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 810 
 
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SOLAR HEAT 
 
 
SOLAR H EAT 
 
 Its Practical Applications 
 
 BY 
 
 CHARLES HENRY POPE, A. M. 
 
 \\; 
 
 Author of " Solar Enginery," " The 
 
 Pioneers of Massachusetts,'* 
 
 and other works 
 
 BOSTON, MASS. 
 PUBLISHED BY CHARLES H. POPE 
 
 221 Columbus Avenue 
 1903 
 

 
 A 
 
 t 
 
 Copyright, 1903 
 BY CHARLES H. POPE 
 
 Colonial 
 
 Electrotyped and Printed by C. H. Slmonda & Co. 
 Boston, Mass., U. S. A, 
 
PREFACE. 
 
 SUNLIGHT is a common word, its meaning 
 early and universally appreciated. 
 
 Why should not " sunheat " be as fully under- 
 stood, as highly estimated as its twin? For 
 every ray of illumination which comes to us from 
 the sun is entwined with a ray of caloric, 
 equally strong, equally beneficial. And as the 
 light of our orb of day has obtained admiration 
 and won praise for vitalizing and enriching 
 processes in nature and art, why should not fervid 
 poetry and cool ledgers give due credit ;o the 
 heat of the sun for the life, health, power, and 
 wealth which it is capable of conferring to a 
 degree but slightly recognized? And why shall 
 we not take possession of this opulence promptly, 
 eagerly, masterfully? 
 
 This book seeks to arouse every one of its 
 readers, especially the young and progressive, 
 to take part in and help forward a world-wide 
 movement in the appropriation of the vast treas- 
 ures which sunheat offers. 
 
 258161 
 
CONTENTS 
 
 PAGE 
 
 INTRODUCTION : Man's ability to accomplish much by 
 simple manual labor ; his reaching out to procure aux- 
 iliary forces, as domestic animals, the wind, flowing 
 water, heat, steam, galvanism, magnetism, electricity; 
 the great waste of fuel going on and the need of other 
 auxiliaries ; personal experiences of the writer which led 
 to the present treatise ; experiments, caveat, pamphlet . 9 
 
 SOME HISTORY OF SPECIAL UTILIZATIONS 
 OF SOLAR HEAT: The work of Archimedes, 
 De Tralles, Bacon, Hoesen, De Caus, Buffon, De Saus- 
 sure, Belidor, Poncon, Mclvor, Colborne, St. George, 
 Mouchot (notice of his inventions and writings, see also 
 Appendix), Hittell, Deitzler, The Solar Heat Power 
 Company of California, Mauzey, Molera, Cebrian, Cal- 
 ver, Ericsson, Adams, Pifre (Printing by Solar Heat 
 Power), the Auteuil method of raising water by solar 
 heat, the Pasadena, Cal., pumping engine . . .25 
 
 SOME TECHNICAL STUDY OF THE SUBJECT: 
 
 Nomenclature ; premises ; Reception of solar heat ; lo- 
 cating the meridian, value of glass covering ; Reflection 
 of solar heat ; form, material and arrangement of mir- 
 
viii CONTENTS 
 
 PAGB 
 
 rors; Refraction of solar heat; various shapes and 
 cutting of lenses ; lighthouse lanterns ; call for pro- 
 gressive methods in lens-manufacture to meet this 
 want ; Electric Storage of Solar Heat Power ; Applica- 
 tions of Solar Heat 89 
 
 LOCALITIES PECULIARLY ADAPTED TO THE 
 UTILIZATION OF SOLAR HEAT: The "West- 
 ern Highland " region of the United States of America 
 (tables of sunshine) ; Algeria, Egypt, India, The Soudan, 
 South America, Australia, etc.; call for government 
 aid in the development of the enterprise . . .130 
 
 GENERAL DISCUSSION OF THE SUBJECT: Why 
 has so little been done hitherto ? some " captain of 
 industry " may do a great work ; the Costless Engine ; 
 proportion of time available ; solar heat always enrich- 
 ing, never impoverishing ; subject ought to interest the 
 noblest minds 142 
 
 APPENDIX : Review of La Chaleur Solaire, Ses Applica- 
 tions Industriclles, with its table of contents . . 155 
 
INTRODUCTION. 
 
 MAN, relying only upon his own strength, the 
 exercise of human muscular force, can accom- 
 plish very much. He may fell trees, rive their 
 trunks into timbers, boards, shingles, pins, and 
 tools, and put these together, making for him- 
 self a commodious and convenient dwelling. 
 With one of the bits of stone or metal that Na- 
 ture has strewn upon the surface of the ground, 
 he may chip off other chips, and bring to an edge 
 tools for his use in cutting wood, stone, and 
 metals. Learning by experiment what can be 
 done with the wedge, the lever, and the roller, 
 he can move great masses and build structures 
 of immense size. Braiding the fibres of plants 
 into ropes, he can draw and lift weighty arti- 
 cles; twisting them into yarns and cords, he 
 can then weave them into cloths for a great va- 
 
 9 
 
io INTRODUCTION 
 
 riety of uses, to protect and ornament the body 
 and perfect the convenience and comfort of his 
 dwelling. On instruments made entirely by 
 hand wonderful melodies and harmonies have 
 been produced; on hand-smoothed wood and 
 hand-woven cloth poems and histories have been 
 written, mathematical problems calculated, and 
 artistic conceptions wrought. Making use of the 
 vital energy which he finds operating in plants 
 and animals, he tills the soil and raises stock, 
 till farm and garden and flock and herd reward 
 his toil. 
 
 Having discovered fire (first becoming ac- 
 quainted with it, perhaps, as a product of light- 
 ning), experiment shows him the value of heat 
 to improve the quality of fruit and flesh and to 
 bring metals into plastic condition. Then, still 
 making use of human power alone, he has gone 
 on enlarging the sphere of his activities, the 
 wealth of his achievements. 
 
 But at a period very remote, man learned to 
 domesticate animals, and add their force to his 
 own. He bade them draw his plow, tread out 
 his grain, move his heavy loads, and bear his 
 
INTRODUCTION n 
 
 burdens. Next, he turned to the wind, which 
 often hindered his movements, and tamed it to 
 be his servant. Stretching with his own hands 
 the fans and sails of his mill, he calmly awaited 
 the approach of the gale, and laughed as the 
 attacking party became his servant. He spread 
 the cloth his hands had woven on the spars his 
 fingers had shaped, and the conquered wind be- 
 came his galley-slave. The torrent rushing down 
 the hillside was caught by his nimble fingers, and 
 made to do his bidding, turning his water-wheel. 
 By and by a compound force was invented, 
 Steam, child of the father Fire and the mother 
 Water, a very Samson. Now the progress of 
 man's achievements became, shall we say, a thou- 
 sandfold greater than before? Surely man, with 
 the auxiliary steam, has been writing history 
 at a prodigious rate compared with his former 
 movements. 
 
 One more tremendous force has been brought 
 into man's possession and use, rather a triad 
 of forces, Magnetism, Galvanism, and Electric- 
 ity. The first was domesticated by the almond- 
 eyed citizens of the Central Flowery Kingdom 
 
iz INTRODUCTION 
 
 many centuries ago in the mariner's compass; 
 the other two coquetted with philosophers for a 
 long period ; but the trio to-day are saddled and 
 harnessed for the every-day service of the rich 
 and poor alike in a multitude of ways. 
 
 What more do we need? Have we not forces 
 and machinery sufficient for all present and pro- 
 spective uses? We are still improving all the 
 auxiliaries which we have adapted to our use; 
 still learning the laws of heat; still improving 
 the breeds of our domestic animals; still inves- 
 tigating agricultural processes; making innu- 
 merable improvements in steam and electrical 
 enginery, and so on. 
 
 MAN IS CRIPPLED FOR LACK OF AUXILIARIES. 
 
 But meantime, the opportunities and demands 
 of human activity have increased far more rap- 
 idly than the exercise of human power, or the 
 application of known principles, or the appropri- 
 ation of external forces; and man is crippled 
 to-day for lack of auxiliaries. It costs too much 
 to raise many of the articles which are needful 
 
INTRODUCTION 13 
 
 for the support of life ; it costs too much to make 
 many of the things which have come to be rec- 
 ognized as essential to a complete existence and 
 happiness; and an immense sphere for discovery 
 and appropriation still awaits us after all the 
 years of man's residence on this planet. We 
 must have more of the sort of help that the wind 
 gives; more of such aid as steam furnishes; 
 more of the service now rendered us by flowing 
 streams and burning liquids and gases. Some 
 other Titan must be found to bear our loads, 
 till our fields, warm our dwellings, develop our 
 mines, and extend the sway of our race over the 
 irrational and inanimate. 
 
 One large motive to this search for, and appro- 
 priation of, a new auxiliary is the frightful de- 
 struction of material which is carried on by our 
 fuel systems. Forests are being swept away from 
 hills and valleys; coal is being drawn up from 
 miles and miles of mines. The year 1902 has 
 added an awful chapter to the history of our need 
 of a new source of heat and power, by the wide 
 suffering and impoverishment of the people of 
 the eastern United States, in consequence of the 
 
14 INTRODUCTION . 
 
 Pennsylvania coal strikes. Can we not discover 
 or use, if already discovered, something which 
 will be obtainable without the consent of either 
 " operators " or " organized laborers ? " Can 
 we not employ something which will still remain 
 for to-morrow after we have used it to-day? As 
 the flowing stream gives its aid, so may not other 
 natural movements be harnessed into our ser- 
 vice? And is there not something more stable 
 than the river current, which depends for its 
 fulness on rainfall and other conditions? 
 
 PERSONAL EXPERIENCES OF THE WRITER. 
 
 This quest has long interested the writer. Be- 
 coming a resident of California in 1865, he saw 
 much of the country from North to South. In 
 the year 1875, living in Oakland, he began a 
 series of experiments in the investigation of 
 
 SOLAR HEAT. 
 
 He used lenses first, " burning glasses," read- 
 ing-glasses, photographic lenses, etc. It was 
 
INTRODUCTION 15 
 
 interesting to watch the varying operation of 
 lenses of different size. A pocket magnify ing- 
 glass, one inch and an eighth in diameter, would 
 concentrate heat enough to set paper on fire in 
 a tiny spot in a second or more. The larger the 
 lens, the broader the spot or section, which would 
 flame up and burn out the paper in the same time. 
 A glass three inches wide would set wood afire; 
 one six inches across would bore a hole through 
 a shingle; one of eight inches diameter would 
 burn very hard wood, and inflame a disc the 
 size of a dollar on the paper. Then the investi- 
 gator turned his attention to reflectors. He saw 
 the light streaming out in front of a locomotive 
 from the silvered headlight reflector; there the 
 rays of a lamp were sent against the inner walls 
 of the reflector and then turned away in parallel 
 lines along the track. The old maxim came to 
 his mind : " What will fetch will carry ; " the 
 rays of the sun, falling in parallel lines on the 
 inner surface of the reflector, will be reflected 
 to the focus where now the lamp is placed. And 
 the heat of the sun can be concentrated as well 
 as its light, since both are under the same laws 
 
16 INTRODUCTION 
 
 of undulation. Impressed with this idea, he bor- 
 rowed of the master mechanic at the railroad 
 shop a spare headlight reflector; took it to his 
 residence; set it up in a simply constructed 
 framework, and inserted at the focus, where the 
 lamp had been, a tube of galvanized iron, black- 
 ened. Turning the frame toward the sun, so 
 that the rays fell directly into it, he waited five 
 minutes only, when the quart of water he had 
 poured into the tube began to boil; later he 
 cooked eggs in the water, and did other culinary 
 performances not needful to detail. Placing 
 pieces of wood at the focus, he found them 
 quickly burned ; antimony glance, a metal of low 
 melting point, soon flowed at the focus, and some 
 other metallic compounds yielded also. 
 
 If the parson had been a mechanical man, able 
 to construct apparatus, or, if he had possessed 
 spare cash for the employment of skilled helpers, 
 there might have been some valuable progress 
 made. Unable to pursue the investigations far- 
 ther at that time, he contented himself with fil- 
 ing, through the patent agency of The Scientific 
 Press, of San Francisco, a caveat for an inven- 
 
INTRODUCTION 17 
 
 tion of a transmitter of heat obtained from con- 
 centrated solar rays. 
 
 EXTRACTS FROM THE CAVEAT. 
 
 The Theory. 
 
 ist. That the rays of the sun fall in parallel 
 lines, and may be focalized in a point by refrac- 
 tion on one side of a given plane, or, by reflection, 
 meeting like the radii of a sphere at its centre, 
 from every side except that exposed to direct 
 rays. 
 
 2d. That the parabolic mirror is the best form 
 of reflector, and that its surface may either be 
 polished or glistening white, e. g. " hard finish ; " 
 the latter by far the least expensive. 
 
 3d. That machinery of the simplest sort will 
 give to such a mirror a motion which will keep 
 its face toward the sun, even if its size be ex- 
 ceedingly large. 
 
 4th. That the degree and amount of heat at 
 the focus will be proportionate to the area of the 
 opening of the lens or mirror ; and that, thus, the 
 only limit to the temperature which may be 
 
i8 INTRODUCTION 
 
 reached is the size to which such lenses and 
 mirrors may be constructed and revolved. 
 
 5th. That the temperature of the air through 
 which rays pass immediately before focalization 
 affects the focal temperature. From which it 
 would follow that the hot, rainless districts of 
 the Sierra Nevada et ah. will afford a very high 
 degree of heat, and that there would be some 
 accumulation of heat in some proportion to the 
 time of exposure of surface. 
 
 6th. That any substance may (practically) be 
 heated at or near the focus which does not in- 
 jure the surface of the reflector by steam, smoke, 
 or decrepitation; and any substance may be re- 
 torted there. 
 
 7th. That the best form of retort is spherical 
 or spheroid, with conical apertures pointing 
 toward the centre; which would multiply the 
 heating surface like boiler tubes. The delivery 
 pipe from this retort to be passed (i) directly 
 back through the shaded portion of the reflector, 
 or (2) forward and down through a slit in the 
 reflector on to a rotating table. For melting 
 
INTRODUCTION 19 
 
 ores, the first may admit the ore, the latter con- 
 duct out the liquid. 
 
 The claim was then given : 
 
 "A is a parabolic mirror, which is mounted 
 upon a suitable frame, and with the proper solar 
 mechanism for rotating it, with its face con- 
 stantly to the sun." 
 
 The device for which the inventor particularly 
 sought protection was described as " An opaque, 
 globular retort, B, provided with numerous con- 
 ical spaces which extend radially toward the 
 centre, and serve to carry the heat throughout 
 the interior space, from which it is conveyed by 
 a tube, C, through the rear of the mirror to the 
 distributor, D. The discharger may consist of 
 numerous conical spaces, E, which project radi- 
 ally in every direction from the central globe, D, 
 into the medium to be heated, and by this or 
 some equivalent device I am enabled to utilize 
 the heat of the sun for many purposes. The con- 
 centrating and diffusing devices are especially 
 useful for many other purposes, and I desire to 
 especially protect myself in the use of these 
 parts," etc. 
 
20 INTRODUCTION 
 
 This, the writer believes, was the first appli- 
 cation at the United States Patent Office for any- 
 thing relating to solar heat. 
 
 It may be of small value; but the point was 
 made as a beginning of inventions for which 
 he hoped to get time later on. He made the 
 matter no secret; talked with many friends and 
 acquaintances of it. One friend was a reader of 
 the Scientific American, and called the writer's 
 attention to the article which appeared in that 
 journal, touching the French discoveries and 
 constructions in the matter, of which he had been 
 utterly ignorant before. From that time he re- 
 garded himself as a pledged student of the sub- 
 ject, and read what he could find, and find time 
 for. 
 
 The date of the application for the caveat 
 above mentioned was April 10, 1875; the date 
 of the Scientific American's article on the French 
 invention was September 13, 1875. The writer 
 allowed the matter to pass until after he had 
 removed to the Atlantic coast again. March 
 22, 1883, residing at Farmington, Maine, he 
 contributed to the Lewiston Evening Journal 
 
INTRODUCTION 21 
 
 (known as "Congressman Dingley's paper") 
 an article, in which he gave some history of the 
 development of the applications of solar heat; 
 and this paper was reprinted from the Journal, 
 and issued in pamphlet form under the title, 
 " Solar Enginery." Copies of the pamphlet were 
 placed in a number of the leading libraries of the 
 world, and. sent to some persons notable in science 
 or prominent in government; responses came 
 back from a good number of them; and the 
 writer had much pleasure in finding that he had 
 opened a new field of thought and investigation 
 to quite a large number of persons. Certain 
 errors in his historical statements were kindly 
 pointed out, and proffers of assistance and coop- 
 eration made by some. But a very busy life hin- 
 dered him from contributing anything of impor- 
 tance to the study. He spent some money and 
 time in experiments in certain classes of appa- 
 ratus, but without marked success. Some of his 
 correspondents were aided by him and did better. 
 He has seen some progress made in public 
 interest in the subject; carping criticism and 
 
22 INTRODUCTION 
 
 scorn have passed pretty much away ; every time 
 he has given " talks " on the matter, he has been 
 rewarded by active questioning and by positive 
 respect shown the topic and his statements. 
 Meantime the enterprise of California and Mas- 
 sachusetts has, as public fame declares, brought 
 things to a practical success in certain cases ; the 
 demonstration is complete along some lines ; and 
 there ought to be from this very point definite 
 progress along the whole front. There is a hesi- 
 tation, however, a failure to advance rapidly. 
 The writer believes that 
 
 SOME CALL TO THE PEOPLE 
 
 is needed; some information on the subject fur- 
 nished in a manner to arouse interest and make 
 a demand for the ovens, furnaces, engines, which 
 it is possible now for manufacturers to produce. 
 It is also necessary that some stir come to invent- 
 ors, to ingenious men, handy men, to anybody 
 who can find out new ways of " catching the 
 sunbeams " and extracting gold from them. 
 
INTRODUCTION 23 
 
 THE PURPOSE OF THIS BOOK. 
 
 Therefore he comes before the public in the 
 present treatise, in which he endeavors to trace 
 the history of attempts and successes in the utili- 
 zation of solar heat; examine a portion of the 
 laws and limitations of the subject; discuss ways 
 and means; and attempt to arouse his readers 
 to give to the matter their energy and invention, 
 their brain and capital; that we may very soon 
 see solar enginery take its place by the side of 
 steam enginery and electrical enginery and gas 
 enginery in the public estimation, in technical 
 schools, in mechanical journals, and in myriads 
 of practical, labor-saving constructions. 
 
