 
 of men,'' should have also made of the same ma- 
 terial the priceless brilliant which adorns the dia- 
 dem of the prince, and the soot which begrimes the 
 cabin of the humblest peasant! How different the 
 estimation in which these two forms of carbon are 
 held ! and yet, if the marks of Divine wisdom can 
 give nobility to a substance, the one is as excellent 
 as the other. 
 
 But carbon exists in still a third modification, dif- 
 fering as much from the diamond as that differs from 
 charcoal. Every one who has used a common lead 
 pencil is familiar with graphite, and it is a fact as 
 remarkable as the one just noticed, that the same 
 carbon which forms the letters of a printed page fills 
 
 * Diamonds of minute dimensions have, it is stated^ been lately- 
 produced by chemical process. 
 
DIAMOND, GRAPHITE, COAL. 171 
 
 also the lines of the pencil sketch. Graphite is sim- 
 ply a modification of charcoal, and if this fact is not 
 so well known as the humble relationship of the dia- 
 mond, it probably arises from the circumstance that 
 graphite has been generally called plumbago, or 
 black-lead, a misnomer which has given a very er- 
 roneous conception of its nature. Graphite is fre- 
 quently mixed with impurities, but it never contains 
 lead, and in its finest condition it is nearly pure car- 
 bon. Compare now graphite with the diamond. 
 Could there be two substances more unlike ? the one 
 the softest of minerals, the other the very hardest ; 
 the one dull and opaque, the other brilliant and 
 transparent. But besides these external differences 
 they have also a different crystalline form, a differ- 
 ent specific gravity, a different capacity for heat, 
 and, in fine, excepting that they are both infusible 
 and combustible, there is not one point of resem- 
 blance between them. How then, you will ask, do 
 we know that they are both the same elementary 
 substance? Simply because, when combined with 
 oxygen, they both yield the self-same compound. 
 
 All three of the modifications of carbon are com- 
 bustible, although they take fire at very different 
 temperatures. Charcoal will burn at a red heat, the 
 diamond at a white heat, while graphite requires the 
 highest temperature which can be attained by art. 
 But however different may be the temperatures re- 
 quired, the process is the same in all cases, and the 
 result is the same. The burning is simply combina- 
 tion with the oxygen of the air, and the result of 
 that combination is carbonic dioxide gas. More- 
 
172 ALLOTROPISM. 
 
 over, it has been proved by the most careful expe- 
 riments that a given weight of either substance 
 yields precisely the same weight of carbonic dioxide. 
 Chemically considered, then, the diamond, graphite, 
 and charcoal are the same substance, although, 
 physically regarded, no substances could be more 
 unlike. Chemical identity, therefore, does not con- 
 sist in identity of properties, and we must admit 
 that the same chemical element may manifest itself 
 under utterly different physical aspects. 
 
 This remarkable phenomenon, which has been 
 fully recognized only of late years, has been called 
 by chemists allotropismy^ and the diamond, plum- 
 bago, and charcoal are different allotropic modifica- 
 tions of the element carbon. Such differences of 
 manifestation, moreover, are not confined to car- 
 bon, nor are they exceptional occurrences among 
 the elements. We have already seen that oxygen 
 may exist in an active and in a passive modifica- 
 tion, which stand in as striking antithesis to each 
 other as the diamond and charcoal, and the same is 
 true of the different conditions of sulphur, phos- 
 phorus, and silicon. Again, these phenomena are 
 not limited to the elementary substances, for they 
 have been observed in many compounds as well, 
 and every year enriches our knowledge with fresh 
 examples. In what, then, are such developments 
 to end ? If substances so utterly unlike as the dia- 
 mond, graphite, and charcoal are merely modifica- 
 tions of the same element, why may not all substances 
 
 * Derived from two Greek words signifying difference of condition. 
 
ALLOTROPISM. 1 73 
 
 be merely different allotropic states of a few universal 
 principles, or possibly of only one single essence ? 
 Such, and many similar questions, arise in the mind 
 of the chemist while contemplating these obscure 
 phenomena. They cannot be satisfactorily answered 
 in the present state of chemistry,^ and they throw 
 
 * The only explanation which we can as yet give of these phe- 
 nomena is based on the distinction which modern chemistry makes 
 between the molecules of a substance and the elementary atoms of 
 which these molecules themselves are made up. The molecules are 
 the ultimate particles in which the qualities of a substance inhere, 
 and there are necessarily as many kinds of molecules as there are dif- 
 ferent substances. But there are only as many kinds of atoms as there 
 are chemical elements, and the infinite variety of molecules is formed 
 by the different combinations of the seventy kinds of elementary 
 atoms now known, and chemical action consists in the breaking up 
 of the molecules of the substances which enter into the chemical 
 change and the regrouping of their atoms.to form the molecules of 
 the substances which result from it. 
 
 It is evident, from this theory, that different molecules — and hence, 
 different substances — may result not only from the grouping of dif- 
 ferent atoms, and from the grouping of the same atoms in different 
 proportions, but also from the grouping of the same number of the 
 same atoms in different ways. Thus, to take a single example, four 
 atoms of carbon, eight atoms of hydrogen, and two atoms of oxygen 
 grouped in one way form a molecule of butyric acid, while grouped 
 in a different way the same atoms form a molecule of acetic ether, 
 both substances consisting of the same elements united in the same 
 proportions. 
 
 The same principle may be extended to the elementary substances 
 themselves. They, like compound substances, are aggregates of mole- 
 cules, which determine their properties, but these molecules consist 
 of atoms of one kind only. Diamonds, graphite, and charcoal are 
 distinct substances, and consist, therefore, of different molecules 
 although in all cases the molecules are formed from carbon atoms 
 only. But although every carbon atom in the universe is exactly like 
 eveiy other carbon atom, yet we may suppose that the differences in 
 
174 ALLOTROPISM. 
 
 a degree of uncertainty and doubt on its whole 
 philosophy. I shall have occasion to dwell upon 
 this subject more at -length in another lecture, and 
 have adduced the facts at this time chiefly as further 
 illustrations of that fertility of resources which so 
 strikingly marks all the results of creative skill. To 
 me this characteristic of the works of nature is one 
 of the most convincing evidences of divinity. While 
 studying the simple adaptation of means to ends 
 which we find everywhere around us, we recognize 
 in the plan something analogous to the creations of 
 human skill, and we almost feel a conscious relation- 
 ship with its Author. But when we consider this 
 incomprehensible power, by which the same ele- 
 ment has been endowed with entirely different and 
 incompatible properties, and not only this, but has 
 been adapted in each condition with equal skill to 
 produce the most opposite and seemingly irreconcil- 
 able results, we are also made to feel most keenly 
 that, although man was created in the image of his 
 Maker, he resembles the Divine Original only as the 
 finite can resemble the Infinite. *^ For my thoughts 
 are not your thoughts, neither are your ways my 
 ways, saith the Lord. For as the heavens are higher 
 
 what we have called the three allotropic modifications of carbon 
 result either from the grouping of a different number of carbon 
 atoms in each case, or from the grouping of the same number in a 
 different way, or from both causes combined. On account of the 
 great hardness of the diamond, and its great density, as compared 
 with the other varieties of carbon, it has been assumed that the mole- 
 cules of this gem consist of a large number of carbon atoms compacted 
 together. 
 
HARD-COAL FIRE. 1 75 
 
 than the earth, so are my ways higher than your 
 ways, and my thoughts than your thoughts/* 
 
 Of all the properties of coal, the one with which 
 we are most familiar is its combustibility ; and while 
 we have been discussing its external properties, the 
 hard-coal fire has been built in the grate, and it is 
 ready to be lighted. The combustion of coal in one 
 or the other of its varieties is the great source of all 
 the artificial heat used by man. Although so entirely 
 passive towards atmospheric agents at the ordinary 
 temperature, yet when heated to a red heat it takes 
 fire and combines with the oxygen of the air with 
 great rapidity. The burning of coal is so familiar to 
 every one that it would seem hardly necessary to 
 dwell upon the subject ' here. But although the 
 experiment is repeated every day in every grate 
 of the city, and although it has been familiar to you 
 all from infancy, there are, nevertheless, phenomena 
 connected with it which few have observed and still 
 fewer fully appreciated. It is a great mistake, but a 
 mistake too frequently made even by scientific men, 
 to suppose that new knowledge can be gathered 
 only from the unexplored fields of science, when by 
 the most familiar walks of life there are countless 
 riches of truth which the reapers in the hurry of the 
 harvest have passed unnoticed, and which will 
 abundantly reward the careful gleaners. In the 
 coal fire on which you daily gaze, there is enough to 
 be discovered to engross the attention of the most 
 diligent student of nature. Let us see, therefore, if 
 we, too, cannot learn something new, at least to us, 
 from the burning coals. 
 
176 POINT OF IGNITION. 
 
 The first fact to which I would call your atten- 
 tion is the dfficulty experienced in lighting coal. 
 In order to kindle the fire we have placed on the 
 bottom of the grate, first, some shavings, then some 
 charcoal, and, last of all, the hard anthracite coal. 
 We can readily set fire to the shavings with a match, 
 and they in their turn will ignite the charcoal ; but 
 it requires the intense heat of the burning charcoal 
 to ignite the anthracite. Charcoal will not burn 
 unless at a full red-heat, and hard coal requires a 
 still higher temperature. But notice now another 
 fact : when once inflamed, the heat evolved by the 
 combination of the carbon with oxygen is sufficient 
 to sustain the temperature at the point of ignition. 
 Here, again, we see most admirably illustrated the 
 adaptation of the properties of the chemical elements 
 to entirely different ends. In order that carbon 
 might serve as the solid substratum of all organized 
 beings, it was necessary that it should be made unal- 
 terable by the air within the limits of terrestial tem- 
 perature, but at the same time the economy of na- 
 ture required that it should be made combustible, 
 that is, endowed with strong affinities for oxygen ; 
 yet these affinities have been so carefully regulated, 
 that they are called into play only at a high temper- 
 ature, and are thus placed entirely under the con- 
 trol of man. 
 
 Now that the coal is in violent combustion, com- 
 bining rapidly with oxygen, notice that it burns en- 
 tirely without flame. We have here rapid chemical 
 combination, with all the phenomena of active burn- 
 ing, and yet no flame, simply because flame is al- 
 
FLAME AND LIGHT. 1 7/ 
 
 ways burning gas, and in a hard-coal fire it is not 
 gas, but a highly fixed solid, that is burning. Char- 
 coal and anthracite are almost the only combustibles 
 which burn in this way. Most others, even when 
 naturally solids, are converted into gases at a high 
 temperature, and therefore burn with flame ; but car- 
 bon in all its forms, when uncombined, persistently 
 retains its solid condition, even in the hottest fire. 
 
 Remark, also, that this combustion is attended 
 with a very bright white light, and compare it with 
 the more violent combustion of hydrogen, with 
 which most of the audience must be familiar. 
 Hydrogen burns with a flame because it is a gas ; 
 but this flame is almost invisible because gases, how- 
 ever intensely heated, do not emit a bright light. 
 The charcoal burns without flame because it is a 
 permanent solid ; but for this very reason it emits a 
 great amount of pure white light. So far, at least, 
 as ordinary experience extends, white light is emit- 
 ted only from ignited solid matter.^ Therefore 
 neither white light nor flame is a necessary concom- 
 itant even of the most rapid combustion, the first 
 depending solely on the solid, and the last on the 
 
 * I use the phrase white light because an ignited gas or vapor may 
 emit a colored light, and it has been found that the color is in each 
 case determined by the chemical composition of the ignited mass ; 
 but the light emitted from the gases or vapors of which the flames of 
 ordinary combustibles consist, is, at best, very feeble. The light of 
 such flames, as will soon appear, comes almost entirely from solid 
 particles of charcoal, and when these, from any cause, are not present, 
 the flames only yield a very faint, blue light. The appearance of 
 the whole flame is then the same as that which may always be seen 
 near the orifice of a bat-wing gas-burner. 
 8* 
 
178 INFUSIBILITY OF CARBON. 
 
 aeriform, condition of the burning substance. If, 
 as in the burning of a candle, both flame and white 
 light attend the process, it is because both solid and 
 aeriform matter are there burning; and when we 
 come to examine this phenomenon more closely, we 
 shall find that the result is produced by a most 
 delicate adaptation of properties. 
 
 Let me next call your attention to the importance 
 of the infusibility of charcoal in connection with its 
 use as fuel. However high the temperature at 
 which it burns, however intense the furnace heat, 
 charcoal never loses its solid condition, and on this 
 wholly depends its application for generating heat. 
 Were coal fusible, even at a very high temperature, it 
 would melt and run out from our grates and furnaces, 
 and the genial fire could not, as now, have been lo- 
 calized on the hearth. The enjoyment of the social 
 fireside is thus closely connected with a familiar 
 property of this wonderful element. 
 
 But our fire is slowly burning away, and already 
 more than one-half of the coal has been consumed. 
 What has become of it ? Do you point to the ashes ? 
 These are only the earthy impurities, which are 
 more or less mixed with the pure carbon, and con- 
 stitute but a small fraction of the whole mass of the 
 coal. The carbon itself has combined with the oxy- 
 gen of the air and formed a colorless and invisible 
 gas, which has escaped by the chimney, which, as I 
 have already stated in the lecture on Oxygen, is 
 called carbonic dioxide. Reflect now on the im- 
 portance of the circumstance, that this compound 
 of oxygen and carbon is aeriform, and consider what 
 
PRODUCT OF COMBUSTION. 1 79 
 
 a marked evidence of design and adaptation is to be 
 found in the very fact that the products of ordinary- 
 combustion are invisible gases, which ascend our 
 chimneys and are wafted away by the currents of 
 the atmosphere. As common experience is con- 
 fined to the burning of coal, wood, oil, and similar 
 combustibles, consisting mainly of carbon and hydro- 
 gen, men naturally associate with smoke the idea 
 of a gas, and are apt to think that the aeriform con- 
 dition is a necessary result of the nature of things. 
 But it is not so. This peculiar provision in the case 
 of carbon and hydrogen is an exception to the gen- 
 eral rule. The two combustible elements which are 
 most closely allied to carbon in all their properties 
 — boron and silicon — not only form solids by burn- 
 ing, but two of the most fixed solids known in nature, 
 one of which — silica — constitutes, as we have seen, at 
 least one-half of the rocky crust of our globe ; and 
 the same is true of almost all the other combustible 
 elements. A very interesting experiment in illustra- 
 tion of this fact may be made by burning a piece of 
 phosphorus under a dry glass receiver. The smoke 
 of phosphorus is solid, and it will fall in thick white 
 flakes, producing within the glass the appearance of 
 a miniature snow-storm. Picture to yourself the 
 desolation which would be produced were the order 
 of nature so far changed as to make the products 
 of burning coal like those of burning phosphorus. 
 Every furnace would become a volcano, and we 
 should soon be buried beneath the smoke of our 
 own fires. When, now, we consider that a special 
 provision has been made in the case of that sub- 
 
l8o THE PRODUCT HARMLESS. 
 
 stance whose combustion administers to our wants 
 by evolving light and heat, what evidence does it 
 open to us of the all-wise forethought of the Great 
 Original ! 
 
 But this is not all. Let me now call your atten- 
 tion to an additional fact in regard to the carbonic 
 dioxide which is escaping from our coal fire. The gas 
 is entirely devoid both of odor and of taste, and, 
 moreover, when in a sufficiently diluted condition it 
 can be breathed with impunity. Consider what an 
 amount of this product is daily formed, and you will 
 then be able to appreciate the importance of this cir- 
 cumstance. The amount of carbonic dioxide which 
 escapes from an average-sized iron blast-furnace in 
 the course of a single hour is equal to at least two 
 tons, and the amount which is generated even by 
 our coal fire is surprisingly large. Moreover, no less 
 than two hundred tons* of this gas are breathed 
 into the air by the population of this city in a single 
 day. If carbonic dioxide had been a pungent or 
 corrosive gas, coal could not have been used as fuel ; 
 for its combustion, like that of sulphur, would soon 
 have rendered the air irrespirable. But so entirely 
 destitute is it of any perceptible odor or taste, that, 
 although it has been evolved in these immense 
 quantities from every fire lighted by man since he 
 appeared on the globe, it so entirely escaped no- 
 tice that its existence w^as not even suspected 
 until it was discovered by Dr. Black about a century 
 ago. 
 
 * Calculated for 400,000 inhabitants. 
 
HEAT EVOLVED. l8l 
 
 There is still another remarkable phenomenon 
 attending a coal fire, which, although it cannot be 
 made evident to the senses, has been substantiated 
 again and again by the most accurate experiments. 
 The volume of carbonic dioxide gas formed by the 
 combustion is exactly equal to the volume of oxygen 
 ^ consumed. It is a consequence of this fact, that 
 the volume of the air is not in the slightest degree 
 increased by the vast quantity of carbonic dioxide 
 gas which is daily poured into it. The gas occu- 
 pies precisely the same space as the oxygen re- 
 moved during the combustion, and thus the equilib- 
 rium of the atmosphere is not disturbed. It is true 
 that we probably cannot see all the bearings of this 
 simple provision ; but we know enough to recognize 
 in it a most marked evidence of design. 
 
 The last fact in connection with the coal fire to 
 which I would direct your attention is the large 
 amount of heat which the combustion of coal lib- 
 erates, and on which its use as fuel very largely 
 depends. One pound of charcoal, in burning com- 
 pletely, generates sufficient heat to raise the tem- 
 perature of 80.8 pounds of water from the freezing 
 to the boiling point. Every pound of charcoal may, 
 therefore, be regarded as containing sufficient heat 
 to boil eighty pounds of ice-cold water. What a 
 vast amount of heat then lies buried in those inex- 
 haustible beds of mineral coal, in which our country 
 is so rich! And have we not another remarkable 
 evidence of Divine wisdom in the fact that carbon, 
 a substance which, on account of its infusibility and 
 other qualities, is so well adapted for fuel, has been 
 
1 82 TESTIMONY OF BURNING COALS. 
 
 made a great reservoir of heat, from which man can 
 draw an unlimited supply? When we remember 
 that this heat, through the expansion of steam, may 
 be converted into mechanical force, and that hence 
 these beds of coal are not only magazines of heat, 
 but stores of force, which have been accumulating 
 from the foundation of the globe for the use of civ- 
 ilized man, and when we reflect that it is this force 
 which is animating our commerce, weaving our cloth, 
 forging our iron, and impelling the printing-press, 
 how can we express our praise at the foresight of 
 that Providence which endowed coal with such 
 wonderful qualities, made it a vast repository of 
 heat and of force, and then spread it bountifully 
 over the globe? 
 
 We have discovered all these wonderful indica- 
 tions of design and adaptation in this simple ex- 
 periment, so familiar as to be almost trite, so fre- 
 quently repeated as to pass unnoticed, and they 
 are constantly speaking to us of the great Au- 
 thor of nature from the fireside of every home, 
 and from the furnace of every workshop in the 
 land. The followers of Zoroaster still worship, in 
 India, fire as divinity, and regard these burning 
 coals as sacred. Behind this superstition and idol- 
 atry there is concealed true wisdom, by which we 
 may well profit. Fire is neither divinity, nor yet 
 its emblem. It has no other reality than as a phe- 
 nomenon attending a chemical change ; but in the 
 qualities with which carbon has been endowed in 
 order to produce this phenomenon, in the delicate 
 adjustment of forces by which the destructive change 
 
SOFT COAL FIRE. 1 83 
 
 is confined within due limits, there are indications 
 of divinity which may well make us thoughtful, 
 and consecrate with additional sanctity the family 
 hearth; and if I have succeeded, however imper- 
 fectly, in making audible to your intellectual ear 
 this mute eloquence of burning coal, our time has 
 not been spent in vain. 
 
 I have thus far drawn all my illustrations from 
 the burning of charcoal and hard coal, simply be- 
 cause these familiar forms of fuel are nearly pure 
 carbon, and the phenomena attending their combus- 
 tion are comparatively simple. They burn, as we 
 have seen, without flame, for the reason that car- 
 bon does not volatilize, even at the highest temper- 
 atures. It is different, however, with soft coal, wood, 
 oil, wax, and all other combustible materials which 
 are used for generating light. These do not consist 
 wholly of carbon ; but this latter element is always 
 combined with hydrogen, and most of the combusti- 
 bles named contain also, in addition, a limited amount 
 of oxygen. When heated, they all evolve common 
 illuminating-gas, and for this reason burn with a 
 flame. In fact, the gas we are burning here to- 
 night was made from just such materials. If you 
 visit the gas-works of this city, you will see long 
 rows of iron retorts, firmly built into large brick fur- 
 naces. In these retorts the gas is made, and they 
 are connected by means of a complicated system of 
 tubes with all the numberless gas-burners of this 
 large city. Every few hours the retorts are charged 
 with soft coal, which soon becomes heated to a low 
 red heat. At this temperature it slowly gives off 
 
1 84 ILLUMINATING GAS. 
 
 gas, and it is the gas thus formed which is now 
 illuminating this hall. After three or four hours, the 
 gas has been all driven off, but there is still left in 
 the retorts the greater part of the carbon of the 
 coal, in a condition which is called coke. This is 
 then removed and used for feeding the furnaces, and 
 a new charge of soft coal is introduced in its place. 
 Coke is an excellent fuel, but, like charcoal, it burns 
 without flame. 
 
 The processes which, in the manufacture and use 
 of illuminating-gas, are spread over a whole city, are 
 united in every soft-coal fire. The gas which is 
 burning at this jet was generated in the retorts of 
 the gas-works, and brought here in iron tubes to be 
 burnt. In the grate the gas is made and burnt in 
 successive moments, but the process is identical in 
 both cases. When you throw a fresh supply of soft 
 coal on the grate, the first effect of the heat is to 
 generate illuminating-gas, which at once takes fire 
 and burns with a brilliant blaze. But after some 
 time the flame ceases, because all the volatile ele- 
 ments of the coal have been expelled, and the coke 
 which is left 'merely smoulders, like charcoal or an- 
 thracite. What is true of soft coal is also true of 
 wood and of all this class of combustibles. 
 
 Flame, as I have before stated, is in all cases burn- 
 ing gas. As we are generally familiar with it, flame 
 is a cloud of illuminating-gas combining on its exte- 
 rior surface with the oxygen of the air. In a gas lamp 
 the gas is supplied ready made at the jet. In an oil 
 lamp or a candle, the gas is manufactured as fast as 
 it burns. The use which we make of the flame, in 
 
SIMPLE GAS-FACTORY. 1 85 
 
 all these cases, is to generate light, and the qualities 
 of carbon have been most admirably adjusted to 
 produce that result. This is the point which I wish 
 next to illustrate, and we shall understand this beau- 
 tiful example of adaptation more readily by analyz- 
 ing the burning of some one of the light-generating 
 materials. I will, therefore, select a common wax 
 candle as my example, because it is familiar to 
 every one, and illustrates all the points I have in 
 view. 
 
 Nothing could be simpler than the candle itself. 
 It is a long cylinder of wax formed around a string 
 made of loose cotton threads, which we call the 
 wick. The wax, that familiar secretion of the honey- 
 bee, is composed, chemically, of carbon, hydrogen, 
 and a little oxygen ; the wick, as the microscope 
 would show us, is merely a collection of fine vege- 
 table tubes. Let us now light the candle. For that 
 purpose we apply the flame of a friction match to 
 the end of the wick, and mark the result. The heat 
 of the match melts the wax around the base of the 
 wick, and now the peculiar virtue of these vege- 
 table tubes come into play. All fine tubes have the 
 power of sucking up liquid, and the finer the tube, 
 the greater the height to which the liquid is thus 
 elevated. The tubes of the wick act in this way, 
 and the melted wax is at once drawn up to the 
 flame of the match. There it is volatilized by the 
 high temperature, and a cloud of red-hot combusti- 
 ble gas forms around the summit of the wick. Like 
 the rain-drop, or any other fluid body in a free state, 
 it assumes a spherical form, but being much lighter 
 
1 86 SIMPLE GAS-FACTORY. 
 
 than the air, this sphere of gas no sooner forms than 
 it begins to ascend, and, being very combustible, is 
 burnt up by the oxygen of the air with great rapid- 
 ity, so that before it has risen an inch from the wick 
 it is reduced to a point. Meanwhile, however, the 
 first sphere is followed by others, which in rapid 
 succession meet with the same fate, and at any 
 moment we have a large number of these little 
 spheres, one above the other, rapidly diminishing in 
 size from the lowest to the highest, which has then 
 become a mere point. Hence results the familiar 
 conical form of the flame. But our match is long 
 since burnt out, and what, you will ask, now volatil- 
 izes the wax ? Solely the heat evolved by the burn- 
 ing gas. This heat converts the wax into vapor as 
 fast as it creeps up the wick, and thus the flame being 
 constantly supplied with combustible gas, the can- 
 dle continues to burn until it is all consumed. The 
 candle-flame is, then, merely a cone of volatilized 
 wax, rapidly combining on its exterior surface with 
 the oxygen of the air, and as rapidly replenished from 
 below by the constant conversion of fresh wax into 
 vapor. In this process light and heat are evolved ; 
 but these are generated solely on the exterior sur- 
 face of the flame, where the burning takes place. 
 Within it is perfectly dark, as can be easily shown 
 by pressing down upon it a piece of window glass, 
 through which the interior may be seen. Let us 
 now study this chemical process more carefully, 
 as the whole illuminating power of the flame de- 
 pends on a very delicate play of aflinities. 
 
 The combustible gas formed from wax is com- 
 
LIGHT OF THE FLAME. 1 8/ 
 
 posed essentially of charcoal and hydrogen. The 
 light and combustible hydrogen has so great a ten- 
 dency to retain its aeriform condition, that, when 
 combined with carbon, it renders even this, the most 
 fixed of all the elements, aeriform ; but the moment 
 the bonds of chemical affinity are loosened, the car- 
 bon resumes its solid condition. Such a change 
 takes place in the flame, and it is the particles of 
 solid charcoal thus liberated that render it lumin- 
 ous. Of the two elements of the gas, hydrogen has 
 the greatest affinity for oxygen, and therefore burns 
 first, momentarily setting free the carbon, which is 
 sprinkled in a fine powder through the burning gas. 
 This is at once intensely heated, and each glov/ing 
 particle becomes a centre of radiation, throwing out 
 its luminous pulsations in every direction. The 
 sparks last, however, but an instant ; for the next 
 moment the charcoal is itself consumed by the fierce 
 oxygen, now aroused to full activity, and nothing 
 but a transparent gas rises from the flame. But 
 the same process continues ; other particles succeed, 
 which become ignited in their turn, and hence, al- 
 though the sparks are evanescent, the light is con- 
 tinuous. 
 
 Thus it appears that all our artificial light, the 
 light which we are enjoying this evening, depends 
 upon this provision, by which the particles of char- 
 coal linger for a moment in the flame before they 
 are burnt. Let me again repeat, white light is emit- 
 ted by ignited solid matter. The flame of pure hy- 
 drogen gives very little light, because there are in it 
 no solid particles, and were the affinity of oxygen 
 
LIGHT OF THE FLAME. 
 
 for carbon slightly greater than at present, the flame 
 of the candle would be as little luminous : then the 
 carbon would burn simultaneously with the hydro- 
 gen, and there would be no pulyerized charcoal in 
 the flame to radiate light. On the other hand, were 
 the affinity of oxygen for carbon a little less than at 
 present, the carbon particles would not burn in the 
 flame, but would escape from it in clouds of dense 
 soot. Our Heavenly Father has so carefully ad- 
 justed the relative affinity of oxygen for the two ele- 
 ments of these light-giving gases, that the hydrogen 
 should burn a small fractional part of a second be- 
 fore the carbon. During this brief interval of time, 
 imperceptible to our unaided senses, the solid parti- 
 cles of charcoal are set free, become ignited, and 
 give motion, perhaps, to a single wave of light ; but 
 the instant after, they too rush into combination with 
 the great fire-element, and not a particle is left to dim 
 the transparency of the air. The smallest variation in 
 either force would destroy the adjustment by which 
 this result is produced, and our lamps and candles 
 would cease to give their light. How delicate the 
 adjustment ! How beneficent the result ! How evi- 
 dent the design ! 
 
 To me the marks of God*s designing hand are 
 more conspicuous in that familiar candle-flame than 
 in the grand cycles of astronomy, or in the wonder- 
 ful mechanism of the human body. I return to it 
 again and again with renewed confidence, and al- 
 ways find fresh satisfaction and increasing faith. 
 There are many who believe, with Laplace, that this 
 glorious system of suns and planets, with all its 
 
MARKS OF DESIGN. 1 89 
 
 complex movements and adjustments, might be 
 evolved out of a nebulous chaos by the sole action 
 of the primary laws of motion ; and now, after the 
 great French mathematician has furnished a world 
 to begin with, a modern naturalist asks us to believe 
 that this hand of mine, with all its wonderful com- 
 bination of nerves, bones, and muscles, was devel- 
 oped out of the claw of an animalcule, or some such 
 thing, by what he calls ^^ the law of natural selec- 
 tion ; " and although these and similar theories may 
 be held consistently with a belief in a Divine Dis- 
 poser, yet it is too true that to many of their advo- 
 cates the order of nature signifies nothing higher 
 than self-existing matter, directed by inexorable 
 necessity. But no cosmogonist has been able to go 
 behind the chemical elements, and until human phi- 
 losophy can show how these forms of matter, with 
 all the marvellous adjustments among their prop- 
 erties, have been evolved out of the " star dust '' of 
 the original chaos, or out of nothing, and can adjust 
 by natural causes the delicate play of forces in that 
 most familiar of all phenomena, a candle-flame, it 
 will not be able to overthrow the evidence of design 
 afforded by this genial winter-evening light. The 
 fact that these would-be world-makers explain most 
 satisfactorily what men know least about, is, it 
 must be confessed, not in favor of their theories. 
 Yes, my friends, it is these most familiar evidences 
 of design which are the most impregnable against 
 the attacks of materialism. It is these household 
 altars that we find always burning to enlighten 
 our dull understanding, to disperse our gloomy 
 
IQO SMELTING OF ORES. 
 
 doubts, and to reveal to us the presence of our 
 God. 
 
