March 17, 1882.] 



• KNOWLEDGE ♦ 



417 



V AN ILLiL&IRATED ^^' /^ 



MAG^ZlNEo?SC;iENCE^ I 



P LAINLrVfORDED -EXACTlVDESCRIBED \ 



LONDON.- FRIDAY, MARCH 17, 1882. 

 Contents of No. 20. 



Ou the Conscrration of Solar Euergj-. 



Bv Dr. \V. B. Carpralcr '... -417 



Xoles on Koiving. By an Old Club 



Captain ; 418 



Future of tho Earth and Moon. By 



Dr. Ball, Astronomer-Royal for 



Ireland. Part III 420 



Illusions of Motion and Strobic 



Circles. By Thomas Foster. 



mimtrattil) 121 



Sewconib's Popular .^stronorav 423 



The Crystal Palace Elcctrieal feihj. 



bili.iii. Sixth Notice. (Illiisl.) ... 12.5 

 Brain Troubles. The Echo Sign ... 427 

 Easv LcHsons in Blovrpipe Chomislrr. 



BV Lieut .-Colonel W. A. Ross, 



late K.A. (IllH,tru/„l) -laS 



•,* Our Exchange and Sixpenny Sale 

 advertising col 



The l%e of the Tricvcle. Bv Dr. B. 

 W. Kiohardson, P.R.S 



Change of Habit in .Animals 



The "Sound" of Fishes 



Electro-Magnetic Theory of Light... 



Our Ancestors 



CoBRESPONDKKCE ; — Vegetariiint*m 

 — Plants in Bedrooms — Tele- 

 scopes—The Potato, 4c 431 



Special Notice 



Queries 



Replies to Queries 



Answers to Correspondents 



Notes on Art and Science 



I Our Mathematical Column 



Our Whist Column 



1 Our Chess Column 



Columns appear on Page IV.— in our 

 imns this week. 



ON THE CONSERVATIOX OF 80LAR 

 ENERGY. 



By Dh. W. B. Carpenter. 



rpHE met^ting of the Royal Society on Jlarch l-'iicl was 

 .L rendered unusually interesting, tirist, by the admission 

 of H. R H. the Prince of Wales, as a Fellow of the Society ; 

 second, by a communication given by Prof. Huxley on the 

 fungous origin of the " Salmon Disease," which is destroying 

 large numbers of fish in the rivers of the South of Scotland 

 and the North of England, from the Tay to the Conway ; 

 and last, but by no means least, by the exposition given by 

 Dr. Siemens of an " idea " regarding the mode of main- 

 tenance of the Solar energy, which he lias been for some 

 time maturing, and has at last determined to submit to the 

 criticism of the scientific world. Of this most ingenious 

 and suggestive speculation, the following sketch will, I 

 hope, prove as interesting to the readers of Knowledge, 

 as Dr. Siemens's own admirable and more detailed statement 

 of it was to the members of the large scientific gathering 

 to which it was addressed. 



In the first place, he reminded us of the enormous 

 amount of heat which is constantly radiating from the Sun 

 into space ; thi.s, according to the best measurements that 

 have been made, being such as would be maintained for 

 only thirty-six hours by the complete combustion (as in 

 the most perfectly-constructed furnace) of a mass of the 

 best coal equal to the Earth in bulk. Now, if the sun were 

 surrounded by a solid sphere of a radius equal to the mean 

 distance of the earth, the whole of this heat would be inter- 

 cepted by it ; but since the diameter of the earth, as seen 

 from the sun, is only seventeen seconds, so that its surface 

 is only 1-2, ■250,000,000th part of the whole area of such a 

 sphere, only that proportion of the entire heat radiated 

 from the sun will fall upon the earth. Supposing the 

 aggregate of all the Planetary bodies to intercept ten times 

 as much as the earth, the total amount of solar heat thus 

 utilised will be only one part in 225,000,000 of the total 

 radiated from tlie sun ; the other 224,1199,999 parts to all 

 appearance going to waste — in other words, doing no work. 

 Now the mode in which this enormous supply is kept 

 up has been in all ages a question of great interest ; but 



only in modern times could any scientific solution of it be 

 even attempted. Of course, Chemical action would be the 

 first source tliat would occur to almost every one — radia- 

 tion of heat from a fire being the nearest thing within our 

 cxpirience to the heating effect of the solar beams. But, 

 putting aside other diliicultics arLsing out of the revela- 

 tions of the spectroscope, the ordinary chemical hypothesis 

 is met by the objection, that the accumulation of the pro- 

 ducts of combustion on the surface of the sun would in 

 time form a barrier against further action. And, sup- 

 posing this barrier disposed of, it is obvious that the 

 nuiintenance of this combustion must bo attended with a 

 continual ii-asting-airaii of the sun, at a rate which would 

 make itself perceptible in the disturbant e of planetiiry equili- 

 brium, wlien the loss is estimated for long pt-riods of time. 



An opposite idea was suggcstid some years ago by Sir 

 William Thomson : that of a continual rain of Meteorites 

 upon the sun — the velocity they would acquire from its 

 attraction causing them to impinge upon its surface with 

 such force, as to generate a large amount of heat when their 

 motion is checked. But hert^ we are met Viy two diffi- 

 culties : first, that of conceiving of any supply of meteorites 

 that would be competent thus to keep up the amount of 

 heat which we know to be always radiating from the sun ; 

 and secondly, the progressive increase in the bulk of tlie 

 sun that would be produced by any ad(;quate supply, dis- 

 turbing the planetary equilibrium in the contrary sense to 

 the preceding. 



It has been supposed by llelmholtz, and accepted by 

 many physicists on his authority, that tht; radiant energy 

 of the sun is the result of a progressive sliriuktujc of his 

 bulk and condensation of his substance. But tlie giving- 

 out from his surface of the heat thus generated in his 

 interior, could only be accomplished through some medium 

 of much gi-eater conductivity than is possessed by any 

 material known to us ; and on this process, again, a limit is 

 oliviously imposed, since a time would come when (as seems 

 now the case with the Moon, and nearly so with the Earth, 

 Venus, and Mars) the limit of consolidation would be 

 reached. 



Dr. Siemens, as every one knows, is the inventor of 

 the regenerative furnace now coining into general use ; in 

 which a large proportion of the heat that ordinarily goes 

 up the furnace-chimney, and runs to waste, is recovered 

 from the products of combustion, carried back into the 

 furnace, and made to do its proper work - thus obtaining 

 an enormous advantage in economy of fuel. IMentally 

 projecting this terrestrial experience into the realms of 

 space, he was led to the conviction " that the prodigious and 

 seemingly wanton dissipation of solar heat is unnecessary 

 to satisfy accepted principles regarding the conservation of 

 energy ; but that it may be arrested and returned over 

 and over again to the sun, in a manner somewhat 

 analogous to the action of the hea1>recuperator in the 

 regenerative gas-furnace." The fundamental conditions of 

 his hypothesis are three. 



I. Everyone who has followed the recent progress of 

 Celestial Physics, is aware of the increasing reasons which 

 there are for regarding not only planetary, but stellar 

 space as occupied by matter in a very attenuated condition ; 

 and Dr. Siemens starts with the assumption that this matter 

 chiefly consists of hydrogen, oxygen, nitrogen, carbon, and 

 their compounds (especially aqueous vapour and carbonic 

 acid), besides solid material in the form of dust. The 

 existence of oxygen, nitrogen, and carbon he considers 

 to be indicated by the presence of those elements in our 

 own atmosphere, to which (according to the molecular theory 

 of gases) no such limit as was formerly assigned to it can 

 now be admitted. We get a clue to the gaseous components 