SOLAR HEAT 
 
 Its Practical Applications 
 
 CHAPTER I. 
 
 SOME HISTORY OF SPECIAL UTILIZATIONS OF 
 SOLAR HEAT. 
 
 THE earliest instance on record of the practical 
 application of solar heat to aid man in his under- 
 takings is the alleged attack of a Syracusan 
 scholar upon the Roman fleet in the year 
 214 B. c. with burning mirrors. 
 
 Syracuse was the largest city of ancient Sicily. 
 Long independent, many years an ally of Rome 
 while its intelligent king, Hiero, lived, it had 
 been estranged from the Italian government by 
 his grandson and successor, Hieronymus, and 
 
 25 
 
26 SOLAR HEAT 
 
 had allied its fortunes to those of Carthage. 
 Marcellus, the Roman ruler, came down upon 
 the city with his imposing force of ships, and 
 the struggle was severe. Archimedes, the most 
 renowned mechanician of the age, discoverer of 
 the ratio between the circumference and diameter, 
 and of the law of specific gravity, who had been 
 a pupil of Euclid in Alexandria, set himself 
 to work to aid his native land. He bethought 
 himself of the mighty power of the sun. So 
 he caused, as is supposed, a number of brazen 
 plates to be constructed; had their surfaces pol- 
 ished to the highest degree possible, and then 
 arranged them along the shore in some way not 
 clearly described, so that the reflected rays were 
 concentrated upon the hulls and rigging of the 
 Roman ships which lay in the harbor or sailed 
 near the shore, setting some of them on fire, and 
 striking terror into the hearts of the sailors to 
 such an extent that the fleet was temporarily 
 scattered, and the city rid of their presence for 
 a brief period. The siege was renewed after a 
 little, to be sure; the inventor was struck down 
 by the sword of a Roman soldier; and Syracuse 
 
ITS PRACTICAL APPLICATIONS 27 
 
 became a Roman province. But the philosopher's 
 use of the sun's heat had taken its place upon 
 the world's arena, and was entered in the world's 
 records. * Later historians made something of it ; 
 
 1 Anthemius de Tralles, a celebrated architect, whose 
 chief monument is the superb basilica of Ste. Sophia in 
 Constantinople, dying in the year 584 A. D., left among 
 his writings four treatises upon burning mirrors, fragments 
 of which are still extant. The second of these is on the 
 problem, " How to construct a machine capable of setting 
 an object on fire at a distance by means of solar rays." 
 
 Roger Bacon, an English monk, advocated the use of 
 burning mirrors about the year 1280 A. D., and actually 
 constructed and offered for sale at 10 apiece some excel- 
 lent ones of steel. But his genius and progressiveness made 
 him enemies, and brought him obloquy and long imprison- 
 ment. He died in the year 1294. 
 
 Mirrors were manufactured in Dresden, about 1755, by 
 a mechanic named Hoesen, of parabolic form, nine feet 
 and a half in diameter, constructed with wooden frames, 
 having thin plates of brass for a reflecting surface within. 
 With these he and his patrons experimented in setting fire 
 to objects at various distances; but we have no record 
 of their applying them to the needs of the home or the 
 factory. 
 
 Salamon de Caus (1576 1626), a French engineer, in- 
 vented and described in 1615 the first machine for raising 
 water by means of the heat of the sun. Another French 
 engineer, Bernard Foret de Belidor (16971761), gives an 
 excellent account of this "continual fountain," as its 
 designer termed it 
 
SOLAR HEAT 
 
 [) I 
 
 THE CONTINUAL FOUNTAIN OF SALAMON 
 DE CAUS (l6l5). 
 
ITS PRACTICAL APPLICATIONS 29 
 
 but it would seem that the event was looked 
 upon as a freak, a piece of magic, an eccentricity ; 
 no successor of the great Archimedes arose for 
 centuries to carry out his incomplete designs, or 
 produce in full what he had performed in em- 
 bryo. In fact, the time came when many stu- 
 dents of history scoffed at the record of the 
 burning of the fleet, and called the story a fable, 
 a canard. 
 
 But there arose a man, after nineteen centuries 
 had gone, who determined to test the practicabil- 
 ity of the alleged performance of Archimedes. 
 The French naturalist and philosopher, Buffon, 
 about the year 1747, made a series of experi- 
 
 After filling the dome, A B N C, to the line B C, the 
 heat of the sun on the dome so expands the air in its 
 upper portion that the pressure drives part of the water 
 (which cannot go down on account of the valve at K) up 
 through the valve F into the reservoir H. When (at night, 
 for example) the globe is cooled and the air in it ex- 
 panded, water will rise from below through the valve K 
 and the tube K N, until the air in the globe is condensed 
 to the same degree as the outer air which presses upon the 
 surface, M I, of the water below. This cycle will be 
 repeated every day and night when the one is sufficiently 
 warm and the other sufficiently cool. Of course artificial 
 cooling might be applied and frequent cycles secured- 
 [Mouchot.] 
 
30 SOLAR HEAT 
 
 ments which demonstrated completely the entire 
 practicability of the performance attributed to 
 the Syracusan in the third century before Christ. 
 
 M. Buffon caused a large framework to be 
 built, on which he hung pieces of silvered glass, 
 whose reflections were all turned on one point. 
 Then he varied the number of pieces and the dis- 
 tances of objects, which he subjected to the focal- 
 ized heat of the sun, and tabulated the results. 
 
 With 17 mirrors, at 20 feet, he heated thin 
 pieces of iron to redness. 
 
 With 45 mirrors, at 20 feet, he melted a pew- 
 ter flask of six pounds' weight. 
 
 With 128 mirrors, at 150 feet, he burned a 
 tarred plank. 
 
 With 154 mirrors, at 150 feet, he made a 
 tarred plank smoke in two minutes when the 
 sky was obscured. 
 
 With 154 mirrors, at 250 feet, he burned 
 chips of wood covered with charcoal and sulphur. 
 
 All this was done in France, where the tem- 
 perature of solar rays could not have been as 
 high as at Syracuse, making a perfect proof of 
 the historical probability of the story told by the 
 
ITS PRACTICAL APPLICATIONS 31 
 
 old historians concerning the Syracuse ship- 
 burning. 
 
 M. Buffon afterward had a burning mirror, 
 of parabolic form, constructed, having a diameter 
 of forty-six inches, and performed many experi- 
 ments with wonderful results. He does not ap- 
 pear to have looked on the sun as a tamable 
 force for man's daily use, an ally for human 
 enterprise; and all his experiments were classed 
 by the annalists of the period as play, or, at the 
 highest, scientific curiosities. 
 
 De Saussure, a Swiss philosopher (174099), 
 in letters to Buffon and to La Journal de Paris 
 described a set of concentric glass chambers which 
 he had constructed, and in the interior of which 
 he had cooked soup. About the same time a 
 French physicist, Ducarla, constructed a some- 
 what similar apparatus and performed much the 
 same work with it. [Mouchot] 
 
 In 1764, B. F. Belidor published, at Amster- 
 dam, the results of certain investigations of his 
 own; but the world received no impulse toward 
 the appropriation of the energy of sunbeams for 
 real service. Even Sir John Herschel, when at 
 
32 SOLAR HEAT 
 
 the Cape of Good Hope, in 1838, he was im- 
 pressed with the tremendous power of the sun, 
 failed to arouse anything of a practical spirit in 
 the British mind. 
 
 For further accounts of ancient studies and con- 
 structions, see extracts from Mouchot in the 
 Appendix. 
 
 Antoine Poncon, in 1854, obtained a patent in 
 London, the first of which I have found any rec- 
 ord, for an invention to utilize solar heat. 
 
 " My invention," says the patentee, " consists 
 in using the sun's rays to create a vacuum in a 
 suitable vessel, elevated at the height of a column 
 of water, which, in the above vacuum, is kept 
 in equilibrium by the pressure of the atmosphere. 
 Such vacuum being formed, I fill it with water 
 acted upon by the external pressure of the atmos- 
 phere, and thus obtain a head of water which 
 may be applied as a motive power." Nothing 
 more can be learned of this invention. Whether 
 M. Poncon actually constructed a machine and 
 produced a vacuum after this sort, and did ob- 
 tain a head of water which he really used as a 
 
ITS PRACTICAL APPLICATIONS 33 
 
 motive power, or whether he obtained a patent 
 for an idea (as many an inventor has vainly tried 
 to do under our American laws), no man informs 
 us. 
 
 In 1865, William Graham Mclvor, superin- 
 tendent of the Government Botanical Garden 
 and Cinchona Plantation in the Presidency of 
 Madras, India, obtained a patent in England, 
 also, and Colborne and St. George a little later; 
 but there comes to the reader a strong suspicion 
 that the Patent Office admitted essayists, rather 
 than inventors, to their lists; and that these 
 men were not actual makers of machines which 
 did what they claimed. Especially is this true 
 of Mclvor, who tells us, " on the average we 
 have 280 bright days in a year, when the uncon- 
 centrated heat of the sun is all the way from 120 
 to 1 60 Fahrenheit." But he does not explain 
 anything he had done to utilize it. 
 
 While these studies and declarations were going 
 on in Great Britain, and nothing more tangible 
 is recorded, there was a definite advance made 
 in France, the home of Buffon, above mentioned. 
 
34 SOLAR HEAT 
 
 AUGUST MOUCHOT, 
 
 a professor in the Lycee d'Alengon, at Tours, in 
 the southern part of France, pursuing studies 
 in mathematics, the department in which he was 
 an instructor, achieved some very practical re- 
 sults. He made a reflector of a general parabolic 
 form, like the headlight reflector of the locomo- 
 tive (see Introduction), and placed at the focus 
 a boiler filled with water, covering it with a bell- 
 glass ; he connected the boiler with a small steam- 
 engine, which was run by the heat of the sun 
 alone. This " insolator " was a success to some 
 extent; he seems to have actually had it in 
 operation as early as the year 1860. At about 
 the same time he invented ovens, " les mar- 
 mites solaires" in which he cooked food to a 
 certain amount. He exhibited a solar pumping- 
 engine in Paris in 1866. [Revue des Deux 
 Mondes, 1876.] 
 
 The government became interested in his 
 work, and aided him; employed him, in fact, to 
 construct a number of pumping-engines for use 
 in their province of Algeria, on the desert. 
 
ITS PRACTICAL APPLICATIONS 35 
 
 These were not made, perhaps, before the' ex- 
 hibition, in 1875, of his perfected reflector and 
 engine, but some of them were in operation in 
 1878. He exhibited at Tours, and afterward at 
 the Paris Exposition in 1878, a reflector 112.3 
 inches wide, 39.3 inches at base, with an engine 
 at the focus, which pumped water very rapidly 
 and worked successfully. He obtained patents 
 for various forms and parts of his inventions in 
 France, and also in England. 
 
 All must unite in honoring him as the greatest 
 of the pioneers in solar enginery. The world 
 owes him a large debt. 
 
 POSTSCRIPT. 
 
 After the present work had gone to press the 
 writer, being in London, saw for the first time 
 M. Mouchot's book, "La Chaleur Solaire, Ses 
 Applications Indwtrielles" in the library of the 
 British Museum. He immediately ordered a copy 
 and read it, with keen interest and admiration. 
 From its pages he made, on his return to America, 
 a few extracts which he incorporated in the final 
 
36 SOLAR HEAT 
 
 proof-reading of this volume, giving credit for 
 the same in every case; he also added in an 
 appendix a translation of the title and contents of 
 M. Mouchot's work, in order that his readers 
 might get something of the benefit which the 
 professor's pages afford. 
 
 M. Mouchot began to give his attention to the 
 study of solar heat in 1860. He received a patent 
 from the French government in 1861. In 1864 
 and 1865 he made valuable inventions in pumping 
 apparatus based on the " continual fountain " 
 of De Caus, and exhibited also parabolic mirrors 
 with suitable receivers. His studies resulted in 
 1869 in his invention of a mirror of conical form, 
 in the focal line of which he placed a blackened 
 metallic vessel covered by a thin, clear glass jar 
 to hold the heat which the rays of the sun poured 
 through its transparent sides upon the vessel. 
 There he cooked beef a la mode in 1^/2 hours; 
 potatoes in an hour ; baked bread in three-quarters 
 of an hour, broiled (roasted) beef in 22 minutes, 
 saving its juice in the bottom of the pot. 
 
 In 1868 Ericsson announced that he had con- 
 
ITS PRACTICAL APPLICATIONS 37 
 
 structed three small solar engines, upon which 
 he and some others based the claim that he was 
 earlier in his discoveries than Mouchot. But 
 careful investigation must lead any person to 
 award priority both of design and construction 
 to Mouchot. 
 
 In October, 1875, he reported to the French 
 Academy of Science an apparatus of which his 
 book presents a full description and figure. 
 
 The government assisted him from time to 
 time, and sent him, in 1877, to Algeria for ex- 
 tended observations in this line, which he also 
 reports. On his return they voted him a liberal 
 sum of money to enable him to construct his 
 culminating success, the engine which he ex- 
 hibited at the Exposition in Paris in 1878. 
 
 We give a copy of his own illustration of this 
 great work. 
 
 Those of our readers who do not read French 
 will probably have no difficulty in understanding 
 the important features of the apparatus. 
 
 The mirror had an opening of about 20 square 
 metres (say a circular opening 13^ feet in 
 diameter). The boiler, 6j^ feet long, had a 
 
38 SOLAR HEAT 
 
 capacity of about 21 gallons, into which water 
 to the amount of 16 gallons was poured, while 
 the remaining space was left for steam. 
 
 Placed in the sun at Trocadero (Paris), 
 September 2, 1878, in half an hour its water was 
 boiling and the pressure of 6 atmospheres was 
 quickly reached. The 2Qth of September, with 
 a clear sky, at 11.30 A. M., a pressure of 7 
 atmospheres was attained, and he produced the 
 first block of ice ever made by the heat of the sun. 
 Other most satisfactory achievements followed 
 during that month and the next, in cooking, dis- 
 tilling, pumping, etc., etc. The Exposition 
 awarded him a medal. 
 
 FIRST UNITED STATES PATENT. 
 
 / 
 
 In the United States, the first patent for solar 
 apparatus was issued March 20, 1877, to John S. 
 Hittell and George W. Deitzler, of San Fran- 
 cisco, Cal. Their patent describes a " concave 
 mirror, with which they throw focalized heat 
 upon a mass of iron or other suitable material 
 
 v i 
 
ITS PRACTICAL APPLICATIONS 39 
 
 as a reservoir of the heat; a reservoir chamber, 
 a heat box, a drying chamber," etc., letting the 
 cold air pass in and then pass out again after 
 the sun has heated it, applying it then to ordi- 
 nary hot-air machinery. Mr. Deitzler took out a 
 second patent May 19, 1882, in which he de- 
 scribed " a reflecting mirror, straight one way, 
 curved the other " half of a tube or cylinder, 
 if you please (what we elsewhere call a cylin- 
 drical mirror), and in the line-focus thus formed 
 he placed a tube rilled with the material to be 
 heated. In both patents the ordinary methods 
 were used to keep the apparatus facing the sun. 
 These gentlemen deserve to be enrolled high 
 on the walls of the true Temple of Fame for 
 their contributions to the development of solar 
 calorics. Mr. Hittell had previously earned the 
 gratitude of his fellow citizens by his admirable 
 book, " The Resources of California," which did 
 a great deal to acquaint the world with the fruit 
 and grain capabilities of the State, and its other 
 advantages, attracting both immigration and 
 capital to the coast. Mr. Deitzler entered very 
 practically into the subject, with a mechanical 
 
40 SOLAR HEAT 
 
 GRAND GNRATEUR SOLAIRE INDUSTRIEL 
 
 EXPOSfi 
 
 Dans le Pare du Trocade'ro 
 (Annexe de f Exposition AlgJrienne) 
 
 ET RECOMPENSE D'UNE MEDAILLE D 5 OR 
 LEGENDE 
 
 M. Secteur permettant, au moyen de la vis w, d'incliner 
 1'appareil suivant la latitude du lieu cm Pon opere. 
 
 N. Mouvement a la cardan permettant, par Pintermedi- 
 aire des pignons d'angle, de la roue r et du secteur vu de 
 profil sur la figure ci-contre, d'orienter 1'appareil du lever 
 au coucher du soleil. 
 
 S. Secteur permettant, au moyen de la vis o, d'incliner 
 1'appareil suivant Pepoque de Pannde ou Pon expeVimente. 
 
 F. Chaudiere tubulaire entoure'e du manchon de verre. 
 
 H. Dome de vapeur. 
 
 I. Soupape de surete*. 
 
 La vis ci-contre munie d'un volant servait de contrevente- 
 ment a 1'appareil une fois place* suivant 1'angle de la latitude. 
 Le refle*teur compose* de fers a T supportant les plaques 
 rdfldchissantes dtait fix sur la base en fonte de la chaudiere. 
 Cette derniere, composde de tubes en fer avait une capacite' 
 de 100 litres, 70 pour Peau, 30 pour la vapeur. Son alimen- 
 tation se faisait au moyen d'un injecteur. 
 
ITS PRACTICAL APPLICATIONS 
 
 GRAND GENERATEUR SOLAIRE INDUSTRIE!, 
 PAR PROF. A. MOUCHOT (1878) 
 
42 SOLAR HEAT 
 
 skill and business energy which attracted the 
 attention of a considerable number of men of 
 affairs to this matter. 
 
 THE SOLAR HEAT POWER COMPANY OF 
 CALIFORNIA 
 
 was formed in 1883, of which Wm. H. Birch, 
 A. F. Knorp, Geo. A. Dickson, Geo. W. Deitzler, 
 and H. C. Biggs were directors, with Oscar 
 Hines secretary, which both expressed and in- 
 creased general interest in the matter. [See San 
 Francisco Bulletin, March 12, 1883.] The death 
 of " General Deitzler " interfered with the suc- 
 cess of the company somewhat. 
 
 The second patent issued by our government 
 in this department was given April 27, 1880, to 
 James P. Mauzey, of Blackfoot, Montana; whose 
 design was substantially a framework of rectan- 
 gular form, with mirrors arranged on its (inner) 
 walls, all so placed as to concentrate their rays 
 on the focal point or region, where he put the 
 substance or article to be heated. Of this 
 
ITS PRACTICAL APPLICATIONS 43 
 
 gentleman the writer has failed to learn any 
 particulars. Another patent for solar-heating 
 devices was obtained by Pacific coast men from 
 the British government. Eusebius J. Molera and 
 John C. Cebrian, of San Francisco, Cal., were the 
 persons, and the date of the issue of their patent 
 was October 22, 1880. No special interest at- 
 taches to the specific designs they described. Of 
 them and their work the writer is also unable to 
 learn anything; yet they and Mr. Mauzey must 
 not be forgotten in the coming years of triumph 
 which await the cause of solar heat utilization. 
 