 ( The delicacy with which the affinity of oxygen 
 for carbon has been adjusted appears still more 
 
 /wonderful when we consider another of the uses of 
 this force in nature. The useful metals, which may 
 be said to be the tools of civilized life, are seldom 
 found in nature in a pure state. They generally 
 occur combined with oxygen, and this compound, 
 which is called the ore of the metal, is found in 
 beds or veins of the rocks, where it has been depos- 
 ited through the agency of water. After the miner 
 has dug out the ore from the earth, and washed 
 it free from impurities, it is the business of the 
 smelter to melt out the pure metal. Now in this 
 ore the metal is combined with oxygen, and unless 
 the smelter could break this bond, the highest tem- 
 perature of his furnace would be unavailing. But 
 the merciful Parent of mankind, when he thus 
 locked up these his choicest gifts, gave to man a 
 key which would unlock the treasure-house, but left 
 him to find out. its use ; and as in the progress of 
 humanity the metals were required to advance 
 civilization and multiply the comforts of life, the 
 secret was discovered, and the treasures one by one 
 were brought to light. This needed key was char- 
 coal. The Creator has endowed carbon with a power 
 so strong, that it readily overcomes the force by 
 which the metals are united to oxygen, and by 
 simply heating the ore with charcoal the metal is 
 set free. Would that I could give you an idea of 
 the strength of the force which is required to pro- 
 
SMELTING OF ORES, n (/ 191 ^ 
 
 duce this result. The affinity of carbon for oxygen 
 is one of the most powerful forces known in nature, 
 so great as to be immeasurable by our ordinary 
 human standards, and yet it is this same force which 
 produces that delicate result, the light of a candle- 
 flame. With such wonderful skill does God wield 
 these mighty agents of his power. 
 
 Consider, finally, how this power of reducing the 
 metallic ores has been united in charcoal to those 
 other qualities which render it so valuable as fuel. 
 The smelter heats his furnace with the self-same 
 coals which reduce the ore. These coals remain 
 unchanged in contact with the ore until they have 
 done their work, and then are converted into a 
 colorless and harmless gas, which escapes by the 
 chimney and is wafted away by the air; while, on 
 the other hand, the melted metal, freed from its 
 long imprisonment, flows out below in glowing 
 streams, ready to be cast into thousands of useful 
 forms. 
 
 Review now, for a moment, the qualities of car- 
 bon, and notice how manifold and important are the 
 functions which this element has been appointed to 
 subserve. It has been made hard and brilliant, for 
 the glazier's diamond and the monarch's crown. It 
 has also been made soft and black, for the artist's 
 pencil and the printer's ink. It has been made 
 indestructible by atmospheric agents, and thus has 
 preserved for us the wisdom of past ages, and will 
 transmit our bequests of knowledge to those that are 
 to come. It has been made combustible, and at the 
 same time infusible, in order to localize our fires and 
 
192 SUMMARY. 
 
 confine them within their appointed bounds. It has 
 been made a great reservoir of heat, in order that it 
 might protect us from the winter's cold, and shed its 
 enlivening warmth around the family hearth. It has 
 been endow^ed with a strong affinity for oxygen, in 
 order that it might reduce the metallic ores ; but at 
 the same time this affinity has been so carefully ad- 
 justed that the carbon particles linger in the flame 
 for a moment before passing into invisible gas, and 
 thus become a source of light as well as of heat. 
 Lastly, the product of its combustion is a gas so 
 transparent that it does not even cloud the atmos- 
 phere, and so bland that it bathes the most delicate 
 organisms without harm. What an array of evi- 
 dence have we here ! But this, my friends, is only 
 the first stage of that grand circulation of carbon in 
 nature, which we proposed to ourselves as our sub- 
 ject this evening. The product of all these various 
 processes of combustion is carbonic dioxide, and let 
 us now follow this gas into the atmosphere, and ex- 
 amine some of its more familiar qualities. 
 
 Carbonic dioxide is so perfectly transparent and 
 so devoid of every active quality that its presence 
 cannot be recognized by any of our senses, and we 
 must therefore call in the aid of experiment to make 
 evident its existence. This is the reason why it re- 
 mained so long unknown, the method we now use 
 for detecting its presence having been first discov- 
 ered by Dr. Black only a little more than a century 
 ago. The method is very simple. Carbonic dioxide 
 has a great tendency to combine with lime, and the 
 
CARBONIC DIOXIDE. I93 
 
 result of this combination is the familiar white solid 
 called chalk. Now lime is, to a certain extent, solu- 
 ble in water, while chalk is insoluble ; and hence, if 
 lime-water is exposed to an atmosphere containing 
 carbonic dioxide, the formation of particles of chalk, 
 rendering the transparent solution turbid, will indi- 
 cate the presence of the gas. Such a result is actu- 
 ally obtained by exposing lime-water in a saucer for 
 a few days to the atmosphere, and any one can con- 
 vince himself by this simple experiment of the exist- 
 ence of carbonic dioxide in the medium around us, 
 as well as in the air which is exhaled from the lungs. 
 Indeed, the breath is so loaded with this product of 
 combustion that lime-water is rendered milky by 
 blowing into it for only a few minutes. The quan- 
 tity of carbonic dioxide in the atmosphere, however, 
 is relatively very small, not amounting to more than 
 a few ten-thousandths of its whole weight. It en- 
 ters to a far greater extent into the composition of 
 many rocks. All limestones have the same compo- 
 sition as chalk, and contain nearly one-half of their 
 weight of carbonic dioxide, rendered solid by the 
 force of chemical affinity. These rocks, indeed, are 
 the great reservoirs of this aeriform compound, and 
 when you consider how. widely the limestones are 
 distributed, underlying whole districts of country, 
 reaching down to unknown depths, and piled up into 
 vast mountain chains, you can form some apprecia- 
 tion of the extent to which carbonic dioxide gas was 
 used in laying the foundations of the globe. 
 
 When pure, carbonic dioxide gas will instantly ex- 
 tinguish flame, and is perfectly irrespirable, causing 
 g 
 
194 CARBONIC DIOXIDE. 
 
 the epiglottis to close spasmodically and producing 
 immediate death by asphyxia. When so far diluted 
 as to admit of being received into the lungs, it acts 
 like a narcotic poison, causing drowsiness and insen- 
 sibility, and this even when a candle will burn in the 
 gas. Carbonic dioxide is not, however, poisonous 
 in the strict sense of that term. On the contrary, 
 it is always present in the blood in large quantities, 
 and with it bathes all the tissues of the body. The 
 carbonic dioxide results, as we have seen, from that 
 slow combustion constantly going on in the blood, 
 by which the animal heat is maintained, and it is an 
 essential condition of life that this product should 
 be secreted from the body as fast as it is formed. 
 If the atmosphere contains more than a small per- 
 centage of the gas, the process of secretion is arrest- 
 ed, and fatal results necessarily ensue. 
 
 The density of carbonic dioxide is much greater 
 than that of either of the other constituents of the 
 atmosphere, the same volume weighing one-half as 
 much again as common air. Indeed, it is so heavy 
 that it .can be poured from one vessel to another 
 like water, and the immense volumes of carbonic 
 dioxide which are constantly flowing from our lungs 
 and furnaces would cover the whole surface of the 
 earth with their deadly vapor, were it not that the 
 Creator has provided, by those simple laws of diffu- 
 sion, which we studied in a former chapter, that this 
 noxious gas should be dispersed as fast as generated, 
 and so mixed with the great mass of the atmosphere 
 as to be rendered harmless by extreme dilution. 
 The unfortunate accidents which sometimes occur 
 
CARBONIC DIOXIDE. I95 
 
 to persons who descend incautiously into cellars or 
 wells, where the carbonic dioxide is generated more 
 rapidly than it can be dissipated, constantly remind 
 us that the existence of animal life on the globe 
 depends upon this beneficent provision. The large 
 kilns in which lime is burnt into quicklime are con- 
 stantly pouring out streams of carbonic dioxide gas, 
 and more than one poor, houseless wanderer, attracted 
 by the heat of the kiln, has laid down to rest in the 
 stream, and slept to wake no more. Were the force of 
 diffusion much less than it is, we should all be con- 
 stantly exposed to a similar fate ; and when we lie 
 dow^n at night, it is only this guardian angel which 
 prevents the deadly fumes of our own fires from 
 descending on our beds. 
 
 Carbonic dioxide is soluble in water, a given vol- 
 ume of this liquid being capable of absorbing its 
 own volume of the gas, irrespective of the tempera- 
 ture or pressure. We should therefore expect to 
 find carbonic dioxide in solution in all water ex- 
 posed to the air, and in fact a cubic foot of river, 
 lake, or ocean water generally contains a very mucJiT 
 greater amount of this gas than an eqiial volume of- 
 the atmosphere. Water, when holding carbonic di-? 
 oxide in solution, has its solvent power very greatly 
 increased. It then dissolves, in large quantities, all 
 the varieties of limestone, and even granite rocks 
 cannot wholly resist its action ; but these solutions, 
 when exposed to the air, gradually lose the carbonic 
 dioxide, and with it their solvent power, incrusting 
 with calcareous matter the moss, the twigs, or the 
 walls of caverns on which the liquid may chance to 
 
196 CARBONIC DIOXIDE. 
 
 rest. It is the solvent power of such water, acting 
 slowly through ages of time, that has hollowed out 
 that immense cavern in the limestone strata of Ken- 
 tucky, and it is from the solution thus made that 
 those stalactitic ornaments have been formed which 
 add so much to its beauty and interest. It is also 
 this same agency which in other places has depos- 
 ited beds of calcareous tufa over great areas, and ce- 
 mented together loose sands into firm rocks ; and, 
 finally, it is from the lime dissolved in the water of 
 the ocean, that the Crustacea form their shells and 
 the coral polyps build their reefs.* 
 
 The origin of carbonic dioxide is the same in wa- 
 ter as in air. In the water we have not, of course, 
 active combustion ; but this, as has been shown, 
 is an insignificant source of carbonic dioxide when 
 compared with the never-ceasing functions of res- 
 piration and decay, and these are as active in the 
 rivers, the lakes, and the oceans as in the atmos- 
 phere. Moreover, the purpose which the carbonic 
 dioxide subserves is the same in both cases, and 
 this demands our attentive study. 
 
 I have already intimated that carbonic dioxide is 
 one of the few articles of which the food of plants 
 consists. Let us trace, for a moment, the history of 
 the plant. The seed containing the germ is placed 
 in the soil. The genial warmth of the sun calls it 
 into activity, and it shoots forth its small leaflets 
 
 * The whole peninsula of Florida has been in great measure built 
 up by these little animals with the lime rock which the waters of the 
 Mississippi pour into the Gulf, and which has been dissolved from 
 the lime deposits of our Western States. 
 
FOOD OF PLANTS. I97 
 
 into the air. For a short time the small stock of 
 starch and similar nourishment stored in the seed by 
 a wise Providence serves for its support ; but this is 
 soon exhausted, and for the future the plant must 
 depend for its food upon the soil and upon the 
 air. The articles which compose its diet are exceed- 
 ingly simple. They are water, carbonic dioxide, and 
 ammonia, substances always present in the atmos- 
 phere and in every fertile soil. As soon as the 
 young plant has expanded its green leaves it ab- 
 sorbs these substances, partly through its root- 
 lets from the soil, and partly through its leaves 
 from the air. The leaf, a tissue of minute organic 
 cells, is the laboratory in which, from these few 
 compounds, are elaborated the different organs of 
 the plant. The sun's rays, acting upon the green 
 parts of the leaf, give them the power of absorb- 
 ing water, carbonic dioxide, and ammonia, and of 
 constructing from the materials thus obtained the 
 woody fibre, starch, sugar, and other compounds 
 of which the plant consists. We have analyzed the 
 woody fibre, and we know that it is composed of 
 carbon and water. Twenty-seven ounces of wood 
 contain twelve ounces of carbon and fifteen ounces 
 of water. Moreover, the amount of carbon re- 
 quired to make twenty-seven ounces of wood is 
 contained in forty-four ounces of carbonic dioxide. 
 If, then, we add together forty-four ounces of car- 
 bonic dioxide and fifteen ounces of water, and 
 subtract from this sum thirty-two ounces of oxy- 
 gen, we shall have just the composition of wood. 
 This is what the sun's light accomplishes in the 
 
198 FOOD OF PLANTS. 
 
 leaves of the plant. It decomposes the carbonic 
 dioxide, and unites its carbon to the elements of 
 water to form the wood. 
 
 What I have stated to be true of wood is equally 
 true of starch, gum, sugar, and most of the products 
 of vegetable life. All these, with a few exceptions, 
 which I shall notice in the next lecture, are pre- 
 pared by the plant from carbonic dioxide and water, 
 under the influence of the sun*s light. Why it is 
 that starch is deposited in the cells of the potato, 
 sugar in those of the sugar-cane, and gum and woody 
 fibre, more or less, in all plants, we do not know. 
 These are the mysteries of organic life which no 
 science has been able to solve. This much, however, 
 is certain. The acorn, buried in the ground, grows 
 into the noble oak. Of that wide-spreading tree, at 
 least nine-tenths consist of carbon and water. The 
 water is absorbed, as such, directly from the atmos- 
 phere ; the carbon was recovered from the carbonic 
 dioxide decomposed by the sun's rays. Here is the 
 wonderful fact. The gentle influences of the sun- 
 beam have the power of reversing the process of 
 combustion, of overcoming the intense affinity of the 
 fire-element, tearing it apart from the carbon, and 
 restoring it to the air. How great this power is, I 
 have already endeavored to illustrate. I have stated 
 that the affinity of oxygen for carbon is one of the 
 strongest affinities known to nature, immeasurable 
 by any human standard. In order to decompose 
 carbonic dioxide in our laboratories, we are obliged 
 to resort to the most powerful chemical agents, and 
 to conduct the process in vessels composed of the 
 
BURNING REVERSED. 1 99 
 
 most resisting materials, under all the violent mani- 
 festations of light and heat, and we then succeed in 
 liberating the carbon only by shutting up the oxy- 
 gen in a still stronger prison ; but under the quiet 
 influences of the sunbeam, and in that most delicate 
 of all structures, a vegetable cell, the chains which 
 unite together the two elements fall off, and while 
 the solid carbon is retained to build up the organic 
 structure, the oxygen is allowed to return to its 
 home in the atmosphere. There is not in the whole 
 range of chemistry a process more wonderful than 
 this. We return to it again and again, with ever- 
 increasing wonder and admiration, amazed at the 
 apparent inefficiency of the means, and the stupen- 
 dous magnitude of the result. When standing be- 
 fore a grand conflagration, witnessing the display of 
 mighty energies there in action, and seeing the ele- 
 ments rushing into combination with a force which 
 no human agency can withstand, does it seem as if 
 any power could undo that work of destruction, and 
 rebuild those beams and rafters which are disap- 
 pearing in the flames ? Yet in a few years they will 
 be rebuilt. This mighty force will be overcome ; 
 not, however, as we might expect, amidst the con- 
 vulsion of nature, or the clash of the elements, but 
 silently, in a delicate leaf waving in the sunshine. 
 And this is not all. Those luminous waves which 
 beat upon the green surface of the leaf are there 
 arrested, and their moving power so completely 
 absorbed, that the reflected rays will not even affect 
 the exquisitely sensitive plate of the photographer. 
 But the power of the light has not been lost, and 
 
200 ORIGIN OF COAL. 
 
 when the wood is burnt and the carbon converted 
 back into carbonic dioxide, this power reappears 
 undiminished in the heat which radiates from the 
 burning embers. The heat, therefore, which the 
 wood contains, and which it gives forth on burning, 
 comes from the sun. What a beautiful provision of 
 Providence have we here ! During the summer, 
 when the sun is warming us with his genial rays, he 
 is also laying up in the growing wood vast stores of 
 heat, with which to warm us at the winter evening 
 fireside, when his rays have been withdrawn. 
 
 But you will tell me, it is not wood, it is coal 
 which is burning in the grate, and you will lead me, 
 perhaps, to the mouth of some black coal-pit, and 
 ask if those dismal regions below ever saw the sun. 
 Certainly! and it is one of the most remarkable 
 revelations of modern science, that the stone-like 
 coal was once alive. Coal is the remains of an 
 ancient vegetation, which flourished on the earth 
 ages before man first walked in Eden. The process 
 by which it has been formed and buried in the earth 
 is well known. You can see it now forming in many 
 tropical swamps. There you will find a vast mass 
 of vegetable matter, the result of a rank vegeta- 
 tion, gradually decaying under water. The land is 
 slowly sinking, and as this bed of peat sinks with 
 it, it becomes covered with mud and sand, which 
 numerous streams are constantly washing into the 
 swamp. Thisgoes on year after year, century after 
 century, age after age, until the bed is buried hun- 
 dreds of feet beneath the surface. In the meantime 
 the vegetable tissues undergo a sort of internal com- 
 
ORIGIN OF COAL. 201 
 
 bustion, similar to that which takes place in a char- 
 coal mound. Wood consists, you will remember, of 
 carbon and the elements of water. The oxygen 
 which it contains reacts on the carbon and hydro- 
 gen. Carbonic dioxide and water are formed, which 
 escape, while the rest of the hydrogen and carbon 
 unite together to form the coal. The reaction is a 
 true process of combustion, and the heat thus 
 evolved aids the chemical change, and gives to the 
 coal its baked appearance. This change it requires 
 long ages to complete. Millions and millions of 
 times has the earth repeated its annual revolution 
 around the sun, and the whole external appearance 
 of the globe has changed since those mighty forests 
 grew, which have been petrified in the coal. But 
 though such long intervals have elapsed, their his- 
 tory has not been lost. It has been written on the 
 rocks, the mighty monuments of past ages. The 
 geologists have read it, and we know with as much 
 certainty the form of the leaves and the structure of 
 the stems of those ancient trees, as we do those of 
 the oak or the chestnut. We know, also, that every 
 atom of coal which now lies buried hundreds of feet 
 beneath the surface was once a part of the atmos- 
 phere, and that the heat which it evolves by burn- 
 ing was received from the sun, when the carbonic 
 dioxide was decomposed by the light in the leaves of 
 the ancient trees. Consider for a moment of what 
 immense value to man are those beds of coal. 
 Without them modern civilization would have been 
 impossible. Remember that since the dawn of crea- 
 tion the sun has been employed in accumulating 
 
 9* 
 
202 PREPARATION FOR MAN. 
 
 these vast stores of force, and thus preparing the 
 globe for civilized man. We may admire the genius 
 of a Papin and a Watt, who have told us how to use 
 this force, and who have thus covered the ocean 
 with steamships and the land with railways; but 
 let us not forget that infinitely greater wisdom which 
 saw the end from the beginning, and before the 
 mountains were brought forth, or ever the continents 
 were formed, laid up the beds of coal in the early 
 strata, and preserved them through the long ages of 
 geological time until the earth had become fitted to 
 be the abode of man. 
 
 I have now glanced at some of the distinctive 
 features of the great circulation of carbon in nature, 
 and have endeavored to show that the sun's rays 
 are the prime moving power of the whole. I trust 
 that you have been impressed with the grandeur of 
 its cycles, the delicacy of its adjustments, and the 
 mighty power of that mysterious influence by which 
 it is sustained ; but above all, that I have succeeded 
 in making clear to your intellectual vision those 
 marks of wisdom and of power which have been so 
 visibly stamped upon this Divine economy. 
 
CHAPTER VII. 
 
 TESTIMONY OF NITROGEN. 
 
 In order to complete my very imperfect sketch of 
 the wonderful adaptations which the various qualities 
 and functions of our atmosphere present, I wish in 
 my lecture this evening to examine with you the 
 properties of nitrogen gas. This aeriform substance 
 is the chief constituent of the air, making up no less 
 than four-fifths of its entire mass, and, although so 
 seemingly inert, discharges functions no less impor- 
 tant than those of oxygen gas to the well-being of 
 man. Nitrogen is not, however, like oxygen, an ele- 
 ment widely distributed in nature, and entering as a 
 chief constituent into the composition of the globe. 
 The atmosphere is the only great reservoir of nitro- 
 gen, and to this and to the bodies of organized beings 
 its presence is almost exclusively confined. It seems 
 to be the essential element of all the higher forms of 
 corporeal vitality, and it is frequently called the zoo- 
 gen, or life-generator. By some mysterious process it 
 is constantly being withdrawn from the atmosphere, 
 and entering into the composition of the numberless 
 living forms which clothe the earth with verdure and 
 crowd it with animal life ; but these forms soon pass 
 
 203 
 
204 LIMITED DIFFUSION. 
 
 away, and by the inevitable process of decay the ni- 
 trogen is restored to the great reservoir from which 
 it was originally withdrawn. Science has not, as yet, 
 been able to follow all the steps of this remarkable 
 process ; but, nevertheless, enough is known to show 
 that the properties of nitrogen have been most ad- 
 mirably adapted to the numerous important ends 
 which it has been, appointed to subserve. 
 
 Nitrogen is, then, peculiarly the element of the 
 atmosphere. It not only constitutes the greater 
 part of the aerial ocean, but it exists there in a per- 
 fectly free and uncombined condition, and — with 
 the self-limiting exception just noticed — is found 
 nowhere else. We should naturally expect to find 
 in nitrogen gas, occupying so important a place as it 
 does in the scheme of creation, a substance full of 
 the highest interest. Yet nothing could be less invit- 
 ing than its external properties. A permanent gas, 
 even at the lowest temperatures, without color or 
 odor, it is entirely devoid of every active property. 
 It will extinguish a candle immersed in it, and will 
 not sustain animal life : but these are merely negative 
 qualities ; for animals cannot live in an atmosphere 
 of nitrogen, solely because it does not contain oxy- 
 gen, and it will not support combustion because it is 
 not endowed with active affinities. Moreover, in all 
 other outward aspects nitrogen is equally inert. It 
 exerts.no action whatever upon the most delicate 
 chemical compounds, and, with a few unimportant 
 exceptions, will not enter into direct combination 
 with any of the chemical elements. Consider also 
 the nitrogen as it exists in the atmosphere. Al- 
 
SINGULAR INERTNESS. 205 
 
 though in immediate contact with the most violent 
 of the elements, and exposed to its action when in its 
 fiercest state, under the varying influences of light, 
 heat, and electricity, yet no combination between 
 the two results, except to a very limited extent, 
 and under pecuHarly oblique conditions. Through 
 an ordinary iron blast-furnace there pass, in the 
 course of a single day, many tons of this mixture 
 of nitrogen and oxygen called air. The oxygen, as 
 we know, causes the most violent chemical action; 
 but although the nitrogen is brought into contact 
 with the same intensely heated coal and iron, no 
 combination, at least of any importance, ensues. 
 
 Shall we then conclude that nitrogen is entire- 
 ly unendowed with chemical affections, — that it is 
 capable of forming no compounds, and of produc- 
 ing no powerful effects, — that it is, in fine, a mere 
 dead weight in the atmosphere, placed there, for 
 the want of something better, to fill up the void 
 and to give the required density, as a ship is fre- 
 quently loaded with ballast when there is a lack of 
 freight? Such is the conclusion to which the ap- 
 pearances would naturally lead, and such is the con- 
 clusion at which the chemists arrived in the early 
 stages of their inquiry. Yet no inference could be 
 more at variance with actual facts; for so far is it 
 from true that nitrogen is the uninteresting sub- 
 stance which these negative qualities would seem 
 to indicate, that there are but few elements which 
 form a larger number of compounds, or which are 
 endowed with more varied powers when the neces- 
 sary conditions of combination are fulfilled. Nitro- 
 
206 BALLAST OF THE ATMOSPHERE. 
 
 gen can be made to unite with the other elements 
 only by indirect and circuitous processes. It is one 
 of its most distinctive qualities to avoid direct com- 
 bination ; but when the necessary conditions are 
 present, it surprises us by the readiness with which 
 it combines, and by the great variety and remark- 
 able character of the resulting compounds. When 
 we should least expect it, we find, not single com- 
 pounds, but whole classes, springing into existence, 
 which, while they often defy our investigations by 
 their Protean and 'complex character, yet in other 
 cases excite our admiration by the simplicity of 
 their constitution and by the beauty of the plan 
 according to which they have all been fashioned. 
 The points, then, which especially characterize ni- 
 trogen, and in which the evidences of design in its 
 constitution are to be traced, are, first, its unex- 
 ampled inertness when in a free condition ; sec- 
 ondly, the variety and remarkable nature of its com- 
 pounds ; thirdly, the peculiarly oblique processes by 
 which all these compounds are formed ; and, lastly, 
 their very great instability. 
 
 Nitrogen may be very appropriately termed the 
 ballast of the atmosphere, and this is undoubtedly 
 the most obvious of its functions. Air, you will re- 
 member, is not, in any proper sense of the term, a 
 distinct substance. It is a mixture of several sub- 
 stances, or rather there coexist around the globe at 
 least three different atmospheres — one of nitrogen, 
 one of oxygen, one of aqueous vapor, and perhaps 
 we should add, as a fourth, one of carbonic dioxide 
 — each with its own peculiar characteristics, and so 
 
BALLAST OF THE ATMOSPHER^^. "tlC^j 
 
 entirely distinct that it would ret^in^^^its essential 
 properties were the rest removed." -^.Agai<y when/' >, 
 studying in our fifth lecture the general feature^' pf 
 the great aqueous circulation on the earth, we dtsi / 
 covered that the whole plan turns on the fact that " I. 
 the atmosphere of aqueous vapor is mixed with a 
 large mass of other aeriform matter, which moderates 
 all atmospheric changes and mitigates the violence 
 of their effects. It also appeared in the third lecture 
 that the atmosphere of oxygen had been subjected 
 to a similar restraint, and that the aroused energies 
 of this terrible destroyer had been most carefully 
 tempered by great dilution. As the atmosphere is 
 constituted, the oxygen cannot reach the burning 
 combustible without carrying with it the whole mass 
 of the surrounding air ; but if this mass of aeriform 
 matter were not present, the devouring element 
 would rush upon its prey with a fury which nothing 
 could withstand, and iron^ would burn as readily 
 as straw. Moreover, in several other connections 
 we have shown that it is an essential condition in 
 the scheme of terrestrial nature that the air should 
 have its actual density. See now how beautifully all 
 the conditions are fulfilled in the atmosphere. The 
 proportion of oxygen has been most carefully ad- 
 justed to the necessities of animal life, and made so 
 small that the violence of the fire-element may be 
 restrained within due limits. The amounts of aque- 
 ous vapor and of carbonic dioxide have in like man- 
 ner each been accurately adjusted to the purposes 
 
 * An iron watch-spring burns with the greatest readiness in a jar 
 of pure oxygen gas. 
 
208 SPECIAL RELATIONS. 
 
 which they were appointed to subserve, and then, in 
 order to make up the required density, a large mass 
 of a perfectly inert gas has been added. Thus in the 
 very inertness of nitrogen we find the most obvious 
 evidence of adaptation. Its negative qualities are 
 precisely those required in a substance which is 
 designed to act as so much dead material, adding to 
 the density of the atmosphere without interfering 
 with the functions of its active agents. 
 
 Consider, also, how very greatly this evidence of 
 design is enhanced by the fact that nitrogen is found 
 only in the atmosphere and in the bodies of organ- 
 ized beings, into which it has been temporarily with- 
 drawn. It is not, like oxygen, carbonic acid, or 
 water, a main constituent of the globe, and cannot 
 therefore be regarded, as the fatalists would have us 
 believe, as so much material left over after the solid 
 globe had been condensed by the molecular forces 
 from a chaotic nebula. Nitrogen is not only exactly 
 adapted to the functions it subserves in the atmos- 
 phere, but, moreover, these are its only uses, and I 
 cannot see how it is possible to resist the conclusion 
 that it was especially designed for the place it fills. 
 That you may appreciate the strength of this evi- 
 dence, let me illustrate the subject by an example 
 from common life, which will be more to our pur- 
 pose than a philosophical analysis of the argument 
 itself. 
 
 It does not follow that the square granite blocks 
 which form the greater part of the front of yonder 
 magnificent warehouse, however well adjusted they 
 may be, were actually cut with reference to this 
 
STRENGTH OF THE EVIDENCE. 209 
 
 building, although the strong presumption is that 
 they were. Nor does it follow that those highly- 
 ornamented window-caps and that elaborate cornice 
 were originally designed for this particular edifice, 
 although the presumption that such was the case is 
 still stronger than before. Nay, more, it is not even 
 absolutely certain that those skilfully carved orna- 
 ments which adorn the front, and are built into the 
 walls, were originally intended to be placed where 
 they are, although to doubt this conclusion would 
 be the extreme of incredulity. I admit, it is barely 
 possible that they were originally made for another 
 building, rejected, perhaps, for some defect, and 
 afterwards put up here. But I will show you where 
 there is an evidence of design in the building-mate- 
 rial of this warehouse which you will be forced to 
 accept. It is not conspicuous, and might be over- 
 looked. Just here at the corner of the building 
 there is a very peculiarly shaped block of stone. 
 You never saw one like it before. This extraordi- 
 nary shape was required by the peculiar form of the 
 building lot and the position of the walls on the ad- 
 joining estate. The sides of the lot are not perpen- 
 dicular to the front, and the block has been cut to 
 the precise angle of the bevel, and at the same time 
 exactly fits the adjacent walls. The conclusion that 
 this block was designed for that place is irresistible. 
 No sane mind would doubt it for a moment. I do 
 not say there is not one chance in many millions, 
 estimated on the doctrine of probabilities, that a 
 block of this exact size and shape might have been 
 found among the refuse stock of the stone-cutter's 
 
2IO STRENGTH OF THE EVIDENCE. . 
 
 yards ; but I do say, that, in the absence of absolute 
 proof to the contrary, the certainty that this granite 
 block was wrought with reference to the place it fills, 
 and that the exact correspondence of its dimension 
 and angles was the result of measurement, is as great 
 as it is possible to attain by any process of reasoning 
 short of a mathematical demonstration; moreover, 
 it is as great as can be obtained in physical science, 
 or in any department of human knowledge one step 
 removed from the facts of consciousness or of obser- 
 vation. 
 
 The evidence that nitrogen was designed for the 
 place which it fills in the atmosphere is vastly 
 stronger than this. The force of the argument in 
 the illustration just cited evidently increases very 
 rapidly the more singular the shape of the granite 
 block, and the more accurately its form has been 
 adjusted to the place it fills. Now nitrogen is as 
 unique among the chemical elements as water is 
 among the compounds. Its external properties are 
 so entirely different from those even of the class of 
 elements to which it belongs, that chemists can 
 hardly believe that it is a simple substance, and for 
 the last fifty years have been vainly attempting to 
 decompose it ; but it has resisted all their efforts, 
 and the more intimately they have become ac- 
 quainted with its properties, the more singular and 
 exceptional it has appeared. At the same time, 
 while presenting these remarkable anomalies, nitro- 
 gen has been fitted to the unique place which it fills 
 in the scheme of creation, with a nicety and pre- 
 cision which it is as much beyond our powers of 
 
STRENGTH OF THE EVIDENCE. 211 
 
 thought to conceive, as it is beyond my feeble lan- 
 guage to describe. It is not only that one or two of 
 the corners of this block of nature's edifice have been 
 bevelled to an exact angle, but it has been adjusted 
 at every point to the ten thousand conditions of 
 that comple:?^, structure I have been imperfectly 
 describing during this course of lectures, with a 
 skill immeasurably beyond all human art, and with 
 an intelligence which " looketh to the ends of the 
 earth and seeth under the whole heaven." If this 
 be so, — and you will find that my guarded expres- 
 sions fall far short of the truth, — why not use in 
 these matters of faith the same common sense 
 which w^e apply with so much success in common 
 life, and which in our daily intercourse it would 
 be nothing short of madness to disregard? We 
 do not hesitate to trust the skill and honesty of 
 a fellow-man, whom we not only have never seen, 
 but even as to whose character our sole evidence is 
 the most indefinite testimony. Why, then, not ac- 
 cept the precious and comforting truths of religion, 
 and repose equal faith in the providence of our 
 Heavenly Father, on evidence which, we must ad- 
 mit, is ten thousand-fold stronger, and when we 
 have everything to gain, and nothing to lose ? Is it 
 said. There is still room for doubt ? Of course there 
 is. God be thanked ! there is no relation in life in 
 which there is not doubt. Were there no doubt, 
 there would be no faith, no trust, no confidence, no 
 love ; the heart would be absorbed in the intellect, 
 religion would become an axiom, and morality a 
 formula of mathematics. Use but one-half of the 
 
212 STRENGTH OF THE EVIDENCE. 
 
 observation, one-half of the inteUigence, which are 
 never at fault in the business of life, and these marks 
 of the Creator's wisdom and providence which lie all 
 around us will become as evident as the sun. Act 
 on this evidence, and the door of grace will be 
 opened, new light will stream into th^ soul, and all 
 nature will be seen radiant with a Father's love. 
 
 All this striking evidence of design and adapta- 
 tion we have discovered in the most obvious of the 
 attributes of nitrogen, — in those merely negative 
 qualities in virtue of which it increases the density 
 of the atmosphere without interfering with the func- 
 tions of its active constituents. It would not, how- 
 ever, be in accordance with that economy of resources 
 which we find everywhere in nature, that the uses 
 of nitrogen should be limited to this single object ; 
 and after what we have already seen to be true in the 
 case of oxygen, we shall not be surprised to find 
 this singular element suddenly changing its char- 
 acter and appearing in a new condition. The sec- 
 ond point, as you will rem.ember, which I am to 
 illustrate in regard to nitrogen, is the variety and 
 remarkable nature of its compounds, as well as 
 the singularly oblique processes by which they are 
 formed ; and, having examined the marks of design 
 it bears in its first manifestations, let us now study 
 the no less impressive evidence presented by the 
 second. It would be entirely out of place in a 
 popular work like the present, to describe in de- 
 tail any of the countless nitrogenized compounds 
 which are known to chemistry, and it would re- 
 quire a separate volume merely to illustrate the 
 
COMPOUNDS OF NITROGEN. 21 3 
 
 characteristic features of the great classes into which 
 they may be subdivided. I shall be able only to 
 glance at a few general facts which illustrate the 
 point now under discussion, and also the part which 
 nitrogen plays in organic nature. 
 
 Although nitrogen presents such an indifferent 
 exterior towards the oxygen of the atmosphere, it 
 can, nevertheless, be made to combine with it by 
 resorting to certain oblique processes, and there 
 may thus result no less than five different com- 
 pounds. Every one is familiar with that highly 
 corrosive liquid called nitric acid, and this is formed 
 by the union with water of one of the compounds 
 in question. Under certain conditions this acid re- 
 sults from the union of the oxygen, nitrogen, and 
 aqueous vapor which are mixed together in the air. 
 Indeed, the only essential difference between the 
 bland atmospheric air and this highly active chem- 
 ical agent consists in the fact that while in air the 
 elements are only mixed together, in the acid they 
 are chemically combined. Were nitrogen to be 
 suddenly endowed with the active affinities which 
 from its position among the chemical elements we 
 might naturally expect it to possess, then nitric 
 acid would be formed in the atmosphere in large 
 quantities, and it is only the unexampled inertness 
 of nitrogen which prevents a result which would be 
 fatal to all organic life. But although so corrosive 
 when pure, nitric acid when immensely diluted is 
 one of the few materials which nourish and sustain 
 the plant, and therefore provision has been made 
 that it should be formed in the atmosphere, but 
 
214 HOW PRODUCED. 
 
 only under very restricted conditions, and to a very 
 limited extent. When electrical sparks are passed 
 through a confined quantity of air, in the presence 
 of some alkaline substance, such as potash, soda, or 
 lime, a very partial combination takes place between 
 the two elements, and an infinitesimal quantity of 
 nitric acid is formed. So, also, when organic matter 
 decays in the presence of these same alkalies, a sim- 
 ilar combination, although to a very slight extent, 
 results. Nitric acid is endowed with such violent 
 affinities that it doiSs not remain in a free state. It 
 at once enters into combination with the alkalies, 
 forming a class of salts, of which saltpetre is the 
 best known example, and from which the com- 
 mon nitric acid is extracted for the uses of the arts. 
 Nitrogen, you will notice, acts here very much like 
 a self-willed child. All the powers of nature cannot 
 compel it to combine directly with oxygen ; but if 
 you offer to it these alkalies as an inducement, and 
 make your approaches sufficiently indirect, you can 
 coax it to combine, and nitric acid is then formed. 
 We do not understand how the peculiar conditions 
 just mentioned conspire to produce the result ; but 
 the whole phenomenon seems to be mysteriously 
 connected with ozonized oxygen, and is undoubt- 
 edly another phase of that obscure subject, allotrop- 
 ism, to which we alluded in a previous lecture. See 
 now how beautifully this attribute of nitrogen has 
 been adapted to the conditions of vegetable life, 
 and made the means by which the plant is furnished 
 with one of the articles of its food. Every discharge 
 of lightning is accompanied by a partial combina- 
 
COMPOUNDS OF NITROGEN 21 5 
 
 tion of the elements of the atmosphere, and the 
 nitric acid which is thus formed and washed down 
 by the rain-water serves to fertihze the soil and 
 bring the growing corn to maturity. So in like man- 
 ner, when life is extinct, and the organized forms are 
 resolved into their original elements, the very pro- 
 cess of decay causes a similar combination, and thus 
 sweetens the flowers which spring from the grave. 
 
 But not only does nitrogen combine with oxygen. 
 It unites also with hydrogen, that element which is 
 the very antithesis of oxygen, and forms a most 
 remarkable compound called ammonia. This sub- 
 stance is the very reverse of mtrrc^acid in all its 
 chemical relations, but, like nitric acid, it is a highly 
 active and caustic agent. I need not dwell upon 
 this fact ; for the common smelling-bottle has made 
 every one familiar with this pungent substance. 
 Nitrogen manifests the same indifference towards 
 hydrogen that it does towards oxygen, and the two 
 elements can be made to unite only by indirect pro- 
 cesses, which are not well understood. The most 
 important of these is the process of decay. This 
 destructive change in all the higher forms of organ- 
 ized beings is attended with the formation of am- 
 monia, and the same nitrogenized compound is a 
 uniform result of the normal functions of animal life. 
 You will not, therefore, be surprised to learn that 
 traces of ammonia, as of nitric acid, are found in the 
 atmosphere and in all rain-water. Indeed, it is gen- 
 erally supposed that the two are in combination, 
 forming a salt called nitrate of ammonia, but the 
 amount present is, at best, very small. 
 
2l6 HOW PRODUCED. 
 
 Ammonia is thought by many to be a more im- 
 portant article of vegetable diet than nitric acid ; 
 but our knowledge of agricultural chemistry is very 
 imperfect, and chemists are not agreed on many of 
 the most fundamental points."^ Still, as I have 
 before stated, nitrogen is an essential element of all 
 the higher forms of corporeal vitality, and compounds 
 like those we have been considering are the ap- 
 pointed channels by which it is introduced into the 
 organization of the plant. Had these compounds 
 been allowed to form to any extent in the atmos- 
 phere, they would soon have rendered the globe 
 uninhabitable. It was therefore essential that nitro- 
 
 * Since this book was written, it has been stated by several investi- 
 gators that the chief nitrogen compound in the atmosphere and in 
 rain-water is nitrite of anwionia^ which differs from the nitrate of 
 ain?nonia mentioned above only in containing a smaller proportion of 
 oxygen. Whether the last is also normally present does not yet 
 appear, and to what extent the one or the other may be concerned in 
 the processes of vegetable growth, has not been determined. From 
 one point of view, nitrite of ammonia may be regarded as composed 
 of nitrogen gas and water, and some chemists believe that it is formed 
 by the direct union of these two substances, and that this union is 
 favored by the processes of evaporation, combustion, and decay 
 which are constantly going on in the atmosphere. This theory is 
 certainly supported by many facts, and those who hold it generally 
 believe that nitrite of ammonia is the chief, if not the sole, source 
 from which the plants derive their supply of nitrogen, while others 
 attach only a secondary importance to the recent experiments. If the 
 theory is correct, the foraiation of nitrite of ammonia — the presence 
 of which in surface-water, and in the soil, under certain conditions, is 
 beyond doubt — would be the natural result of the subsequent union 
 of nitrite of ammonia (formed as just described) with the oxygen of 
 the air ; but, as intimated above, the whole subject is still very 
 obscure, and from any experiments yet made we should not be justi- 
 fied in drawing definite conclusions. 
 
PECULIAR INSTABILITY. 21/ 
 
 gen should be endowed with that unexampled inert- 
 ness which it manifests in its gaseous state. But 
 had not at the same time a power of combination, 
 under certain restricted conditions, been granted, 
 this chemical element would not only have been an 
 isolated phenomenon in nature, an exception to its 
 general laws, but its usefulness would have been 
 restricted to the least remarkable of its functions. 
 Unlike the results of human skill, this creation of 
 Divine wisdom has been adapted to the most varied 
 and apparently incompatible ends ; and while in the 
 atmosphere it is a mere dead weight, it is also the 
 most plastic of the elements, is capable of entering 
 into the most complex relations, and thus serves as 
 the peculiar substratum of all the higher forms of 
 organized being. 
 
 - The last point I am to illustrate in regard to ni- 
 trogen is, perhaps, the most characteristic of its fea- 
 tures, and it is one on which its relations in the 
 scheme of organized nature very greatly depend. 
 All the compounds of nitrogen are very unstable, 
 and the slightest force is generally sufficient to over- 
 power the delicate affinities by which the elements 
 are held together, when the nitrogen at once returns 
 to its home in the atmosphere. Although this inert 
 element may be coaxed into combination, it never 
 forms strong compounds. Its affinities, although so 
 varied, are at best very feeble and delicate. It is 
 always a weak timber in a chemical structure, and 
 when this timber breaks, as it certainly will, sooner 
 or later, the whole falls. You will need no further 
 illustration of this fact than to be told that gunpow- 
 
2l8 PRONENESS TO DECAY. 
 
 der, percussion-powder, and gun-cotton are.all nitro- 
 genized compounds, and oweTKeTr well-known prop- 
 erties to the weak affinities of this element. Nitric 
 acid is only a little more stable than these explo- 
 sive agents, and ammonia, although one of the most 
 permanent of nitrogenized compounds, is still very 
 easily decomposed. Passing next to organized sub- 
 stances, we find this distinguishing character still 
 more conspicuous. As we have already seen, it is 
 always the nitrogenized compounds which start the 
 decay in vegetable or animal structures ; and thus 
 the great characteristic feature of all organized mat- 
 ter, its proneness to change and decay, nay, even 
 death itself, is clearly foreshadowed in the proper- 
 ties of nitrogen. When the Creator first endowed 
 this element with its feeble affinities, He also passed 
 the doom of all living creatures : ^^ Dust thou art, 
 and unto dust shalt thou return." 
 
 Here I must leave this division of my subject. It 
 would be highly interesting to study the innumer- 
 able phases in which nitrogen manifests itself in the 
 world of living matter; to trace how, under the 
 guidance of that mysterious principle of life, the 
 mpst complex organic compounds are educed from 
 such simple materials as water, carbonic dioxide, 
 ammonia, and nitric acid ; to follow these nitrogen- 
 ized compounds through their varied history, from 
 the time they are first generated in the plant until 
 they are incorporated into the brain, the muscles, 
 and the bones of man ; to notice at every stage the 
 same instability which so strikingly characterizes all 
 the compounds of this singular element, capable of 
 
CIRCULATION OF NITROGEN. 219 
 
 existing only under the continued influence of the 
 vital principle, and, when that ceases to act, gradu- 
 ally degenerating and falling back into the simple 
 products from which they sprang ; but all such de- 
 tails would be incompatible with the plan of these 
 lectures, and must therefore be reluctantly passed 
 by. If, however, I have been able to place before 
 you in a clear light the main features of this remark- 
 able element,j^its isolated existence in the atmos- 
 phere, its unparalleled inertness in the aeriform con- 
 dition, its power of combination under restricted 
 conditions, the great variety and complexity of its 
 compounds, and, finally, their singular proneness to 
 decomposition and decay ,-\it is all that I could ex- 
 pect. We have seen thatin each of these respects 
 nitrogen has been adapted with exquisite skill to 
 the unique part which it plays in the scheme of the 
 world ; and this element, although outwardly so un- 
 attractive and dull, has borne the richest testimony 
 to the wisdom of the Maker. 
 
 Having now become acquainted with the charac- 
 teristic features of nitrogen, let us next consider the 
 part which this element plays in that grand circula- 
 tion of matter in organic nature, which has been al- 
 ready in part described. I have before stated that 
 the plant is a true apparatus of reduction, in whose 
 leaves carbonic dioxide is decomposed hy the solar 
 light. The plant absorbs carbonic dioxide partly 
 through its leaves from the air, and partly through 
 its roots from the soil. The sun's rays, acting upon 
 the green surface of the leaf, decompose in some 
 
220 THE PLANT A PRODUCER. 
 
 mysterious way the carbonic dioxide, overcoming 
 the intense affinities of its elements, fixing the car- 
 bon, and setting free the oxygen, to be restored to 
 the air. From the carbon thus obtained, and from 
 the water, ammonia, and nitric acid which are the 
 other articles of its food, together with a few inor- 
 ganic salts, the plant constructs its tissues. If in 
 their production carbonic dioxide and water alone 
 take part, there result such substances as woody 
 fibre, starch, gum, and sugar, and of these nine- 
 tenths of all vegetable structures consist. If the 
 nitrogen compounds are likewise employed in tfie 
 process, there are formed, besides, suchnitrogenized.- 
 products as albumen, caseine , and fibrin e. These 
 last names may not be so familiar to you as the first, 
 but you are equally familiar with the substances, 
 and will recognize them at once when told that the 
 white of an egg is nearly pure albumen, that cheese 
 consists almost entirely of caseine, and meat of 
 fibrine. Although these substances are best known 
 to us as animal products, they are likewise found in 
 all those vegetables which are articles of food. Al- 
 bumen and caseine can readily be extracted from 
 either peas or potatoes, and gluten, the substance 
 which gives tenacity to flour-paste, has essentially 
 the same composition as animal fibrine. 
 
 The animal, unlike the plant, has not the power 
 of forming the substance of its tissues from inor- 
 ganic compounds, but it receives them ready formed 
 from the vegetable kingdom. It transmutes the 
 vegetable products into a thousand shapes in order 
 to adapt them to its uses, but its peculiar province 
 
THE ANIMAL A CONSUMER. 221 
 
 is to assimilate and consume, not to produce. The 
 nitrogenized compounds just referred to are the 
 portion of its food which suppHes the constant waste 
 attending all the vital processes. The non-nitro- 
 genized starch and sugar, although they; form the 
 greater part of our food, are never actually incorpo- 
 rated into the tissues of the body, and, as we have 
 already seen, are^ merely the fuel by which its tem- 
 P^erature is maintained. The animal may either re- 
 ceive its nitrogenized food directly from the plant, 
 as is the case with all herbivora, or only indirectly^ 
 like the carnivora ; but in either case the origin is 
 the same, and by the process of digestion these, 
 originally at least, vegetable products are assimilated 
 and converted into bones, muscles, or nerves, as the 
 necessities of the animal may require. We find that 
 during this process these substances do not undergo 
 any fundamental change, but merely become parts 
 of more finely organized tissues. We discover in 
 the blood albumen and caseine, having precisely the 
 same composition as that which may be prepared 
 from potatoes, and the substance of the muscle 
 does not differ essentially from the gluten of flour- 
 meal.. 
 
 Do not, however, suppose that the part played by 
 the animal is less noble than that of the plant. It is 
 really much higher. We must be careful to make 
 a distinction, too frequently overlooked, between 
 the organized structure and the material of which it 
 consists. There is the same difference here as be- 
 tween a house and the bricks of which it is built. 
 It was formerly supposed that organic matter was 
 
222 MATTER AND ORGANISM. 
 
 formed under peculiar influences, and subject to 
 special laws. But it is now known that animal and 
 vegetable substances obey the same laws of affinity 
 as mineral matter, and the recent progress of chem- 
 istry has given us great reason to believe that we 
 may be able one day to prepare all the materials of 
 which plants and animals build their cells. Here, 
 however, chemistry stops and creation begins. The 
 great Architect of nature alone can fashion this dead 
 material into living forms."^ The vegetable kingdom 
 is a great laboratory, in which the sun's rays manu- 
 facture from the gases of the atmosphere, and from 
 a few earthy salts of the soil, the different materials 
 which the organic builders employ. There the bricks 
 are made, and from these the animal builds his bones 
 and muscles. He does not make the bricks, but he 
 does what is far more glorious, he builds with them 
 his delicate frame, and as the work of the builder is 
 higher than that of the brick-maker, so in the scale 
 of being is the animal higher than the plant, and the 
 more noble in proportion as its structure is more 
 intricate and elaborate. 
 
 While the plant is a true apparatus of reduction, 
 the animal is a true apparatus of combustion, in 
 which the substances it has derived from the vegeta- 
 ble are burnt and restored to the atmosphere in the 
 
 * I do not forget the alleged facts of spontaneous generation ; but 
 even after the very extended investigations of the last ten years, it 
 may still be stated as the general result of the innumerable experi- 
 ments which have been made, that, in no case has even the lowest 
 type of an organic cell been produced from unorganized matter, unless 
 through the natural processes of growth from a pre-existing germ. 
 
ORIGIN OF MUSCULAR POWER. 223 
 
 form of carbonic dioxide, water, and ammonia, ready 
 to be again absorbed by the plant and to repass 
 through the phases of organic life. Our bodies are 
 furnaces, — furnaces continually burning, — whose 
 fuel is our flesh, and whose smoke is the breath of 
 our nostrils. Every time I strike a blow a portion 
 of the muscle is consumed, actually burnt up in 
 producing the force. In every muscular effort I 
 make, in every word I utter, in every step I take, 
 a portion of the muscles concerned is burnt, and 
 motion can no more be produced in the animal 
 body without a combustion of its tissues, than it can 
 be generated in a steam-engine without burning fuel 
 under its boiler. As in the steam-engine the burning 
 fuel is the source of its power, so in the animal body 
 the burning muscle is the immediate cause of all its 
 motions. I will to strike a blow, but my will is not 
 the moving power. The power is in the muscle, and 
 in the exertion the muscle is consumed. The muscle, 
 however, does not originate the motion, any more 
 than the fuel originates the motion of the steam- 
 engine. The_Riel, we have seen, does not originate 
 heat. It is merely a reservoir of heat, and in burn- 
 ing it merely givesup the heat it once received from 
 the sun. So the muscle is merely a reservoir of 
 force, and in burning it gives out the force it con- 
 tains. The force it contains it also received from 
 the sun, when its substance was formed by the sun's 
 rays acting upon the leaves of the plants. 
 
 What a wonderful revelation is this ! Muscular 
 power originates in the sun. We do not create the 
 force ; we do not originate it ; we merely excite it. 
 
224 THE ANIMAL MACHINE. 
 
 The force which originally came from the sun lies 
 dormant in the muscles until our will calls it into 
 activity. Our bodies are machines, perfect ma- 
 chines it is true, but yet machines. Like all other 
 machines, they merely transmit power, they cannot 
 create it. They very closely resemble a steam-en- 
 gine. As we must constantly feed the engine with 
 fuel, so we must supply our bodies with food in or- 
 der to repair the muscle burnt, and we can no 
 more be said to originate that force which mani- 
 fests itself in our bodies, than the stoker, who shov- 
 els the fuel into the grate, can be said to originate 
 the force of the steam-engine. We are not our bod- 
 ies, although we live in them, and direct their mo- 
 tions. They move by forces which emanate from a 
 source far higher than we, and we stand in the same 
 relation to them in which an engineer does to his 
 machine. Certainly Lavoisier, the great father of 
 modern chemistry, had caught a glimpse of the re- 
 sults which it was left for more modern science 
 to establish, when he wrote : " Organization, sensa- 
 tion, voluntary motion, life, only exist on the surface 
 of the earth, and in places exposed to the light. It 
 might be said, indeed, that the fable of Prometheus 
 was an expression of a philosophical truth, which 
 had not escaped the penetration of the ancients. 
 Without light, nature were without life and without 
 soul ; a beneficent God, in shedding light over cre- 
 ation, strewed the surface of the earth with organi- 
 zation, with sensation, and with thought." 
 
 Although it thus appears that our bodies are 
 mere channels of force, machines whose motive 
 
MIND CONTROLS THE MACHINE. 22$ 
 
 power emanates from the great centre of the solar 
 system, let us, while we recognize this startling re- 
 sult of science, remember the no less certain fact of 
 consciousness, — that we are not our bodies, though 
 we live in them, — that this conscious personality is 
 something entirely apart from, and infinitely superior 
 to, these corporeal atoms in which it is temporarily 
 enshrined, surviving as it does all their changes. Let 
 us also keep clearly in view the still more glorious 
 truth, that this machine, with all its infinite capabil- 
 ities of good and evil, is put entirely at our com- 
 mand ; that not one conscious motion can take place 
 unless we will it ; and that this will of ours can set 
 in action a chain of causes which no space can bound 
 and no time can limit. Let us then well consider 
 how great is the power which has thus been dele- 
 gated to us, let us duly weigh the awful responsi- 
 bility it involves, and so act that, when the Master 
 claims his own, we may not be ashamed to render up 
 the account of our stewardship. 
 
 Moreover, although it is true that these bodies 
 themselves are constantly dissolving into air, that 
 the material atoms w^hich compose them will in a few 
 short weeks all be gone, and that there is nothing 
 but the shadow of our forms which we can call our 
 own, we must also remember that there is a myste- 
 rious principle within, constantly renewing and re- 
 pairing our wasting frames, — a cunning architect 
 superintending a thousand builders who are con- 
 stantly reconstructing, with materials prepared by 
 vegetation, the bones, the muscles, and the nerves, 
 as fast as they are wasted and consumed; making, 
 
 lO* 
 
226 THE VITAL PRINCIPLE. 
 
 in a most mysterious way, beyond all human com- 
 prehension, here the fibre of a muscle, there the fila- 
 ment of a nerve, here building up a bone, there unit- 
 ing a tendon, fashioning each with scrupulous nicety, 
 and fitting each to its place with never-failing skill. 
 But no sooner is the work of the architect done, than 
 another great power comes in to destroy it. The 
 oxygen gas which the blood absorbs in the lungs and 
 carries to the different parts of the body burns up 
 these carefully elaborated tissues, converting them 
 into carbonic dioxide, water, and ammonia, which 
 pass into the atmosphere, from which they originally 
 came. Life is, in fact, a constant struggle between 
 the builders and the destroying element of the air; 
 and when its short term is ended, and the builders 
 cease because they are wearied and few, then '' the 
 dust returns to the earth as it was, and the spirit re- 
 turns unto God who gave it." 
 
 But let us not sorrow as those who have no hope ; 
 " for we know that if our earthly house of this tab- 
 ernacle were dissolved, we have a building of God, 
 an house not made with hands, eternal in the heav- 
 ens." And cannot He who hath clothed us with 
 our earthly house provide for us a better and more 
 enduring mansion? and are not all these wonderful 
 changes in our present bodies a foreshadowing of 
 the final consummation, when our earnest desire '^ to 
 be clothed upon" shall be satisfied, and " mortality 
 shall be swallowed up of life " ? 
 
 Such is a very imperfect sketch of that great cycle 
 of changes, of which all organic nature is merely a 
 passing phase. Let us review for a moment its main 
 
THE ORGANIC CYCLE. 22y 
 
 features. When the foundations of the globe were 
 laid, there were collected in the atmosphere all the 
 essential elements of organized beings. From this 
 inexhaustible storehouse the plant absorbs water, 
 carbonic dioxide, and ammonia, which were placed 
 there for its use, and which have been made to serve 
 as its nourishment and food. It is the special 
 office of the plants to elaborate from these few 
 mineral substances, and a small amount of earthy- 
 salts, all the materials of organized beings. The 
 animal receives these crude materials already pre- 
 pared, and builds with them its various tissues; but 
 no sooner are the cell-walls finished, and the struc- 
 ture ready to discharge its vital functions, than it is 
 consumed by almost the very act which gave it life. 
 The carbonic dioxide, water, and ammonia are re- 
 stored to the atmosphere, and the cycle is complete. 
 Of this Divine economy the sun's rays are the 
 great moving cause, and it is their mysterious power 
 which is constantly reappearing in all the varied 
 phases of organic life. And not in these alone ; for, 
 as we have seen, this same gentle influence keeps in 
 motion the aerial currents which blow our ships 
 across the ocean. It raises the water which turns 
 the wheels of our factories. It drives the locomotive 
 over the iron road, and impels the steamer through 
 the waves. It roars at the cannon's mouth, and 
 charges the grander artillery of the skies. There is 
 no motion on the globe which cannot be traced 
 directly or indirectly to the sun, and were his rays 
 to lose their mysterious power, all nature would be- 
 come silent, motionless, and dead. 
 
228 THE FIRST CAUSE. 
 
 But in thus tracing to the sun all these varied 
 phenomena, let us not forget that we have not yet 
 found the great First Cause. The problem is not 
 yet solved ; the profoundest truth has yet to be 
 told. This mysterious force, which the sun pours 
 in ceaseless floods upon the earth, — whence comes 
 it ? You have already answered the question. The 
 answer is on your lips. I have but to re-echo it, and 
 how can I better do this than in the words of that 
 blind poet to whom misfortune had revealed the true 
 meaning of light : 
 
 *' Hail, holy Light ! offspring of Heaven first born ; 
 Or of the Eternal co-eternal beam 
 May I express thee unblamed ? since God is light, 
 And never but in unapproached light 
 Dwelt from eternity, dv^elt then in thee, 
 Bright effluence of bright essence increate." 
 
CHAPTER VIII. 
 
 ARGUMENT FROM SPECIAL ADAPTATIONS. 
 