 In December, 1883, W. Calver, of Washing- 
 ton, D. C., patented a car containing interior 
 reflecting surfaces, which revolved on a circular 
 track, so as to face the sun. 
 
 Another name which deserves to be placed 
 high on the roll of the fostering friends of solar 
 enginery is that of Captain John Ericsson, of 
 New York City, the renowned inventor and 
 builder of the Monitor. He was a builder of 
 hot-air engines and other mechanical construc- 
 tions. He made elaborate experiments ; invented 
 
44 SOLAR HEAT 
 
 an instrument for the measurement of the heat 
 which comes from the sun ; also designed a boiler 
 and engine for the operation of machinery by 
 solar heat, a cut of which we reproduce from 
 the Scientific American of May 5, 1877, by per- 
 mission of the publishers. He calculated that 
 " the heat radiated by the sun during nine hours 
 per day, for all the latitudes comprised between 
 the equator and the forty-fifth parallel, corre- 
 sponds per minute and per square foot of 
 normal surface to 3.5 thermo units of 772 foot 
 pounds. This would give a power of 270.000 
 foot pounds, or from 8 to 9 horse power on a 
 surface of 100 square feet. The engine illus- 
 trated was built on the caloric system, and had 
 run at 420 revolutions per minute, with the sun 
 near the zenith and during fine weather." 
 
 By the kindness of Mr. T. M. McDonough, 
 of Montclair, N. J., our attention was called to 
 the following article contributed by Captain 
 Ericsson to Nature, and there printed January 3, 
 1884; reprinted in the Scientific American of 
 February 2, 1884, describing his second design. 
 
ERICSSON'S SUN MOTOR, ERECTED AT NEW YORK, 1883 
 
ITS PRACTICAL APPLICATIONS 47 
 
 " THE SUN MOTOR AND THE SUN'S TEM- 
 PERATURE. 
 
 " The annexed illustration represents a per- 
 spective view of a sun motor constructed by the 
 writer and put in operation last summer. This 
 mechanical device for utilizing the sun's radiant 
 heat is the result of experiments conducted dur- 
 ing a series of twenty years; a succession of 
 experimental machines of similar general design, 
 but varying in detail, having been built during 
 that period. The leading feature of the sun 
 motor is that of concentrating the radiant heat by 
 means of a rectangular trough having a curved 
 bottom lined on the inside with polished plates, 
 so arranged that they reflect the sun's rays 
 toward a cylindrical heater placed longitudinally 
 above the trough. This heater, it is scarcely 
 necessary to state, contains the acting medium, 
 steam or air, employed to transfer the solar 
 energy to the motor; the transfer being effected 
 by means of cylinders provided with pistons and 
 valves resembling those of motive engines of the 
 ordinary type. Practical engineers, as well as 
 
48 SOLAR HEAT 
 
 scientists, have demonstrated that solar energy 
 cannot be rendered available for producing mo- 
 tive power, in consequence of the feebleness of 
 solar radiation. The great cost of large reflect- 
 ors, and the difficulty of producing accurate 
 curvature on a large scale, besides the great 
 amount of labor called for in preventing the pol- 
 ished surface from becoming tarnished, are ob- 
 jections which have been supposed to render 
 direct solar energy practically useless for pro- 
 ducing mechanical power. 
 
 " The device under consideration overcomes 
 the stated objections by very simple means, as 
 will be seen by the following description. The 
 bottom of the rectangular trough consists of 
 straight wooden staves, supported by iron ribs 
 of parabolic curvature secured to the sides of the 
 trough. On these staves the reflecting plates, 
 consisting of flat window glass silvered on the 
 under side, are fastened. It will be readily under- 
 stood that the method thus adopted for concen- 
 trating the radiant heat does not call for a 
 structure of great accuracy, provided the wooden 
 staves are secured to the iron ribs in such a 
 
ERICSSON'S SOLAR CALORIC ENGINE 
 
ITS PRACTICAL APPLICATIONS 51 
 
 position that the silvered plates attached to the 
 same reflect the solar rays toward the heater. 
 Fig. 2 represents a transverse section of the lat- 
 ter, part of the bottom of the trough, and sec- 
 tions of the reflecting plates, the direct and 
 reflected solar rays being indicated by vertical 
 and diagonal lines. 
 
 " Referring to the illustration, it will be seen 
 that the trough, n feet long and 16 feet broad, 
 including a parallel opening in the bottom, 12 
 inches wide, is sustained by a light truss attached 
 to each end, the heater being supported by verti- 
 cal plates secured to the truss. The heater is 
 6% inches in diameter, n feet long, exposing 
 130 x 9.8 1,274 superficial inches to the action 
 of the reflected solar rays. The reflecting plates, 
 each 3 inches wide and 26 inches long, intercept 
 a sunbeam of 130 x 180 23,400 square inch sec- 
 tion. The trough is supported by a central 
 pivot, round which it revolves. The change of 
 inclination is effected by means of a horizontal 
 axle concealed by the trough the entire 
 mass being so accurately balanced that a pull of 
 5 pounds applied at the extremity enables a per- 
 
52 SOLAR HEAT 
 
 son to change the inclination or cause the whole 
 to revolve. A single revolution of the motive 
 engine develops more power than needed to turn 
 the trough and regulate its inclination so as to 
 face the sun during a day's operation. 
 
 " The motor shown by the illustration is a 
 steam-engine, the working cylinder being 6 
 inches in diameter with 8 inches stroke. The 
 piston-rod, passing through the bottom of the 
 cylinder, operates a force-pump of 5 inches diam- 
 eter. By means of an ordinary cross-head se- 
 cured to the piston-rod below the steam cylinder, 
 and by ordinary connecting rods, motion is im- 
 parted to a crank shaft and fly wheel, applied at 
 the top of the engine frame; the object of this 
 arrangement being that of showing the capability 
 of the engine to work either pumps or mills. It 
 should be noticed that the flexible steam-pipe em- 
 ployed to convey the steam to the engine, as well 
 as the steam-chamber attached to the upper end 
 of the heater, have been excluded in the illustra- 
 tion. The average speed of the engine during the 
 trials last summer was 120 turns per minute, the 
 absolute pressure on the working piston being 
 
ITS PRACTICAL APPLICATIONS 53 
 
 35 pounds per square inch. The steam was 
 worked expansively in the ratio of i to 3, with 
 a nearly perfect vacuum kept up in the condenser 
 enclosed in the pedestal which supports the engine 
 frame. 
 
 " In view of the foregoing, experts need not 
 be told that the sun motor can be carried out on 
 a sufficient scale to benefit very materially the 
 sunburnt regions of our planet. 
 
 " With reference to solar temperature, the 
 power developed by the sun motor establishes 
 relations between diffusion and energy of solar 
 radiation, which show that Newton's estimate 
 of solar temperature must be accepted. 
 
 " The following demonstration, based on the 
 foregoing particulars, will be readily compre- 
 hended. The area of a sphere whose radius is 
 equal to the earth's mean distance from the sun 
 being to the area of the latter as 214.$* :i, while 
 the reflector of the solar motor intercepts a sun- 
 beam of 23,400 square inches section, it follows 
 that the reflector will receive the heat developed 
 by 0.508 square inch of the solar surface. 
 Hence, as the heater of the motor contains 
 
54 SOLAR HEAT 
 
 1,274 square inches, we establish the fact that the 
 reflected solar rays, acting on the same, are 
 diffused in the ratio of 1,274:0.508 2,507:1. 
 Practice has now shown that, notwithstanding 
 this extreme diffusion, the radiant energy trans- 
 mitted to the reflector, by the sun, is capable of 
 imparting a temperature to the heater of 520 F. 
 above that of the atmosphere. The practical 
 demonstration thus furnished by the sun motor 
 enables us to determine with sufficient exactness 
 the minimum temperature of the solar surface. 
 It also enables us to prove that the calculations 
 made by certain French scientists, indicating 
 that solar temperature does not exceed the 
 temperatures produced in the laboratory, are 
 wholly erroneous. Had Pouillet known that solar 
 radiation, after suffering a two thousand five 
 hundred and sevenfold diffusion, retains a radi- 
 ant energy of 520 F., he would not have 
 asserted that the temperature of the solar surface 
 is 1,760 C. Accepting Newton's law that 'the 
 temperature is as the density of the rays/ the 
 temperature imparted to the heater of the sun 
 motor proves that the temperature of the solar 
 
ITS PRACTICAL APPLICATIONS 55 
 
 surface cannot be less than 520 x 2,507 1,303,- 
 640 F. Let us bear in mind that, while at- 
 tempts have been made to establish a much lower 
 temperature than Newton's estimate, no dem- 
 onstration whatever has yet been produced tend- 
 ing to prove that the said law is unsound. On 
 the contrary, the most careful investigations 
 show that the temperature produced by radiant 
 heat emanating from incandescent spherical bod- 
 ies diminishes inversely as the diffusion of the 
 heat rays. Again, the writer has proved by his 
 vacuum actinometer, enclosed in a vessel main- 
 tained at a constant temperature during the ob- 
 servations, that for equal zenith distance the 
 intensity of solar radiation at midsummer is 
 5.48 F. less than during the winter solstice. 
 This diminution of the sun's radiant heat in 
 aphelion, it will be found, corresponds within 
 0.40 of the temperature which Newton's law 
 demands. It is proposed to discuss this branch 
 of the subject more fully on a future occasion. 
 " The operation of the sun motor, it will be 
 well to add, furnishes another proof in support 
 of Newton's assumption that the energy increases 
 
56 SOLAR HEAT 
 
 as the density of the rays. The foregoing ex- 
 planation concerning the reflection of the rays 
 see Fig. 2 shows that no augmentation of 
 temperature takes place during their transmission 
 from the reflector to the heater. Yet we find that 
 an increase of the number of reflecting plates 
 increases proportionally the power of the motor. 
 Considering that the parallelism of the rays 
 absolutely prevents augmentation of temperature 
 during the transmission, it will be asked : What 
 causes the observed increase of mechanical 
 power? Obviously, the energy produced by the 
 increased density of the rays acting on the heater. 
 The truth of the Newtonian doctrine, that the 
 energy increases as the density of the rays, has 
 thus been verified by a practical test which can- 
 not be questioned. 
 
 " It is scarcely necessary to observe that our 
 computation of temperature 1,303.640 F. 
 does not show maximum solar intensity, the fol- 
 lowing points, besides atmospheric absorption, 
 not having been considered : ( i ) The diminution 
 of energy attending the passage of the heat rays 
 through the substance of the reflecting plates; 
 
ITS PRACTICAL APPLICATIONS 57 
 
 (2) the diminution consequent on the great 
 amount of heat radiated by the blackened surface 
 of the heater; (3) the diminution of tempera- 
 ture in the heater caused by convection. 
 
 "J. ERICSSON." 
 
 After Mr. Ericsson's death, there was consid- 
 erable disappointment felt by his admirers that 
 no complete development of his inventions in 
 this department was found among his effects; it 
 would appear that advancing years prevented 
 that great concentration of his faculties on this 
 point, which had made him so successful in the 
 building of the Monitor, and which might have 
 wrought greater success in the arts of peace had 
 he lived to develop all he had planned. 
 
 INDIA OFFERS A FINE FIELD FOR THE UTILIZA- 
 TION OF SOLAR HEAT. 
 
 Mr. W. Adams, an English resident of Bom- 
 bay, India, made very diligent study of this sub- 
 ject, and developed an apparatus for which he 
 obtained a patent. A public trial of his invention 
 
58 SOLAR HEAT 
 
 was made at Bombay in presence of officials and 
 representatives of the press and others. In The 
 Times a full account of the exhibition was pre- 
 sented, and this was reprinted in the Scientific 
 American of June 5, 1878; two weeks later the 
 latter paper published a letter from Mr. Adams, 
 detailing many interesting facts about the mat- 
 ter, and presenting a cut of the apparatus. We 
 reprint these by permission of Messrs. Munn & 
 Co. 
 
 " COOKING BY SOLAR HEAT. 
 
 " To the Editor of the S dentine 'American: 
 
 " I send you a short account of my experi- 
 ments, made in Bombay, on the utilization of 
 solar heat for cooking. The accompanying en- 
 graving will give an idea of the principle of the 
 cooking apparatus. It consists of a conical re- 
 flector, A, made of wood and lined with common 
 silvered sheet glass. Inside there is placed a 
 copper cylindrical vessel, B, covered by a glass 
 cover, C. The cooking vessel is raised about 
 four inches from the bottom, and the glass cover 
 is five inches longer than the vessel, and two 
 
ITS PRACTICAL APPLICATIONS 61 
 
 inches wider, which leaves an interval of four 
 inches of hot air under the boiler,^ and one inch 
 all round and at the top. The wedge under the 
 apparatus is to keep it inclined, so that the rays 
 of the sun may fall perpendicularly on the boiler. 
 Glass being diathermanous to the direct or re- 
 flected rays of the sun, and non-diathermanous 
 to obscure heat, the rays penetrate the glass, and, 
 striking on the vessel, become transformed into 
 obscure heat, when they are retained by the glass. 
 The glass cover over the boiler is made octagonal, 
 because, in that form, common window glass can 
 be used. Of course a glass dome, such as is used 
 for covering clocks or statuettes, would be better, 
 and, equally, of course, a copper reflector electro- 
 plated with silver would be better than my re- 
 flector; but both of these articles are made 
 octagonal in order that cheap material may be 
 employed. The position of the apparatus re- 
 quires to be changed about every half-hour, to 
 face the sun in its apparent course from east to 
 west. 
 
 " The rations of seven soldiers, consisting of 
 meat and vegetables, are thoroughly cooked by 
 
62 SOLAR HEAT 
 
 it in two hours, in January, the coldest month 
 of the year in Bombay, and the men declare the 
 food to be cooked much better than in the ordi- 
 nary manner. Several people in Bombay and in 
 the Deccan have tried it, and always with success. 
 If the steam be retained, the dish is a stew or 
 a boil; if it be allowed to escape, the food is 
 baked. 
 
 " The reflector is two feet four inches in 
 diameter. The intensity of the heat is increased 
 by increasing the diameter of the reflector. One 
 advantage of this apparatus is that the food will 
 keep hot for a long time after the apparatus has 
 been withdrawn from the solar rays. I withdrew 
 it at 4 p. M., brought it into a room, and threw 
 a railway rug over it. At 8 P. M., when it was 
 uncovered, the metal vessel was too hot to be 
 handled by the bare hand. I have a letter from 
 a surgeon-general in the service, which informs 
 me that he cooked a leg of mutton in it, and 
 that it ' kept hot for four hours ' after having 
 been removed from the air. 
 
 " I am getting one made six feet in diameter, 
 which will differ from that represented in the 
 
ITS PRACTICAL APPLICATIONS 63 
 
 engraving by consisting of fourteen flat glasses 
 instead of eight, and by having an angle of 45 
 until it is on a level with the middle of the 
 vessel, and thence upward an angle of about 60, 
 by which arrangement the whole of the rays 
 reflected from the silvered glass \vill fall on the 
 lower half. Besides cooking food, I am making 
 a series of experiments for heating steam-boilers 
 by concentrating the rays of the sun upon them. 
 " For this purpose I use a combination of flat 
 mirrors, of common sheet glass, silvered, fixed 
 in rectangular frames so as to concentrate the 
 solar rays to a focus at a distance of 20 feet. 
 The focus is about 2 feet in diameter. The plan 
 is on the same principle as that of Archimedes, 
 by which he burned the Roman fleet, which, 
 under Marcellus, was blockading Syracuse 
 the same plan as that suggested by Anthemius 
 of Tralles in the problems by which he proved 
 the exploit of Archimedes to be possible; and as 
 that suggested by Kircher, and in 1747 adopted 
 by Buffon. With 72 pieces of silvered sheet 
 glass, each 15 x io l / 2 inches, at midday, in the 
 month of May, a focus was formed, at a distance 
 
64 SOLAR HEAT 
 
 of 20 feet, of a temperature above 1,088 F. I 
 arrived at that estimate as follows: 18 glasses 
 raised the mercury in the thermometer to 360 ; 
 36 glasses raised it to over 644, when the mer- 
 cury entered into ebullition, and consequently 
 any further rise could not be registered. The 
 ebullition of the mercury was very violent. 
 Placing the temperature produced by the 36 
 glasses at 644, the boiling point of mercury, 
 and deducting 100 as the initial temperature 
 of the atmosphere (the thermometer was in the 
 shade), there remain 544 produced by 36 
 glasses. The focus from the remaining 36 
 glasses was then added, making 72 glasses; and 
 I think it may be inferred that the temperature 
 was then above 1,088. Every kind of wood 
 placed in this focus was instantly ignited, without 
 being, as in BufYon's experiment, previously 
 smeared with tar and shreds of wool. A solid 
 cylinder of water, 18x8 inches, contained in a 
 vertical copper vessel, provided with a steam- 
 pipe, was then placed in the focus, and it boiled 
 in exactly 20 minutes. The ebullition was ex- 
 ceedingly violent In January last I made an- 
 
ITS PRACTICAL APPLICATIONS 65 
 
 other experiment with 198 glasses, each 15x1054 
 inches, fixed in 10 rectangular frames. A cop- 
 per boiler containing 9 gallons of cold water was 
 placed in the focus at 9.25 A. M. It commenced 
 to boil in exactly 30 minutes. It was allowed 
 to boil for exactly i hour, and at 10.55 tne focus 
 was turned off, when 3% gallons of water were 
 found to have been evaporated. 
 
 " My next experiment will be made with about 
 500 of these glasses, fixed in 20 rectangular 
 frames, each 6 feet by about 4 feet. The focus 
 will be about 2 feet in diameter, and (according 
 to the calculation made on the basis of the results 
 of the experiment with 72 glasses) the tempera- 
 ture will be over 7,616 F. The objects of that 
 experiment will be to ascertain how soon after 
 sunrise the water can be provoked to boil, the 
 pressure that can be obtained in a given period, 
 and the quantity of water that can be vaporized 
 in a given time, Other experiments will be made, 
 such as exposing different metals to the focus, 
 etc. The boiler that will be used on that occasion 
 is a vertical boiler, 2 feet 7 inches high and 16 
 inches in diameter, with an annular cylinder of 
 
66 SOLAR HEAT 
 
 water 3 inches in diameter up to half its height. 
 It is made of beaten copper, J4 mcn thick, which 
 will stand any pressure that can be produced in 
 a boiler of those dimensions. It is provided with 
 a steam-pipe, a steam-gauge, and a safety valve, 
 and with no other fittings. The 20 frames will 
 stand in two rows of 10 each, the second row 
 on a platform 6 feet 6 inches high, forming a 
 segment of a circle of 40 feet in diameter. 
 
 " As there is no limit whatever to the number 
 of these mirrors that can be used at once, there is 
 none to the intensity of heat that can be produced, 
 and consequently no limit to the force of the 
 steam that can be generated. The cost of the 
 reflecting material is next to nothing, and it is 
 almost everlasting. There is no mechanical diffi- 
 culty in keeping the focus on the boiler from 
 soon after sunrise to a little before sunset. 
 
 " I am aware of the force of the objection 
 that the solar rays are sometimes intercepted 
 by clouds, even in India; but as an auxiliary to 
 the ordinary boilers, I believe that solar heat 
 could be used so as to save at least 25 per cent. 
 of coal throughout the year by my plan. As 
 
ITS PRACTICAL APPLICATIONS 67 
 
 coal in the seaports of India is never under 30 
 shillings per ton, and double that rate in the 
 interior, such a saving would be exceedingly 
 important. There are many other purposes to 
 which it could be applied besides driving steam 
 machinery or cooking food, such as distilling 
 and rectifying spirits, etc. At Aden, for exam- 
 ple, the sun always shines, and potable water is 
 only obtained by distilling it from salt water. 
 
 " I shall be very glad to have any expression 
 from your readers upon the subject, especially 
 upon the result of the experiment that I have 
 described. W. ADAMS. 
 
 "Bombay, India" 
 
 FRANCE CONTINUES MOUCHOT*S WORK. 
 
 The following very interesting article was 
 translated and reprinted in the Scientific 'Ameri- 
 can of May 13, 1882, from that valuable journal, 
 La Nature. We reprint the article by permis- 
 sion, reproducing, also, the cut which illustrated 
 the original article. It would be of great interest 
 to us to learn more about the labors of M. Pifre, 
 
68 SOLAR HEAT 
 
 who thus carried out ideas of M. Mouchot, and 
 elaborated new applications of his own. 
 
 " PRINTING BY SOLAR HEAT. 
 
 " Our readers already know of Mr. Mouchot's 
 curious solar generators, and of the remarkable 
 experiments that have been performed by that 
 ingenious physicist for the purpose of turning 
 to account that immense reservoir of heat and 
 motive power, the sun. Mr. Abel Pifre, an en- 
 gineer, has recently taken up the labors of Mr. 
 Mouchot, and has constructed upon the same 
 principles as those employed by his predecessor 
 as the base of his apparatus, an insolator, which 
 gathers the heat of the solar rays in the focus 
 of a mirror, and converts it into mechanical 
 motion. 
 
 " On the occasion of the fete of the ' Union 
 Franchise de la Jeunesse/ which occurred Sun- 
 day, August 6, 1882, in the Garden of the Tui- 
 leries at Paris, there was witnessed a remarkable 
 experiment with Mr. Pi f re's latest improvements 
 in the solar generator. 
 
ITS PRACTICAL APPLICATIONS 71 
 
 " There was set up on this occasion in the 
 garden, near the large reservoir, at the foot of the 
 Jeu de Paume stairs, an insolator that measured 
 3.5 metres in diameter at the opening of the 
 reflector. The steam obtained in the boiler car- 
 ried by the reflector at its focus was utilized by 
 a small verical motor, of 30 kilogrammetres 
 power, which actuated a Marinoni printing-press. 
 Although the sun was not very hot, and its radi- 
 ation was interfered with by frequent clouds, 
 the press was able to work with regularity be- 
 tween one and five o'clock in the afternoon, and 
 to print on an average five hundred copies 
 per hour of a journal specially composed for 
 the occasion, and entitled Soleil- Journal (Sun 
 Journal). This is not a revolution m the art of 
 printing, but the result is sufficient to allow us to 
 judge of the services that insolators might ren- 
 der in latitudes submitted to a radiation at once 
 more active and constant. 
 
 " We could not allow this splendid experiment 
 to pass without preserving a souvenir of it. 
 Our engraving faithfully represents the arrange- 
 ments adopted. The Pifre insolator is seen in 
 
72 SOLAR HEAT 
 
 the centre of the cut, with its large parabolic mir- 
 ror; the engine actuated by it is figured at its 
 side ; while m the foreground to the right is seen 
 the Marinoni press printing the journal. It 
 seems evident to us that in hot countries the use 
 of heliodynamics ought sometimes 'to prove ef- 
 fective and economical." La Nature. 
 
 May 13, 1882, there appeared in the Ameri- 
 can an account of an invention wrought out by 
 Prof. E. S. Morse, of Salem, Mass., for " Util- 
 izing the Sun's Rays in Warming Houses." " It 
 consists of a surface of blackened slate under 
 glass, fixed to the sunny side of a house with 
 vents in the walls, so arranged that the cold air 
 of a room is let out at the bottom of the slate 
 and forced in again at the top by the ascending 
 heated column between the slate and the glass." 
 The statement was made that the inventor's 
 house at Salem was then heated by the means 
 described in fine weather. The idea thus brought 
 forward has been met within recent years by 
 some very practical devices, which are now on the 
 market. 
 
 In the issue of the American of December 30, 
 
ITS PRACTICAL APPLICATIONS 73 
 
 1882, an account is given of the " solar cannon 
 of the Palais Royal in Paris, France, which is 
 fired by the heat of the sun at noon, concentrated 
 by means of a burning glass, falling on the pow- 
 der priming of the cannon." The device is very 
 ancient; a traveller, Neel, writing in 1751, de- 
 scribes it. The same journal, in the number for 
 August 1 8, 1883, contained an appeal, written 
 by one who signed only the letter " A," intended 
 to awaken the public to a sense of the value of 
 solar heat utilization. He called attention, espe- 
 cially, to the importance of the invention and 
 construction of lenses of great size at moderate 
 cost, reminding the reader that the concentra- 
 tion of solar heat would not require anything 
 like the exact and achromatic degree of nicety 
 which astronomical work demands. 
 
 A contribution of no slight consequence to 
 this subject appeared in the Scientific American 
 October 3, 1885, translated from La Nature. We 
 copy the article and illustration by permission. 
 
74 SOLAR HEAT 
 
 "THE UTILIZATION OF SOLAR HEAT FOR THE 
 ELEVATION OF WATER. 
 
 " This article will treat of the combined appli- 
 cation of two natural forces to the elevation 
 of water. These forces are: first, the heat of 
 the atmosphere; and second, the comparatively 
 low temperature of the water to be raised. 
 
 " The accompanying drawing shows the gen- 
 eral arrangement of an apparatus worked on this 
 principle. This apparatus has been built at 
 Auteuil, where it operates very well, although 
 our climate is not favorable to the operation of 
 such a device. 
 
 " F is a small building covered by a roof, E, 
 which is exposed to the south, and this roof is 
 formed of ten metallic plates, which are num- 
 bered i, 2, 3, 4, 5, 6, 7, 8, 9, 10. Each of these 
 plates consists of two sheets of iron riveted to- 
 gether on all their edges, and separated slightly 
 by filling pieces. Each plate thus constitutes a 
 water-tight receptacle, in which a volatile liquid 
 can be held. Various liquids can be used, but I 
 prefer a solution of ammonia. Under the influ- 
 
ITS PRACTICAL APPLICATIONS 75 
 
 ence of atmospheric heat, the solution emits 
 vapors, and said vapors or gases escape through 
 tubes, one of which is provided for each plate, 
 and are conducted to the receptacle N. Any 
 liquid which may have been carried along by 
 the gas is taken back to the plates by a tube. 
 By another tube the gas escapes from the vessel, 
 N. This gas has a pressure of i, 2, or 3 atmos- 
 pheres, according to the work which is to be 
 done. It is conducted through a tube to a hollow 
 sphere, which is placed in the well or tank from 
 which the water is to be elevated. This sphere 
 contains a rubber diaphragm, which can attach 
 itself to either half of the sphere. 
 
 " Let us suppose, for instance, that the sphere 
 is full of water; the rubber diaphragm, conse- 
 quently, will rest against the upper half or hemi- 
 sphere. If, now, the pressure of the ammonia 
 gas is brought to bear on the diaphragm, it will 
 be forced to rest on the lower hemisphere; but 
 in order to do this, the diaphragm must eject 
 the water which fills the sphere. This causes 
 the formation of a jet of water, as shown above 
 the tank, R, near the letter G. But the gas must 
 
76 SOLAR HEAT 
 
 be driven from the sphere after it has been 
 emptied of water, so that the operation may be 
 renewed. 
 
 " This is accomplished in the following man- 
 ner: In the centre of the diaphragm a float is 
 inserted, which carries a rod by which a slide 
 is actuated. One of the apertures in this slide 
 coincides with the gas inlet, and the other with 
 the outlet. When the diaphragm rests on the 
 upper hemisphere the inlet is opened, and the 
 water escapes; when it moves toward the lower 
 hemisphere the inlet is closed, the outlet is 
 opened, the sphere is filled with water again, 
 and so on. 
 
 " This would complete the operation if the am- 
 monia gas did not cost anything, but as it is 
 expensive it must be used over and over indefi- 
 nitely. Here we are aided by the low temperature 
 of the water, which is made to pass through a 
 serpentine pipe contained in a water-tight vessel 
 containing part of the ammonia solution used. 
 The solution is cooled by the water in the pipe, 
 and is ready to absorb ammonia. Then, as soon 
 as the outlet is opened, the ammonia gas con- 
 
ITS PRACTICAL APPLICATIONS 77 
 
 ducted into it is absorbed, the pressure which was 
 exerted in the sphere is removed, and water can 
 again enter the sphere. 
 
 " A final precaution is taken, which is to at- 
 tach a little pump to the float, by means of which 
 the ammonia solution can be pumped back into 
 the roof, E. 
 
 " The apparatus at Auteuil raises over 300 
 gallons of water per hour. In warm countries 
 the same apparatus would raise 792 gallons a 
 distance of 65 feet. The calculation of the re- 
 sults to be obtained by this apparatus is based 
 on the following considerations: 
 
 " A sheet of metal one yard square absorbs 1 1 
 calories for a difference of one degree. Each 
 plate which has a surface of 4 square yards ab- 
 sorbs 44 calories per hour. If there is a differ- 
 ence of 6 degrees, 264 calories will be taken from 
 the atmosphere every hour; and by combining 
 this quantity of heat with the cooling action of 
 the water, it is easy, by the difference of tension 
 produced, to obtain an inexpensive force for 
 raising water. 
 
 " This apparatus differs from the numerous 
 
78 SOLAR HEAT 
 
 devices by which attempts have been made to 
 utilize solar heat by means of the Archimedean 
 mirror, by which only secondary heat is obtained. 
 It is not necessary to concentrate the heat by 
 metallic or other mirrors; the atmospheric heat 
 is the basis of the operation, and all roofs ex- 
 posed to the sun can be used for this purpose. 
 In this manner a valuable motive power can be 
 obtained in warm countries without loss of room. 
 Generating plates, such as we have described, 
 can be applied to any roof, and if we consider 
 that with only ten such plates 792 gallons can 
 be raised 65 feet per hour, we can easily under- 
 stand that a great elevating power can be ob- 
 tained by increasing the number of plates." 
 
 THE PASADENA PUMPING - ENGINE. 
 
 Prof. Charles F. Holder, of California, widely 
 famous for his learning and his writings, con- 
 tributed to the Scientific American of March 16, 
 1901, a very readable article upon solar mo- 
 te "s. He went over the history of the subject 
 to some extent; mentioned a "burning mirror," 
 
THE PASADENA PUMPING-ENGINE 
 Front View 
 
ITS PRACTICAL APPLICATIONS 81 
 
 which was made by a Frenchman named Vil- 
 lette, 4 feet in diameter, at whose focus the heat 
 was so intense that cast-iron was melted there 
 in sixteen seconds; that an Englishman named 
 Parker built a lens about 3 feet in diameter, at 
 the focus of which a cube of cast iron was melted 
 in three seconds, and a block of granite fused in 
 one minute. After other instances and discus- 
 sion, he went on to describe a motor which had 
 been buildeji^at the Ostrich Farm in South Pasa- 
 dena, California. 
 
 " The machine is exhibited at the Ostrich 
 Farm, and has attracted the attention of a vast 
 number of people, especially as Southern Cali- 
 fornia is now thronged with tourists. In appear- 
 ance the motor resembles a huge disk of glass, 
 and at a distance might be taken for a windmill 
 of some kind; but the disk is a reflector 33 feet 
 6 inches in diameter on top, and 15 feet on the 
 bottom. The inner surface is made up of 1,788 
 small mirrors, all arranged so that they can con- 
 centrate the sun upon the central or focal point. 
 Here, as shown in the accompanying illustration, 
 is suspended the boiler, which is 13 feet 6 inches 
 
82 SOLAR HEAT 
 
 in length, and holds 100 gallons of water, leav 
 ing 8 cubic feet for steam. 
 
 " At the time of the writer's visit to the farm 
 the motor was the subject of no little comment 
 and the attendant stated, confidentially, that som 
 of the questions were remarkable. One mai 
 assumed that it had something to do with th 
 incubation of the ostrich eggs; and many aske 
 what made it go, being unable to understand o 
 appreciate the idea. The motor is attractive ii 
 appearance, built lightly, supported by seemingl 
 delicate shafts, though in reality strong enoug 
 to resist a wind pressure of one hundred miles a: 
 hour. The reflector must face the sun exactl} 
 and, as heavy as it is, weighing tons, it can b 
 easily moved. It stands, after the fashion o 
 the telescope, upon an equatorial mounting, th 
 axis being north and south. The reflector fol 
 lows the sun, regulated by a clock, the work bein 
 automatic, as, in fact, is everything about 11 
 The true focus is shown by an indicator; and i 
 about an hour after it is adjusted the boiler i 
 seen to have attained a white heat, and the stearr 
 gauge registers 150 pounds. The steam is cai 
 
THE PASADENA PUMPING-ENGINE 
 Side View 
 
ITS PRACTICAL APPLICATIONS 85 
 
 ried from the suspended boiler to the engine in 
 a flexible phosphor-bronze tube, and returns again 
 from the condenser to the boiler in the form 
 of water, so that the boiler is kept automatically 
 full. The engine is oiled automatically, and 
 when the disk is once turned, facing the sun, 
 it runs all day as independent of an engineer 
 as does a windmill. 
 
 " The amount of heat concentrated in the 
 boiler by the seventeen hundred and odd mirrors 
 cannot be realized, as nothing can be seen but a 
 small cloud of escaping steam ; but should a man 
 climb upon the disk and attempt to cross it, he 
 would be literally burned to a crisp in a few 
 seconds. Copper is melted in a short time here, 
 and a pole of wood thrust into the magic circle 
 flames up like a match. That the motor is a 
 success is seen by the work that it is doing 
 pumping water from a well, illustrating the pos- 
 sibilities of cheap irrigation by lifting up 1,400 
 gallons per minute equal to 155 miner's inches. 
 Up to the present time, the motor has produced 
 results equal to about ten horse-power, but fifteen 
 horse-power is claimed for it. 
 
86 SOLAR HEAT 
 
 " This motor is the result of a number of ex- 
 periments by a band of Boston capitalists. One 
 of the first productions was a silver reflector, 
 which cost many thousands of dollars, but was 
 abandoned. The next was modelled after the 
 Ericsson machine of 1884; but it was a failure. 
 A third was erected at Longwood, proving also 
 a failure. A fourth attempt was made, this time 
 at Denver, Colo., which was fairly successful, 
 doing one-half of the work since performed by 
 the Pasadena model. This latter was at length 
 produced, and found to be a success. 
 
 .."No invention of modern times has given 
 such an impetus to the development of arid lands 
 as the solar motor, and it has been visited by 
 many interested in the question. The develop- 
 ment of Southern California has been seriously 
 hindered by the lack of fuel, the country being 
 dry and barren in localities where rich mines are 
 known to exist. The country is cloudless for 
 months, in every sense the land for solar mo- 
 tors, as water underlies the surface almost every- 
 where, and, when pumped up and sent out upon 
 
ITS PRACTICAL APPLICATIONS 87 
 
 the soil, the region ceases to be a desert, and can 
 be made to blossom as the rose." 
 
 A WORD FROM AN AMERICAN IN INDIA. 
 
 June 15, 1901, there appeared in the Scientific 
 American a letter from Rev. Walter T. Scudder, 
 an American missionary at Vellere, in the pres- 
 idency of Madras, India, which should be noted 
 here. He seems not to have known of the ex- 
 periments and successes of Mr. Adams at Bom- 
 bay in a former year, nor of other historical 
 illustrations of solar heat in service; he had, 
 however, read the article just quoted from Pro- 
 fessor Holder, and fully endorsed its reasonings, 
 and accepted its testimony from the standpoint 
 of a resident in India. He gave the results of 
 some experiments he had made in testing the 
 actual heat of the rays of the sun by the use 
 of ordinary thermometers. Hanging one in- 
 strument in the open air, where the sun shone full 
 upon it, he placed another in a cardboard box, 
 covered with glass, through which the rays of 
 the sun were admitted, the heated air being en- 
 
88 SOLAR HEAT 
 
 closed by the box. April 7, 1901, he found that 
 the former thermometer indicated 126 R, and 
 the latter 157 ; five days later, in a similar trial, 
 he obtained 127 and 159. He thus demon- 
 strated the fact that the heat of the sun may be 
 economized by sheltering and accumulating the 
 rays. This fact might have been deduced from 
 the common practice of people in cold countries 
 of using double windows for the purpose of econ- 
 omizing fuel and keeping part of the heat of the 
 sun when it comes upon them. M. Mouchot, 
 too, used this principle in the glass cover which 
 he placed over his boiler at the focus of his 
 reflector. The idea is capable of very large ap- 
 plication. 
 
CHAPTER II. 
 
 SOME TECHNICAL STUDY OF THE SUBJECT. 
 
 LET me ask you to note carefully at the outset 
 these two points first, that this treatise does not 
 concern itself at all with the nature of the sun, 
 or its rays; the orb may be of flame or of ice; 
 the rays may be dependent on or affected by 
 local conditions at the sun, or by the quality of 
 our atmosphere, or both. None of these partic- 
 ulars, these questions, affect the practical matter 
 we have in hand. We find sunshine coming upon 
 us; we learn from experience that we can get 
 heat from the rays as they fall, and can combine 
 the force of a number of rays in a beam of in- 
 creased intensity. 
 