 I HAVE endeavored thus far in this course of lec- 
 tures to present a few of the prominent illustrations 
 of the attributes of God, which have been discov- 
 ered in the adaptations of the atmosphere to the 
 conditions of organic life on the earth. We have 
 read together one brief chapter of that evidence of 
 design with which the book of nature is filled, and 
 I cannot but trust that we have gained from our 
 study nobler conceptions and more enlarged views 
 of the wisdom, power, and goodness of our Heav- 
 enly Father. Every one who accepts the Bible as 
 a divine revelation will rejoice to find how beauti- 
 fully and how entirely the facts of science confirm 
 its great fundamental truths. But have not these 
 evidences of nature a greater value even than this ? 
 Do they not prove, independently of all revelation, 
 the existence of a wise and omnipotent First Cause, 
 at least so far as there is any moral certainty in the 
 world ? I am persuaded that they do, and I believe 
 that they furnish the only logical ground on which 
 a system of revealed religion can be based. In my 
 introductory lecture I stated that I preferred to 
 
 22g 
 
230 CHARACTER OF THE ARGUMENT. 
 
 discuss the adaptations of nature as illustrations of 
 the attributes of God, rather than as absolute proofs 
 of His being; but now that we have surveyed the 
 ground, let us consider whether they are not really 
 moral proofs, with all the certainty that any proof 
 not strictly a mathematical demonstration can give. 
 The argument from adaptation is one which ad- 
 dresses itself to every human being. It is suited to 
 every intellect, and comes home to every man's ex- 
 perience. It is based on a principle of the human 
 mind, — whether the result of experience or of intu- 
 ition we need not inquire, — which compels it to infer 
 design when it sees adaptation. Who doubts that 
 the flint arrow-heads and stone implements found 
 in New England, rough and misshapen as they are, 
 were made by men ? To question the universal 
 belief would be regarded as little short of insanity. 
 Why then not apply the same common sense to the 
 interpretation of nature ? The unlettered do, and 
 believe, in their simple faith, that the feathered 
 songster and the delicate flower were made by their 
 Heavenly Father's hand. It is only those of us 
 whose minds have been unsettled by the subtilties 
 of logic who doubt, and, if we could analyze our 
 doubts, I think they would be found, in most cases, 
 to arise from a vague fear that, since nature stands 
 on a level so much above man's experience, the 
 ordinary principles of reasoning may possibly not 
 apply, and we may be misled by apparent analogies. 
 But why this fear? There is no essential difference 
 between the adaptations found in nature and the 
 adaptations made by men. Both employ means to 
 
CHARACTER OF THE ARGUMENT. 23 1 
 
 attain some important result, and in many cases 
 they secure the end by precisely the same means. 
 The telescope and microscope are but reproductions 
 of the eye, and imitate in all their essential features 
 this beautiful optical apparatus of nature."^ It is 
 true that the adaptations of nature are vastly supe- 
 rior to the results of human skill, and it is also true 
 that their origin is beyond our personal experience. 
 We have seen the process of making a watch and the 
 process of making a telescope. We know how the 
 principles of both were discovered, and the whole 
 subject lies within the range of our experience ; but 
 no man ever made or ever can make an eye, and the 
 whole process of its growth and development is ut- 
 terly beyond the range even of man's conception. 
 All this is true ; but if you reflect a moment, you will 
 find that this is just what is to be expected, seeing 
 that God is the Creator and we are His creatures, 
 and so far from weakening, this very characteristic 
 greatly strengthens the evidence. Moreover, it must 
 be remembered that, if the design is of an infinitely 
 
 * The power which the eye possesses of adaptation to near and dis- 
 tant objects, combining the uses of the microscope and the telescope, 
 and the capacity of self-adjustment, preserving always a perfect achro- 
 matism and freedom from spherical aberration, have never been 
 reached in nearly the same degree by art. Moreover, in the eye this 
 perfection is attained with a focal length of only half an inch, which 
 vastly increases the difficulty. It is also a fact worthy of notice, that 
 the improvements in optical instruments have preceded rather than 
 followed the discoveries of physiologists, thus serving to explain the 
 functions of the eye ; and inventions like that of achromatic lenses, to 
 which men have been led by theoretical study, have been found to be 
 anticipated in nature. 
 
232 THE ARGUMENT CUMULATIVE. 
 
 higher order, the evidence of the design is infinitely 
 more ample. A rude, misshapen image is a con- 
 vincing evidence of human intelligence ; but all 
 nature, with its numberless adaptations — from the 
 properties of the crude elements up to the wonder- 
 ful structure of the human frame — is given us as 
 evidence of the wisdom of God. 
 
 The argument from the adaptations of nature is 
 of the kind we call cumulative. Its force depends 
 on the concurrence of many and varied examples. 
 It is not based on one isolated case of adaptation, 
 or even on a thousand ; but there is a host of con- 
 ditions, which no man can number, each adjusted to 
 each, and all bound together in one harmonious 
 whole. Consider only the examples we have dis- 
 covered in the very narrow field to which we have 
 limited our study. How numberless are the condi- 
 tions on which the harmonious working of the varied 
 functions of the atmosphere depends ! In the first 
 place, there is the expansive tendency of the air, 
 sustained by the solar heat, and restrained by the 
 force of gravity, by which alone it is held to the 
 surface of the globe. Then there is the density, 
 exactly adjusted to the human organism, and depend- 
 ing on the measures and weights of the solar system. 
 Next there are all the delicate relations to light, 
 heat, and electricity. Passing to the separate con- 
 stituents of the atmosphere, there is oxygen, with 
 its three distinct modifications, endowed with fiery 
 afifinities, and yet so carefully guarded as to be a 
 beneficent servant of man, intrusted with most varied 
 and seemingly incompatible functions, and discharg- 
 
FACTS REVIEWED. 233 
 
 ing each with equal fideHty and precision ; next, 
 there is water, nourishing all nature with its dews 
 and rains, tempering the polar climates with the 
 latent warmth of its genial currents, and protecting 
 with its great frost-blanket the delicate plants from 
 the winter's cold, — exceptional in all its qualities, 
 and each adapted to some beneficent end ; then 
 comes carbonic dioxide, concealing in its transparent 
 folds the solid framework of all organized beings, 
 and the source of those priceless beds of coal, with 
 their inexhaustible stores of heat and force ; and 
 lastly, but not least in interest or importance, there 
 is nitrogen, so remarkably inert, and yet endowed 
 with such varied affinities, forming such numberless 
 compounds, and imparting to all such singular in- 
 stability. As we thus hastily review the ground we 
 have surveyed together, you will recall the numer- 
 ous adaptations we discovered while studying the 
 wonderful cycles of change in which all these sub- 
 stances conspire, wheel revolving within wheel, and 
 yet all moving with such delicacy and beauty of ad- 
 justment that no jar is felt through all this compli- 
 cated mechanism, and not the slightest derangement 
 occurs in any of its ten thousand parts. 
 
 Now the argument for design unfolded in this 
 brief chapter of the book of nature comes home to 
 us with the cumulative weight of all this testimony. 
 Perhaps plausible objections might be urged against 
 individual examples of adaptation which have been 
 advanced ; but any one who questions the general 
 fact must be prepared to disprove all. Were there 
 but a single instance of adaptation, or only two or 
 
234 THE ARGUMENT SUMMED UP. 
 
 three, the sceptic might urge with a show of reason 
 that this was the result of accident, — arose from the 
 *' fortuitous concourse of atoms " ; but the examples 
 of adaptations which we have discovered merely in 
 the atmosphere, all interlacing with each other, and 
 all working together in the general scheme, are by 
 themselves alone so great a number that, if we take 
 no higher ground than the mathematical theory of 
 probabilities, the chances against the supposition 
 that this system, even as we know it, was the result 
 of accident, are almost infinite, and can be expressed 
 numerically only when the sands on the sea-shore 
 are counted. If such, then, is the weight of the 
 evidence which the atmosphere gives, what must be 
 the force of the argument in which all nature gives 
 its united testimony? Truly, the number of atoms 
 in the universe is not sufficiently large to express 
 the probabilities against this forlorn hope of athe- 
 ism ! 
 
 But, my friends, the sceptic should be heard, and, 
 having presented our side, let us listen to what he 
 has to say in reply. The whole argument from 
 special adaptations may be summed up in a few 
 words. Within the sphere of human experience, 
 adaptation proves the existence of an intelligence 
 adequate to the conception and execution of the 
 design. We find in nature adaptations similar to the 
 results of human intelligence, only of an infinitely 
 higher order, and hence by analogy we conclude 
 that these must have issued from an infinitely wise 
 and omnipotent Designer. The argument assumes 
 the reality of the human intelligence as consciously 
 
BURDEN OF PROOF. 235 
 
 a power and an originator within its own sphere, and 
 reasons from this to a similar conscious intelhgence 
 in the Author of nature. The argument assumes, 
 also, the truthfulness of the human faculties as a 
 source of knowledge, without which it is of course 
 useless to reason at all. 
 
 Now the adaptions of nature are facts which every- 
 one must admit, the sceptic among the rest. More- ' 
 over, he must also admit that the conclusion which 
 we have drawn from these premises is the all but 
 universal conclusion of mankind. Plutarch, writing 
 eighteen centuries ago, without the light of the 
 Christian revelation, bears this remarkable testi- 
 mony to the universality of the religious idea: **If 
 you go through the world, you may find cities with- 
 out walls, without letters, without rulers, without 
 dwellings, without wealth, without money, without 
 theatres and manly sports ; but there was never yet 
 seen, nor shall be seen, by man a single city without 
 temples and gods, or without prayers, oaths, proph- 
 ecies, and sacrifices, used to obtain blessings and 
 benefits, or to avert curses and calamities. Nay, I 
 am of opinion that a city might be sooner built 
 without any ground beneath it, than a common- 
 wealth could be constituted altogether destitute of 
 belief in the gods, or, being constituted, could be 
 preserved.*' * The discoveries of modern travellers 
 
 ■^ Evftoi'^ 6^ ay kitiwv TtoXei^ dretxidrov^f dypaj.i).idTov<^, 
 d/JadiXevTov<5, domovS, dxf^r/udrovS, vof.n6uaTo<i uij dsojue- 
 ra'5, dTtei'fjovS OedrpGov xai yvjuvadiGDV dvtspov Ss TtoXsaoi 
 nai dOeov, jtii) XP^M^'^V'^ tvxctl?, juj^de opHoi<^, jtcf^de tuayreiaii, 
 jLir/de Ovdi'aiS kii^ dya^oi^, juf/d^ dnorpoitali HaKcoy, ovdei<5 
 
236 PLUTARCH'S STATEMENT. 
 
 have not more fully confirmed the general truth of 
 Plutarch's statement, than the experiments of mod- 
 ern socialists have proved the soundness of his 
 opinion. No savage tribe has yet been found on 
 which a belief in a higher power has not at least 
 glimmered, and no community which has attempted 
 to ignore religion has lasted a century. The scep- 
 tic, then, if he rejects our conclusion, is bound 
 to prove that the natural inference of man is based 
 in error. If he sets aside the general rule of faith, 
 and refuses assent to the universal creed, — " Quod 
 semper, quod ubique, quod ab omnibus creditum 
 est,*'"^ — he must explain, whatever theory he may 
 adopt, how it comes to pass that all mankind have 
 been duped, and all nature has issued in a lie. The 
 burden of proof is with him, and how does he meet 
 it ? Generally in one of two ways. 
 
 In the first place, he attacks the validity of the 
 conclusion on purely speculative grounds, saying 
 that adaptation is no longer an evidence of design 
 when applied to subjects beyond the range of all 
 human experience. He may urge, and urge with 
 reason, that in nature we have no sure criterion by 
 which we can distinguish between means and ends, 
 between what is cause and what is effect. He may 
 support this position by questioning, with Hume, 
 the competency of the human faculties as a source 
 
 Idriv ov8^ edrax ysyovcbi Bearjj'i' dXXd 7t6Xi<^ ar JlLoi 8okeX 
 l^idXXor lddq)OV^ X^P^^f V TtoXirela TTJi Ttepi OecSv do^r^S vq)ai- 
 pEf)8i6r/<^ 7tarrd7ta6i, 6vdra6ir XafSelv, rf Xa/Jovda rr/prjdai, 
 Plutarch, Upo? KoXg6t?/v, xxxi. 
 
 * Vincentius Lerinensis, written 434 A. D. 
 
^^ ^/ 
 
 DEMONSTRATION NOT CLAIMED. 237 
 
 of knowledge, or, like Comte, he may deny all knowl- 
 edge of final causes, and maintain that there is no \ 
 evidence of anything behind the external phenomena 
 of nature; but whatever form the scepticism may 
 assume, the conclusion is the same, and the argu- 
 ment for design is ruled out as invalid. 
 
 With regard to this position I have only a few 
 words to say. Design in nature, I admit, cannot be 
 demonstrated ; for the truths of natural religion can- 
 not be evolved from a mathematical formula. The 
 argument is based on analogy, and although the 
 analogies are so close and so broad that, to my mind, 
 they amount to moral proofs, and the conclusion 
 appears as certain as any theorem of geometry, still 
 I admit that the evidence is probable, and not 
 demonstrative. But as a student of physical science 
 it is not my business to defend the credibility of the 
 human faculties, or to discuss the doctrine of causa- 
 tion. The task belongs to the metaphysicians, and, 
 as I stated in my first lecture, I shall not encroach 
 on their peculiar province. Nor do I think it im- 
 portant to dwell on the value of analogical reason- 
 ing. Modern writers have not been able to add 
 much to Bishop Butler's masterly discussion of the 
 subject, and every man, however sceptical he may 
 be in his speculative opinions, must admit, with the 
 author of " The Analogy," that " probability is the 
 very guide of life." One consideration, however, 
 may be of value in answering objections, namely, 
 that since the difficulties which are found in natural 
 theology reappear with equal strength in all depart- 
 ments of knowledge, no objections can be reason- 
 
238 PROVINCE OF DEMONSTRATION. 
 
 ably urged against the methods of the former, which 
 do not apply equally well to our most familiar pro- 
 cesses of thought. It may be fairly presumed that 
 such objections are more apparent than real, and that 
 they indicate not the inconsequence of our logic, 
 but only the necessary limitations of our faculties. 
 
 Now analogy is not only the guide of common 
 life, but it is also the basis on which physical 
 science chiefly rests ; and if this method of reason- 
 ing be disallowed, all the results of science beyond 
 those of mere observation and demonstration must 
 fall with it. It is frequently said, that scientific 
 truth can be demonstrated, but religious truth must 
 be accepted on faith ; and in part this is true ; but 
 the statement is one of those loose sayings whose 
 partial truth only renders the latent error more 
 dangerous. No word is more frequently misused 
 than "demonstration." Technically, this term only 
 applies to that form of absolute proof with which we 
 deal in geometry or pure logic ; but, popularly, a 
 principle is said to be demonstrated when all that 
 can be claimed for it is a high degree of moral 
 certainty. In this double use of the term the error 
 of the above statement lies, for it is made in one 
 sense, and — frequently at least — understood in the 
 other. Truth wholly new is never reached by the 
 methods of demonstration ; for demonstration can- 
 not yield what is not already implied in the premises 
 with which it starts. The truths of geometry and 
 mechanics may be demonstrated ; but then they are 
 virtually contained in the axioms and definitions on 
 which these sciences rest. All scientific generaliza- 
 
ANALOGY THE CHIEF GUIDE. 239 
 
 tion is based on analogy ; and moreover, a great 
 mass of the scientific truth which lies within the 
 range of direct observation we owe to the same 
 principle ; for even here analogy directed the stu- 
 dent to what he subsequently observed. 
 
 Indeed, the great inspiring and directing power 
 in the minds of the successful investigators of nature 
 is the force of analogy. It is this which constantly 
 leads them to pronounce conclusions unsound, al- 
 though apparently sustained by experiment, and to 
 accept others which are seemingly at variance with 
 facts. It is this which leads them through long and 
 laborious investigations to establish principles which 
 they believe to be true, and sustains them in their 
 efforts through successive failures to ultimate suc- 
 cess. As indefinite and uncertain as the analogies 
 of nature frequently seem to be, as unsatisfactory as 
 they may appear to the great mass of mankind, and 
 as impossible as it is to make them intelligible ex- 
 cept to those already versed in scientific inquiries, 
 yet the history of science shows that, when based 
 on an extended knowledge and a mature experience, 
 they very seldom lead astray. 
 
 The method of scientific discovery is frequently 
 misunderstood, and the philosophy of Bacon, how- 
 ever important in correcting old abuses, has done 
 not a little towards creating the misapprehension. 
 Many persons seem to think that the author of 
 the Novum Organum gave to man a rule, by which, 
 with the aid of a sort of mechanical logic called 
 induction, the laws of nature may be discovered 
 very much as a last is turned out by a lathe. Yet 
 
240 METHOD OF SCIENTIFIC DISCOVERY. 
 
 nothing could be further from the truth. So far as 
 the observation of phenomena is concerned, — which 
 must always be the occupation of the great mass of 
 scientific men, — the methods are as mechanical as 
 those of other learned professions, requiring chiefly 
 a quick eye, a delicate touch, a ready perception, 
 and, most of all, a clear head capable of discriminat- 
 ing between the accidentals and the essentials, which 
 are always singularly blended in natural phenomena. 
 But the great generalizations, which form the frame- 
 work of knowledge, are not reached by rule ; nor, as 
 a general thing, are they in their inception of slow 
 growth. On the contrary, they usually come like 
 intuitions to the mind, with the rapidity of the 
 lightning's flash, and it is frequently possible to 
 mark the day and the hour when the revelation was 
 made. But such revelations of scientific truth are 
 vouchsafed only to those highly favored minds which 
 through long study and patient investigation have 
 been brought into perfect sympathy with the har- 
 monies of nature ; and if we analyze the conditions 
 of the mental process, we shall find that these great 
 discoveries are really the result of analogical rea- 
 soning. 
 
 But although the conception is thus sudden, the 
 verification of the truth is frequently long and labo- 
 rious. Great discoveries are not achieved in an hour 
 or a day. Nature has so concealed her truths, and 
 surrounded them by so many adventitious circum- 
 stances, that they can be disclosed to the world only 
 after long and careful study. First comes the con- 
 ception, afterwards the toilsome investigation by 
 
METHOD OF SCIENTIFIC DISCOVERY. 24I 
 
 which it is proved that the facts of nature accord 
 with the generalization. The investigation may 
 lead to a great modification of the original idea, or 
 may show that it must be wholly abandoned, and 
 meanwhile another may have taken its place, to go 
 through the same scrutiny in its turn ; but still the 
 conception which proves to be the law of nature is 
 the real discovery. This, as we have seen, is the re- 
 sult of analogy, and most clearly vindicates the re- 
 lationship of the mind of man to the Intelligence 
 whence issued the universe. 
 
 Every great scientific generalization will illustrate 
 more or less clearly the principles here stated. It 
 is true that many minds frequently concur in de- 
 veloping one grand idea, and the evolution may oc- 
 cupy so long an interval of time that the new truth 
 appears to be the growth of an age, rather than the 
 gift of any one man. Yet it is possible in almost 
 every case to trace the successive steps of the dis- 
 covery. This is especially true of the law of gravi- 
 tation. Whether the first idea was suggested to 
 Newton by the fall of an apple, it is not important 
 to inquire; but the popular anecdote illustrates the 
 nature of the original thought, which was undoubt- 
 edly sudden and intuitive, although, as Newton has 
 himself expressly stated, it was the result of ana- 
 logical reasoning. The conception once formed, the 
 work of verification was long and laborious, and the 
 results were at first so unsatisfactory that Newton at 
 one time abandoned his theory altogether, as un- 
 supported by observation. It was not, indeed, un- 
 til a new arc of the meridian had been measured by 
 
242 METHOD OF NATURAL RELIGION. 
 
 Picard in France — several years after the first con- 
 ception — that the facts were found to agree even 
 approximately with the theory, and astronomers have 
 been occupied ever since in verifying the grand 
 thought. The same general facts reappear in the 
 case of the wave-theory of light, first conceived by 
 Huyghens and subsequently verified by the succes- 
 sive discoveries of Malus, Fresnel, and Young ; and 
 we may lay it down as an almost universal principle, 
 that scientific truth is discovered through analogy 
 and verified by comparison with the facts of nature. 
 
 If now you will turn to the great central truth of 
 natural religion, you will find that it has as ^ood 
 credentials as the best established laws of science. 
 We have first the conception, — not only the concep- 
 tion of a few highly gifted minds, but the universal 
 conception of mankind. We find afterwards this 
 conception verified, — not only in the history of the 
 race, but also in the experience of each individual 
 man, and moreover, the conception is apparently in- 
 tuitive in every mind. Even if the sceptic denies 
 the reality of both special and general providence, 
 he must admit that, as the most universal rule, both 
 history and experience have only served to confirm 
 and strengthen the religious idea. 
 
 We now return to the remark above quoted, bet- 
 ter able both to appreciate the truth it contains and 
 to unmask the fallacy it conceals. A large part of 
 the results of science may be demonstrated, but 
 only such truths as are already contained in the 
 premises on which the demonstration rests are capa- 
 ble of this absolute proof ; and these are in all cases 
 
PROVINCE OF FAITH. 243 
 
 reached by the human intelligence working on its 
 own definitions and processes of thought, and this, 
 too, even when the theoretical truth is afterwards 
 found realized in nature. The highest forms of sci- 
 entific truth are not capable of demonstration, and 
 rest only on probable evidence, although the prob- 
 ability in their favor may be so great as to beget 
 the highest degree of moral certainty. In like man- 
 ner, a great part of the truths of religion must be ac- 
 cepted on faith ; but then the evidence in favor of 
 the great fundamental truth of natural religion is 
 as strong as the evidence for any theory of science, 
 and the certainty is as great. Moreover, faith is not 
 peculiar to religion. All our knowledge not the 
 resuir^STp^Fsonal observation and investigation is 
 held on faith, that is, on trust in other men, and 
 absolutely all knowledge is held on trust in the 
 authority of our own mental powers. Much of the 
 knowledge which we hold without question, it is 
 utterly beyond the capacity of our own intellects to 
 verify, and moreover, no one doubts the existence of 
 truths which now lie beyond the scope of the most 
 gifted genius, but which hereafter may be attained 
 by man. The scientific truths which it is not essen- 
 tial for us to know are left in the dark on purpose 
 to stimulate study, and thus to educate the human 
 race. Religious truths, on the other hand, it is es- 
 sential for us to know, and, since they in like manner 
 transcend our present powers, they have been spe- 
 cially revealed. We are called upon to accept them 
 on sufficient evidence, and this is all that is meant 
 by faith. Faith, then, is as truly a ground of belief 
 
244 REPLY TO THE SCEPTIC. 
 
 in science and in common life as it is in religion, 
 and it occupies a more important place in religion 
 only because religious truth is itself so important, 
 and so greatly transcends, in its essence, our limited 
 human faculties. 
 
 Our reply, then, to the first position of the sceptic 
 is this. Your objections apply as well to all knowl- 
 edge as they do to religious truth, and, if you are 
 consistent with yourself, you must reject the evi- 
 dences of science as well as the evidences of religion."^ 
 As we are not prepared to go this length, we shall 
 with equal consistency hold to both. It is but jus- 
 tice to state that Hume, the most philosophical of 
 the sceptics, pushed his speculations to their neces- 
 sary consequences, and denied the existence of 
 matter and spirit alike. But although from its very 
 boldness difficult to refute, this form of scepticism 
 is by no means the most dangerous; for in the 
 present age of the world a system of philosophy is 
 not likely to gain many adherents which, in the 
 first article of its creed, utterly shocks all human 
 self-conceit by declaring that man neither knows 
 nor can know anything with certainty. 
 
 In the second place, the sceptic attacks the argu- 
 ment for design by setting up a theory of his own 
 to explain the origin of the universe. He tacitly 
 admits that the burden of proof is with him, and 
 that, if he rejects the popular belief, he is bound to 
 show how this cosmos might have been issued with- 
 
 * See this point well reasoned in Balfour's Defe7tce of Philosophic 
 Doubt 
 
ABSOLUTE MATERIALISM. 245 
 
 out intelligence and without a God. This he at- 
 tempts to do, and the result is nearly as many the- 
 ories as there have been strong scientific intellects 
 in the world united with unbelieving hearts.' To 
 refute each of these theories in detail would be a 
 labor like that of Hercules in slaying the Lernaean 
 Hydra ; for until Almighty Power shall sear the foul 
 sore from which the whole brood proceeds, their 
 unholy heads will start up more rapidly than they 
 can be cut down. The most daring theories of this 
 kind are those of the German materialists of the 
 present day. As much as they may differ among 
 themselves in regard to details, the boldest of these 
 speculators agree in maintaining that absolutely 
 nothing exists, or ever has existed, except matter 
 and motion ; that matter in its essence is uncreated 
 and eternal ; that motion is self-sustained ; that mind 
 is only a mode of motion, and that all the phenom- 
 ena both of matter and of mind are the working 
 out of an inexorable necessity. Hence they con- 
 clude that religion is a fable, and immortality a 
 dream. 
 
 Here is atheism. This is the natural fruit of 
 materialism ; and we are glad that it has ripened, 
 that men may see how disgusting and revolting it is, 
 and how corrupt the tree must be which can bear 
 such fruit. We are glad that men should know 
 what must be the result of all their vain speculation 
 and the seeking after false gods. The theory is 
 perfectly consistent with itself, and an absolute 
 necessity if nature be divorced from its Creator ; 
 for all philosophy has proved that either the the- 
 
246 ABSOLUTE MATERIALISM. 
 
 ory of the Christian, or this theory of the materi- 
 ahst, with all its enormity, must be true. There is 
 no half-way halting-place between. This course of 
 lectures has been a continued protest against the 
 materialist's interpretation of nature, and I have 
 not another word to add ; for if a man wishes to 
 believe that his purest loves and his holiest affec- 
 tions are only motions of brain-particles, nothing 
 that can be said would have the slightest weight. 
 If he has not already the refutation in his own con- 
 sciousness of being, human power cannot aid him ; 
 no philosophy can extricate him from the slough. 
 *' Ephraim is joined to idols ; let him alone." 
 
 It is seldom, however, that materialism shows its 
 revolting features among us. It is too cunning and 
 too cautious. It always appears disguised, and is 
 for this reason far more seductive. It presents the 
 attraction of great learning and of great apparent 
 profundity, entangling many in its meshes before 
 they are aware of their danger. It does not deny 
 the reality of the human intellect, but, on the con- 
 trary, takes pride in its authority and power. It 
 even admits the evidence of design, but at the same 
 time insidiously undermines all religious belief ; not 
 so much, however, by what it declares, as by what 
 it leaves to be inferred ; not so much by the doc- 
 trines it inculcates, as by the spirit it keeps alive 
 and fosters. In this refined form, materialism is by 
 far the most prevalent phase of the unbelief of our 
 time, and it is difficult to meet chiefly on account of 
 its very vagueness and simulation. It lives almost 
 entirely in the ever-changing theories and specula- 
 
DEVELOPMENT THEORIES. 247 
 
 tions of science, which it utterly misinterprets and 
 misapplies, forgetting that they are merely pro- 
 visional expedients, which the next wave of advanc- 
 ing knowledge may wash away. Development is the 
 pet word of its philosophy, and it constantly aims 
 to show how the whole scheme of nature, with all 
 its adaptations, might have been evolved through 
 the concurrent action of various unintelligent causes 
 alone. As it attacks the argument for design on 
 scientific grounds, it becomes the duty of the stu- 
 dent of nature to expose its errors. It is, however, 
 a most Protean antagonist, and no sooner is it de- 
 feated in one form than it reappears in another. 
 Every new development theory in any department 
 of science furnishes it with fresh food. For a long 
 time the famous nebular hypothesis, broached in 
 Laplace's Systhne du Monde, supplied it with abun- 
 dant nourishment ; and within the last twenty years 
 it has taken a fresh start, and grown most vigorously, 
 on Mr. Darwin's very ingenious book entitled The 
 Origin of Species, But these are only two examples 
 of a large number of similar works, which, being 
 less able and less original, have had their day and 
 been forgotten. 
 
 The danger of these works lies not so much in 
 what they actually contain, as in their general ten- 
 dency ; not so much in the theories of their authors, 
 as in the wrong conclusions which will inevitably be 
 drawn from them, and to which in many cases they 
 logically lead. Darwin, for example, professes to 
 show that all the living forms of plants and animals, 
 man included, have been, during the geological ages, 
 
248 DUTY OF SCIENTIFIC TEACHERS. 
 
 slowly developed from a few germs, or possibly from 
 only one, by the action of a principle which he calls 
 the *' law of natural selection," and he sustains the 
 hypothesis by a most formidable array of experi- 
 ments and facts. Such a theory as this, ingenious 
 if not true, professing to explain one of the great- 
 est mysteries, and presented in a fascinating style, 
 finds converts everywhere, and this, too, on grounds 
 entirely independent of its scientific merit. That 
 very same noble aspiration which leads men to im- 
 peril even life itself in investigating the secrets of 
 nature, makes them also ready to lend a willing ear 
 to any theory which professes to explain the mystery 
 of creation. Hence the reason why works like the 
 Vestiges of Creation^ and those just mentioned, cap- 
 tivate and injure so many. If they merely stimu- 
 lated curiosity, and led to study, no one could object 
 to their influence, however erroneous he might think 
 their philosophy. But, unfortunately, most readers, 
 of whom it is no disparagement to say that they are 
 not in a condition to weigh the evidence, accept the 
 theory without examination, and, if sceptically in- 
 clined, their whole belief in an overruling Providence 
 is shaken to its base. 
 
 It is in vain to urge that these theories may be 
 consistent with a pure faith ; for as long as they are 
 not so regarded by the popular mind, — which invari- 
 ably appeals to them as proofs of materialism, — the 
 evil which they cause is not remedied. It may be 
 said, and said with some justice, that a writer cannot 
 be blamed for the abuse of his theory ; but it must 
 be admitted that the abuse is a great evil, and an 
 
DESIGN NOT INVALIDATED. 249 
 
 author, if he be a rehgious man, is bound to guard 
 against it by every means in his power. We should 
 be very slow to charge any man with infidelity, for 
 we know how often the human mind, in its eccen- 
 tricities and inconsistencies, has united a true faith 
 to the most sceptical and subversive speculations. 
 But we do say, that the least a Christian philosopher 
 can do for his faith is to give such a tone and spirit 
 to his work as to render misinterpretation impos- 
 sible ; and if he neglects to do this, he has no right 
 to complain if his own opinions are misjudged. 
 