 Our problems are along these two lines : How 
 can we best receive and accumulate the heat 
 89 
 
90 SOLAR HEAT 
 
 which the sun brings to us ? The " technical 
 study" here attempted is most practical in its 
 quality; intended for the man of the farm and 
 the shop quite as much as the man of the school 
 or the laboratory. A future stage of the art 
 will necessarily take up deep questions of theory 
 for the higher development of the subject; but 
 now and always the chiefly important side of the 
 matter is the practical. How can we get and use 
 the largest amount of solar heat? 
 
 And, second, the manner of treatment here 
 given to the problems in hand is one which aims 
 to inform the man who has no technical library 
 at hand, to aid the ranchman and the prospector 
 in devising offhand appliances, as well as to help 
 the educated and skilled artisan and manufacturer 
 along their paths, by a few blunt, crude hints 
 and by the suggestive force of the historical ac- 
 counts herein presented. 
 
 NOMENCLATURE. 
 
 What are the proper terms to be used in de- 
 scribing the subject of this discussion? 
 
ITS PRACTICAL APPLICATIONS 91 
 
 The writer selected as the title of his former 
 work the phrase, "Solar Enginery" intending 
 to include all appliances for the collection and 
 use of the heat of the sun, whether a simple 
 heat-box or a steam-engine, maintained by solar 
 caloric. Some objection was made by critics on 
 the ground that the terms might apply equally 
 well to a study of the motion of the sun and its 
 satellites; and because the furnace heated by 
 solar rays is hardly an " engine.'* Solar Calorics 
 is a correct expression for a treatise on the nature 
 and laws of the heat derived from the sun; but 
 is not suggestive of practical utilities. " The 
 Utilization of Solar Heat " is a cumbrous phrase, 
 well enough for the index to patents, but not 
 popular in its sound. The well-known term of 
 the schools, Ther mo-dynamics, would be a good 
 title, but it has so broad a meaning that it does 
 not confine the subject to the limits we have 
 given ourselves; Helio-thermo-dynamics (helios, 
 the sun; therme, heat; and dnnamis, power) is 
 the precise word for us; only it would not at- 
 tract the average reader; and this book is made 
 for the every-day man, the unprofessional, prac- 
 
92 SOLAR HEAT 
 
 tical person, who has a clearer idea of English 
 than of the Greek language, from which the 
 scientific terms have been customarily drawn. 
 Solar Heat: Its Practical Applications, is a title 
 which carries its notion to any reader. 
 
 PREMISES. 
 
 1. The first of the principles to be stated is 
 this : We have no power to increase or diminish 
 the actual heat which comes to us from the sun 
 at any time; the regulation of that heat is alto- 
 gether superior to us, depending upon the state 
 of the atmosphere, the wind, dust, clouds, fog, or 
 other things over which we can never acquire 
 any control; we can simply take what comes. 
 There is no such thing as making a greater fire 
 under our boilers, raising the temperature by 
 skilful manipulation of the fire, except by meth- 
 ods of a secondary sort mentioned below. 
 
 2. We are able, however, to keep what we get ; 
 to fend off winds from our apparatus, to guard 
 our machinery from dust by glass coverings, 
 small or large, movable or stationary, as the 
 
ITS PRACTICAL APPLICATIONS 93 
 
 case may demand; we can use means, in case 
 it seems best, to keep our articles or surfaces 
 to be heated facing the sun throughout the day, 
 so as to avail ourselves of all that comes our 
 way; and we can select such localities as are 
 most favorable in all respects for the business. 
 We are also able, by various methods, to connect 
 as many furnaces or engines as we wish, so that 
 the heat of each may contribute to a total result 
 far larger than could be attained by a single 
 apparatus; and we may store up the heat and 
 the power obtained from it for use at some other 
 time or place. 
 
 3. While the rays of the sun come to us in 
 parallel lines with a uniform temperature on 
 either hand, and would heat every part of an 
 exposed surface as hot as any other, the laws 
 of heat rays are those of undulation or wave 
 motion in general, the same as those of a ball, 
 thrown on a floor, or a beam of light falling 
 on a table, or a sound-wave reaching a listener. 
 These rays may, therefore, be gathered together, 
 made to unite, as if they became one denser, 
 stronger, hotter ray, so that the temperature of 
 
94 SOLAR HEAT 
 
 the condensed rays will be raised in proportion 
 to the number of rays blended ; and we can thus 
 cause the heat to increase to any degree our 
 apparatus can be enlarged. By secondary means, 
 then, we can secure a hotter fire in our solar 
 furnace than there is in the open air or on a 
 plain surface. And the art of solar enginery is 
 a reaching after the best means of thus taking, 
 guarding, uniting, and directing these gathered 
 rays for domestic and industrial uses. 
 
 The subject has four natural divisions: (A) 
 The Reception of Solar Rays, (B) The Reflec- 
 tion of Solar Rays, (C) The Refraction of Solar 
 Rays, (D) The Application of Solar Heat. 
 
 (A) The Reception of Solar Rays. First of 
 all, the article which we desire to heat must be 
 placed directly in the path of the beams of the 
 sun, at right angles to that path. Almost any 
 material has some tendency to refuse admission 
 to the heat of the sun, or, as we say, to reflect 
 away part of what falls upon it; therefore, we 
 must place it so that the rays shall have the best 
 opportunity to enter its very substance. The 
 best color for the article or receptacle is black, and 
 
ITS PRACTICAL APPLICATIONS 95 
 
 that free from any sheen or gloss or polish what- 
 ever. It is an advantage if the surface be rough, 
 porous, or provided with openings of some kind 
 into which the rays can enter and be lost, so to 
 speak. The receptacle may be furnished with 
 a glass cover, which will admit all the rays (or 
 nearly all), and will hold them back from es- 
 caping from the surface after it has become hot. 
 Such protection is particularly important in the 
 windy, dusty regions, where most solar machines 
 must be located. Glass houses like botanical 
 conservatories may be built for this purpose, 
 or " sash-beds " or bell-glass coverings may meet 
 the case sometimes. 
 
 The article or receptacle to be heated may re- 
 main stationary or be swung around at the same 
 speed as the sun, keeping its face toward that orb 
 all the day. Which course is the better will de- 
 pend upon the nature of the substance to be 
 heated and the use to be made of the heat. Many 
 cases will occur where enough caloric will be ob- 
 tained by simple " hello-stats" i. e. stationary 
 furnaces or ovens. Even water-raising appara- 
 tus has been made successful in this way [see 
 
96 SOLAR HEAT 
 
 the Auteuil experiment]. There is a large field 
 for investigation and invention here. 
 
 But in most cases the article or receptacle 
 must be made to turn as the sun (apparently) 
 turns. Machinery must be used which will cause 
 the structure to revolve as fast as the sun moves. 
 As astronomers have " orienting " machinery to 
 keep their telescopes in the path of the stars, so 
 we must have gear to keep the solar furnace " in 
 the eye of the sun." Two movements are to be 
 regarded; the daily motion across the meridian, 
 or in a westerly course, and the continual change 
 of the path of the sun to a more northerly 
 or southerly position, astronomically speaking. 
 That is to say, during six months the path of the 
 sun is higher above the horizon each day till it 
 reaches its highest, hottest, midsummer altitude; 
 then, during the next six months, the path is 
 daily lower and lower till the lowest, coldest, mid- 
 winter altitude is reached. (This statement is 
 entirely unscientific in form, but substantially 
 accurate. ) 
 
 Our apparatus, for this reason, must be so 
 constructed as to change its path daily, either 
 
ITS PRACTICAL APPLICATIONS 97 
 
 automatically or by the hand of an attendant, if 
 we would secure absolutely exact reception of the 
 rays. But the problem is easy, since a simple 
 turning over from left to right (east to west) 
 of a structure lying in the meridian, and a daily 
 change of the elevation of the northern end of 
 the apparatus is all that is needful. Any man of 
 ordinary intelligence can practically locate the 
 meridian, i. e. the true north and south line, by 
 driving two stakes at night in the direction of 
 the North Star ; l and the latitude of the place, 
 subtracted from 90, gives the highest degree 
 of altitude that the sun will reach at that point. 
 Nature has provided some admirable localities 
 for this business in hillsides that slope toward 
 the south; and apparatus may there be placed 
 at an angle midway of the local range of altitude 
 
 1 Strictly speaking, the North Star is not " fixed." It has 
 a rotary motion in an orbit of what we may practically call 
 very narrow limits. To get the precise meridian, it is 
 necessary to make a series of observations upon the pole- 
 star so as to get the extreme east and west positions of the 
 star and their central or average position. But for ordi- 
 nary solar heating apparatus the line established by a 
 single observation will be sufficiently near the true me- 
 ridian. 
 
98 SOLAR HEAT 
 
 during the season or period when the apparatus 
 is to be most used ; and it will then require very 
 little change from day to day in that respect. 
 As, at a place in latitude 39, the receiver may 
 be located on a slope which has an inclination 
 of 39 30 min. ; because the lowest noon alti- 
 tude of the sun being 23 less than its highest, 
 and the middle point 11 and 30 min. below the 
 highest; subtracting the latitude from 90, we 
 have 51 as the highest altitude; 23 below that 
 is 28 as the lowest; and 39 30 min. as the 
 medium. 
 
 THE REFLECTION OF SOLAR HEAT. 
 
 The rays of the sun may be brought to a 
 focus, gathered into a knot, directed to one spot, 
 made to combine their energy on a point. (See 
 Ericsson's discussion of this subject, page 56). 
 Although we cannot increase the heat of a ray, 
 we can increase the temperature of a spot on 
 which a number of rays thus unite. This is done, 
 sometimes by reflection, i. e. by bending the rays 
 from their course; if they strike on a smooth, light 
 surface, into which they cannot enter, or which 
 
ITS PRACTICAL APPLICATIONS 99 
 
 they have more tendency to turn away from than 
 to penetrate, they will be bent away in a new 
 direction. The course they take will depend upon 
 the course in which they came; as the geomet- 
 rical statement is, " The angle of reflection is 
 equal to that of incidence." 
 
 We can, then, construct and arrange our re- 
 flecting substances in such forms as will bring 
 these newly directed rays of solar heat into our 
 service most advantageously. 
 
 The simplest form is a Plane Mirror (Fig. i). 
 This does not converge the rays at all, but throws 
 them upon the exposed surface in a mass, which 
 will be shaped exactly like the area of the mirror 
 if they are reflected back in the precise direction 
 from which they came; but, if they are thrown 
 to one side, the shape of the mass will be changed 
 according to the angle of reflection, taking the 
 form of a parallelogram whose shorter diameter 
 will be reduced as the plane of the reflector and 
 that of the incident rays approach one another, 
 till it becomes almost a mere line. An indefinite 
 number of rays may be massed by plane mirrors, 
 although not strictly concentrated. 
 
100 
 
 SOLAR HEAT 
 
 \ 
 
 V 
 
 FIGURE I 
 
ITS PRACTICAL APPLICATIONS 101 
 
 If we take a plane mirror and bend it in a 
 cylindrical form, we may bring the rays to a 
 line, more or less accurately according to the 
 curvature. A parabolic form will secure the 
 closest approximation to this result (Fig. 2). 
 A pipe, or several parallel pipes, may be heated 
 by this means to a temperature depending on the 
 width of the mirror and the perfection of the 
 reflecting substance. Captain Ericsson's second 
 design made use of this law. 
 
 If, now, we construct a Concave, Parabolic 
 mirror, the rays will be concentrated on a single 
 point, approaching it from all parts of the mirror. 
 Modifications of this form may be made, by 
 which the focal point may be within the enclo- 
 sure of the mirror, or at a distance in front of it 
 
 (Fig. 3). 
 
 The simplest form of this mirror is that which 
 is used in locomotives to throw the rays of a 
 lamp ahead along the track in parallel lines. This 
 use of the reflector is exactly the opposite of 
 our application of it; but the headlight reversed 
 is a striking illustration of the solar heating 
 apparatus. This general form the parabolic, 
 
IO2 
 
 SOLAR HEAT 
 
 FIGURE 2 
 
ITS PRACTICAL APPLICATIONS 103 
 
 
 
 ^ s 
 
 
 ^r / s 
 
 
 A ! / Z 
 
 
 /i / / / / 
 
 
 B3772L 
 
 
 SSSu. 
 
 
 r-^ 
 
 
 X/.'\\\N 
 
 
 v n\\ \ 
 
 
 \J \ \ \ N 
 
 
 X\ \ \ X 
 
 
 ^^^ \ ^ 
 
 
 ""*"^\_ X 
 
 
 ^-^s^^^ 
 
 
 FIGURE 3 
 
104 SOLAR HEAT 
 
 concave mirror may be preserved, while its 
 walls are modified; as separate, plane mirrors 
 may be arranged in a frame so as to throw their 
 rays in masses on a central or focal spot, piling 
 up the heat on whatever one desires to heat. 
 Or segments of the parabola may be made, each 
 a plane mirror (chord to the curve), bent in 
 only one direction (radially) to the general 
 direction of parabolic walls. The advantage of 
 the parabolic form is the concentration of rays 
 about one point, losing none, but utilizing all 
 that fall on the apparatus. There is special dif- 
 ficulty in the polishing of the surface thus shaped ; 
 and the construction also requires great care. 
 Mouchot, after using it in his early engines, dis- 
 carded it for a combination of plane mirrors in 
 a truncated cone, preserving, however, the enclos- 
 ing feature of the parabolic mirror. Experience 
 must determine for each manufacturer the form 
 which best suits his special purposes. 
 
 Plane reflectors may be of great service some- 
 times. Stand at the sunny side of a high board 
 fence which has been whitewashed, if you would 
 test this; lay any article on the ground by the 
 
ITS PRACTICAL APPLICATIONS 105 
 
 side of such a fence, and see how quickly it will 
 become heated, and how very hot it will get when 
 the fence stands exactly at right angles to the 
 path of the sun's rays. No doubt, simple fences 
 of this sort, extending from east to west or from 
 north to south, may be employed as concentrating 
 apparatus for some purposes ; or a pair of fences, 
 inclined a little from the perpendicular, away 
 from each other, may throw down a powerful 
 heat at their base. 
 
 THE MATERIAL FOR REFLECTORS. 
 
 The finest of all reflectors is one of burnished 
 gold; a thin plating of gold upon a copper or 
 composition metal surface would give almost as 
 perfect effect. Next to gold stands silver. This 
 has been used in the arts a great deal for reflectors 
 of various sorts. Glass plates, silvered, are very 
 practical and effective. Speculum metal, an alloy, 
 has been employed for the reflectors of astronom- 
 ical apparatus. Copper, burnished, gives very 
 high percentage of reflection; tin, nickel, and 
 other substances are of value. White paper, 
 
106 SOLAR HEAT 
 
 especially when calendered or polished, may be 
 proved to have considerable value. Snow gives 
 surprising results. The writer, in Farmington, 
 Me., in 1883, dug a hole in a snow-drift, shaping 
 it in a general parabolic shape with a shovel, and 
 raised the thermometer 60 above the tempera- 
 ture of the surrounding air in a cold day. A 
 scientifically constructed mirror of this sort, made 
 for the Arctic traveller or the resident of a north- 
 ern clime, and placed on a sled, could be turned 
 to face the sun, and obtain a temperature hot 
 enough for water-boiling and cooking very easily. 
 If the sun can blind the ordinary traveller by 
 its glare, and cause violent optical disease to 
 those who dwell upon its whiteness, it can be 
 made to atone for its cruelties by doing service 
 as a fuel and a kinetic. 
 
 Ice is as good as snow for reflecting purposes, 
 if not better. The Arctic explorer of the future 
 must avail himself of these two substances and 
 the heat of the sun in the polar summer day, 
 with its long duration. Who can tell what sur- 
 prising results will be attained when these agents 
 are harnessed in, more tractable than Esquimaux 
 
ITS PRACTICAL APPLICATIONS 107 
 
 dogs, less expensive than coal or wood, obtainable 
 on the largest scale? Taking patterns from home, 
 carrying some portable apparatus for use when 
 not stationed at a particular spot, the coming 
 searcher for the pole will go forth with confi- 
 dence of victory. 
 
 Reflectors have some disadvantages. They are 
 hard to make and difficult to keep in order. 
 Rust, dust, chemical alteration of the metallic 
 surfaces, the careless scratching done by those 
 who undertake to clean them, the wild abrasion 
 of dust-storms in some localities, such are 
 some of the drawbacks to their use. They are 
 often very expensive. The weight of large ones 
 is formidable; the work of repairing them may 
 require skilled workmen, who are not always 
 available; and other troubles may assail the 
 owner of a reflecting heliostat. But these diffi- 
 culties are no greater than the burdens which 
 a man assumes when he buys or sets up a steam- 
 engine with fuel-burning attachment; the trou- 
 bles and expenses are of another sort, but the 
 incubus is probably no heavier on the solar side. 
 
io8 SOLAR HEAT 
 
 And the lack of cost for fuel will be a large pre- 
 mium on the latter side. 
 
 REFRACTION OF SOLAR HEAT. 
 
 (C) Solar rays move on in a straight course 
 so long as they are passing through a material of 
 uniform density, where the resistance offered to 
 their progress is the same. But when they pass 
 into a medium of different density, they are bent 
 or refracted out of their course. If the body 
 through which they now pass is parallel-sided, 
 like a common pane of glass, the rays resume their 
 former course on leaving it (Fig. 4). If the sur- 
 face they entered was at right angles to their for- 
 mer course, they suffered no change of direction 
 whatever. If it was inclined at all, they were 
 set aside, so to speak, and then restored to their 
 previous line on leaving. And this is true, what- 
 ever their relative density. But if the surface 
 through which a ray enters the new medium is 
 inclined to the surface through which it departs, 
 the ray takes a new course, bending toward the 
 thicker side of the medium. We may suppose 
 
ITS PRACTICAL APPLICATIONS 109 
 
 Ilill! 
 
 FIGURE 4 
 
no SOLAR HEAT 
 
 that this law applies to all substances which are 
 diathermous, whether they be wood, metal, solid, 
 or liquid; perhaps inventors may develop new 
 lenses out of materials hitherto never thought of 
 for the purpose. But we can see the effect of the 
 transmission of rays of light and heat through 
 what we call transparent substances. The best 
 of these is crystal salt, which delivers the largest 
 percentage of .the heat which is given to it. 
 Quartz crystal is next; then come the various 
 grades of glass; the latter are the prevalent 
 materials to-day, because of their comparative 
 cheapness. Glass vessels, shaped as lenses, entire 
 or cut, filled with water, gas or any other fluid 
 which is a good transmitter of the rays, furnish 
 the least expensive material. Whatever the ma- 
 terial, the laws of refraction are the same. Each 
 substance has its peculiar " refractive angle " or 
 degree of turning the ray aside; each has its 
 special clearness or opacity. It is the province 
 of the manufacturer to investigate these things, 
 and determine for himself which material is the 
 best for the special class of goods he is making; 
 sometimes the cost of raw materials may decide 
 
ITS PRACTICAL APPLICATIONS in 
 
 the question; a great many sorts of refractors 
 may be effective under proper management. The 
 tables of diathermacity are of slight value com- 
 pared with actual experiment and practical test 
 in operation. 
 
 If the two surfaces through which a ray passes 
 are both " plane," and form an angle, the rays 
 passing through will all be turned aside parallel, 
 and will fall in a mass as the rays reflected by a 
 plane mirror (Fig. 5). This wedge-shaped or 
 triangular prism separates the normal ray into 
 its separate (prismatic) colors, which differ in 
 temperature, the red rays being hottest ; but when 
 we pile one of these masses of rays upon another, 
 by refraction from a group of prismatic panes, 
 there is no loss of heat by reason of the disper- 
 sion. Indeed it will be possible to obtain some 
 advantage from it if the combination of refracted 
 rays is made with reference to such a result. 
 If one of the surfaces is plane and the other 
 curved in a circular form (i. e. making an arc 
 of a circle) , the rays will be refracted to a centre 
 or focus; and, if this circular surface is plane 
 in the other direction, like a piece of metal bent 
 
112 
 
 SOLAR HEAT 
 
 
ITS PRACTICAL APPLICATIONS 113 
 
 in one direction, forming a partial cylinder, then 
 the rays will be focalized along a line. If stopped 
 by a tube or pipe, placed at the focus, they will 
 heat the tube. Captain Ericsson's second solar 
 engine used a reflector which gave this N effect; 
 other experimenters have reached the same result 
 with piano-cylindrical lenses, such as we are de- 
 scribing (Fig. 6). 
 
 If we have a medium, one of whose surfaces 
 is plane and the other convex, i. e. forming a 
 segment of a sphere or bounded by an arc 
 of a circle in each direction, all the rays 
 which enter at right angles to the plane sur- 
 face (whether that be the entering or the de- 
 parting surface) will be refracted to a focus 
 at the centre of the curve of which the convex 
 side is a segment, or to a point equidistant on 
 the opposite side. This plano-convex lens is a 
 very common form of condensing lens for the 
 magic lantern and for other uses (Fig. 7). 
 
 If we have both surfaces of the lens convex 
 (Fig. 8), the result is precisely the same so far 
 as focalizing the rays to a centre; only the dis- 
 tance of the focal spot is only one-half that of 
 
SOLAR HEAT 
 
ITS PRACTICAL APPLICATIONS 115 
 
 FIGURE 7 
 
n6 SOLAR HEAT 
 
 the former, since double the amount of bending 
 is done in the lens. 
 
 The last is the ordinary " burning glass " 
 form. Extraordinary things have been done 
 with large lenses of this form. They are used 
 in the telescope, field-glass, opera-glass, photo- 
 graphic camera, and many other instruments. 
 Manufacturers of such articles have wrought out 
 many problems as to the combination of these 
 lenses with the same and with different forms. 
 Solar engineers may profit by these lessons ; there 
 is a very wide field for experiment in the applica- 
 tion of the lessons of practical optics to the art 
 of heliodynamics. 
 
 A fact of very great importance to this art 
 is the effect of " cutting " lenses. When a wedge 
 is so cut down that the same angle is kept but 
 the wedge thinned in some parts ; 1 or when a 
 
 1 A pane of glass, ribbed in such a way as to form 
 a connected series of parallel triangular wedges of the 
 same size, has been invented by a Mr. Pennacook and sold 
 to persons who desired to throw light into dark rooms. 
 Of course such a device cannot increase the light, as is 
 sometimes represented by the ignorant; but the rays are 
 all turned one way, in the direction of the thicker diameter 
 of the triangles. If the panes were made with the trian- 
 
ITS PRACTICAL APPLICATIONS 117 
 
 FIGURE 8 
 
n8 SOLAR HEAT 
 
 curvilinear lens is cut so that its true curve is 
 retained while the thickness is reduced, the re- 
 fraction is not altered. But a large reduction 
 of the absorbing or retarding power of the lens 
 is made; far more heat will be carried through a 
 " cut " lens than the original from which it was 
 reduced. Each of the foregoing forms is shown 
 in its cut condition above. A familiar example of 
 this may be seen in the lanterns used at switches 
 and other points about a railroad station. Now 
 it is entirely practicable to make very wide lenses 
 for the concentrating of solar heat by cutting 
 them. Of course this is to be done in the orig- 
 inal plan, not after the full-thickness article has 
 been cast or rolled. A circular cut lens may be 
 made in sections, like panes of glass, all corre- 
 sponding to the single plan. 
 
 If one would know how magnificent results 
 can be attained by this means, let him examine 
 the glasses of a lighthouse lantern. Each pane 
 or block of glass is a part of a lens system; 
 
 gular wedges of different depth, steadily increasing from 
 one side to the other, there would be a concentration of 
 the masses on one band or space. 
 
ITS PRACTICAL APPLICATIONS 119 
 
 through all, as one, the rays of the lamp within 
 are thrown out in a sheet of light above the sur- 
 face of the sea, for the mariner's convenience 
 and safety. By day, the glasses are covered with 
 a curtain; because the sun's rays, striking on 
 them, would be concentrated upon the lamp and 
 set it afire, to the great injury of its form and 
 contents. The cost of these lighthouse lens- 
 systems is very large, for all lamps are feeble 
 compared with the illumination desired from 
 them, so that the manufacturer has to secure a 
 very high degree of accuracy in his refractors. 
 The maker of refractors for solar heat will have 
 so generous a supply of heat to draw from that 
 he need not attain to anything like the same 
 degree of nicety, though following some of the 
 same rules and lessons. And it will be found, 
 after a strong demand has developed, that glass 
 men will overcome the conservatism which has 
 led them to decline applications, hitherto, in many 
 instances. 1 Lenses have many advantages. They 
 
 *It must be said right here that glass manufacturers 
 are very slow to enter on new work; and they have stood 
 aloof from the task of making lenses suitable for the 
 concentrating of solar heat. The writer applied some years 
 
120 SOLAR HEAT 
 
 give a larger percentage of the heat that falls 
 on them than reflectors of the same relative de- 
 gree of exactness. They require less continual 
 care; if made in sections (panes) they may be 
 put up and repaired by less skilled workmen. 
 Their surface is not in the same danger of cor- 
 rosion or abrasion as soft metal, like silver. For 
 these and other reasons many will prefer them. 
 Those who advocate the superiority of reflec- 
 tors over lenses for solar heat concentration may 
 well consider the fact that we use lenses for our 
 sight in eye-glasses, microscopes, and telescopes 
 to secure the most perfect concentration of light; 
 
 ago to Alvan Clarke & Sons, of Cambridge, Mass., to pro- 
 duce what he desired at one stage of his experiments; 
 they responded that they were already more than full of 
 orders in their special, astronomical line, and referred him 
 to some French manufacturers. He then applied to the 
 well-known house of Darlot, celebrated for the production 
 of photographic lenses, etc. Mr. Darlot responded that 
 he had already undertaken a similar commission for a 
 French physicist ; had spent " some hundreds of francs " 
 in experiments in the matter, and found it impracticable. 
 At the Columbian Exposition the agent of a distinguished 
 French manufacturer of lighthouse lenses was approached 
 on the same errand ; standing beside the firm's magnificent 
 display of lanterns of the largest size, we asked him if 
 
ITS PRACTICAL APPLICATIONS 121 
 
 why should we not do the same for the concen- 
 tration of heat ? 
 
 (D) THE APPLICATION OF SOLAR HEAT. 
 
 All that can be done with heat derived from 
 combustion can be done with solar heat. The 
 reader who has carefully read the reports of his- 
 torical experiments must have noticed how wide 
 is their range. The cook fills her stove with 
 wood or coal to get heat or cooking bread, meat, 
 fish, fruit, confections; she may open her solar 
 oven to the sunshine, and have as much and as 
 steady heat many of the days, in the lands where 
 
 it would not be an easy task for such a house to construct 
 "cut-lenses" of suitable character for heat concentration; 
 after careful reflection he answered that he did not think 
 the firm would be willing to undertake the work on account 
 of the high cost involved and the narrow margin for 
 profit. 
 
 The very large profits of the lighthouse lens manufac- 
 ture from the government's liberal appropriations have 
 spoiled those men for the plain, practical business which 
 opens before the maker of solar-heat lenses. But the 
 writer believes that the task presents no real difficulties; 
 and is confident that there will be manufacturers yet found, 
 of sufficient progressiveness and ingenuity, to take this task 
 in hand and make successful results for themselves as well 
 as for the public. 
 
122 SOLAR HEAT 
 
 sunshine has sway. The manufacturer of wooden 
 or metallic goods consumes costly stores of car- 
 bon, and handles great quantities of ashes, in his 
 attempt to get heat for sawing, planing, forging, 
 drying, bending, cutting, and every way working 
 his materials; his steam or hot-air engine de- 
 pends on this hard-sought and dear-bought ca- 
 loric; but the rays of the sun offer him as high 
 degree of temperature when they are condensed 
 and combined suitably. The miner finds on the 
 surface or beneath it masses of rock which con- 
 tain fortunes; he wants power to hoist, trans- 
 port, separate, melt, and refine his ores; all this 
 can be done by solar heat properly received, con- 
 centrated and converted into kinetic and caloric 
 of the degree he desires. The farmer is in need 
 of stationary engines to thresh, husk, and grind ; 
 of locomotives to plough, harrow, sow, reap, 
 mow, pile, draw, to connect him and his work 
 with the marts of the world. The grain-grower 
 and the orchardist and horticulturist join him 
 in asking for water-raising apparatus; and the 
 Auteuil machine and the Pasadena engine are his 
 reply. Pure country power may be had as well 
 
ITS PRACTICAL APPLICATIONS 123 
 
 as " pure country milk ; " and the costless engine 
 may replace the expensive ones now enjoyed by 
 but a small part of the people who need them. 
 
 ELECTRIC STORAGE OF SOLAR HEAT. 
 
 The most significant fact bearing upon solar 
 heat utilization to-day is the development of 
 electric storage. With this feature, the art takes 
 on mighty strength. By the aid of storage bat- 
 teries, mines may be lighted throughout the day 
 and night; distant cities may be illumined from 
 some " lone, sequestered vale," where sunshine 
 bestows its noiseless benison. Great reservoirs 
 of water may be pumped full in hot days, and 
 drawn from for long days afterward. 
 
 By this means a hundred stations may be com- 
 bined in one grand dynamic unit. It may be 
 that a larger concentration of heat and energy 
 for any purpose can be secured from solar ap- 
 paratus than from any other source of which 
 we now know. Given a single " section " of land 
 in a favored locality, cover its 640 acres for half 
 their extent with furnaces and motors, leaving 
 the remainder for roads, cabins, repair-shops, 
 
i2 4 SOLAR HEAT 
 
 storage-sheds, etc. ; stretch wires from side to 
 side, in air or underground, as may be cheapest; 
 bring all their currents to one spot near the rail- 
 road, where materials for heating, refining, man- 
 ufacturing, or what not shall be accumulated ; and 
 the great manufacturing centres of the whole 
 world will be outdone. Add section to section, 
 if you please; Niagara itself cannot be stronger 
 than the gathered power of a Nevada ranch or 
 an Arizona claim. If one, why not many such 
 gigantic plants, ranging along the lines of our 
 transcontinental railroads, inviting, not simply 
 manufacturers already at work in other (coal or 
 gas burning) places, but new companies, formed 
 to grapple with some of those cyclopean enter- 
 prises which have been dreams thus far in human 
 history, but may be realized through the vast 
 reach of this gratuitous force. Trains of cars 
 can be hauled by trolley or storage-battery meth- 
 ods ; city carting, sprinkling, sweeping, and other 
 public work may be done by this means; any 
 public or private operations are feasible by its 
 aid. 
 
 One of the most valuable pieces of work to be 
 
ITS PRACTICAL APPLICATIONS 125 
 
 performed by heliothermic means is the manu- 
 facture of ice. Towns which lie on the coast 
 are now furnished with natural ice at low cost; 
 but interior towns have to meet burdensome 
 freight charges for the article from its northern 
 sources, or else pay prohibitive rates for the 
 manufactured article. With sun heat, the farmer 
 may have his own ice-house and cold-storage 
 room, where he will hold his reserves of butter, 
 eggs, poultry, fruit, vegetables, and other pro- 
 ductions till convenient time for shipment and 
 prospects of favorable prices come around. 
 
 Ice will enter into the very process of his 
 machinery, too, as in the use of hot-air engines; 
 for the contrast between the temperature of the 
 sun and that of ice, kept in the shadow under 
 the concentrating apparatus, will be great enough 
 to give a capital basis for the cycles of compres- 
 sion and expansion necessary in the hot-air en- 
 gine. 
 
 The world does not yet know how to make 
 the electric current spring directly from sub- 
 stances simply heated; but there may soon be 
 an unfolding of this scheme in season to create 
 
126 SOLAR HEAT 
 
 a nascent electric current from some substance 
 by means of solar heat. 
 
 Droughts, produced by excess of sunshine, as 
 the world has hitherto viewed the matter, may 
 now be overcome by that very means, since water 
 for irrigation and domestic use lies at no consid- 
 erable depth in great sections of the country 
 whose surface is habitually parched; and the 
 heat of the sun is available where most needed 
 in this as in many other respects. Famine will 
 leave India when solar engines enter and possess 
 the land. 
 
 Solar heat is not different from other heat; 
 it may be used, as has been observed, in connec- 
 tion with any apparatus which could employ the 
 heat of burning wood or coal or oil or gas. As 
 in those cases, there must be a way for the fuel 
 that is the sunbeams to enter the heat re- 
 ceptacle, and this door must be always open ; 
 this fire can be " banked " by curtains. Clouds 
 will diminish the amount of caloric, and no stir- 
 ring or increased draft will then help the fireman ; 
 devices must be employed to adapt the machinery 
 or other applications to this variability of the 
 
ITS PRACTICAL APPLICATIONS 127 
 
 heat, in certain cases, but not in all. Some proc- 
 esses will merely be faster or slower, as the sky 
 is clear or obscured; and the caretaker must 
 test the work being done from time to time, as 
 a cook watches the contents of her oven, or as 
 stationary and locomotive engineers watch fire 
 and "load." 
 
 Hot-air engines ought to be a favorite method 
 of applying solar heat because of the absolute 
 inexpensiveness of the material; because air is 
 everywhere, while water, for steam-making, will 
 be hard to get, or absolutely unprocurable in 
 some spots where sunshine is abundant. Erics- 
 son approved of this type of engine for the pur- 
 pose most heartily. The* form of the engine is 
 not within our province to discuss. Treatises 
 on mechanics will inform an inquirer; a gen- 
 uine mechanical engineer must take up the prob- 
 lem in any given case where large interests are 
 involved. 
 
 Steam engines have been the principal method 
 of utilization with Mouchot and other distin- 
 guished inventors. The reason may be that the 
 steam-engine has had wonderful development in 
 
128 SOLAR HEAT 
 
 its three-quarters of a century, and is well in 
 hand in economies and conveniencies ; because, 
 too, the enormous difference between one pint 
 of water and 1,700 pints of vapor makes a tre- 
 mendous force. Where water is easily obtain- 
 able, the steam-engine is to-day the most available, 
 probably, for the development of power from 
 sunbeams. 
 
 Ammonia gas has great advantage in its low 
 evaporating point; the Auteuil pumping-plant is 
 an illustration of the manner in which this may 
 be used; this will be a resort of not a few per- 
 sons for certain uses. Other substances which 
 vaporize at low temperature will come into use 
 of like quality, wherever the requirement is for 
 inexpensive works, and where these easy evap- 
 orators are cheap and abundant. 
 
 When once we have gathered our heat rays 
 in masses or in focalized intensity, the problems 
 of practical application are not at all different 
 from those which confront a man who has a fire 
 of wood, coal, oil, or gas. Here is the fire; do 
 with it what you like. 
 
 Any machinery requires human oversight; a 
 
ITS PRACTICAL APPLICATIONS 129 
 
 solar bakery for a private house will have to be 
 watched by the housewife or servant, as a coal 
 or wood or oil stove would need to be; a dozen 
 great furnaces with motors attached may all be 
 attended by a single person. It seems probable 
 that this work may be done by persons not the 
 strongest or most athletic; men and women who 
 have too little strength or health to bear common 
 burdens of toil may be able to give the prudent 
 care and trustworthy attention which will be 
 called for in the running of solar apparatus. Of 
 course extensive plants, connected with great 
 manufactories, would have to be cared for by 
 skilled mechanics and engineers. 
 
CHAPTER III. 
 
 LOCALITIES WHERE SOLAR HEAT MAY BE OF 
 DOMESTIC AND INDUSTRIAL VALUE. 
 
 IN general, any spot where the sun shines is a 
 place for gathering and using its beams of heat. 
 For an hour or a day or a small number of 
 days one can utilize this force anywhere. There 
 is an undoubted field for the utilization of solar 
 heat anywhere wherever the sun shines. But 
 the object of the present work is to point out 
 the localities where solar heat may be made a 
 valuable addition to the forces which enrich a 
 people and build up business enterprises. 
 
 The ideal place for a solar heat plant would 
 be one of those spots in South America where, 
 if we may believe popular reports, no rain ever 
 falls and no clouds linger in any day. Perhaps 
 there are such regions in fact. More likely there 
 130 
 
ITS PRACTICAL APPLICATIONS 131 
 
 are none in which all possible sunshine is afforded 
 through all the days of the year. But there are 
 many thousand square miles of territory in both 
 Americas and in Asia, Africa, and Australia 
 where the rainy days are very few, clouds rare, 
 and the great majority of the hours of possible 
 sunshine afford clear shining. Eminent examples 
 of this class are Yuma, Arizona, with 301 days of 
 unobstructed sunshine, 52 days partly cloudy, 12 
 cloudy, and only 7 days of rain in the round year ; 
 and Independence, California, with a record of 
 284 clear days, 72 partly cloudy, and but 9 days 
 when a solar apparatus would be of no use. It 
 has been demonstrated that the heat of the sun 
 penetrates haze and thin clouds, which would be 
 called " partly cloudy " condition ; and the rain 
 is concentrated into sufficiently short periods so 
 that interruptions of the working of the appa- 
 ratus would usually be short. 
 