 I shall not attempt to discuss the intrinsic value 
 of the various theories of development, but leaving 
 this task to those who are competent judges, let us 
 inquire what bearing they have on the evidence of de- 
 sign. I answer, absolutely none. Assuming that Mr. 
 Darwin could establish his peculiar theory in all its 
 generality, — and I have no doubt that it has a large 
 element of truth, — it would not impair the evidence 
 of design in the slightest degree, and the same is 
 true of any development theory whatsoever, short of 
 absolute materialism. Those persons who imagine 
 that they overthrow natural religion, fall into a capi- 
 tal error. It requires manifestly the same infinite 
 intelligence to creaTte a universe by a process of de- 
 velopment as by a single creative fiat. Your belief 
 that the beautiful piece of mechanism standing on 
 your mantel-shelf was made by an intelligent man, 
 would not be impaired if you were told that the ar- 
 tist was employed several years in its construction. 
 The evidence of design in the clock is in its beauti- 
 fully adjusted mechanism. The evidence of design 
 
250 A LOGICAL THEFT. 
 
 in nature is in the wonderful adaptation of its parts. 
 We can easily go back in the geological records to 
 the time when the present order of nature did not 
 exist, and the fact that the innumerable forms of or- 
 ganic life, with the adaptations of currents, soil, and 
 climate essential to their being, have been developed 
 out of the conditions which existed on the globe 
 during the coal epoch, is no less an evidence of 
 design than the fact that the clock was developed 
 out of the crude iron and brass used in its con- 
 struction. 
 
 "We lament," says Dr. Martineau,"^ "to see the 
 question between a sudden and a gradual genesis of 
 organic types discussed on both sides — not, indeed, 
 by the principals in the dispute, but by secondary 
 advocates — too much as if it were a question be- 
 tween God and no God. In not a few of the pro- 
 gressionists the weak illusion is unmistakable, that 
 with time enough you may get everything out of 
 next to nothing. Grant us, they seem to say, any 
 tiniest granule of power, so close upon zero that it 
 is not worth begrudging; allow it some trifling ten- 
 dency to infinitesimal increment ; and we will show 
 you how this little stock became the cosmos with- 
 out ever taking a step worth thinking of, much less 
 constituting a case for design. The argument is a 
 mere appeal to an incompetency in the human 
 imagination, in virtue of which magnitudes evading 
 conception are treated as out of existence, and an 
 aggregate of inappreciable increments is simultane- 
 
 * Essays, Nature and God. 
 
TOPSYS ANSWER. 251 
 
 ously equated in its cause to nothing, in its effect to 
 the whole of things. You manifestly want the same 
 causality, whether concentrated on a moment or 
 distributed through incalculable ages, only, in draw- 
 ing upon it, a logical theft is more easily committed 
 piecemeal than wholesale. Surely it is a mean de- 
 vice for a philosopher thus to crib causation by hair- 
 breadths, to put it out at compound interest through 
 all time, and then disown the debt ; and it is in vain, 
 after all ; for dilute the intensity and change the 
 form as you will of the Power that has issued the 
 universe, it remains, except to your subjective illu- 
 sion, nothing less than infinite, and nothing lower 
 than divine.'* 
 
 The genesis of nature has been unquestionably a 
 process of development. But let us not be frightened 
 by words. Development is only another name for 
 growth, and it obviously brings us no nearer to the 
 final cause of a given product to say that it has grown. 
 Topsy in answering her catechist's " Do you know 
 who made you ? '* with " Nobody as I knows on — I 
 spect I growed," was fully as wise and far more hum- 
 ble-minded than those philosophers who attempt to 
 cover up the same answer under high-sounding tech- 
 nical phraseology. Growth is the order of nature, 
 but even in its simplest phases it is as mysterious a 
 phenomenon to-day as it was when the mind of 
 man was first conscious of the fact. That of two mi- 
 nute eggs, in which no anatomist can discover any 
 structural difference, the one should in a few short 
 years develop an intelligence like Newton's, while the 
 other soon ends in a Guinea-pig, is certainly as great 
 
252 GENESIS OF SPECIES. 
 
 a mystery as that in the course of unnumbered ages 
 monkeys by insensible gradations should grow into 
 men. The growth of each man from a microscopic 
 germ is not understood one whit more fully than the 
 genesis of a species, and the only difference is that 
 while in the first case we are familiar with all the stages 
 of the growth, in the last case we know nothing with 
 certainty except the final result. Surely no one 
 really imagines that the first man came " full armed, 
 like Minerva from the brain of Jove.'* There must 
 have been growth, and how utterly immaterial it is to 
 our present discussion at what point the growth 
 began. Moreover, how evident it is that the growth 
 of a species is as legitimate an object of scientific 
 investigation as the growth of an individual; and 
 further, that if we were as familiar with the successive 
 stages in the growth of a species as we are with those 
 in the growth of each individual man, we should be 
 just as far from a knowledge of the efficient causes 
 in the first case as, with all our careful observation 
 and study, we now are in the last case. But although 
 a knowledge of the efficient causes may in either 
 case be beyond the reach of positive science, yet 
 we have reason to expect that further investigation 
 will lead to the same kind of knowledge in regard 
 to the growth of a species that we now have in 
 regard to the growth of each individual animal or 
 plant. 
 
 Again, as we well know, growth in nature is very 
 greatly influenced by secondary causes of various 
 kinds, such, for example, as soil and climate ; and as 
 with the growth of the individual, so, undoubtedly, 
 
DARWIN*S THEORY. 253 
 
 with the growth of the species. Moreover, no one can 
 doubt the potency of the causes which have been 
 so acutely studied by Mr. Darwin. It is the busi- 
 ness of science to study these secondary causes, 
 and the nature and extent of their influence are 
 questions of fact to be decided by scientific investi- 
 gation, and by that alone. The action of these sec- 
 ondary causes, however, is obviously irregular, pro- 
 ducing retrogression quite as frequently as progres- 
 sion, and causing those fluctuations which are so 
 characteristic of the growth of nature ; but who 
 can fail to see that during the geological ages 
 there has been a great advance, and the present 
 • complex result, which we call nature, with all its 
 intricate adjustments and relations, can be no 'more 
 rationally ascribed to the causes which have pro- 
 duced variations of details, however great, than can 
 the mechanism of a clock be referred to the cir- 
 cumstances which in different localities have often 
 determined large and important changes in the ma- 
 terials or plan of its construction. 
 
 I repeat, therefore, no development theory can 
 impair the evidence of design, for that evidence is 
 based on facts wholly independent of any theory of 
 cosmogony, and to which all theories must conform. 
 If they do not, they will inevitably fall. The diffi- 
 culty, to my mind, in Mr. Darwin's particular theory, 
 is not in its development feature, nor in its princi- 
 ple of " natural selection " as a proximate cause of 
 variation in species, but in the at least tacit assump- 
 tion made by so many of its advocates that this 
 principle is the one and only efficient cause of the 
 
254 THE FINAL CRITERION. 
 
 resulting adaptations In nature. As a temporary- 
 mode of correlating facts, and as a working hy- 
 pothesis which has pointed out fruitful lines of in- 
 vestigation, the theory of Mr. Darwin must be re- 
 garded as one of the most important contributions 
 to modern science; but a naturalist must ignore the 
 whole history of physical science who would claim 
 that this theory was more than a very partial truth, 
 and unless it can be shown that it is consistent 
 with the action of an intelligent first cause, it will 
 soon be forgotten like those that have gone before it. 
 This is the criterion by which all such theories are 
 finally judged after the excitement of the controversy 
 by which they were heralded has passed, and after 
 the common sense of mankind has settled down upon 
 its sober second thought. Let us insist that all 
 theories of cosmogony shall be judged on their own 
 merits as scientific theories, but let us also insist 
 that they shall be kept within their own sphere, and 
 not allowed to have a voice in questions of religious 
 faith, on which they have absolutely no bearing. 
 That they have an injurious influence while they 
 last, is frequently more the fault of the secondary- 
 advocates than of the principals in the dispute, and 
 we must not expect to cure the evil by indiscrimi- 
 nate censure or by social excommunication. So long 
 as man thinks, he will speculate ; and I rejoice that 
 neither political nor ecclesiastical tyranny can touch 
 this prerogative of free thought. The true remedy 
 consists in exposing the fallacy of the shallow phi- 
 losophy which is so ready to bring forward these 
 crude speculations as proofs of materialism, and also 
 
FIRM BASIS OF THE ARGUMENT. 255 
 
 in diffusing among educated people more spiritual 
 views of nature and its laws. 
 
 To this subject I shall return in the next chap- 
 ter. But so far as the argument for design is con- 
 cerned, all these considerations are unnecessary. 
 The evidence is so ample, that we can afford to 
 waive all that part of it which has been called in 
 question by the progressionists, without weakening 
 in the slightest degree the force of the argument. 
 Before the first organic cell could exist, and before 
 Mr. Darwin's principle of natural selection could 
 begin that work of unnumbered ages which was to 
 end in developing a perfect man, nay, even before 
 the solid globe itself could be condensed from La- 
 place's nebula, the chemical elements must have 
 been created, and endowed with those properties 
 by which alone the existence of that cell is rendered 
 possible. 
 
 But although, for the sake of argument, we might 
 yield to the progressionists all those examples of 
 adaptation which they claim to explain by their the- 
 ories, such a concession is really of no value. The 
 parts of nature, as we have seen, are so intimately 
 linked together that, if there be design anywhere, 
 there is design everywhere ; and as the structure of 
 the human body was prefigured by the earliest verte- 
 brate forms buried in the geological strata, so, and as 
 unquestionably, the whole scheme of organic life was 
 prefigured in the gases composing the atmosphere. 
 If, therefore, I have proved that there is evidence 
 of design in the constitution of the atmosphere, I 
 have also proved that the whole scheme of nature is 
 
2S6 HONEST DOUBTS. 
 
 the result of Divine Intelligence, and that the great 
 argument of natural theology rests on a basis which 
 no present theories'^ of development can touch. To 
 show that there is evidence of design in these stones 
 of nature's edifice has been my chief object in 
 this book. It has been my constant aim to set 
 forth in a clear light the startling fact that the 
 footprints of the Creator are nowhere more plainly 
 visible than on that very matter which the materi- 
 alists so vainly worship, and if I have thus been able 
 to remove doubts from the mind of any honest 
 seeker after God, I shall feel that my labor has not 
 been lost. 
 
 But however earnest the purpose or sincere the 
 convictions, the spectres of our doubts will some- 
 times return, and hover around these evidences of 
 our faith. Treat them not lightly either in yourself 
 or in those you love. Respect all honest doubts ; 
 for it is the noblest natures which feel them and 
 suffer most. His must be a dull heart which is not 
 sometimes appalled by the mystery of our being. 
 Remember, however, that these doubts are from 
 within, not from without. They are the offspring of 
 your fears, and not of your science. The evidence 
 is ample. It is more faith that you need. Fight, 
 then, these spectres of your mind as the enemies of 
 your peace, not with doubtful disputations, but 
 
 * We of course refer only to such theories and speculations as are 
 based on observed facts ; for no others are worthy of serious consid- 
 eration. Science has not as yet gone one step behind the chemical ele- 
 ments, and until it has, no speculations in regard to a primordial con- 
 dition of matter can have any bearing on our subject. 
 
HONEST DOUBTS. 2$/ 
 
 with earnest thought and prayer, and Power shall 
 be with you 
 
 " in the night, 
 Which makes the darkness and the light, 
 And dwells not in the night alone."* 
 
 * Read in this connection Canto cxxii. of the ** In Memoriam." 
 
CHAPTER IX. 
 
 ARGUMENT FROM GENERAL PLAN. 
 
 It has been my object in the previous chapters 
 of this work to develop before you the great argu- 
 ment of Natural Theology as it is presented by the 
 atmosphere. I have endeavored to show that there 
 is abundant evidence of design, even in the proper- 
 ties of the chemical elements, and hence that the 
 argument rests upon a basis which no present theo- 
 ries of development can shake. Having dwelt upon 
 the argument from special adaptations at as great 
 length as my plan will permit, I wish in this chapter 
 to present another class of evidences of the Divine 
 attributes, which, although less conspicuous, may be 
 even more impressive to some minds than those we 
 have studied. The indications of an Infinite Intelli- 
 gence are not only to be found in the adaptations 
 of nature, but they also appear in the grand laws by 
 which the whole material universe is directed. 
 
 I am well aware that the laws of nature, so far 
 from being regarded as evidences of the existence 
 of a beneficent God, are felt by many minds to be 
 actual hinderances to their faith. They are thought 
 to give to the whole scheme of nature a mechanical 
 
 258 
 
DEFINITION OF PHYSICAL LAWS. 259 
 
 aspect, and to be inconsistent with belief in a super- 
 intending Providence. I also know that there are 
 many scientific men who regard the laws of nature 
 as the manifestation of blind physical forces, and 
 who recognize a Providence, if at all, only in the 
 very few recorded instances where the normal action 
 of these forces has been averted by a special mi- 
 raculous interposition. But even admitting this phi- 
 losophy, still I think it will appear that these laws 
 bear so conspicuously the marks of Intelligence, and 
 are so analogous to the results of human thought, 
 that we cannot resist the conclusion that they were 
 originally, at least, ordained by an intelligent Crea- 
 tor, or, in other words, that the laws of nature are 
 the thoughts of God. For myself, I regard the 
 laws of nature as the most direct evidence possi- 
 ble of Infinite wisdom, and it will be my object to 
 show that this opinion is sustained by the strongest 
 analogies. 
 
 Regarded from a scientific point of view, physical 
 laws are merely our human expressions of that order 
 which we discover in the material universe. In its 
 highest form, the law is capable of a precise quanti- 
 tative statement, and gives the basis for mathe- 
 matical calculation and prediction. Thus the law 
 of gravitation enables the astronomer to calculate 
 what will be the position of the bodies of the solar 
 system at any future epoch, and to predict, almost 
 to the very second, the exact time when an eclipse 
 will begin, and what will be the precise path of its 
 shadow over the earth. The greater part of the 
 laws of nature do not, however, admit of precise 
 
26o DEFINITION OF PHYSICAL LAWS. • 
 
 mathematical statement, and are merely the expres- 
 sions of the order which has been observed in the 
 phenomena of nature, whether in respect to form, 
 in respect to number, or in any other particular. It 
 is convenient to distinguish these merely phenomenal 
 laws from the higher class, which are usually called 
 dynamical ; but the distinction is an artificial one, 
 for it is probable, at least, that in all cases the 
 phenomenal laws are merely the phases of some 
 higher dynamical law not yet discovered. More- 
 over, if we believe that all phenomena are direct 
 manifestations of the Divine Will, then there is no 
 law apart from God. His action is not necessitated 
 or prescribed by any conditions, even although im- 
 posed by Himself. He is constantly acting in nature, 
 consciously and freely ; but He acts uniformly, con- 
 sistently, and with a plan, because He is omniscient 
 and omnipotent. Man acts with inconstancy, be- 
 cause he is a finite being, and must^ be guided by 
 probabilities ; but with God, w^ho seeth the end from 
 tiTe beginning, there is no "variableness, neither 
 shadow of turning.'* 
 
 The whole material universe may then be re- 
 garded as the manifestation of one grand compre- 
 hensive creative thought, which God is slowly work- 
 ing out in nature. To study this thought in all its 
 details is the prerogative of man, and this study has 
 been the appointed means of cultivating his intellect 
 and elevating his condition. From time to time the 
 more gifted students have caught glimpses of parts 
 of the grand thought, and these glimpses we call 
 laws ; but even the law of gravitation, the most per- 
 

 IDEA OF SYMMETJ... , , - . 
 
 f 
 
 feet of all, is felt to be but a partial f a^^ ana' we ^/ 
 look confidently for the discovery of a Widfep . law /' , 
 which will comprehend Newton's great discover)^ as ^ 
 one only of its manifestations. Let us now, in ordfery 
 to elucidate and confirm this simple doctrine, com- ^ 
 pare some of the laws of nature with the results of 
 human thought, and, whatever may be our theory of 
 causation, we cannot but be impressed with the 
 striking analogy between the two. 
 
 The idea of symmetry is inherent in every human 
 mind. It may be more or less cultivated by experi- 
 ence, but the germs of the idea are found even in 
 the savage. However rude his condition, man is 
 pleased with a symmetrical disposition of objects, 
 and his taste is offended when the laws of sym- 
 metry are grossly violated, although he may have 
 no name for the idea. Corresponding with this 
 idea in our minds, we find symmetry everywhere m 
 nature. The parts of an animal are symmetrically 
 arranged around the body, and the leaves of a plant 
 are symmetrically disposed around the stem, but 
 nowhere in nature is the idea of symmetry so fully 
 developed as in the mineral kingdom. 
 
 Almost every solid substance, when slowly depos- 
 ited from a liquid or aeriform condition, assumes 
 a definite symmetrical shape which is peculiar to 
 the substance. These symmetrical forms are called 
 crystals, and the process by which they are ob- 
 tained is called crystallization. Freedom of motion 
 — such as the particles of matter have in the fluid 
 state — is an essential condition of crystallization. 
 Moreover, as the substance becomes solid, the par- 
 
262 IDEA OF SYMMETRY. 
 
 tides must have sufficient time to arrange themselves 
 in accordance with the tendency of the molecular 
 forces, and the longer the time occupied in the 
 process of crystallization, the more perfect we find 
 the crystals. The crystal represents the natural 
 condition of a substance, and the peculiar form is 
 the most essential and characteristic of all its prop- 
 erties. 
 
 Crystals are always polyhedrons, that is, solids 
 bounded by plane faces. Assuming this fact of ob- 
 servation, geometry teaches that the relative posi- 
 tions of the faces of a crystal may be defined by 
 means of three straight lines not all in one plane, but 
 crossing each other at a single point. These lines 
 are called axes, and the common point is called their 
 origin. Now, we can easily conceive of all the pos- 
 sible ways in which three such lines can be arranged, 
 and although the number of possible variations is 
 evidently infinite, yet they can all be classified under 
 a few categories. Again, taking in turn each of these 
 systems of axes, as they are called, we can read- 
 ily arrange planes symmetrically around the three 
 lines selected for reference, and thus by a process of 
 pure thought, with no other guide than the idea of 
 symmetry as it exists in our minds, we can develop 
 the corresponding geometrical forms, and it is these 
 forms, and these alone, which we find on actual crys- 
 tals. Moreover, the systems of possible axes corre- 
 spond to the families under which these crystals are 
 naturally classified. 
 
 In the first edition of this book, I attempted to 
 illustrate the truth we are discussing by showing 
 
IDEA OF SYMMETRY. 263 
 
 how the forms of what in crystallography is called 
 the regular system, may be developed by arranging 
 planes symmetrically around a system of axes con- 
 sisting of three lines of equal length at right angles 
 to each other ; but, as a consequence of the attempt 
 to popularize the subject, the illustration was neces- 
 sarily imperfect, and it became evident that the 
 conceptions involved could only be made intelligi- 
 ble to those who already had some knowledge of 
 crystallography. I shall therefore, in the present 
 volume, leave to the student the task of investigating 
 the details, and simply make the following general 
 statements. Crystals may be studied from two 
 points of view : first, as products of pure thought, 
 like the solids of geometry; secondly, as objects of 
 natural history; and the specimens found in nature 
 correspond, as far as they have been observed, to 
 the deductions of geometry. Furthermore, the lines 
 which we use in constructing mentally the theoretical 
 forms are directions which in the actual crystals are 
 distinguished by well defined physical relations. 
 
 The products of Nature's laboratory correspond, 
 then, exactly to the results of our own thoughts ; 
 and how can we resist the conclusion that they are 
 the manifestations of the thoughts of an intelligent 
 Creator ? In the language of science, the crystal is 
 said to obey the law of symmetry ; but obviously 
 this law is merely the reflection of the same simple 
 idea which exists in our own minds, and which must 
 have previously existed in the mind of God. The 
 whole science of crystallography is a development 
 of this idea of symmetry. Like geometry, it is a 
 
264 IDEA OF NUMBER. 
 
 product of pure thought, and its truths are entirely 
 independent of their material forms. Indeed, the 
 mineral kingdom, so far as it is known, does not per- 
 fectly represent the idea of symmetry, even as it 
 exists in the human mind. There are possible forms 
 which have never been obtained in nature, and the 
 science, even as we know it, could never have been 
 developed by observation alone. 
 
 By following out the simple idea of symmetry, 
 which is common to all men, we have found that the 
 results of our own thought perfectly agree with the 
 facts of nature. Let us now take another of the 
 primary ideas which exist in the human mind, and 
 see how fully that is realized in the material cre- 
 ation. The idea of number is as inherent in the 
 mind as that oT symmetry. I shall not attempt to 
 discuss its~dngih " or trace its development ; but as- 
 suming, as all will admit, that the results of human 
 skill constantly exhibit simple numerical relations, 
 let us inquire whether the same characteristic may 
 not be discovered in nature. 
 
 We have already referred to the well-known prin- 
 ciple that the position of a plane may be fixed by 
 means of three straight lines or axes crossing at a 
 common point called the origin. If the plane is suf- 
 ficiently extended it must, of course, cross each of 
 the three axes either at a finite or at an infinite dis- 
 tance from the origin, and if these distances, which 
 we call " parameters," are measured or calculated, the 
 position of the plane is defined. Again, on the crystals 
 of many substances — for example on those of the well- 
 known minerals quartz, calcite, and barite — we find a 
 
RATIO OF PARAMETERS. 265 
 
 great number of different planes, which, if not on any- 
 single crystal, have all been seen on the different crys- 
 tals of the substance that have been examined. If, 
 now, each of these planes is defined by its parameters, 
 it appears, on comparing the parameters measured on 
 a given axis, that, for crystals of the same substance, 
 the parameters of all the planes are simple numerical 
 multiples of each other. When a plane is parallel to 
 an axis, the parameter on this axis is of course infin- 
 ity, and this is the most commonly occurring case. 
 
 As an illustration of the law we. are considering, 
 we may take the crystals of barite — the mineralogi- 
 cal name of the chemical compound called baric sul- 
 phate. One of the most commonly occurring planes 
 on the crystals of this substance has parameters 
 which, when measured on the lines usually selected 
 as axes, have the relative values a : b : c = 1.6107: i : 
 1.2276. There have been observed on crystals of 
 barite no less than thirty-four different planes, and in 
 every case the parameters of these planes conform to 
 the expression a^: b': c^ = m x 1.6107: n x i : px 
 1.2276, in which m, n, and p are either simple whole 
 numbers, or else infinity. Thus we have for m, n, 
 and p such values as i22; 231 ; 112; 326; 142, etc., 
 and similar facts are true of the crystals of any other 
 substance. Indeed this law of simple numerical 
 ratios is the fundamental law of crystallography, and 
 gives to the science a mathematical basis. 
 
 Similar numerical relations appear when we study 
 the formation of chemical compounds. I have al- 
 ready defined a chemical element as a substance 
 which has never as yet been decomposed, and all 
 
266 LAW OF DEFINITE PROPORTIONS. 
 
 the matter with which man is now acquainted is 
 composed of one or more of at most seventy ele- 
 mentary substances. When two of these elements 
 unite together to form a compound body, the pro- 
 portions in which they combine are not decided by 
 chance. You cannot unite these elementary sub- 
 stances in any proportion you please. The propor- 
 tion in each case is determined by an unvarying law, 
 and the amounts required of either substance are 
 weighed out by Nature in her delicate scales with a 
 nicety which no art can attain. Thus, for example, 
 23 ounces of sodium will unite with exactly 35.5 
 ounces of chlorine ; and if you use precisely these 
 proportions of the two elements, the whole of each 
 will disappear and become merged in the compound 
 which is our common table salt. But if, in attempt- 
 ing to make salt, we bring together clumsily 23.5 
 ounces of sodium and 35.5 ounces of chlorine. Na- 
 ture will simply put the extra half-ounce of sodium 
 on one side, and the rest will unite. This law, which 
 governs all chemical combinations, is known as the 
 " law of definite proportions." 
 
 Tables will be found in works on chemistry which 
 give, opposite to the name of each elementary sub- 
 stance, a numerical value, usually called its atomic 
 weight, and in all cases, where the elements are capa- 
 ble of combining with each other, they either unite 
 in the exact proportions indicated by these numbers, 
 or else in some simple multiple of these proportions. 
 
 The following are the atomic weights which are 
 believed by the author to have been determined 
 with the greatest accuracy : 
 
ATOMIC WEIGHTS. 
 
 267 
 
 Aluminum 27.02 
 
 Antimony 120.00 
 
 Barium i37-i4 
 
 Bromine 79-95 
 
 Calcium 40.00 
 
 Carbon 12.00 
 
 Chlorine 35-46 
 
 Hydrogen i.oo 
 
 Iodine 126.85 
 
 Lead 206.91 
 
 Lithium 7.01 
 
 Magnesium 24.00 
 
 Nitrogen 14.04 
 
 Oxygen 16.00 
 
 Potassium 39- 14 
 
 Phosphorus 31 -05 
 
 Silver io7-93 
 
 Sodium 23.05 
 
 Sulphur , 32.07 
 
 Thallium 204.11 
 
 These values are called atomic weights because, 
 according to our modern chemical theory, they rep- 
 resent the relative weights of the ultimate atoms of 
 the elements. If this be the case, it is evident that 
 when the atoms group themselves together to form 
 the molecules"^ of various substances, the elements 
 must combine by whole atoms, that is, in the propor- 
 tion of the atomic weights, or of a simple multiple 
 of these proportions ; and thus this atomic theory 
 explains the law of definite proportions. 
 
 In connection with this table a most remarkable 
 fact should be noticed, which indicates the deep 
 significance of this series of values. They are all 
 mutually dependent, so that the same numbers 
 which represent the proportions in which two ele- 
 mentary substances combine with the same quantity 
 of a third substance, represent also the proportion, 
 or a multiple of the proportion, in which they com- 
 
 * The molecule of a substance is the smallest mass of the substance 
 that can exist by itself, and, when subdivided, it breaks up into ele- 
 mentary atoms, which, however, at once group themselves to form 
 new molecules. 
 
268 PROUT*S HYPOTHESIS. 
 
 bine with each other. Thus not only do i6 parts of 
 oxygen combine either with 1 2 parts of carbon or with 
 14 parts of nitrogen to form in the first case carbonic 
 oxide, and in the second case nitric oxide, but also 
 12 parts of carbon combine with 14 parts of nitro- 
 gen to form cyanogen ; and the same principle holds 
 for the other weights given in the table, when- 
 ever the elements are capable of combining, al- 
 though, in most cases, only the multiple values 
 appear in the formation of known compounds. 
 
 The standard of these weights is of course arbi- 
 trary ; but if one number stands for pounds, all the 
 rest stand for pounds, or if one stands for ounces, all 
 the rest stand for ounces. It is usual, however, to 
 leave the standard indefinite, and speak of so many 
 parts. Again, the weights have only relative values ; 
 but if we give to any one a definite value, all the 
 rest assume definite values. Our units must neces- 
 sarily be more or less arbitrary. Most chemists take 
 hydrogen for the unit of weight, and the numbers 
 given in the table express the atomic weights of 
 the other elements calculated on this assumption. 
 But we might take any one of the elem.ents as our 
 starting-point, and formerly the European chemists 
 used a system of weights calculated on the as- 
 sumption that the equivalent of oxygen was 100. 
 This assumption gives an entirely different system 
 of numbers ; but the difference is of no practical im- 
 portance so long as the relative values remain un- 
 changed. 
 
 Dr. Prout was the first to notice that many of the 
 atomic weights were simple multiples of that of 
 
PROUT^S HYPOTHESIS. 269 
 
 hydrogen, and he thought that, if the weight of 
 hydrogen was taken as unity, the other atomic 
 weights could all be expressed by whole numbers. 
 The progress of chemistry for a long time, however, 
 did not seem to confirm this view — since most of the 
 accurate experiments made for the purpose of fixing 
 these constants gave incommensurable values, and 
 this was especially true of a most noteworthy inves- 
 tigation, undertaken by Professor Stas, of Brussels, 
 with the view of testing Prout's hypothesis. His 
 experiments, which were conducted with extreme 
 care, and with very large amounts of material, 
 gave incommensurable values, and the results were 
 thought at the time to show that the hypothesis in 
 question was wholly illusory. Still it was remark- 
 able that the values obtained by Stas differed from 
 whole numbers only by a small fraction of a unit, 
 and in the accurate determinations which have since 
 been made by other chemists, the same striking feat- 
 ure appears. The nineteen atomic weights, whose 
 values are given in the above table, may be fairly 
 considered as the only ones which have been deter- 
 mined, with reference to hydrogen, with the greatest 
 attainable precision, or a near approach thereto, and 
 it will be noticed that, with the exception of the 
 atomic weight of chlorine, the values differ in no case 
 from a whole number by more than fifteen-hun- 
 dredths of an integer, and generally by much less. If 
 the atomic weights are in fact whole numbers, such 
 slight differences from the true values as these in 
 the observed results are exactly what we should 
 expect, seeing that no determinations of this kind 
 
270 LAW OF MULTIPLE PROPORTIONS. 
 
 can with certainty be freed from the influence of 
 constant experimental errors. On the other hand, 
 if the true weights are incommensurable and distrib- 
 uted by chance, the probability that the observed 
 values would all lie so near to whole numbers as 
 they do would be exceedingly small, and hence the 
 total result, as far as it goes, may be said to confirm 
 rather than invalidate Prout's hypothesis. But leav- 
 ing this question to be decided by further investiga- 
 tion, let us turn to an allied class of facts, which 
 exhibit a very simple numerical relation, that can- 
 not be questioned, and which, indeed, by analogy 
 furnish a certain presumption in favor of the hypo- 
 thesis of Prout. 
 
 In very many cases the same elements, by uniting 
 in different proportions, form several distinct com- 
 pounds, and we invariably find that the proportions 
 of the elements in the different compounds bear a 
 very simple numerical relation to each other. Thus 
 there are five compounds of oxygen and nitrogen, 
 which contain these elements in the proportions 
 indicated in the following table. 
 
 Compounds of Oxygen and Nitrogen, 
 
 Nitrogen. Oxygen. 
 
 Nitrogen Monoxide 14 parts. 8 parts. 
 
 Nitrogen Dioxide 14 " 8x2 = 16 " 
 
 Nitrogen Trioxide 14 " 8 x 3 = 24 " 
 
 Nitrogen Tetroxide 14 " 8 x 4=32 " 
 
 Nitrogen Pentoxide 14 " 8x5 =40 " 
 
 It will be noticed that the proportions of oxygen in 
 
LAW OF MULTIPLE PROPORTIONS. 2/1 
 
 these compounds are in all cases simple multiples of 
 eight, the proportion in the first. In like manner, 
 the compounds of manganese with oxygen show 
 similar relations. 
 
 Compounds of Oxygen and Manganese. 
 
 Manganese. Oxygen. 
 
 Manganese Monoxide 27.5 parts. 8 parts. 
 
 Red Manganese Oxide 27.5 " io|==8 x \\ " 
 
 Manganese Sesquioxide 27.5 " 12 =8xi|- " 
 
 Manganese Dioxide 27.5 " 16 =8x2 " 
 
 Manganese Heptoxide 27.5 " 28 =8 x 3J " 
 
 The relation is not quite so simple as in the other 
 case, but still the same general truth is evident, and 
 these two examples are fair illustrations of what has 
 been observed throughout the whole range of chem- 
 ical compounds. Thus we find in these elementary- 
 forms of matter — the blocks with which the universe 
 has been built — the same simple numerical relations 
 which everywhere appear in the constructions of man. 
 Similar numerical relations are found throughout 
 the whole universe of matter. In the solar system, 
 for example, with the exception of Neptune, the 
 intervals between the orbit of Mercury and the 
 orbits of the other planets go on doubling, or nearly 
 so, as we recede from the Sun. Thus the interval 
 between the Earth and Mercury is nearly twice as 
 great as that between Venus and Mercury, the 
 interval between Mars and Mercury nearly twice 
 as great as that between the Earth and Mercury, 
 and so on. Again, if we compare the periods of 
 revolution around the Sun, expressed in days, we 
 
2/2 LAW OF PERIODIC TIMES. 
 
 shall find another simple numerical relation, as 
 shown by the following table. 
 
 Law of Periodic Times. 
 
 Observed. Theoretical. Fractions. 
 
 Neptune 60,129 62,000 
 
 Uranus 3o>687 31,000 \ 
 
 Saturn io,759 ^^^ZZZ \ 
 
 Jupiter 4,333 4,133 I 
 
 Asteroids 1,200 to 2,000 1,550 f 
 
 Mars 687 596 -f^ 
 
 Earth 365 Z^^^^X _s 
 
 Venus 225 227 l^f ) ^^ 
 
 Mercury 88 87 \l 
 
 It will be noticed that the period of Uranus is \ 
 that of Neptune, the period of Saturn \ that of 
 Uranus, the period of Jupiter about f that of Saturn, 
 the period of the Asteroids about f that of Jupiter, 
 the period of Mars about -^ that of the Asteroids, 
 the period of Venus about /y that of Mars, and the 
 period of Mercury about if that of Venus. The 
 successive fractions are very simply related to each 
 other, as will at once appear on writing them in a 
 series, 
 
 112 3 5 8 1J? /?rr 
 
 Notice that, after the first two, each succeeding 
 fraction is obtained by adding together the numera- 
 tors of the two preceding fractions for a new numera- 
 tor, and the denominators for a new denominator. 
 From this series, however, the Earth is excluded. 
 Its time of revolution is almost exactly -^^ of that 
 
LAW OF PHYLLOTAXIS. 2/3 
 
 of Mars, and that of Venus nearly -|f of that of the 
 Earth ; but although these fractions do not fall into 
 the above series, they are members of a comple- 
 mentary series beginning 
 
 This simple relation was discovered by Professor 
 Peirce, and he has proposed an explanation for the 
 anomaly presented by the Earth. But it is not 
 important to dwell on this point. My only object 
 has been to show that simple numerical relations ap- 
 pear in the planetary system, and this, as I trust, 
 has been fully illustrated. 
 
 Passing now to the vegetable kingdom, we fina 
 again the same numerical laws. The leaves of a 
 plant are always arranged in spirals around the 
 stem. If we start from any one leaf, and count the 
 number of leaves around the stalk and the number 
 of turns of the spiral until we come to a second leaf 
 immediately over the first, we find that for any given 
 plant, as an apple-tree fqr example, the number of 
 leaves and the number of turns of the spiral are al- 
 ways absolutely the same. The simplest arrange- 
 ment is where the coincidence occurs at the second 
 leaf, after a single turn of the spiral ; and this may 
 be expressed by the fraction ^, whose numerator de- 
 notes the number of turns of the spiral, and whose 
 denominator the number of leaves. The next sim^ 
 plest arrangement is when the coincidence occurs at 
 the third leaf, after a single turn of the spiral, and 
 may be expressed by the fraction i. These two 
 fractions express respectively the greatest and the 
 
274 
 
 LAW OF PHYLLOTAXIS. 
 
 smallest divergence between two successive leaves 
 which has been observed. The angle between two 
 successive leaves, therefore, is never greater than 
 1 80°, or half the circumference of the stem, and 
 never less than 120^, or one-third of the circumfer- 
 ence. The arrangement next in simplicity is where 
 the coincidence occurs at the fifth leaf, after two 
 turns of the spiral, as is represented in the preced- 
 ing figures. Other examples are given in the table 
 
 Law of Phyllotaxis (Leaf -Arrangement), 
 
 Name of Plant. 
 
 Number of 
 
 Turns 
 of Spiral.* 
 
 Number of 
 Leaves.* 
 
 Fraction, 
 
 Angle of Divergence 
 
 between two 
 successive Leaves. 
 
 Grasses 
 
 I 
 I 
 
 2 
 3 
 
 5 
 
 8 
 
 13 
 21 
 
 2 
 3 
 
 5 
 
 8 
 
 13 
 
 21 
 
 34 
 
 55 
 
 1 
 f 
 -1% 
 
 180" 
 120° 
 
 144° 
 
 135° 
 138° 28' 
 
 137° 9' 
 
 137° 39' 
 137° 27' 
 
 137° 30' 28" 
 
 Sedges 
 
 Apple, ) 
 
 Cherry, \ 
 
 Poplar, ) 
 Holly, ) 
 
 Callistemon, >• 
 
 Aconite, ) 
 Rosettes of the 1 
 
 Houseleek, 1 , , 
 Cones of the | 
 White Pine, J 
 Cones of the Euro- ) 
 pean Larch, \ 
 Certain Pine Cones, 
 Certain Pine Cones, 
 
 Typical arrangement which would expose to the . 
 Sun's rays the greatest leaf-surface, 
 
 which follows, and it will be seen that we have pre- 
 cisely the same series of fractions in the arrange- 
 ment of leaves around the stem of a plant which 
 
 * Before a leaf occurs vertically over the first. 
 
ARGUMENT FROM GENERAL PLAN. 2/5 
 
 appears in the periods of the planets. The fractions 
 of this series are all gradual approximations to a 
 mean fraction between ^ and |, which would give 
 the most nearly uniform distribution possible to the 
 leaves, and expose the greatest surface to the sun. 
 
 But this law does not stop with the plants. The 
 same series of fractions expresses also the spiral 
 arrangement of the tentacles of the Polyp and of the 
 spines of the Echinus. Thus through the whole 
 realm of nature, from the structure of the crystals to 
 the dimensions of the human form, a similar numeri- 
 cal simplicity is preserved. 
 
 Have you never recognized the composition of 
 your friend in some anonymous literary article, by a 
 peculiar phraseology, a turn of style, or a method of 
 thought which no artifice could conceal ? Have you 
 never felt a glow of pleasure when you unexpectedly 
 discovered on the walls of a picture-gallery the work 
 of a well-known artist, marked by some peculiarity 
 of grouping or coloring? Has your attention never 
 been quickened when an orchestra has suddenly 
 struck into a new theme of a favorite composer, 
 never heard before, but unquestionably his? If you 
 have experienced these or similar emotions, you 
 know something of the force with which such nu- 
 merical laws impress the mind of the student of 
 nature, and you also know how difficult it is to make 
 the power of such impressions understood. I wish 
 I could givQ you a full conception of this power ; 
 for you cannot otherwise feel the full force of the 
 evidence which these facts afford. They point di- 
 rectly to an intelligence in nature like our own, and 
 
276 ARGUMENT FROM GENERAL PLAN. 
 
 they are a seal to the declaration of the Bible, that 
 man was created in the image of his God. 
 
 The broken porticoes of the Parthenon still stand 
 on the Acropolis at Athens to incite the imitation 
 and win the admiration of the architect. That beau- 
 ty of outline and those faultless proportions, which 
 modern art has copied but never excelled, all depend 
 on an exact conformity of all the parts to the laws 
 of symmetry and to simple numerical ratios. We 
 justly regard that ruined temple as the evidence of 
 the highest intelligence ; and when we find the same 
 symmetry, the same numerical ratios, appearing 
 everywhere in nature, how can we refuse to admit 
 that they also are the evidence of intelligence and 
 thought ? Moreover, since the laws of symmetry 
 and number pervade the whole universe, from the 
 structure of the solar system down to the organiza- 
 tion of a worm, they prove, if they prove anything, 
 that the whole is the manifestation of the thoughts 
 of the one great Jehovah, who " in the beginning " 
 created all things by the word of His power. 
 
 I have thus endeavored to show that the laws of 
 nature, so far from proving that the world is governed 
 by an inexorable necessity, furnish the strongest evi- 
 dence of an overruling mind. We must be careful, 
 however, not to misinterpret this evidence ; for an- 
 alogies like those we have studied led Schelling and 
 the philosophers of his school to regard outward 
 nature not merely as the result of Divine Thought, 
 but as identical with that thought, and inseparable 
 from it. Indeed, there are many among us who re- 
 
ERROR OF PANTHEISM. 2// 
 
 gard the material universe as the manifestation of 
 God, in the same intimate sense in which our bodies 
 are the manifestation of our own personality; who 
 therefore believe that the world is and always has 
 been a part of His Eternal Being, and who look 
 upon the laws of nature not merely as the mani- 
 festation of an Infinite Intelligence, but as a part of 
 that Intelligence itself. 
 
 This philosophy may be made to appear very 
 attractive, and even very reverential ; but when fol- 
 lowed out to its logical consequences, it reduces God 
 to the level of nature, and merges His being in the 
 matter He created.. We must be as careful to avoid 
 the snares of pantheism, as the slough of material- 
 ism. Both are equally destructive of true religion, 
 and, although they lie on opposite sides of the Chris- 
 tian's path, they lead to the same result ; and if once 
 enticed from the narrow way, the Christian will be 
 fortunate if Faith rescues him from the peril before 
 he falls into the gulf of atheism. We must not con- 
 found the Creator with the creature. There is a per- 
 sonal God above all and over all, and although na- 
 ture manifests His intelligence, its material forms are 
 only the reflection, not the substance, of His Being. 
 The error of the pantheist arises from a too superficial 
 study of nature, and if we examine more closely the 
 analogies between the laws of nature and the results 
 of human thought, I am confident we shall find that 
 the created forms may be readily distinguished from 
 the Intelligence which gave them being. 
 
 In every human work we may always distinguish 
 two things, the conception and the execution, and the 
 
278 CONCEPTION AND EXECUTION. 
 
 last never exactly conforms to the first. For ex- 
 ample, in one of the grand Gothic cathedrals of our 
 mother country we see united in the plan, first, the 
 idea of the cross, the emblem of our Christian faith ; 
 then the spire, typifying the aspiration of the soul ; 
 and lastly, the long aisles, whose pointed arches and 
 delicate tracery have been copied from the interlac- 
 ing branches of God's first temple. The combina- 
 tion of these ideas may be said to be the conception 
 of the cathedral ; but how differently has this con- 
 ception been embodied in the numerous cathedral 
 churches of England ! Besides the peculiar caprices 
 of the architect or builder, we can trace in each 
 church an evident adaptation of the parts to special 
 purposes. Here a " lady chapel ** has been included 
 in the design, and here the mausoleum of a king or 
 a prelate ; here a portion has been adapted to the 
 reading of the service, and here to the session of the 
 ecclesiastical court ; but however varied the execu- 
 tion, the same conception is evident in all. So it is 
 in all architecture. Our modern dwellings are built 
 after a few general types, and the conception is very 
 nearly the same in all houses of any one class. But 
 how differently a skilful architect will arrange the 
 details, and adjust them to the circumstances of the 
 location, to the wants of the family, or the taste of 
 the owner! and no one knows better than he that 
 the conception of the building is one thing, and the 
 execution of that conception a very different thing. 
 
 In the higher forms of art, the same truth appears 
 even more strikingly. The Transfiguration of Ra- 
 phael, that masterpiece of painting, does not hold 
 
DISTINCTION ILLUSTRATED. 279 
 
 you breathless before it so much by what it actually 
 represents, as by what it embodies and helps you to 
 realize. He who sees merely what is painted on the 
 canvas will turn away disappointed, but in the soul 
 of the true student of art, who enters into the spirit 
 of the great painter, the conception grows as he 
 gazes, until he becomes transported and gains a 
 vision of the splendors of the Mount. In like man- 
 ner, it is not that lovely female face which has en- 
 deared the Sistine Madonna to so many hearts, and 
 made Dresden one of the shrines of the world. In 
 mere point of execution, this picture may be sur- 
 passed by many works of living artists ; but the con- 
 ception of a pure mother's love has been nowhere 
 embodied as there, and that is the charm. You 
 stand before the Laocoon until the blood runs cold 
 and the muscles writhe in sympathy, and then you 
 look at the motionless statue and wonder whence 
 comes the power. It is not in the skilfully chiselled 
 marble, but it is in the conception of the unknown 
 artist, which the petrified forms suggest. So it is 
 everywhere with the works of man ; the conception 
 can always be distinguished from the embodied fact. 
 But what need of illustration ? Who does not know 
 the difference between the two, and who has not 
 sadly experienced how far his best efforts fall short 
 of his ideal? The thought, the conception, how 
 noble ! the execution, the reality, how humble ! 
 
 Turning now to Nature, we find the same distinc- 
 tion there between the conception and the facts. Na- 
 ture does not, of course, like man, fall below her ideal 
 for want of power, but she departs from it in order to 
 
28o ILLUSTRATED BY CRYSTALS. 
 
 adapt her work to specific ends, or to accommodate 
 it to conditions and accidents of various kinds ; and 
 everywhere the conception, or, as we generally call 
 it, the law, is modified in the execution, so that the 
 actual can be plainly distinguished from that which 
 our minds have recognized as the ideal. Review for 
 a moment, with this idea, a few examples of nat- 
 ural laws, beginning with the law of symmetry. 
 
 We seldom, if ever, find in nature crystals having 
 that regularity of form or that perfection of outline 
 represented in our figures. Natural crystals are 
 almost invariably more or less distorted or imperfect, 
 and a perfect crystal is at best a very rare excep- 
 tion. It is true that in all cases of distortion the 
 relative inclination of the planes is very nearly con- 
 stant ; but even this is liable to a slight variation. 
 Moreover, many of the ideal forms of crystals are 
 never found in nature, or if at all, not in their per- 
 fection. They are at best merely shadowed forth, 
 as it were, on other forms, and so partially that the 
 unpractised eye would never detect them. So true 
 is this, that, as I have before stated, the present 
 science of crystallography could never have been 
 developed by observation alone. How evident, 
 then, the distinction between the actual crystals and 
 the thought which they embody ! 
 
 Crystallography is worthy of special study from 
 this point of view. Of all the departments of natural 
 history it most nearly approaches a perfect science. 
 The conceptions involved are so simple that they 
 have been grasped by the human understanding 
 with a completeness which has nowhere else been 
 
ILLUSTRATED BY CHEMISTRY. 28 1 ^ {^ 
 
 reached, and we feel confidence that, to a great ex- 
 tent at least, we comprehend the plan. Hence in 
 this science the distinction on which we are here in- 
 sisting becomes plainly marked, but of course the 
 truth can be realized in its fulness only by the stu- 
 dents who have mastered the subject. 
 
 In striking contrast to the completeness of the 
 science of crystallography, is the present obviously 
 rudimentary condition of the theory of chemistry ; 
 but even in this subject, although the thought has 
 been so imperfectly comprehended, the distinction 
 between the governing plan and the material mani- 
 festation is perfectly clear. The various attempts 
 to classify the chemical elements according to their 
 natural affinities have never been more than very par- 
 tially successful. This arises chiefly from the com- 
 plex relationship which many of the elementary 
 substances manifest, and different authors may rea- 
 sonably assign to such elements different places in 
 their system of classification, according as they chiefly 
 view them in one or the other aspect. Indeed, no 
 classification in independent groups can satisfy the 
 complex relations of the elements. These relations 
 cannot be exhibited by a system of parallel series, 
 but only by a web of crossing lines, in which the same 
 element may be represented as a member of two or 
 more series at once, and as affiliating in different 
 directions with very different classes of substances. 
 
 These attempts at classification have, however, 
 made conspicuous one feature in the scheme of the 
 chemical elements, which seems to be fundamental. 
 It appears that as the atomic weight increases, ele- 
 
282 SCHEME OF THE CHEMICAL ELEMENT. 
 
 merits having closely allied properties occur at nearly- 
 regular intervals, so that with Mendelejeff we can 
 arrange the elements in the order of their atomic 
 weights in a series of horizontal lines containing 
 each about seven members, and bring into the same 
 vertical columns only elements which belong to the 
 same natural family, or at least are allied in some 
 respect. Tables of the elements so arranged will be 
 found in most of the recent works on chemistry,^ but 
 necessarily the scheme is intelligible only to those 
 who are already familiar with the properties of the 
 elementary substances, and it would be out of place 
 to enter into the details in this book. As in almost 
 all classifications of natural objects, the observed 
 facts require considerable humoring in order to 
 accommodate them to the scheme, and, moreover, the 
 elements that are brought together in the vertical 
 columns are frequently allied by only one set of 
 their properties, while in other respects they are 
 equally or even more closely related to elements 
 from which they are widely separated by the system. 
 Still no one who studies the subject can fail to be 
 impressed with the general fact that there is an 
 orderly recurrence of similar qualities in the series 
 of the elements. Moreover, the discovery of the 
 new element gallium has filled one of the obvious 
 gaps in the series, as originally constructed by Men- 
 delejeff, and the qualities of this remarkable metal 
 closely conform to those which he had predicted for 
 the missing member of the series ; furthermore, some 
 
 * See Roscoe and Schorlemmer's Treatise, Vol. II., page 507. 
 
THE RARE ELEMENTS. 283 
 
 of the irregularities in the original classification have 
 been harmonized by redeterminations of doubtful 
 atomic weights. 
 
 The glimpses that we have thus been able to gain 
 of the order in the constitution of matter, give us 
 grounds for believing that there is a unity of plan 
 pervading the whole scheme, and encourage a con- 
 fident expectation, that hereafter, when our knowl- 
 edge becomes more complete, chemists may attain to 
 at least such a partial conception of this plan as will 
 enable them to classify both elementary and com- 
 pound substances under some natural system ; and 
 in imagination we may even look forward to the 
 time when science shall succeed in expressing all 
 the possibilities of this scheme in a few general for- 
 mulae, which will enable the chemist to predict with 
 absolute certainty the qualities and relations of 
 any given combination of materials and conditions. 
 But although to a very slight extent the idea has 
 been realized for the compounds of carbon, yet, 
 as a whole, this grand conception is to-day only a 
 dream. 
 
 There is a point connected with the classification 
 of the chemical elements which is deserving of our 
 notice in this connection. We have already seen 
 that, although some seventy elements have been 
 discovered — several of which, however, are as yet of 
 doubtful authenticity — -the greater portion of the 
 earth/s crust consists of only ten or twelve. In- 
 deed, if the remaining fifty elements were suddenly 
 annihilated, the mass of the globe, so far as we know, 
 would not be sensibly diminished. Indeed, a large 
 
284 THE RARE ELEMENTS. 
 
 number of the elements occur in such minute quanti- 
 ties that they can be detected only by the most skil- 
 ful chemical analysis. That these very rare elements 
 were designed by the Creator to subserve important 
 ends, we need not doubt ; but it is certain that they 
 play a very subordinate part on the surface of the 
 globe. For bromine and iodine, and a few others, 
 important applications have been discovered in the 
 arts or in medicine ; but the rest, comprising at 
 least one-third of all the known elements, have no 
 apparent value except as parts of a general plan. 
 In the light of a utilitarian philosophy they must 
 appear useless ; but to the true student of nature 
 they have a significance which transcends everything 
 else. They are parts of a universal order, of a Di- 
 vine cosmos, which would be incomplete without 
 them. They are the manifestation of Infinite In- 
 telligence. They embody the thoughts of God. In 
 the words of Chevalier Bunsen, " Law is the su- 
 preme rule of the universe, and this law is intel- 
 lect, is reason, whether viewed in the formation 
 of a planetary system or in the organization of a 
 worm.'* 
 
 But we must remember, in discussing this ques- 
 tion, that it does not follow, because we cannot dis- 
 cover any important end which these elements 
 subserve on our earth, that they have no practical 
 utility. For after acknowledging the dignity which 
 they acquire when regarded as the characters of that 
 language in which the creative thoughts have been 
 written, and as the appointed means of educating 
 the human race, still it does not seem consistent 
 
POSSIBLE USES. 285 
 
 with that economy of resources which appears in all 
 parts of the Divine plan, that they should have no 
 special functions to discharge in the cosmos. Now 
 I would suggest, but I offer the suggestion in all 
 humility, that these very rare elements may be 
 adapted by their peculiar properties to the thermal 
 conditions of some other planet or some other stel- 
 lar system. We have seen that those elements 
 which are the most widely distributed over the 
 earth are such as are adapted by their properties to 
 the conditions of organic life on the third planet of 
 the solar system, and it is certainly possible that 
 some different scheme of organic life may be sus- 
 tained on Mercury or Uranus, in which elements 
 rare to us take the place of oxygen, nitrogen, hydro- 
 gen, and carbon, and perhaps also the elements 
 missing in our classification may be found in some 
 other world, revolving around Sirius or Arcturus, 
 where oxygen, sulphur, and iron may be among the 
 rarities of science. 
 
 All this is, of course, the purest hypothesis, and 
 such speculation can lead to no positive results ; but 
 the very possibility of such speculations as those 
 in which we have been indulging in this connec- 
 tion illustrates most pointedly the great truth I 
 am endeavoring to enforce. The thought em- 
 bodied in the scheme of chemical elements is 
 something entirely apart from their material forms, 
 and the moment this thought is apprehended by 
 man, it opens to his imagination vistas of possible 
 realities which entirely transcend all human ex- 
 perience. 
 
286 ILLUSTRATED IN ASTRONOMY. 
 
 If next we compare, more carefully than before, 
 the periods of revolution of the planets around the 
 Sun, we shall find that the same general principle 
 holds true. The observed periods, you will notice 
 by the table on page 272, do not exactly correspond 
 to the simple ratios which express the law, and the 
 same is true of the distribution of leaves around the 
 stem of a plant, and in fact of all classes of phenom- 
 ena in nature. In each we observe only a tendency 
 towards a maximum effect, which is the perfect 
 expression of the law, but which is seldom fully 
 reached. The limits of variation are broader in 
 some cases than in others, but we find no case in 
 which the accordance is absolute. 
 
 In none, however, of the purely physical laws is 
 this character so strongly marked as in the structure 
 of animals and plants. It is well known that all 
 organized forms, although so wonderfully diversi-* 
 fied, are fashioned after a few general types. In the 
 animal kingdom there are only four general plans, 
 represented by the Radiata, the Mollusca, the Arti- 
 culata, and the Vertebrata, and all the animals of 
 any one of these great divisions are organized alike. 
 For example, in all vertebrate animals we find 
 essentially the same parts ; and similar homologies, 
 as they are called, may be traced throughout the 
 animal kingdom, and any anatomist will point out 
 to you in the skeleton of a fish, of a reptile, of a 
 bird, or of a quadruped, the bones which correspond 
 to the various parts in the skeleton of a man. In 
 the wings of a bat the bones of the human arm may 
 readily be traced. Moreover, very frequently when 
 
ILLUSTRATED IN ZOOLOGY. 28/ 
 
 there is no use for a given organ, it is still present in 
 a rudimentary condition. Professor Wyman found 
 rudimentary eyes in the so-called eyeless fishes of the 
 Mammoth Cave, and equally striking examples of the 
 same general truth are familiar to every one. 
 
 Here, then, is a most obvious distinction between 
 the conception and the execution, and the general 
 plan of the skeleton is preserved, even where there 
 is no use for certain parts, and where we might per- 
 haps conceive of a simpler arrangement without 
 them. But, more than this, we find that the varia- 
 tions from what we may regard as the typical form 
 have been obviously made in order to adapt the 
 organs to certain specific ends. The same plan 
 which, developed in its full perfection, appears in 
 the human hand and arm, reappears, more or less 
 fully carried out, in the fore legs of a horse, in the 
 wings of an eagle, and in the pectoral fins of a dol- 
 phin ; and in each case the organ has been obviously 
 adapted to some special purpose. Special adapta- 
 tion has thus been most beautifully harmonized with 
 general law, and the conception has been varied in 
 the execution in order to secure some wise and 
 important end. 
 
 We, of course, do not forget that the rudimentary 
 organs to which we have referred are looked upon 
 by the evolutionists from a very different point of 
 view, and constantly cited as among the strongest 
 evidences cf the truth of their theories ; that they 
 are regarded by them as the survivals of a previous, 
 condition in which they played their appropriate 
 parts, and as an inheritance which marks the ancestry 
 
288 SURVIVALS AND TYPES. 
 
 of a species, as family traits often mark the ancestry 
 of an individual : and although, as it seems to us, 
 this explanation of the origin of rudimentary organs 
 will not hold in all cases, we at once admit its wide 
 application, and we leave all such questions of proxi- 
 mate causes to the naturalists, to be decided on 
 scientific evidence, and on that alone. But we 
 claim that the facts are perfectly consistent with the 
 operation of an intelligent first cause, and that this 
 more comprehensive interpretation, so far from ex- 
 cluding, includes all temporary influences and sub- 
 ordinate effects. 
 
 This subject is capable of almost indefinite illus- 
 tration, and the vegetable kingdom is as rich in ex- 
 amples of the principle we have been discussing as 
 the animal. I have not, however, time for further 
 details. The whole ground has been most carefully 
 surveyed by McCosh and Dickie in their excellent 
 work entitled ^* Typical Forms and Special Ends in 
 Creation," and to this I would refer those who may 
 be interested to pursue the study of these singular 
 facts. Sufficient, I trust, has already been said to 
 show that the phenomena of nature and the results 
 of human thought resemble each other in their very 
 incompleteness. 
 
 While, therefore, a more careful study has tended 
 to confirm the result at which we arrived in the last 
 chapter, and has strengthened the impression that 
 the universe was created by an intelligence like our 
 own, we have also found that the analogies of nature 
 point with equal distinctness to the conclusion that 
 this intelligence is a being entirely apart from and 
 
MANIFESTATION OF INTELLEGENCE. 289 
 
 infinitely superior to the matter he created or the 
 laws he ordained. If these analogies are worth any- 
 thing, they point not to a spirit of the universe, 
 pervading and energizing matter, but they prove 
 the existence of a personal God ; one who can sus- 
 tain to us the relations of Father, Saviour, and 
 Sanctifier; one whom we can love, worship, and 
 adore. 
 
 But it may be urged that I have drawn my illus- 
 trations wholly from the phenomenal laws of nature, 
 and entirely overlooked the great dynamical laws, 
 which, like the law of gravitation, are more precise. 
 Moreover, it will be said that the history of astron- 
 omy gives us every reason to believe that these very 
 variations, to which I have assigned such importance, 
 are merely necessary consequences of some higher 
 law not yet discovered, just as the perturbations of 
 the planetary orbits are the legitimate results of the 
 very law they seemed at first to invalidate. I have 
 no doubt that in part, at least, this will be found to 
 be the case. But even in regard to the law of gravi- 
 tation, there always have been residual phenomena, 
 unexplained by the law, and so probably there 
 always will be, until, as we go on widening our gen- 
 eralizations, the last generalization of all brings us 
 into the presence of that First Cause through whom 
 and by whom all things are sustained. 
 
 I trust that the striking analogies between the 
 phenomena of nature and the results of human 
 thought, which I have been able so imperfectly to 
 illustrate, have impressed you, as they impress me, 
 with the profound conviction that the order of nature 
 13 
 
290 ASPECT OF NATURE. 
 
 is the manifestation of an Infinite Intelligence, but 
 of an Intelligence apart from, and superior to, the 
 cosmos which it once created and now upholds. If 
 I have failed in my object, it is because I have been 
 unable to bring home these analogies to your under- 
 standing. The resemblances are so striking, that I 
 do not believe a mind which is conversant with the 
 facts, and unbiassed by the prejudices of philosophy 
 or of education, can resist the conclusion that this 
 scheme of nature is the manifestation of an intelli- 
 gence like our own, at least so far as the Infinite can 
 be said to resemble the finite. Men may reasonably 
 entertain differences of opinion in regard to the 
 mode of action of that Being who has created the 
 universe. They may believe that a certain amount 
 of power, together with the germ of all future exist- 
 ence, was implanted in the original chaos, and that 
 the Deity has never interfered with the natural action 
 and the unfolding of the causes which He has thus 
 ordained ; but whatever theories of cosmogony may 
 be entertained, short of absolute materiahsm, he 
 must be indeed blinded by his prejudices who refuses 
 to recognize in these analogies the evidence of intel- 
 ligence and thought. 
 