 The long, dry summers of the western sections 
 of the United States are admirable times for the 
 running of the plants we are advocating; and 
 even in winter there are often periods of five 
 or six weeks at a time when the days are rain- 
 
132 SOLAR HEAT 
 
 less, so that the working of the furnaces and 
 motors could continue with but brief intervals. 
 
 Let us see what the extent of our own hello- 
 thermic area is. After one has crossed the great 
 River Mississippi and the main trunk of its 
 grand tributary, the Missouri, there begins a 
 vast region of prevalent sunshine. The pastures 
 where cattle in innumerable herds feed; the 
 stretches of wheat and corn land; the ridings 
 where buffalo but yesterday roamed, pursued by 
 red-skinned hunters ; the downs over which pro's- 
 pectors have sought not vainly for signs of gold 
 and silver; the lands which give track for rail- 
 roads, along which the traveller seeks in vain 
 for a shrub as high as a man, till he reaches one 
 plainly called " the Thousand Mile Tree; " those 
 quiet valleys in Utah, where Joseph Smith's fol- 
 lowers found refuge ; the " plains," over which 
 thousands of miners passed in the fifties, lured 
 by pictures of Eldorado, the alkali plains on 
 which hundreds left their bleaching bones; the 
 slopes of the mighty Nevada chain and the Coast 
 and Contra Costa Ranges, and the wide sweep 
 of fertile land in the valleys of the Sacramento 
 
ITS PRACTICAL APPLICATIONS 133 
 
 and San Joaquin systems; the borders of the 
 Golden Gate and its inland seas; the rich lands 
 of Southern California, where Pacific breezes 
 modify semi-tropical heat for the resident; the 
 great majority of the land that is contained in 
 and borders on these regions is the destined home 
 of the solar engine. 
 
 Note well, however, that this broad scope of 
 country is not homogeneous. Among these dry 
 places one finds some very moist spots. Moun- 
 tains which force clouds upward on the wind- 
 ward side allow their moisture to fall on the lee- 
 ward slope. Not far away from a place of eighty 
 per cent, of possible sunshine, you may come to 
 a region of but half the year clear. And years 
 vary exceedingly, too; which makes the figures 
 of a particular year sometimes really deceptive 
 as to the average conditions. The admirable 
 work now being done under direction of our 
 National Weather Bureau will give us a series 
 of tables soon, whose averages may afford trust- 
 worthy data for coming students. The govern- 
 ment ought to consider this subject worthy of 
 special and expert investigation, since the re- 
 
134 SOLAR HEAT 
 
 sources of our domain are capable of being devel- 
 oped more economically and extensively through 
 this channel than through any other. But enough 
 is known to-day to authorize the statement that, 
 what used to be vaguely called " The Great 
 American Desert," with its borders extending 
 into Montana in the north and Oklahoma in the 
 south, stretching over Wyoming, Colorado, New 
 Mexico, Idaho, Utah, Nevada, Arizona, portions 
 of Eastern Washington and Oregon, and the 
 principal part of California, in short, what 
 our schoolchildren are now taught to call the 
 " Western Highland States," are generally 
 adapted to the use of solar-heating apparatus. 
 The following tables, consisting of extracts 
 from reports of the United States Weather Bu- 
 reau, give figures of sunshine and shade for some 
 places for certain years, which are instructive. 
 They vary, partly from the difference of suc- 
 cessive years, partly, it may be, from defective 
 observation in some cases. But they attest the 
 great possibilities of solar heat as an element for 
 the enrichment and development of our Western 
 country. 
 
ITS PRACTICAL APPLICATIONS 135 
 SOME STATISTICS OF SUNSHINE. 
 
 PLACES 
 
 1899 
 
 1900 
 
 1901 
 
 | 
 
 u 
 
 Partly Cloudy 
 
 >> 
 
 rt 
 
 JB 
 
 - 
 
 Partly Cloudy 
 
 >, 
 
 1 
 u 
 
 Partly Cloudy 
 
 >. 
 
 'O 
 
 
 
 Belmont, Nev. 
 
 194 
 
 46 
 
 9- 
 
 
 
 
 
 
 
 Carlin 
 
 
 
 
 166 
 
 
 T 59 
 
 
 
 
 Carson City .... 
 Cheyenne, Wy. 
 Crane's Ranch, Nev. 
 
 155 
 "3 
 
 118 
 144 
 
 & 
 
 192 
 
 227 
 
 I2 5 
 
 57 
 
 48 
 81 
 
 203 
 209 
 
 115 
 40 
 
 47 
 85 
 
 Denver, Col 
 
 205 
 
 109 
 
 5 1 
 
 
 
 
 
 
 
 Elko, Nev 
 
 
 
 
 198 
 
 127 
 
 40 
 
 218 
 
 144 
 
 3 
 
 Fenelon 
 
 
 
 
 181 
 
 37 
 
 M7 
 
 189 
 
 15 
 
 I 3 l 
 
 Fresno, Cal 
 
 226 
 
 56 
 
 83 
 
 
 
 
 
 
 
 Golconda, Nev. 
 
 
 
 
 211 
 
 77 
 
 77 
 
 216 
 
 77 
 
 72 
 
 Hot Springs .... 
 
 
 
 
 203 
 
 38 
 
 124 
 
 
 
 
 Humboldt .... 
 
 
 
 
 229 
 
 40 
 
 96 
 
 252 
 
 16 
 
 97 
 
 Independence, Cal. 
 
 284 
 
 72 
 
 9 
 
 
 
 
 
 
 
 Las Vegas, Nev. 
 
 
 
 
 J 93 
 
 66 
 
 14 
 
 
 
 
 Lewer's Ranch 
 
 
 
 
 182 
 
 122 
 
 3 
 
 178 
 
 149 
 
 38 
 
 Lovelock .... 
 
 
 
 
 208 
 
 58 
 
 99 
 
 240 
 
 ii 
 
 114 
 
 Martin's Ranch 
 
 
 
 
 263 
 
 37 
 
 65 
 
 227 
 
 24 
 
 47 
 
 Miles City, Mont. . 
 
 158 
 
 T 35 
 
 72 
 
 
 
 
 
 
 
 Mt. Tamalpais, Cal. 
 
 196 
 
 80 
 
 89 
 
 
 
 
 
 
 
 Oklahoma, Okl. 
 
 212 
 
 72 
 
 81 
 
 
 
 
 
 
 
 Owyhee, Nev. 
 
 
 
 
 206 
 
 82 
 
 77 
 
 !93 
 
 84 
 
 88 
 
 Palisade .... 
 
 
 
 
 230 
 
 
 J 35 
 
 197 
 
 7 
 
 161 
 
 Palmetto .... 
 
 
 
 
 230 
 
 7i 
 
 64 
 
 224 
 
 76 
 
 65 
 
 Phoenix, Ariz 
 
 245 
 
 86 
 
 34 
 
 
 
 
 
 
 
 Red Bluff, Cal. ... 
 
 219 
 
 74 
 
 72 
 
 
 
 
 
 
 
 Reno, Nev. . . . 
 
 
 
 
 162 
 
 107 
 
 65 
 
 178 
 
 103 
 
 84 
 
 Sacramento, Cal. 
 
 2OI 
 
 76 
 
 88 
 
 
 
 
 
 
 
 Salt Lake, Utah 
 
 15 
 
 1 20 
 
 95 
 
 
 
 
 
 
 
 San Diego, Cal. 
 
 280 
 
 40 
 
 45 
 
 
 
 
 
 
 
 San Luis Obispo, Cal. 
 
 208 
 
 95 
 
 62 
 
 
 
 
 
 
 
 San Francisco, Cal. . 
 
 I8 5 
 
 104 
 
 76 
 
 
 
 
 
 
 
 Santa Fe, New Mexico . 
 
 234 
 
 90 
 
 3 2 
 
 
 
 
 
 
 
 Wads worth, Nev. . 
 
 
 
 
 
 
 
 232 
 
 35 
 
 67 
 
 Yuma, Ariz 
 
 3OI 
 
 5 2 
 
 12 
 
 
 
 
 
 
 
SOLAR HEAT 
 
 PERCENTAGE OF POSSIBLE SUNSHINE. 
 
 PLACES 
 
 1898 
 
 i8 99 
 
 Boston, Mass. 
 
 
 
 
 
 
 5 2 
 
 59 
 
 Cheyenne, Wy. 
 
 
 
 
 
 
 69 
 
 65 
 
 Chicago, 111. 
 
 
 
 
 
 
 53 
 
 53 
 
 Columbus, O. 
 
 
 
 
 
 
 61 
 
 53 
 
 Denver, Col. 
 
 
 
 
 
 
 71 
 
 75 
 
 Eureka, Cal. 
 
 
 
 
 
 
 45 
 
 46 
 
 Fresno, Cal. 
 
 
 
 
 
 
 81 
 
 75 
 
 Los Angeles, Cal. 
 
 
 
 
 
 
 76 
 
 74 
 
 New York, N. Y. 
 
 
 
 
 
 
 5 2 
 
 60 
 
 Mt. Tamalpais, Cal. 
 
 
 
 
 
 
 
 73 
 
 Oklahoma, Okl. 
 
 
 
 
 
 
 73 
 
 72 
 
 Phcenix, Ariz. 
 
 
 
 
 
 
 84 
 
 85 
 
 Philadelphia, Pa. 
 
 
 
 
 
 
 58 
 
 65 
 
 San Diego, Cal. 
 
 
 
 
 
 
 73 
 
 72 
 
 San Francisco, Cal. 
 
 
 
 
 
 
 
 69 
 
 Santa Fe, N. M. 
 Yankton, S. Dak. 
 
 
 
 
 
 
 i 
 
 80 
 64 
 
 Manufacturing establishments have always 
 been located where the power lay at hand. Ban- 
 gor, Me., Berlin, N. H., and such places drew 
 to themselves the great lumber mills; for they 
 had mighty rivers with falls, at which dams 
 could be t)uilt and heads of water made potent 
 for the sawing of tree-trunks into all sorts of 
 what our English cousins call " converted tim- 
 ber." Lowell, Lawrence, Holyoke, and other 
 places similarly furnished, attracted men who 
 
ITS PRACTICAL APPLICATIONS 137 
 
 wished to change the down of cotton into mus- 
 lins and print-cloths, or twine and warp; paper- 
 making, chair construction, machine manufac- 
 ture, all these and many more industries were 
 first established by river sides, where direct or 
 indirect currents of water might furnish the 
 power to aid man's skill. After a time, it was 
 found that the irregularity of water-supply was 
 a menace to the constancy of business; cheap 
 coal tempted the operators to put in steam-en- 
 gines as auxiliaries, and then to use them alto- 
 gether; and then manufacturing plants were 
 located in such regions as furnished cheap coal, 
 either where it was mined, or where railroads 
 or shipping most conveniently supply it. After 
 natural gas appeared, the trend was toward the 
 seats of this convenience, until the recent check 
 of this source of fuel has stayed the movement. 
 What is to hinder the location of numerous 
 manufacturing establishments in our Western 
 sun-lands when once the apparatus for concen- 
 trating and utilizing solar heat is brought to a 
 higher state of perfection? The wares which 
 are now taken to California and Oregon, to 
 
138 SOLAR HEAT 
 
 Nevada and Washington, to Montana and Idaho, 
 to New Mexico and Utah, from Eastern States 
 and European empires may well be manufactured 
 along the "Plains" and "Bad-lands" and 
 canons of " The Great American Desert." On 
 these stretches of country, where now the coyote 
 and gopher and jack-rabbit roam, the middle of 
 this twentieth century may see a farming and 
 manufacturing population of many millions, 
 gathered from all parts of the world, enriched 
 and made happy and contented by the very 
 agency that has heretofore rendered the land 
 desolate. Too much sunshine has kept vegeta- 
 tion down and hindered man's activity. Abun- 
 dant sunshine, concentrated and employed by 
 man, will give those plains and mountain slopes 
 attractions which will draw settlers and capital, 
 and repay toil most abundantly. 
 
 At a large number of points there is water a 
 little way below the surface, which may be easily 
 pumped up for irrigation and for domestic uses. 
 The great reservoirs now projected by speculators 
 and government officials, to be constructed at 
 tremendous expense, will afterward require a 
 
ITS PRACTICAL APPLICATIONS 139 
 
 large annual outlay for repairs; but the use of 
 sun-motors in pumping water for each farmer 
 and manufacturer to use will be a far larger boon 
 to the country, being more economical and less 
 capable of monopoly and tyrannical management. 
 The people are thus interested to have this sun- 
 power developed most perfectly. 
 
 The States which have been mentioned as 
 chiefly endowed with the wealth of sunshine are 
 also opulent in their mineral wealth. Prospect- 
 ors from California began fifty years ago to 
 discover leads of gold and silver and lead in 
 Nevada and Arizona and Idaho and Montana; 
 while equally adventurous prospectors pushed 
 from Black Hills to Pike's Peak and into New 
 Mexico's ancient gulches. All the way from the 
 Mississippi to the Pacific, the hammer and pick 
 and pan and microscope have done their work. 
 And beside all the magnificent mines which have 
 been developed, there have been wonderful dis- 
 coveries made which have not yet rendered any 
 man wealthy. Gold and silver and copper and 
 lead and so on are there : proof of that is plain ; 
 but the cost of carrying coal or wood for engine 
 
1 40 SOLAR HEAT 
 
 and boarding-house to the spot where the shaft 
 ought to be sunk, the cost of provisioning a crew 
 of miners while they worked the deposits would 
 be so frightful, so far above what the mines now 
 promise, that bold explorers have halted; or, 
 venturing too confidently, have lost all they put 
 into the venture. Now let sun-motors be made 
 at reasonable rates, and these myriad mines will 
 speedily yield their treasures up. A pair of men, 
 armed with one plant of this sort, may do what 
 would now require twenty men; hoisting-gear, 
 haul-out-trams, crushing-stamps, reducing-pans, 
 cooking-ovens, electric lights, etc., will all be 
 available for them. 
 
 And this use of the heat of the sun is not to 
 be limited to our own republic's territory by any 
 means. Many lands have large tracts which have 
 heretofore passed as deserts because of the abun- 
 dance of the sun's downpouring; this very fact 
 is destined to make Algeria, the Soudan, Egypt, 
 India, the table-lands of Ecuador, the arid coast 
 of Peru, and scores of other sections grow opu- 
 lent when the utilization of solar heat is carried 
 to the point of simplicity and economy. > An in- 
 
ITS PRACTICAL APPLICATIONS 141 
 
 describably large benefit will accrue to hundreds 
 of millions of people by the subjugation of the 
 sun to common human service. What a motive 
 to the truly humane inventor and capitalist! 
 
 All honor to the government of France for 
 encouraging Mons. Mouchot and aiding the ap- 
 plication of his work in Algeria ; may the British 
 and American governments fall into line with 
 grand force! 
 
CHAPTER IV. 
 
 GENERAL DISCUSSION OF THE SUBJECT. 
 
 THE use of the heat of the sun has been within 
 human reach all the years of humanity's life. 
 Why has it become no more common? If it is 
 as valuable an auxiliary as this treatise main- 
 tains, why has not the public seen the fact? If 
 the desert may be made to blossom, what has 
 prevented Sahara from being turned into one 
 magnificent oasis ? If the sun can furnish a pros- 
 pector the means of testing his discoveries on 
 the spot, the miner and the ranchman a power 
 equal to their needs, why have the magnificent 
 capabilities of great States and Territories re- 
 mained so long undeveloped? 
 
 If " Vox populi, vox Dei " the voice of the 
 people, the voice of God has not the indif- 
 141 
 
ITS PRACTICAL APPLICATIONS 143 
 
 ference of the mass of mankind to this subject 
 proven conclusively that the heat of the sun is 
 of no substantial value? Why do not inventors 
 and investors enter into this field in solid pha- 
 lanx, accompanied by the rush of pens and presses 
 advocating the cause, and why are not common 
 carriers laden with freight of its machinery and 
 produce? Thus the doubter carps at all our his- 
 tories and reasonings, repeating the ancient sneer : 
 " If it were worth anything, somebody would 
 have long ago found it out and made use of it; 
 rank it with schemes for perpetual motion, with 
 the Keeley motor and sea-water gold mines." 
 
 To reply to this is important, for such talk 
 has frightened away many men who had become 
 somewhat interested in the facts of the case ; and 
 it must be met squarely or it will continue to 
 hinder the cause. When the writer asserted, 
 twenty years ago, in " Solar Enginery," that 
 " the use of sun-heat is to-day exactly where 
 the art of steam-enginery was on that October 
 morning when Fulton started up the Hudson, in 
 1807," critics of the pamphlet scoffed. But the 
 parallel is a good one. Scorn and contempt were 
 
i 4 4 SOLAR HEAT 
 
 poured on Fulton's head while he was making 
 a bold trial of his invention; and every tempo- 
 rary failure in his operations was interpreted as 
 meaning that his theories were chimerical; the 
 public despised his " raft on fire," and it took 
 many years to bring the people generally to ap- 
 preciate the grand achievement of the inventor. 
 Professor Joseph Henry taught his pupils that 
 strokes on one end of a wire, charged with elec- 
 tricity, would be repeated at the other end (writ- 
 ing at the end graphein telos) ; he explained the 
 whole idea and had an experimental wire 
 stretched around the class-room ; but these things 
 did not stir America or England. Morse came, 
 with his alphabet and registering machine, after 
 long years ; then the public wondered why the 
 world had so long waited for the means of com- 
 munication which seemed so natural, so easy. 
 Telephone theories lay in the brain of the Eng- 
 lish physicist, Michael Faraday, and found ex- 
 pression in his lectures a long time before Gra- 
 ham and Bell gave form and substance to that 
 teaching. How can any man who knows such 
 facts say a word against the possibility or the 
 
ITS PRACTICAL APPLICATIONS 145 
 
 prospect of developing new resources out of old 
 treasures? The fact that the public has been 
 tardy in the acceptance and appropriation of the 
 natural endowment which we have in sunbeams is 
 not the slightest reason for a cavil at the value 
 of the heat they bring or the practicability of its 
 domestic and industrial use on a magnificent 
 scale. 
 
 Further, the facts of the matter are unanswer- 
 able. The single man, Mouchot, should carry 
 absolute weight with any reader; the individual 
 work of Adams is irrefutable ; the strokes of the 
 Ostrich Farm engine are audible everywhere 
 that travellers report what they have observed, 
 and technical men read the Scientific American. 
 Solar heat is "no dream;" it is: let no man 
 hereafter speak a word of question. 
 