 I do not, of course, regard analogies as proofs, nor 
 do I believe that this argument from general plan 
 could supply the place of the great argument from 
 Design. The last lies at the basis of Natural The- 
 ology, and all the rest is merely subsidiary to the 
 great central light. Moreover, while the argument 
 from design comes home to every man*s understand- 
 ing, these analogies appeal with their full force only 
 
HUMAN SYMPATHY WITH NATURE. 2gi 
 
 to the few who are able to study the processes of 
 nature for themselves, as they alone are familiar 
 with the phenomena in which the resemblances are 
 seen. But to the student, whose life has been passed 
 in successful investigation, and whose soul has been 
 brought into sympathy with the harmonies of nature, 
 these tokens are constantly assuring him of the pres- 
 ence of his God. Every discoverer feels — when in 
 brought face to face with a great truth, he cannot 
 resist the feeling — that, in discovering a law, he has 
 been brought nearer, not to a blind agency, but to 
 Omnipotence itself. To this conclusion he is not led 
 solely by philosophy ; for although he may defend 
 his conviction on reasonable grounds, in its full power 
 it transcends all human philosophy. Man cannot 
 always tell why he knows. But when illuminated 
 from the altar of his faith, all nature wears a new 
 aspect, and his spiritual eye discovers everywhere 
 acting that same Infinite Intelligence which "spake 
 in time past unto the fathers by the prophets," and 
 '* hath in these last days spoken unto us by his 
 Son." 
 
 Do I hear it said that such loose reasoning is a gross 
 violation of the Baconian philosophy, and of that 
 severe induction by which alone science has been 
 built up ? But do we not know, have we not seen, 
 that the whole structure of science rests on no firmer 
 foundation than these very analogies of nature, — 
 that at the beginning of all knowledge, where we 
 should most expect infallibility, we find only uncer- 
 tainty and doubt ? 
 
 Science is a grand temple built by man to glorify 
 
292 SCIENCE RESTS ON FAITH. 
 
 his Maker, its unfinished spire pointing to heaven, 
 but its foundations resting on a cloud. The work 
 has been done as well as faithful hearts and active 
 hands could do it. Examine its walls and its but- 
 tresses, and from base-stone to coping you will find 
 no defect. Each block has been so carefully wrought 
 and so firmly clamped in its place, with all the 
 strength of iron logic, that you will unhesitatingly 
 conclude that the mighty structure has been reared, 
 not for time, but for eternity. Yet it all rests on a 
 cloud. Let that cloud be dispersed, and only God 
 can tell whether the structure shall stand or fall. 
 
 Are we then, you will ask, to mistrust these 
 boasted results of science ? Is this imposing struc- 
 ture all a phantom, a mere day-dream, from which 
 we shall awake on the morning of eternity to find all 
 passed ? Certainly not ! God has not endowed his 
 creature with faculties of observation merely to 
 delude him, and with an intellect solely to lead him 
 into error. He has not raised up the long line of 
 scientific heroes of every age, merely to deceive 
 themselves and mislead the world. No ! the temple 
 of science will stand fast. That cloud on which it 
 rests is a firmer foundation than any granite rock ; 
 for it is not of man, but of God. Yet let us not for- 
 get that this assurance is based only on the same 
 faith which is the " substance of things hoped for, 
 the evidence of things not seen." 
 
 *' We have but faith : we cannot know ; 
 For knowledge is of things we see ; 
 And yet we trust it comes from Thee, 
 A beam in darkness : let it grow." 
 
CHAPTER X. 
 
 NECESSARY LIMITATIONS OF SCIENTIFIC AND RE- 
 LIGIOUS THOUGHT. 
 
 I HAVE endeavored to show that the evidence 
 which all nature affords of a personal God is 
 wholly independent of the theories of cosmogony 
 we may assume. But although our doctrine of 
 causation may not impair the evidence of an origi- 
 nal design, it is not so with the other bearings of 
 the subject. For if nature be a mere machine, 
 weaving the complex web of destiny with the same 
 precision and certainty with which a carpet-loom 
 weaves the pattern of a carpet, then the Christian's 
 idea of a superintending Providence cannot be true. 
 If nature has been evolved solely under necessary 
 conditions and laws, with which the Creator has 
 never interfered since he wound up the immense 
 weight which set the whole in motion and still main- 
 tains the preordained beats of the great pendulum 
 of the universe, — if with an archangel's intellect we 
 could predict every event in nature with the same 
 certainty with which we now foretell the phases of 
 an eclipse, — then I say again that the visions of an 
 overshadowing Providence which have appeared to 
 
 293 
 
294 SUPERINTENDING PROVIDENCE. 
 
 US at those milestones on our life's journey where, 
 wearied and disheartened, we have sat down to rest, 
 are nothing but a delusion and a dream. It does 
 not remove the difficulty here referred to, to say that 
 our lives are parts of this preordained plan, or even 
 to admit that God may interfere in the moral world 
 by influencing the will of man; for every one is con- 
 scious that his will has not been thus directly influ- 
 enced, and knows, moreover, that the circumstances 
 of his condition have always concealed, at the time, 
 the kind Providence by which he has been led. 
 And when your theory leads to this, that man has 
 been put into a world of probation and trial, and 
 there left to walk over pitfalls with his eyes blinded, 
 every unsophisticated mind will feel — say what you 
 will — that the character of the God you worship is 
 more truly symbolized by the car of Juggernaut than 
 by the cross. 
 
 A great deal of false prejudice against scientific 
 study arises from a mistaken impression that the 
 materialist's interpretation of nature is the natural 
 and necessary result of all scientific thought. 
 Hence not a few religious minds have concluded 
 that the methods of science must be all wrong, and 
 its conclusions wholly untrustworthy. It will not, 
 therefore, be out of place in this connection to con- 
 sider briefly whether the materialist's idea of causa- 
 tion is the necessary, or even^the probable conclu- 
 sion to which the observed facts of nature and the 
 legitimate methods of science lead. We must re- 
 member, however, while discussing this subject, that 
 we have passed the limits of human knowledge, and 
 
IDEA OF FORCE. 295 
 
 cannot therefore expect by our unaided processes of 
 thought to prove or disprove anything. We cannot 
 determine absolutely whether the materialist's theory 
 be true or false ; for science has not the knowledge 
 which would enable it to form a decision. The only 
 question for us is, whether this theory is the neces- 
 sary theory, or even the most probable theory ; and 
 if it is not either the one or the other, then the 
 theory is of no weight. One man's theory is as good 
 as another's, provided both are equally consistent 
 with facts. If, then, we can show, on scientific 
 grounds alone, that the Christian's theory of causa- 
 tion is as probable as the materialist's, we shall in 
 regard to this point also fully sustain the position 
 we have taken in regard to scientific studies. Surely 
 science is no more responsible for the excesses of 
 theorists than is religion for the crimes of bigots, 
 and it should be sufficient to satisfy any religious 
 mind, that there is a Christian theory which is per- 
 fectly consistent with all known facts. 
 
 It is easy to understand the relative position of 
 the two theories of causation after we have become 
 acquainted with the facts which both must neces- 
 sarily explain. Let us review, then, very briefly, 
 these facts, which are more or less familiar to every 
 one. An innate principle of the human mind com- 
 pels us to believe that every change must have 
 an adequate cause, and leads us to refer the phe- 
 nomena of nature to what we call forces. Thus the 
 falling of an avalanche, the flowing of the tides, the 
 beating of the waves, the blowing of the winds, the 
 crashing of the lightning, the burning of the fire, 
 
296 IDEA OF FORCE. 
 
 the moving power of steam, and the impression of 
 light, must all have an adequate cause, and to this 
 cause we give the name oi force. We use this word 
 so frequently and so familiarly that we are apt to 
 think that we associate with it a definite conception ; 
 but a moment's reflection will show that in regard 
 to the nature or origin of force we have no absolute 
 knowledge. This word is merely our name for the 
 unknown cause of natural phenomena. The unedu- 
 cated mind naturally refers the origin of all force to 
 the bodies from which it appears to emanate, and 
 regards it either as a quality inherent in matter, as 
 in the phenomena of gravitation, or as a property 
 superimposed upon matter, as in the phenomena of 
 light, heat, magnetism, and electricity. In either 
 case, however, it is regarded as a quality of matter. 
 Moreover, the uneducated mind, impressed most of 
 all by the great diversity in physical phenomena, 
 naturally infers that a similar diversity exists in the 
 forces which produce them, and thus is led to the 
 idea that there are different kinds of force. Hence 
 men have been led to refer the falling of bodies to- 
 wards the earth to a distinct force called gravitatioit, 
 the motion of a steam-engine to another force called 
 heat, the burning of a candle to a third force called 
 chemical affinity, and in like manner to each class of 
 phenomena they have assigned a peculiar and sepa- 
 rate force. 
 
 Such ideas as these are natural in the infancy of 
 knowledge, and we must remember that, with all our 
 boast of progress, the human race, so far at least as 
 physical science is concerned, is yet in its childhood. 
 
IDEA OF FORCE. 29/ 
 
 The law of gravitation was discovered only two 
 centuries ago, and almost the whole of the present 
 sciences of chemistry and physics has been developed 
 within the lifetime of men now living. Many of the 
 present generation were educated in those very 
 natural, but crude notions, and it is not until a com- 
 paratively recent period that even scientific men 
 have been persuaded that these primitive ideas must 
 be wholly abandoned, or at least radically modified. 
 We are now in a transition stage, and hence arises a 
 great difficulty in discussing the subject. The lan- 
 guage even of modern science is based upon the 
 old ideas, and we cannot describe natural phenom- 
 ena without using terms which imply what almost 
 all thinkers now believe to be erroneous notions. 
 Hence, when we attempt to present spiritual views 
 of the origin and nature of force, we are obliged to 
 use terms which imply the opposite, and our very 
 language appears to condemn us, or at least preju- 
 dices our theory. This is especially true of the word 
 force itself, and we must carefully bear in mind that 
 the origin of phenomena is not explained because, in 
 the language of science, they have been referred to 
 an assumed force with a high-sounding name. Names 
 are not things, and we know nothing more of the 
 cause which brings the apple to the ground because 
 Newton has called it the force of gravitation, than 
 we did before. He gave us the law of the motion, 
 and enabled us to predict how every apple would 
 fall, and how every planet would move throughout 
 space, but the cause of the motion is as closely hid- 
 den as ever. In regard to the law of gravitation we 
 13* 
 
298 TRANSFER OF ENERGY. 
 
 know a great deal ; but in regard to the force of 
 gravitation — whatever we may think or believe about 
 it — we know absolutely nothing, and the same is true 
 of every other force. 
 
 The most remarkable feature of modern science 
 has been the constant tendency of all investigations, 
 during the last fifty years, to show that the same 
 energy, if only differently applied, may produce the 
 most diversified phenomena; and now almost all 
 the so-called forces of the old philosophy appear to 
 be mutually convertible. Thus — to begin with a 
 lump of coal — as we have seen, a certain amount of 
 latent energy resides in that black mass, which has 
 been called the force of chemical affinity. Burn the 
 coal, — that is, combine it with oxygen, — and the 
 affinity is satisfied, but the energy reappears as light 
 and heat. If the coal is burnt under a steam-boiler, 
 the heat expands the water and converts it into 
 vapor, and then we find the energy again in the ex- 
 pansive force of steam. The steam expands against 
 the piston of the locomotive, and the energy passes 
 into the moving train. The rapidly moving mass, 
 in forcing its way through the air and over the iron 
 track, is constantly losing its moving power in con- 
 sequence of the friction it encounters ; but the energy 
 is not lost, and if we could follow it, we should find 
 it reappearing somewhere as heat. Suddenly the 
 engineer opens a valve, and a portion of the energy 
 of the steam gives motion to the air, and the effect 
 is a shrill whistle. The brakeman applies the brakes, 
 and the train after a few moments comes to rest. 
 Its moving power is gone, but the energy is not lost. 
 
TRANSFER OF ENERGY. 299 
 
 The motion has been transformed into heat, and the 
 smoking brake shows where the energy has gone. 
 
 Return now again to the lump of coal, and, in- 
 stead of burning it under a steam-boiler, heat it 
 in a properly constructed furnace in contact with 
 roasted zinc ore. This ore is a compound of zinc 
 and oxygen. The coal, in order to satisfy its in- 
 tense affinity, seizes on the oxygen and sets the zinc 
 free. But although the chemical affinity of the coal 
 has been satisfied, no power has been lost ; for the 
 energy which was before latent in the carbon is 
 now latent in the zinc. Dissolve the zinc in dilute 
 sulphuric acid, and the chemical affinity of the zinc 
 will be satisfied, and, if certain conditions are ful- 
 filled, the energy will take the form of a current of 
 electricity. Cause this current to flow through a 
 platinum wire, and this energy will appear in the 
 heat and light radiated from the glowing metal. 
 Cause the same current to flow in spiral lines around 
 a bar of iron, and we find the energy again in the 
 attractive force of an electro-magnet. Connect with 
 the electro-magnet appropriate machinery, and the 
 same energy may be so applied that it will move a 
 light boat or turn a small lathe. Lastly, connect 
 with the dissolving zinc four thousand miles of iron 
 wire, and the energy will be transmitted across a 
 continent with the velocity of thought, and write in 
 a distant city the message which it carries. 
 
 Illustrations like these might be multiplied indefi- 
 nitely ; but enough, I think, has been said to show 
 that, to all appearance at least, the same energy 
 may be transferred from one mass of matter to 
 
300 -POTENTIAL AND ACTIVE ENERGY. 
 
 another, and that thus, while nothing but the mode 
 of application has been changed, the power may re- 
 appear under entirely different manifestations, and 
 produce phenomena wholly unlike those in which it 
 was but a moment before the active cause. The 
 truth of this principle becomes still more evident 
 when we apply in our experiments exact measure- 
 ments ; for we find that in all these transfers of 
 energy from mass to mass the power reappears 
 undiminished. It may remain latent for a time, as 
 in a mass of coal, but sooner or later it will reappear 
 without having undergone the slightest loss. 
 
 We must here dwell for a moment upon an im- 
 portant distinction, which has already been implied, 
 between latent and active energy. It is a distinction 
 with which every one is practically familiar, and it 
 may therefore be made clear by referring to a few 
 examples. A weight falling to the ground from a 
 i given height is an example of active energy, while 
 an equal weight suspended at the same height rep- 
 resents an equivalent amount of latent energy. In 
 winding up a clock, muscular energy becomes latent 
 in the suspended weight, but reappears in mechanical 
 motion as the clock runs down. So also a lump of 
 coal, as already stated, represents a certain amount 
 of latent energy. When the coal burns, its energy 
 becomes active, and takes the form of heat. Again, 
 in smelting zinc ore there is transferred to the pro- 
 duct a portion of the latent energy of the coal used 
 in the furnace ; and if in a voltaic battery the result- 
 ing zinc dissolves in sulphuric acid, this energy 
 becomes active, and reappears in a current of elec- 
 
ENERGY NEVER LOST. 30I 
 
 tricity. Some persons do not like the term latent 
 energy, and speak of energy which is not in action 
 as possible or potential. In like manner they speak 
 of energy in action as actual or kinetic. But terms 
 are of no importance, if only the ideas which they 
 express are fully understood. 
 
 Keeping this distinction in view, we shall better 
 understand the bearings of the important principles 
 just before stated. When energy, in passing from 
 one body to another, changes its mode of manifesta- 
 tion, it seldom flows wholly into one channel, and 
 almost invariably more or less of it becomes latent. 
 Thus — to go back to the example of the steam- 
 engine — of the energy, which is latent in the coal 
 and becomes active in the form of heat when the 
 coal burns, not more than one-tenth, at the most, 
 produces any useful mechanical effect. The rest 
 becomes again latent in changing the water into 
 steam, and in heating and expanding the iron, the 
 bricks, the water, and the air in contact with which 
 the fuel burns. All this heated matter represents a 
 large amount of latent energy. It is in the condi- 
 tion of the wound-up weight of a clock, and, as it 
 cools, this energy is distributed to surrounding 
 bodies. Were it possible, at a given instant after 
 the burning of the coal, to sum up all the energy, 
 both active and latent, which could be traced di- 
 rectly back to the burning fuel, it would be found 
 that not the smallest fraction of the energy origi- 
 nally in the mass of coal had been lost. In this 
 case, of course, accurate experiments are out of the 
 question ; but wherever it has been possible to apply 
 
302 CONSERVATION OF ENERGY. 
 
 measurements, it has been found that the principle 
 here illustrated holds true. I should not be able to 
 make the methods of such investigations intelligible 
 without occupying a great deal of time. Let it then 
 be sufficient to state, that all those who have most 
 carefully studied the subject have arrived at the 
 same results. There is, therefore, every reason to be- 
 lieve that the principle we have been illustrating is 
 universally true. Let us then embody it in a definite 
 statement. All natural phenomena are the manifes- 
 tation of the same omnipresent energy, which is trans- 
 f erred from 07ie portion of matter to another without 
 loss. 
 
 But if the principle as thus stated be accepted, we 
 cannot rest here ; for it involves this further conclu- 
 sion, which, however marvellous, must be true. The 
 sum. total of all the active and latent energies in the 
 universe is cojistant a?id invariable. In other words, 
 power is as indestructible as matter.^ 
 
 This grand truth is generally called the law of 
 conservation of energy, and, if it cannot as yet be 
 regarded as absolutely verified, there can be no 
 question that it stands on a better basis to-day than 
 did the law of gravitation one hundred years ago. 
 
 But how can I give you any conception of the 
 sublimity of the truth which this formal language im- 
 plies, but which no language is adequate to express? 
 Even poetry, in the highest flights of fancy, has 
 never seen such a vision as these vistas of actual 
 
 * Many philosophers believe, with Newton, that matter in its es- 
 sence is only a manifestation of power, and if so the conservation of 
 mass in nature is only a phase of the conservation of energy. 
 
CONSERVATION OF ENERGY. 303 
 
 realities open to the intellect and imagination of 
 man. Review in the light of this grand generali- 
 zation the subsidiary truth which from time to 
 time I have endeavored to illustrate in this work, 
 — namely, that all terrestrial energy comes from 
 the sun. The accumulated power of the sun's deli- 
 cate rays produces, as we before saw, every mo- 
 tion and every change which takes place on the 
 surface of this planet, from the falling of an ava- 
 lanche to the. crawling of a worm. But that energy, 
 as we now know, is not exhausted on the earth. 
 To use the eloquent language of another : ^^ Our 
 world is a halting-place where this energy is con- 
 ditioned. Here the Proteus works his spells ; 
 the selfsame essence takes a million shapes and 
 hues, and finally dissolves into its primitive and 
 almost formless form. The sun comes to us as heat ; 
 he quits us as heat ; and between his entrance and 
 departure the multiform powers of our globe appear. 
 They are all special forms of solar power, — the 
 moulds into which his strength is temporarily 
 poured, in passing from its source through infini- 
 tude." ^ 
 
 Attempt now to bring together in imagination all 
 the energies acting at one moment on the earth, and 
 unite them in one tremendous aggregate. Begin 
 with the moving power of the air, the hurricanes, 
 the tornadoes, the storms, and the gentler winds 
 which are everywhere at work from the Arctic to the 
 Antarctic Pole, omitting in making the estimate, if 
 
 * Professor John Tyndall, in the work already quoted, "Heat 
 considered as a Mode of Motion." 
 
304 SOURCE OF ENERGY. 
 
 you choose, the Hghtning and the thunder, which, 
 though brilliant and noisy demonstrations of power, 
 would hardly increase by a unit the vast sum. Add 
 to this the mechanical power in the mighty flow of 
 waters, the ocean currents, the rivers, the cataracts, 
 the glacier-streams, and the avalanches, all over the 
 globe. Bring into the calculation the forces at work 
 in the various phases of animal and vegetable life. 
 Remember the conflagrations, the furnaces, the fires, 
 and the other manifestations of the terrible energies 
 of the atmospheric oxygen, whenever it is aroused. 
 Do not even forget the comparatively insignificant 
 power which man is wielding with the aid of powder 
 and of steam. Making now an immense allowance 
 for what you must have overlooked, sum this all up, 
 — if you can without bewilderment, — and what part 
 is it of the whole ? Why, it has been calculated 
 that it is equal to but one 2,300,000,000th of the 
 force which the sun is every moment pouring into 
 space. And what is the sun? A small star in the 
 infinitude of space, where shine Sirius and Arcturus, 
 Regulus and Aldebaran, Procyon and Capella, with 
 unnumbered others, all shedding forth a far mightier 
 effluence than our feeble star : yet the grand total 
 of the powers streaming from all the suns which 
 human eye has seen, or which still lie undiscovered 
 in the depths of space, alone represents the active 
 energy of the universe. My friends, there are two 
 theories of causation. One regards this energy as 
 an unintelligent power. The other sees in it simply 
 the will of the Almighty. They are both theories. 
 We cannot substantiate either. But which do you 
 
 i 
 
ENERGY APPEARS AS MOTION. 305 
 
 think is the more probable? Let us not pass hasty 
 judgment, but soberly weigh all the testimony, and 
 base our decision on the best scientifie evidence we 
 can obtain, and on that alone. 
 
 Thus far in our discussion we have been dealing 
 with facts and principles which every theory of 
 causation must explain. But we now pass into 
 what is rather the region of speculation, and we 
 must step more cautiously. I have used thus far the 
 terms ^;^^r^and transfer of energy ^v^WhowX. expect- 
 ing that you would attach to them any more definite 
 meaning than that which is conveyed by the words 
 in their most familiar use. Energy is a definite 
 thing, which is as palpable to our senses as matter, 
 and which, in most cases at least, we can measure 
 as accurately. Any one who has been stunned by 
 a blow, bruised by a fall, burnt by a fire, dazzled 
 by the sun, or paralyzed by a shock of electricity, 
 knows well enough what energy is; and the doc- 
 trine of the conservation of energy is wholly in- 
 dependent of any theory which men may entertain 
 in regard to its essence. For this reason, I have 
 aimed to present the grand doctrine of modern sci- 
 ence entirely free from all speculations whatsoever ; 
 but now that we are seeking to go behind the 
 external phenomena, it will be well for us to con- 
 sider very briefly a theory which, although it does 
 not profess to explain what energy is in its essence, 
 nevertheless may give to the mind a more definite 
 conception of its mode of action. The theory, it is 
 true, cannot be regarded as fully established ; but 
 it represents the undoubted tendency of science, 
 
3o6 MOTION OF MOLECULES. 
 
 and the materialists would, of all others, be the first 
 to accept it. According to the modern view, all en- 
 ergy appears as motion, and this too whether it be 
 manifested in mechanical work, or in the more sub- 
 tile phenomena of sound, light, heat, chemical affin- 
 nity, electricity, or magnetism. We must, however, 
 extend our idea of motion, and not limit it, as is usu- 
 ally done, to the motion of visible masses of matter. 
 Even the smallest material masses perceptible to 
 our senses must be regarded as aggregates of still 
 smaller masses, which we call molecules. These 
 molecules, moreover, even in the densest bodies, 
 cannot be in contact, and we must picture them to 
 our imagination each as a tiny world poised in space. 
 The same relation which the worlds bear to the cos- 
 mos, we conceive that these molecules bear to the 
 microcosmos which every mass of matter represents, 
 and it is believed that the motions of suns and sys- 
 tems have their miniature in the motions of these 
 molecules. The ether, also, of which I spoke in the 
 second chapter as filling celestial space, is supposed 
 to pervade equally the molecular spaces, to surround 
 each molecule with a highly elastic atmosphere, and 
 to be the medium by which motion is transmitted 
 throughout a universe which includes the infinitesi- 
 mal as well as the infinite. Moreover, we conceive 
 that the motion of the molecule is the exact 
 counterpart of the motion of a world or of the mo- 
 tion of a ball, and that all motion obeys the selfsame 
 laws. As when an ivory billiard-ball strikes another, 
 it gives up the whole or a part of its motion to the 
 second ball, so we believe that one molecule may 
 
MOTION OF MOLECULES. 307 
 
 transmit motion to another. In like manner, as an 
 impulse is transmitted through a long line of billiard- 
 balls, and the last ball only appears to move, so also 
 we conceive that the electrical impulse is transmitted 
 from molecule to molecule through the telegraph 
 wire, and produces perceptible motion only when 
 transformed into magnetism at the end of a thousand 
 miles. Again, motion may be transmitted from mole- 
 cules to masses of matter ; for although the impulse 
 imparted by a single molecule may be as nothing, the 
 accumulated effect of millions on millions of these 
 impulses may be immense. In this way, as we con- 
 ceive, the motions of the ether particles in the sun- 
 beams unite to produce all the grand phenomena of 
 nature. On the other hand, the motion of great 
 masses may be suddenly resolved into the motions 
 of the molecules composing these masses, and thus, 
 when motion outwardly appears to cease, it may 
 only be transferred from the previously moving body 
 to the molecules within. When the cannon-balls, 
 with their immense velocity, strike the iron-clad fri- 
 gate and fall harmlessly from her armor-plates, the 
 particles of iron take up the motion of the ball, and 
 indicate by a higher temperature that the energy 
 has not been lost. 
 
 Understanding, then, the term motion in the ex- 
 tended sense just explained, we shall comprehend 
 more clearly the theory stated above. This theory 
 supposes that the phenomena of sound, light, heat, 
 and electricity are produced by the motions of mole- 
 cules, in the same way that the grander phenomena 
 of mechanics and astronomy are caused by the mo- 
 
308 MOTION OF MOLECULES. 
 
 tion of large masses of matter. The transmission 
 of energy is, then, the direct result of the transmis- 
 sion of motion, and the conservation of energy is 
 fully explained by the well-known law of inertia, 
 which the motions of all matter necessarily obey. I 
 have not time to enter into any details in regard to 
 the mode of motion by which light, heat, and all this 
 class of phenomena are produced, other than those 
 already given in the previous chapters of this book ; 
 but I take great pleasure in referring my readers to 
 the work of Professor Tyndall, already frequently 
 quoted, as by far the best popular statement of 
 the subject that has ever been made. Indeed, 
 great differences of opinion in regard to the mode 
 of the molecular motion are entertained by those 
 who accept the theory in its general statement, and 
 in many cases we can form no conception of the 
 peculiar phase which the motion assumes. It is 
 sufficient for my purpose if I have been able to 
 make clear the general principle, and I will only add 
 a few numerical results, which will show what a pre- 
 cise form the theory has taken in the minds of 
 scientific men. 
 
 According to the modern theory, when we heat 
 a body we merely impart to its molecules a greater 
 velocity of motion. Now, according to the experi- 
 ments of Professor Joule, when we raise the tem- 
 perature of a pound of water two P'ahrenheit de- 
 grees, we distribute among the molecules of the 
 liquid an amount of motion equal to that acquired 
 by a weight of two pounds in falling JJl feet; and a 
 simple calculation will show that this is represented 
 
MOTION OF MOLECULES. 309 
 
 by a Minle ball, weighing one-eighteenth of a pound, 
 moving with a velocity of 1,338 feet in a second."^ 
 The amount of motion, therefore, which is imparted 
 to the particles of water in an ordinary tea-kettle 
 during the process of boiling, must be in the aggre- 
 gate vastly greater than that ever acquired by any 
 projectile. We shall arrive at a still more remark- 
 able result if we examine in the light of our theory 
 the process of chemical combination by which water 
 is formed. In this process of burning, one pound 
 of hydrogen gas combines with eight pounds of oxy- 
 gen gas to form nine pounds of water. Although 
 the distances which separate the atoms of the two 
 gases before combination are utterly inapprecia- 
 ble by our senses, yet, in passing over these dis- 
 tances, they acquire a velocity which causes them 
 to clash together with tremendous energy, and in 
 the collision this form of atomic motion is trans- 
 muted into that other mode of motion which we 
 call heat. Incredible as it may appear, the amount 
 of motion which in the act of combination alone is 
 thus transmuted into heat corresponds to the fall of 
 a ton weight down a precipice 22,320 feet high. 
 ,Such illustrations might be multiplied indefinitely ; 
 but you will see from these how purely mechanical 
 the idea is which we associate with the motion of a 
 molecule, and you must have been impressed by 
 the magnitude of the energy which these molecular 
 motions represent. " I have seen,'' says Professor 
 
 * In making the calculation, it must be remembered that the 
 amount of motion is measured by the square of the velocity. 
 
310 CAUSE OF MOTION. 
 
 Tyndall, " the wild stone avalanches of the Alps, 
 which smoke and thunder down the declivities with 
 a vehemence almost sufficient to stun the observer. 
 I have also seen snow-flakes descending so softly as 
 not to hurt the fragile spangles of which they were 
 composed ; yet to produce from aqueous vapor a 
 quantity of that tender material which a child could 
 carry, demands an exertion of energy competent to 
 gather up the shattered blocks of the largest stone 
 avalanche I have ever seen, and pitch them to twice 
 the height from which they fell.'* If such, then, be 
 the measure of these atomic motions, we can easily 
 conceive how the motion of the cannon-ball might 
 be transferred to the particles of the armor-plate 
 without much apparent result, and even how the 
 energy of a world might be maintained by the mo- 
 tion of the molecules in the sunbeam. 
 
 Accepting, then, this new theory of science, and 
 admitting that all energy is manifested in motion, 
 we reduce at once our discussion of the doctrine of 
 causation to this simple question, — What is the 
 primary cause of motion ? If we can explain the 
 simplest case of motion, we have solved the problem 
 for the universe. Take, for example, a boy*s ball, 
 moving through the air under the impulse of a well- 
 directed blow. Do we not know something of the 
 cause of that motion ? Is it not connected with the 
 muscular contraction of the boy's arm, produced by 
 his will ? Is not his volition, acting mysteriously on 
 matter, at least the occasion of the motion? It is 
 perfectly true that the will does not create the mo- 
 tion. The ball is impelled by a portion of that 
 
THEORY OF CAUSATION. 3II 
 
 energy in nature which man can neither increase nor 
 diminish. But still the boy's will is the occasion of 
 the motion. It has opened the channel through 
 which the energy of. nature has flowed to produce 
 the specific result which the boy desired. So, in a 
 thousand other ways, man is able to come down, as 
 it were, upon nature, and to introduce a new condi- 
 tion into the chain of causation. Place the point of 
 contact as far back as you please, theorize about the 
 subject as you may, the fact still remains the same. 
 Our will does act on matter, and does act to produce 
 most efificient results. Here is energy exerted of 
 whose cause we have the consciousness within our- 
 selves, and, if the analogy is worth anything, it points 
 to but one conclusion, — namely, that motion is 
 always the manifestation of will. As the boy's will 
 acted on that particle of matter, which, though moved 
 perhaps but an atom's breadth from its position, set 
 in action — as if by the touching of a spring — the train 
 of natural' causes which gave motion to the ball, so 
 we may suppose that the Divine will acts in nature. 
 According to this view, the energy which sustains 
 the universe is the will of God, and the law of con- 
 servation is only the manifestation of His immutable 
 being, — '^ the same yesterday, and to-day, and for- 
 ever." 
 
 We do not say that this theory can be proved — 
 for certainty here is out of the question — but we do 
 claim that it is based on the only analogy which 
 nature affords, that it is a legitimate deduction of 
 science, and that it is perfectly consistent with 
 Christian faith. On a subject where science can only 
 
312 RELATIVE LIMITATIONS. 
 
 grope, the wildest theories are possible ; but these 
 should not trouble a well-balanced mind, so long as 
 there exists an equally probable theory which can 
 be reconciled with the purest faith. It has been my 
 aim in this chapter to show, not only that such a 
 theory is tenable, but also that the Christian theory 
 of causation is the most probable theory of science ; 
 and my earnest hope is, that, for some minds at 
 least, the considerations I have offered will help to 
 reconcile the apparent conflict between science and 
 religion which materialism is ever striving to foment. 
 Allow me to add, in concluding, one or two other 
 suggestions which may be of value in the same 
 direction. 
 
 I cannot but believe that the appearance of clash- 
 ing between science and religion would be wholly 
 avoided, if the teachers both of God's unwritten and 
 of His written word would pay more regard to the 
 necessary limitations of scientific and religious 
 thought. On subjects where the methods of ac- 
 quiring knowledge are so utterly unlike, where the 
 relations of knowledge to the human understanding 
 are so different, it is in vain to expect literal accord- 
 ance. Science, both in its methods and its results, 
 addresses the understanding exclusively ; Christian- 
 ity appeals chiefly to the heart. Science aims to 
 instruct ; Christianity aims to persuade. Science is 
 attained by study, and is possible only for the few ; 
 Christianity is a free gift from God to all men who 
 will receive His Son. The results of science are 
 fully comprehended, and can be expressed in definite 
 terms ; the truths of Christianity stand on a level 
 
METHOD OF SCIENCE. 313 
 
 above man's intellect, and can only be shadowed 
 forth in types and symbols. The forms of science 
 are constantly changing ; the types and symbols of 
 Christianity are permanent. Lastly, while the lan- 
 guage of science may be so varied from time to time 
 as to express accurately the current ideas, Christian- 
 ity necessarily retains the forms through which it 
 w^as first revealed. Under such conditions, how can 
 it be expected that the letter of revelation should 
 agree with the language of science ? One might as 
 reasonably find fault with nature because its crystals 
 are not perfect, as criticise the Bible because its 
 language, although embodying divine truth, is not 
 free from the necessary limitations and imperfec- 
 tions of the human medium of thought. 
 
 Consider in this connection the method of science 
 which we have already discussed at some length in a 
 previous chapter. Remember that in nature we 
 observe only a sequence of phenomena. The idea of 
 a cause is supplied by our own minds, and every 
 phenomenon is so surrounded and obscured by ad- 
 ventitious circumstances that it is frequently very 
 difficult to establish the causal connection with the 
 antecedents. Science endeavors to discover this 
 connection by a process of elimination, which it con- 
 ducts in various ways. It notices, for example, that 
 while certain antecedents invariably accompany a 
 given effect, others are sometimes absent, and in this 
 way the accidental concomitants may be to a greater 
 or less extent eliminated. The process of elimina- 
 tion is more rapid and satisfactory when the phenom- 
 enon is so far under our control that we can vary the 
 14 
 
314 THE RADIOMETER. 
 
 conditions by experiment. If, then, we find that a 
 given condition may be omitted or varied without 
 influencing the result, we can conclude with great 
 safety that this antecedent is not essential. On the 
 other hand, if we find, either from experiment or ob- 
 servation, that the effect varies with the condition, 
 any change in the antecedent being followed by a cor- 
 responding change in the phenomenon we are study- 
 ing, then we feel great confidence that we have found 
 one at least of the causes we are seeking. When a 
 connection of this kind is established, the effect is 
 said to be a function of its antecedent, and it is 
 frequently possible to express this function by a 
 mathematical formula, so that we can predict with 
 absolute certainty the nature and extent of the 
 effect which will under any given circumstances be 
 produced; and in this case our certainty in regard 
 to the immediate cause of the phenomenon is of 
 the highest order which can be reached in science. 
 An illustration will make the point clearer. 
 
 A few years ago. Professor Crookes, of London, 
 having observed that light pith balls delicately sus- 
 pended in a vacuous tube were under certain con- 
 ditions repelled by the sun's rays, was led on from 
 step to step until he had constructed the instrument 
 now so well known as the radiometer, in which a 
 delicate wheel is rapidly turned by the rays of the 
 sun, or by the rays of any source of bright light, 
 shining on its blackened vanes. 
 
 At first sight the effect seemed to be the result of 
 a direct mechanical action of the rays of light, and 
 this explanation was for a time generally received. 
 
THE RADIOMETER. 
 
 But it soon appeared that if the he^t-givi^fe/rays'*"/ ,^ 
 were absorbed by passing the beam of light throt^gh ^ }- 
 a solution of alum, the motion of the vanes was ar^/ \ . 
 rested, or at least very greatly retarded, while, on the f^i 
 other hand, when the light-giving rays were absorbed 
 by a solution of iodine, a medium which although "^ 
 
 opaque to light is pervious to heat, the motion was 
 maintained with nearly its full activity. Further, it 
 was soon found that the motion could be produced 
 by any cause which determined a slight difference of 
 temperature between the blackened faces of the 
 vanes and the surface of the inclosing glass bulb, and 
 that while the motion was in one direction when 
 the vanes were warmer than the glass, the motion 
 was in the opposite direction when these conditions 
 were reversed ; and further, that, other things being 
 equal, the greater the difference of temperature the 
 more rapid was the motion. Hence, after a long 
 series of experiments, it was concluded that the 
 motion of the radiometer was an effect of a differ- 
 ence of temperature between its parts, or, in other 
 words, that the radiometer is, like the steam engine, 
 simply an example of a heat engine. Thus Pro- 
 fessor Crookes was able to discover the proximate 
 cause of the remarkable phenomenon he had ob- 
 served, and having done this he had learned all that 
 could be known with certainty in regard to it. 
 
 This example is a fair illustration of the method 
 of science, and scientific ability is shown in the 
 power of so directing observations or making experi- 
 ments as to establish the true causal relations in 
 any case. No one supposes, however, that having 
 
3l6 MOLECULAR THEORY. 
 
 established this relation we have discovered an " effi- 
 cient cause." We have found out which are essential 
 and which are accidental antecedents, and estab- 
 lished possibly what we may call the law of succes- 
 sion, but nothing more. There may be a whole chain 
 of such antecedents — we frequently know that there 
 is — and, behind all, the true cause as much concealed 
 as ever. The mind, moreover, refuses to stop at this 
 point, or to rest satisfied with such a result. It at 
 once begins to theorize. Why is it that a difference 
 of temperature causes the steam engine to work, or 
 the radiometer wheel of our illustration to turn ? We 
 cannot answer the question with certainty, but this 
 is our theory : 
 
 " Heat is a mode of motion,'* and its phenomena 
 are the effects of the motion of molecules of matter. 
 Molecules, although of an order of magnitude far 
 removed from our limits of perception, are as real 
 masses as cannon-balls or bullets, and their motions 
 as rapid and as real, and although the moving power 
 of single molecules is as nothing, yet collectively 
 their motion is capable of producing effects com- 
 pared with which the mightiest bombardment is in- 
 significant. 
 
 Now, although the air has been exhausted to a 
 very high degree from the bulb of the radiometer, 
 the interior still contains a vast number of mole- 
 cules of gas, which, unless our calculations are great- 
 ly at fault, must be counted by the million miUion 
 for every cubic inch of capacity. Moreover, at the 
 degree of exhaustion reached in the bulb, the am- 
 plitude of the motion of the little masses becomes 
 
MOLECULAR THEORY. 317 
 
 SO considerable that they bound to and fro between 
 the vanes of the wheel and the surface of the inclos- 
 ing glass, and according to our theory the motion of 
 the wheel is the result of this reaction. This theory is 
 supported by the fact that if we exhaust the air from 
 the bulb of the instrument beyond a certain limit we 
 arrest the motion. It is also true, however, that the 
 motion stops if the amount of air be only slightly in- 
 creased, for the evident reason that there is then less 
 free room for the motion of the separate molecules, 
 and they do not move far enough to cause any re- 
 action between the wheel and the surrounding walls. 
 
 To those who have become familiar with the con- 
 ception of molecular magnitudes this theory is very 
 plausible. If you ask whether the theory is true, I 
 can only answer that we may perhaps regard it as 
 relatively true, seeing that it has explained a great 
 many facts and suggested lines of investigation which 
 have led to new discoveries. But it certainly is not 
 absolutely true in the sense of expressing the whole 
 truth. These molecules are creatures of the scientific 
 imagination, and may be mere fictions, but the value . 
 of the theory lies in its power of directing research, 
 and, as I have before said, I believe that all theories 
 which have this power are partial truths; but no 
 one can regard them as perfect representations of 
 the realities of nature. Men who, in the first flush 
 of discovery, feel the guiding power of a theory, 
 are wont to associate with it an undue reality, but 
 they soon learn their error by experience. 
 
 What we have just said is true of all the great 
 theories of science, but it is especially true of that 
 
3l8 MOLECULAR THEORY. 
 
 form of the atomic theory which is now the chief 
 guide in chemical investigation. 
 
 The chemist is acquainted with numerous groups 
 of substances which we call isomeric compounds, and 
 two substances are said to be isomeric when they not 
 only consist of the same elements united in the same 
 proportions, but also have the same density in the 
 state of vapor, so that according to the molecular 
 theory their molecules must have the same weight. 
 For example, the two substances called butyric acid 
 and acetic ether are isomeric bodies. The vapor 
 density, as we call it, of both substances is forty- 
 four times that of hydrogen, and they both consist 
 of carbon, hydrogen, and oxygen united in precisely 
 the same proportions, yet the two substances differ 
 from each other in their properties most widely. 
 Butyric acid is an oily liquid, with whose offensive 
 smell we are only too familiar, since it is the notice- 
 able ingredient of rancid butter. It does not boil 
 until the temperature reaches 302° on our Fahrenheit 
 scale, and does not readily inflame. Acetic ether, 
 on the other hand, is a limpid liquid with a pleasant 
 fruity smell, highly volatile, boiling at 165'^, and 
 inflaming with the greatest ease. What, now, is 
 the cause of this most marked difference? The 
 phenomenon demands an explanation, and invites 
 theorizing, and the theory we have formed is as 
 follows : 
 
 The molecules of all compound substances are 
 themselves groups of elementary atoms, and the 
 molecules of two isomeric compounds, Hke butyric 
 acid and acetic ether, although consisting of the 
 
STRUCTURAL SYMBOLS. 319 
 
 same number of the same atoms, and therefore hav- 
 ing the same weight, differ from each other in that 
 these atoms are differently grouped. Nay, we go 
 much further than this, for we have formed a scheme 
 of the manner in which the atoms are grouped in 
 each case, thus : 
 
 OHHH HH OH 
 
 I I I I I II Ml 
 
 H-0-C-C-C-C-H H-C-C-0-C-C-H 
 
 ill II I 
 
 HHH HH H 
 
 Butyric Acid. Acetic Ether. 
 
 In these diagrams the capitals stand for atoms of 
 the elementary substances of whose names they are 
 the initial letters, and it is obvious that not only two 
 isomeric compounds, but a great number, might be 
 formed by differently grouping these same atoms ; 
 although the number of possible combinations is 
 greatly diminished by conditions imposed by well- 
 known chemical principles, which it would be out of 
 place to discuss in this connection. Our diagrams, 
 moreover, indicate a great deal more than the gene- 
 ral theory, that the differences between isomeric 
 compounds depend on differences in the grouping 
 of the same atoms ; for the exact grouping in each 
 case is based on the known chemical relations of the 
 substances. There is a reason for the position of 
 each letter in these structural symbols, as they are 
 called. 
 
 We have here given one of the simplest illustrations 
 
320 WORKING THEORIES. 
 
 of the theory of molecular structure which is the basis 
 of modern theoretical chemistry. It is the chief 
 object of chemical investigation at the present time 
 to discover the molecular structure of chemical com- 
 pounds, and there is frequently as earnest discussion 
 about the position of a letter in one of these struct- 
 ural symbols as there is in natural history about the 
 origin of species ; and if there were a point of theo- 
 logical doctrine involved in the controversy, the dis- 
 cussion w^ould be doubtless as personal and as bitter. 
 Yet no one in his sober senses dreams that these 
 diagrams represent realities. If there are such 
 things as atoms and molecules, all analogy would 
 lead us to believe that the parts must sustain rela- 
 tions to the whole similar to those of the members 
 of the solar system, and like the sun and planets 
 must have their orbits and periods of revolution. 
 Still our diagrams give us correct representations 
 of the relations between a large number of facts 
 which they serve to group together, and this theory 
 of molecular structure has been one of the most 
 successful aids in directing investigation which science 
 has known. It has led to the discovery of a process 
 of manufacturing artificially the valuable madder 
 dye called alizarine — a discovery which has revolu- 
 tionized one of the most important industries of the 
 world — and this is but one of hundreds of new dis- 
 coveries with which it has enriched the arts of life 
 or extended chemical science. In a word, it has 
 been a most valuable "working theory," and no 
 other theory except the law of gravitation can be 
 compared with it in efficiency. Hence, absurd as our 
 
WORKING THEORIES. 321 
 
 conceptions of molecular structure certainly would 
 be, if we supposed them realized in the crude forms 
 which our diagrams suggest, yet we cannot but re- 
 gard these representations as the rude symbols 
 of a real truth which in its essence transcends the 
 limits of our present knowledge. That which is true 
 of the molecular theory of modern chemistry is 
 equally true of the two great conceptions which are 
 always cited as examples of the most perfect theo- 
 ries of physical science. The undulatory theory of 
 light involves assumptions in regard to the alleged 
 ether which are simply preposterous, and even the 
 law of gravitation takes for granted action at a 
 distance which is opposed to all experience and to 
 all philosophical thought. Still, to abandon these 
 theories, because we cannot accept their postulates, 
 would be as foolish as to throw away our compass 
 because we cannot agree about the theory of mag- 
 netism. 
 
 Now we are told by the naturalists that Darwin- 
 ism is just such another working theory, and they 
 are, with reason, impatient when blamed for follow- 
 ing its guidance because it cannot be recon- 
 ciled with certain cherished theological dogmas. 
 And, assuming that the dogmas are right, you 
 might as reasonably find fault with the mari- 
 ner for using the magnetic needle, because it does 
 not always point to the true north. Like the 
 needle, our theory points out the path of discovery, 
 and, although the way may at times seem to lead 
 backward, and men, like Columbus, may become 
 frightened at the evident aberrations of their guide, 
 14* 
 
322 DOGMATISM IN SCIENCE. 
 
 yet if, with the brave navigator, they persevere, the 
 trusted guide will certainly conduct them to the true 
 goal in the end, unless truth is a fiction, and the 
 whole issue of the human faculties a lie. Neverthe- 
 less there may be as blind dogmatism in science as 
 has ever existed in theology, and it is dogmatism 
 when men claim as absolute certainty what is at 
 most merely relative truth, and treat with supercil- 
 iousness all who do not accept their authority as fi- 
 nal. Certainly, let us be true to our convictions, and 
 hold fast to our theories as the earthen vessels which 
 contain a precious treasure, but let us remember, 
 
 Our little systems have their day ; 
 
 They have their day and cease to be ; 
 
 They are but broken lights of thee, : 
 And thou, O Lord, art more than they. 
 
 Such, then, being the credentials, and such the 
 methods of science, let us turn for a few moments to 
 the credentials and methods of theology, and ask, in 
 all humility, whether the conditions do not impose 
 limits on human thought in this direction as well as 
 in the other. In theology, as in science, there are 
 certain facts which, although chiefly facts of con- 
 sciousness, and not facts of observation, are no less 
 facts than the phenomena of nature. Prominent 
 among these facts are the moral judgments, the 
 affections, and the aspirations of the soul, which, 
 explain them as you will, are the most important 
 factors of human life — the most potent agents in 
 human society. Corresponding to these affections 
 and aspirations are certain religious beliefs which we 
 
THEOLOGICAL DATA. 323 
 
 have inherited from our ancestors, and which have 
 come down to us with the authority of eighteen cen- 
 turies of human experience. During that period 
 these beHefs have satisfied the highest aspirations of 
 humanity, and have led many of the purest and no- 
 blest men whom the world has known to encounter 
 peril, endure cruel torments, and suffer ignominious 
 death, in attestation of their faith. The origin of 
 this faith was a life which, as portrayed to us in the 
 Gospels, has aroused in every generation of men from 
 its birth the noblest enthusiasm and the warmest 
 love ; a life which has appeared more and more 
 transcendent as civilization has advanced, and which 
 has been the one power that has redeemed man from 
 his selfishness, and enthroned charity among the 
 chief rulers of the earth. Such, then, are the cre- 
 dentials of Christianity — a real want, an adequate 
 satisfaction. Learned men have endeavored to for- 
 mulate the principles of religious beliefs, and hence 
 have come systems of theology, in regard to which 
 we might repeat very nearly the same statements 
 that we have already made in regard to the theories 
 of science. These systems have certainly satisfied 
 the great mass of mankind, and have done a good 
 work in defining and preserving the faith ; but they 
 are all earthen vessels, and, like the working theories 
 
 of science, 
 
 " half reveal 
 And half conceal the soul within." 
 
 Let us remember that as Christianity was revealed 
 in a life, it ever abides as a life in the heart of the 
 believer, and only those who have lived that life can 
 
324 METHODS OF THEOLOGY. 
 
 know how real it is. To all such, however, it is the 
 most real thing in the world, and the theological 
 forms in which it finds expression have the same 
 reason for their being as the forms of science, and 
 are held the more sacred as the truths symbolized 
 are the more dearly cherished. Moreover, it is a 
 fact most worthy of notice, that Christianity is 
 almost co-extensive with civilization, or, as Cole- 
 ridge has expressed it, " Christendom is the best evi- 
 dence of Christianity." 
 
 While, however, the "internal evidences" of Chris- 
 tianity, which we may not inappropriately call the 
 credentials of theology, are so similar to the creden- 
 tials of physical science, the methods of theology are, 
 for the most part, utterly unlike the scientific meth- 
 ods we have been discussing. In the first place, the 
 very data on which the whole body of Christian 
 theology rests cannot be verified by observation. 
 The phenomena of nature are ever with us, and can 
 be closely scrutinized at each repetition ; but the 
 events from which Christianity arose occurred once 
 for all more than eighteen centuries ago ; and if we 
 take the summary of those events given in the primi- 
 tive creeds as representing what is common to the 
 beliefs of the great body of Christians, and as au- 
 thenticated by the experience of the Church, and 
 present this as the subject-matter of theology, we 
 must claim belief in these data on grounds of faith, 
 and not on scientific evidence. We accept these 
 supernatural facts not solely on account of the his- 
 torical evidence adduced in fheir support, but largely 
 in deference to a certain "witness in our hearts," 
 
METHODS OF THEOLOGY. 325 
 
 which disposes us to accept them. To men who 
 know nothing by experience of this inner witness, 
 behefs thus accredited may appear foolishness, and 
 this is too often the case with those who, occupied 
 exclusively with the study of nature, are not accus- 
 tomed to accept any statement as true which cannot 
 be verified by experiment or observation, and who 
 regard the order of nature as the one standard from 
 which there is no appeal. On the other hand, those 
 who have felt its power are persuaded that the wit- 
 ness in themselves is the voice of God speaking to 
 the heart. 
 
 The basis thus established. Christian theology is 
 built up on the textual criticism, interpretation and 
 collation of a written record, a form of study which 
 involves historical research, critical analysis, philo- 
 logical investigation, and metaphysical inquiries. 
 Thus a great mass of learning has been accumulated 
 to which various minds will attach very different 
 degrees of value, according as they are more or less 
 familiar with the methods employed. These, how- 
 ever, are so unlike the methods of physical science 
 that it would be the height of presumption for a 
 physicist to pass any judgment on the results. 
 But certainly no one can claim for them a greater 
 value than for the best working theories of science. 
 
 Seeing, then, that the limits of positive knowledge 
 are so well defined, both in natural science and in 
 theology, we certainly need not be troubled by the 
 apparent conflict between the two modes of thought, 
 so long as the controversy is confined to the debat- 
 able ground which has not been fully explored by 
 
326 RELATIVE LIMITATIONS OF 
 
 either party. Within the well-explored limits there 
 never has been and never can be any actual disagree- 
 ment, and something has been gained if we have 
 been able to make evident that such limits exist, 
 however imperfectly we have succeeded in defining 
 them. The bearing of such considerations is ob- 
 vious, and they lead to important practical conclu- 
 sions. In the first place, they should teach men of 
 science to honor and reverence the forms of religion. 
 They are the types and symbols of a truth higher than 
 any which Science can teach. Let Science vindicate 
 her own methods, and allow no interference within 
 her proper sphere ; but unless she learn that there 
 are other sources of knowledge than material nature, 
 and other channels of truth than the intellect, her 
 own philosophy will be confounded, and her light 
 will go out in darkness. On the other hand, it is 
 equally the duty of the ministers of religion to honor 
 and respect the methods of science. They have 
 been ordained by God, and through these processes 
 of thought He is constantly revealing eternal truths 
 to the mind of man. Insist as strongly as you please 
 that Science should be allowed no voice in matters 
 of faith. Scrutinize as closely as you can every step 
 of her logic ; but so long as she keeps within her 
 legitimate province, allow her the largest liberty, 
 and extend to her the most generous encourage- 
 ment. Watch sharply her results, and expose her 
 fallacies wherever you can find them ; but if your 
 judgment condemns, let it be on scientific grounds, 
 and not by any arbitrary standard of your own. 
 Above all, even if you think your most cherished 
 
SCIENTIFIC AND RELIGIOUS THOUGHT. 327 
 
 Opinions are in danger, do not withdraw your fellow- 
 ship hastily, or be betrayed into undiscriminating 
 censure. Science is paramount within her own prov- 
 ince. Do everything in your power to consecrate 
 her aims and sanctify her spirit, but do not attempt 
 to control her investigations or restrict her free 
 thought. Await God's time. If Science be wrong, 
 she will sooner or later correct her error. If she be 
 right, the *^ Lord of Hosts " is on her side, and you 
 will find yourself " fighting against God." 
 
 Again, a proper appreciation of the necessary lim- 
 its of scientific and religious thought should lead all 
 men to reverence the ** Word of God " as it has been 
 handed down to us through history. In view of the 
 facts already intimated, I cannot look with favor on 
 any attempts at Biblical criticism which aim to square 
 the language of Scripture with the results of modern 
 science. They leave a most unpleasant impression 
 on my mind. Seeing the large element of human 
 ignorance, incapacity, and frailty, which the history 
 of both so conspicuously exhibit, I cannot stake my 
 faith either on the ^* Infallibility of the Church " or 
 the *' Infallibility of the Book." But I do believe 
 that the Bible is inspired with spiritual truth, from 
 the «grand epic of creation, with which it opens, to 
 the glorious vision of the New Jerusalem at its 
 close. I feel that its very words are consecrated by 
 the associations of the ages, and if you are so ready 
 to accommodate any part of them to the shifting 
 phases of science, what certainty can I have in re- 
 gard to the whole? The Bible is no text-book of 
 science, and the attempt to impose an equivocal or 
 
32S RELATIVE LIMITATIONS OF 
 
 mysterious meaning on its simple and obvious state- 
 ments degrades and dishonors it in the minds of de- 
 vout men. The methods by which its truths are 
 expressed may be at times rough and uncouth ; but 
 they are the methods chosen by God, consecrated 
 by the blood of martyrs, and hallowed by the tears 
 of saints; and they have therefore a power which 
 no other language could have. Break not the mould 
 in which the forms of faith have been cast, before 
 they have become firm and hard, lest the precious 
 metal should itself be lost. Finally, leave religion 
 and science to their respective methods, and encour- 
 age both alike in their noble callings. Let science, 
 by cultivating man's intellect, elevate him to nobler 
 and more spiritual views of God's wisdom and power. 
 Let religion, by purifying man's heart, open to him 
 clearer visions of God's purity and love; and, at last, 
 when this material shall have vanished, and when the 
 waters of controversy shall have ceased to roll, the 
 heart and the intellect, made one and washed clean 
 in the blood of the Lamb, shall unite in the song of 
 the angels around the throne, saying, " Blessing, and 
 glory, and wisdom, and thanksgiving, and honor, and 
 power, and might, be unto our God for ever and ever." 
 But while insisting upon the necessary limitations 
 of scientific and religious thought, I must not forget 
 that all such considerations bear with peculiar force 
 upon the questions I have discussed in this book. 
 Therefore, although I have most carefully endeav- 
 ored to guard my argument from the slighest ex- 
 aggeration, I should not feel justified in concluding 
 without distinctly stating how far, in my opinion, 
 
SCIENTIFIC AND RELIGIOUS THOUGHT. 329 
 
 the argument of natural theology may be safely 
 carried, and to what extent unaided science may 
 be said really to prove the fundamental truths of 
 Christianity. 
 
 In the first place, then, I believe that the exist- 
 ence of an intelligent Author of nature, infinite in 
 wisdom and absolute in power, may be proved from 
 the phenomena of the material world with as much 
 certainty as can be any theory of science. In the 
 second place, I am of opinion that the facts of na- 
 ture are throughout consistent with the belief that 
 the Author of nature is a personal being, and the 
 one only and true God revealed to us in the Bible. 
 Lastly, I think that the relations of the human 
 mind to the material world, viewed in the light of 
 modern science, give us strong reason to believe, on 
 scientific grounds alone, that the universe is still 
 sustained in all its parts by the same omnipotent 
 and omniscient Will which first called it into being. 
 
 To the extent I have indicated, I regard the argu- 
 ment of natural theology as logically valid. More- 
 over, I am persuaded that science confirms and 
 illustrates the priceless truth which Christ came 
 on earth to reveal ; but I do not believe that the 
 unaided intellect of man could ever have been 
 assured of even the least of these truths independ- 
 ently of revelation. And, as I stated in my intro- 
 ductory chapter, I feel that the best service which 
 science can render to religion is in the way of con- 
 firmation and illustration, rather than in that of ab- 
 solute proof, and for this reason I have preferred to 
 discuss my subject chiefly from that point of view. 
 
330 VALIDITY OF THE ARGUMENT. 
 
 The subject, as prescribed by the founder of the 
 " Graham Lectures," ^ was '' The power, wisdom, and 
 goodness of God as manifested in His works," and to 
 this form of statement, if interpreted in the sense just 
 indicated, I have nothing to object. I do not beheve, 
 however, in any sense, that nature proves the good- 
 ness of God. When the heart has been once touched 
 by the love of God, as manifested on Calvary, the to- 
 kens of God's goodness are visible everywhere ; but 
 before this, nature, to one who has seen its terrors 
 and felt its power, looks dark indeed ; and the pre- 
 tence that the material universe, unexplained by 
 revelation, manifests a God of unmixed beneficence, 
 not only does harm to religion, but places science 
 in a false light. The most superficial observation 
 shows that this is not true. Lightning and tem- 
 pest, plague, pestilence, and famine, with all their 
 awful accompaniments, are no less facts of nature 
 than the golden sunset, the summer's breeze, and 
 the ripening harvest ; and who does not " know that 
 the whole creation groaneth and travaileth in pain 
 together until now"? It does not change the 
 terrible fact to say that nature has been disordered 
 by man's sin ; for sin is itself the greatest evil in the 
 world, and its ghastly forms meet us at every step. 
 So prominent, indeed, is the evil in nature, and so 
 insidiously and mysteriously does it pervade the 
 whole system, that an argument to prove the ma- 
 lignity of God could be made to appear quite as 
 plausible as the arguments which are frequently 
 
 * See '' Preface to First Edition." 
 
CONCLUSION. 331 
 
 urged to prove His pure beneficence ; and when 
 the unaided human intellect has attempted to make 
 to itself a beneficent God, it has usually made a 
 malignant deity as well. Nature seems to manifest 
 God's wrath no less than His love, and it is a false 
 and sickly philosophy which attempts to keep the 
 awful fact out of sight. God is our Father ; but 
 nature could not teach it, and ** the Word was made 
 flesh " to declare it. God is love ; but nature could 
 not prove it, and the Lamb was " slain from the 
 foundation of the world" to attest it. Nature is 
 but a part of God's system, and not until the natural 
 and the supernatural shall be made one will the mys- 
 tery of evil be solved. 
 
f^ 
 
1 {J I ^^y^l^ 
 
 bmu 
 
 ■mg?