 Adventurous business houses have already 
 spent much energy and money in solving prac- 
 tical problems; and the technical schools ought 
 to make much study of the theoretical side of 
 this matter. But every-day work by the com- 
 paratively rude methods may be performed by 
 untrained hands. A great amount of value may 
 
146 SOLAR HEAT 
 
 be obtained from this vast natural endowment 
 before all the mechanics and dynamics of the sub- 
 ject are wrought out in a suitable fashion; even 
 as steam-engines were a boon to mankind and 
 a source of great individual gains long before 
 triple expansion and vacuum brakes and electric 
 signals were invented, or schools of technology 
 founded. 
 
 Some of the arguments which have been 
 brought against the use of solar heat are that it 
 will cost a great deal to construct any extensive 
 machinery; that there are few workmen familiar 
 with the subject, or trained in such construction, 
 to be found in the chief places of mechanical 
 activity and trade; the fact that none of the 
 distinguished trade schools and scientific depart- 
 ments of colleges have noticed the subject to any 
 worthy extent; such are some of the stumbling- 
 blocks thrown in the path of the " promoter " of 
 solar enginery. 
 
 But it is to be said that the principal mechan- 
 ical centres of our land, Boston, Worcester, 
 Lowell, Providence, Buffalo, Pittsburg, New 
 York, Paterson, Philadelphia, Cleveland, Chi- 
 
ITS PRACTICAL APPLICATIONS 147 
 
 cago, and how many others, are places of more 
 dark days than sunny ones; that solar appara- 
 tus would only be a mockery in their streets ; and 
 that the colleges and technical schools are simply 
 the followers of the mechanic, not his leaders. 
 Besides, the regions which have abundant sun 
 are largely under the heel of that enemy of all 
 industry and science, the mining-stock gambling 
 habit. San Francisco and Denver could in a 
 trice build up a gigantic, useful art in this direc- 
 tion, if they cared for such things. The great 
 railroad corporations might multiply the popu- 
 lation along the line of their roads by developing 
 this industry, if they would show as much dis- 
 position to benefit the country as to reap benefit 
 from its people. A general spirit of selfishness 
 has been responsible for the tardy development 
 of this art, which is capable of actually giving 
 to the country, in a few years, more wealth than 
 all our mines of gold and silver have yet be- 
 stowed. 
 
 Some man or men may arise who will do for 
 this business what one great " Captain of Indus- 
 try " did for the bicycle ; who took a " fad " 
 
i 4 8 SOLAR HEAT 
 
 and made it a business of prodigious dimensions 
 and usefulness ; spending millions in advertising 
 the novel article and informing the public how 
 to use and enjoy it; critically scrutinizing every 
 detail of construction, to the end that safety 
 might go to the purchaser as well as profit to 
 the maker; advocating and promoting good 
 roads and good laws to help and guard the grow- 
 ing business and pleasure; bringing the public 
 up to a point where the horseless carriage could 
 be comprehended and developed at its present 
 rate. Such a combination of shrewd business 
 with large public spirit in one or a number of 
 men will find a magnificent field in the develop- 
 ment of the solar engine. 
 
 To resume the subject of cost, a prominent 
 advantage of solar furnaces is the saving of fuel- 
 cost. Steam plants have to be maintained at a 
 vast outlay for that which is destroyed in their 
 operations, the fuel which they must burn to 
 produce their energy. By all means, the fuel 
 destruction of this day ought to be abridged. 
 We are impoverishing the earth by our fires; 
 every year is consuming the profits of manufac- 
 
ITS PRACTICAL APPLICATIONS 149 
 
 turers and diminishing the resources of our de- 
 scendants and successors. But the sun will give 
 as much to the children of those who become 
 millionaires by its use as to the children of the 
 Indians who have roamed over the desert plains. 
 The absolute freeness of this supply is a point of 
 immense importance, is a lofty argument. This 
 is to be, not alone the horseless, but 
 
 THE COSTLESS ENGINE. 
 
 And regions which are now feeding on the 
 products of neighboring or distant States will 
 be able to feed themselves and supply others 
 when they avail themselves of the wealth which 
 falls in daily opulence upon their ground. 
 
 Increased population will keep up the trade 
 of the country at large; none will grow poorer 
 by the Northwest's enrichment; but the taxable 
 property of our republic will be enlarged, and the 
 whole country will feel a quickening from the 
 growth of a part. 
 
 If a plant costs a thousand dollars, the interest 
 on that sum, at the old-fashioned legal rate of 
 
150 SOLAR HEAT 
 
 six per cent, per annum, would be sixty dollars 
 a year, or one dollar and sixteen cents a week. 
 A ten thousand dollar plant would cost but six 
 hundred dollars a year for the investment; the 
 simple cost of care, which any machinery must 
 have, is slight compared with the expense of 
 wages or fuel. Mechanism for this purpose is 
 no more liable to accidents or wear and tear than 
 any other kind ; and so the whole issue turns on 
 the one fact of the saving of fuel. Now a small 
 steam-engine will consume coal enough to equal 
 the interest on the cost of the plant. But when 
 the supply of fuel is distant, and the price high, 
 the amount saved by the solar furnace is still 
 greater* Wages of laborers are saved by ma- 
 chinery to a large extent ; the cheaper the power 
 the larger the saving in this direction as well 
 as the other. The advantage of retaining land 
 for various other purposes, which would have 
 to be absorbed for the storage of fuel, is no slight 
 item; the independence of the man who needs 
 no fuel, his freedom from anxiety about supply 
 and transportation, etc., are also of much con- 
 sequence. 
 
ITS PRACTICAL APPLICATIONS 151 
 
 WHAT PROPORTION OF THE TIME WILL SOLAR 
 HEAT BENEFIT US? 
 
 Some persons have raised what they consider 
 a serious objection to the use of solar heat in 
 its lack of perfect uniformity; some hours on 
 many days are too cloudy to run these furnaces 
 profitably or at all; some days are wholly or 
 in part rainy or snowy, having no sunshine at 
 all. Every night is debarred from use. Only 
 eighty per cent, (they grant) of possible sun- 
 light can be had, and that means only forty per 
 cent, of the entire twenty-four hours of time. 
 Steam, they remind us, can be kept in operation 
 continually by the use of combustion furnaces. 
 And they ask, would not the loss of time when 
 the sun did not shine be so great that helio- 
 dynamic plants would fail to pay the interest 
 on their cost by the slight contribution they might 
 make in domestic or industrial lines? To this 
 the answer may be made that a vast proportion 
 of the purposes for which the solar apparatus 
 would be used are needed only during the waking 
 hours of men and women; that the period of 
 
152 SOLAR HEAT 
 
 sunshine is longer than the day which laborers 
 are willing to toil now ; and that power to accom- 
 pany the labor of workmen and workwomen is 
 doing enough in many cases if it simply operates 
 while they are actually at work. Thus the sun's 
 heat will serve the domestic and a respectable 
 portion of the industrial purposes as well as 
 steam now does, which is regularly " shut down " 
 when the operatives are ready to go home at 
 the close of their day of toil. 
 
 The storage of power, of which we have 
 treated in previous pages, furnishes a sufficient 
 answer to the question in the case of those opera- 
 tions which have to be continued by second crews 
 of laborers after the sun has set, and those pieces 
 of work which are restricted in their nature to 
 the night, such as street-lighting and the illumi- 
 nation and power-supply of mines at night. By 
 storage batteries these things can be done eco- 
 nomically and effectively. 
 
 The forty per cent, of possible time in the 
 round twenty-four hours, which may be alleged 
 to be the limit of the reception of solar heat, is 
 not, therefore, the total period of our application 
 
ITS PRACTICAL APPLICATIONS 153 
 
 and employment of the natural endowment. It 
 must be acknowledged that we have, with the 
 capability of storage, a practically continuous 
 force. Thus the heat of the sun is a definite 
 addition to the resources of the world now em- 
 ployed of prodigious content. 
 
 ALWAYS ENRICHING, NEVER IMPOVERISHING. 
 
 The sun-power is a pure gain to humanity. 
 It subtracts nothing; the world will not be in 
 the least impoverished to-morrow by the fullest 
 use of " visible solar heat " to-day. Just as much 
 sunshine will fall on a region where intelligent, 
 progressive men are using millions of foot-power 
 and feeding millions of people by the aid of solar 
 caloric as on a spot where all goes to waste. 
 The rays that come down on the miner who 
 develops a bonanza by their assistance will not 
 shrink back on finding that result produced, 
 nor can monopoly increase the price of the fuel! 
 
 We must consider that wood and oil and coal 
 and gas are steadily consumed by use. Not only 
 will the coming generations be less comfortably 
 supplied a thing most of us care very little 
 
154 SOLAR HEAT 
 
 about but the drain to-day may produce dis- 
 tress in our own homes and lay an embargo on 
 our own business to-morrow. The coal strike 
 of the year 1902 has given an appalling lesson 
 on the slavery of coal consumers. Contrast with 
 this the freedom of the people who receive daily 
 gifts of fuel from the Creator, taking all they 
 wish, all they can use, freely. 
 
 Every friend of humanity, then, every man 
 who cares for our race and looks benevolently 
 forward to coming ages, must feel concerned to 
 see this department of economics advance. Every 
 government which builds for to-morrow ought 
 to devote great resources to the rapid develop- 
 ment of this science and industry. Every prac- 
 tical business man, who is looking out for oppor- 
 tunities for better investment of capital and 
 labor, has an interest in the matter. Every man, 
 who holds his soul in sympathy with the great 
 plans and benevolencies of the cosmos, should 
 rejoice at the anticipation of such a magnificent 
 enlargement of human business and happiness as 
 this offers : thankfulness as well as opulence must 
 thrive at every advance of solar enginery. 
 
APPENDIX 
 
 THE first printed book upon the subject of the present 
 volume and its only predecessor, so far as the writer 
 can learn was issued from the press of Gauthier-Villars, 
 55 Quai des Grands Augustins, Paris, France, in the year 
 1869, with the following title : 
 
 "La Chaleur Solaire 
 
 Et Ses 
 Applications Industrielles 
 
 Par 
 A. Mouchot." 
 
 A second edition was published in 1879, 
 
 "Deuxieme Edition 
 Revue et considerablement Augmented." 
 
 It may be interesting to our readers to see the Table 
 of Contents of this remarkable book. We present a some- 
 what liberal translation. 
 
 CHAPTER FIRST. 
 
 SUMMARY. The sun is a source of most intense heat; 
 experimental proof. The function of the solar heat on 
 
 155 
 
156 APPENDIX 
 
 the surface of the globe; it enters into the movement of 
 life. Transformation of heat into energy; the mechan- 
 ical equivalent of heat. Solar heat is the source of the 
 only natural processes (travaux} that man has learned, up 
 to this time, to appropriate. Possibility of taking pos- 
 session of solar heat power directly; advantages which 
 would result to certain countries. A new solar receiver; 
 principles upon which the theory is founded; easy means 
 and slight cost of producing any desired temperature in 
 a boiler by the heat of the sun. Plan of the work. 
 
 CHAPTER SECOND. 
 
 SUMMARY. Of the use of glass among the Ancients. 
 Concentration of solar heat in a glass flask. The Arabs 
 used glass vases to perform certain distilling processes 
 by the aid of the sun. Experiments of De Saussure 
 and of Ducarla. The heat of the sun is like its light, 
 formed of an infinite number of rays of different sorts. 
 Uncolored panes of glass behave with heat rays like 
 colored panes with light rays; experiments leading to 
 this conclusion. Results of the observations of Mellon! 
 and Sir John Herschel. The influence of the nature, sub- 
 stance, source of heat, etc., upon its transmission. 
 Chemical rays beyond the luminous and calorific rays. 
 
 CHAPTER THIRD. 
 
 SUMMARY. Intensity of solar heat at the surface of 
 the sun; results of the observations of De Saussure, De 
 Flaugergues, John Herschel and De Pouillet. Influence 
 of the dryness or moisture of the air on atmospheric con- 
 duction of solar heat. Intensity of solar radiation at 
 
APPENDIX 157 
 
 noon, certainly is the same in summer as in winter. This 
 is very great at mountain tops as long as the air remains 
 clear; experiments of De Saussure on the subject 
 Equatorial regions where the heat is excessive are those 
 where the air is dryest [according to] tests made by Messrs. 
 Soret, Crova, and Violle. Method of concentrating 
 solar heat upon a surface a metre square in one minute, 
 at the latitude of Paris. 
 
 CHAPTER FOURTH. 
 
 SUMMARY. Reflection of light and heat. Properties 
 of mirrors, spherical, cylindrical, and conical. Metallic 
 mirrors well adapted for the purpose of reflecting heat 
 The reflective power of a polished metallic surface depends 
 upon the nature of the heat rays. Experiments of Messrs. 
 Laprovostaye and Dessains. Silver plates reflect solar 
 heat very finely. Metals which may be used. Advan- 
 tages and disadvantages of glass lenses. Metallic re- 
 flectors preferable for ordinary purposes. 
 
 CHAPTER FIFTH. 
 
 SUMMARY. History of burning mirrors. Euclid's 
 treatise on Optics. The Mirrors of Archimedes and of 
 Anthemius of Tralle. Works of Arabians. History of 
 burning mirrors in the Middle Ages and the Renaissance, 
 Experiments of Magini, Kircher, Villette, Duffay, and of 
 Buffon. [Their] experiments prove the superiority of 
 mirrors over lenses. It is not sufficient to consider tem- 
 perature alone in estimating heat values. Hoesen's 
 mirror. Method proposed by Ducarla for protecting from 
 
158 APPENDIX 
 
 cooling the articles which are placed at the focus of a 
 burning mirror. 
 
 CHAPTER SIXTH. 
 
 SUMMARY. A comparison of the methods (appareils) 
 of Ducarla, Herschel, and Franchot. New solar re- 
 ceiver; its applications. The action of solar heat upon 
 confined air; means of utilizing the pressure which results. 
 Raising water by means of the sun; fountains. The 
 boiling of water; a solar kettle (marmite solaire) the. 
 cooking of vegetables and [various sorts of] food ; 
 solar oven; bread-baking; distilling spirits; melting 
 metals. The effects on the future of certain countries 
 which would follow the adoption of these operations. 
 
 CHAPTER SEVENTH. 
 
 SUMMARY. History of mechanical applications of solar 
 heat up to the commencement of this [nineteenth] cen- 
 tury. Hero's engine. The process of Porta. The 
 solar pump of Salamon de Caus ; the method he proposed 
 for increasing the intensity of the heat which falls upon 
 us. Experiments of [the English physicist] Robert Fludd 
 and of Drebbel. Martini's clock. Kircher constructed 
 various solar machines; he recognized the advantage of 
 confining the heated air in a glass vessel. Millet Des- 
 challes proposed to heat that air in order to assist plane or 
 concave mirrors [in reflection]. Bellidor's solar pump. 
 De la Cliche proposed to use the apparatus of Ducarla to 
 heat steam-engines. Oliver Evans [in the United States 
 of America] similarly devoted attention to mechanical 
 applications of solar heat. 
 
APPENDIX 159 
 
 CHAPTER EIGHTH. 
 
 SUMMARY. A study of the constant fountain of Salamon 
 de Caus ; its faults, and the method of correcting them. 
 The solar pump of M. Deliancourt A new solar pump. 
 The machine of Cagniard-Latour ; it can be transformed 
 into a solar motor. The direct use of solar heat in making 
 steam; uses of solar generators. The experiments 
 (essais) of M. Ericsson; imperfection of his receiver, 
 which is that of M. Franchot. Alcohol, ether, ammonia, 
 and hot-air engines. 
 
 CHAPTER NINTH. 
 
 SUMMARY. Great solar machines. That of Meudon; 
 that of Tours. Results. Report of my mission to 
 Algeria. The machine exhibited in the Algerian section of 
 the World's Fair at Paris in 1878. Things done and 
 planned there. The decomposition of water by means of 
 the thermo-electric pile. Means of storing solar heat for 
 night work. Various suggestions. Conclusion. Notes. 
 
 On the last page of the cover of M. Mouchot's book two 
 works, by M. Pifre, ingenieur civil, are announced, viz.: 
 " Les Recepteurs Solaires, Resultats Econontiques de leurs 
 applications industrielles en Algerie," and "Les Recepteurs 
 Solaires en Egypte, Espagne, Italie, Amerique, Indes Ang- 
 laises et Francoises, etc.; " which evidently follow out the 
 lines laid down in the great work of Mouchot. 
 
 Mouchot has given, as this summary shows, an exceed- 
 ingly minute, detailed account of the intellectual move- 
 ment toward the utilization of solar heat, well worth the 
 reading and study of a college professor or student of the 
 subject on its theoretical side. But his book, if translated 
 
160 APPENDIX 
 
 wholly, would be of but little value to that world of 
 practical people for whom the present volume is intended. 
 However, it must always stand as a magnificent monument 
 to his honor and the -first grand beacon in the development 
 of this cause. 
 
Books Published 
 By CHARLES H. POPE 
 
 THE ELWELL FAMILY IN 
 AMERICA 
 
 Robert Elwell, of Dorchester and Gloucester, Mass., 
 and his descendants for four generations, with the 
 author's line completed. By the late Rev. Jacob 
 Thomas Elwell. 
 8vo, pp. 30, 1899 . . Boards, $0.75 
 
 WARE GENEALOGY 
 
 Robert Ware, of Dedham, Mass., and his descendants, 
 with information on others of the name. By the late 
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 8vo, pp. 335, 1901. . . Cloth, $5.00 
 
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 8vo, pp. 492, 1902. Cloth, $6.00 . half leather, $7.00 
 
BOOKS PUBLISHED BY CHARLES H. POPE 
 WORKS OF REV. CHARLES HENRY POPE, A.M. 
 
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 Illustrated. 8vo, pp. 580, 1897. 
 
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 Or, The Life of Jesus Christ as told by Matthew, 
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 narrative ; in the language of revised version, text and 
 margin; words of Our Lord in special type. 
 
 i6mo, pp. 206. Second edition, 1901. Cloth, $0.50 
 
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 A descriptive list of those who settled here, 1620-1650, 
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 4to, pp. 520, 1900, supplement 1902, with fine in- 
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BOOKS PUBLISHED BY CHARLES H. POPE 
 
 SOLAR HEAT, ITS PRACTICAL 
 APPLICATIONS 
 
 By REV. CHARLES HENRY POPE, A. M. 
 A history and discussion of the use of the heat of the 
 sun in the home, field, factory, etc., and a plea for its 
 wide appropriation. First book on the subject in the 
 English language ; in popular style ; adapted to gen- 
 eral reading or class-room study. 
 
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