420 



SCIENCE. 



[N. S. Vol. XVI. ^v. 402. 



transformation of therjnal into dynamic 

 energy in any defined case is measured by 

 the product of the rate of variation of worls 

 with temperature into the measure of the 

 absolute temperature at which the observa- 

 tion or the computation is assumed to be 

 made. If the work-effect is exhibited in 

 change of temperature, in change of volume 

 at constant temperature, or by any single 

 phenomenon in energetics, the formula 

 will have the same form. 



It is now easilj' practicable to obtain the 

 fundamental equation of the science of 

 thermodynamics. 



Thus, on two simple propositions, based 

 Tipon scientific deductions from observa- 

 tions of natural phenomena, and with the 

 facts obtained by scientific research regard- 

 ing specific heats, volumes, pressures and 

 tensions, the whole great and wonderfully 

 important and productive science of ther- 

 modynamics was by these two men of geni- 

 us, independently and with entire original- 

 ity, constructed, and their results were pub- 

 lished practically and simultaneously. Had 

 it been possible to measure the internal 

 forces of the non-gaseous substances, this 

 important science might have been con- 

 structed upon the basis of the first law 

 alone. It is not at all certain that it may 

 not yet prove practicable to eliminate the 

 second law as an essential primary proposi- 

 tion; means being discovered of reducing 

 the perfect gas and the vapor, the liquid 

 and the solid, to a common form of ana- 

 lytical expression involving the four fun- 

 damental factors. The one now impassable 

 obstruction to this simplification of the sci- 

 ence is our inability to measure internal 

 forces and to discover their law of varia- 

 tion. 



Since Thomson has discovered evidence 

 of the possibility of the divisibility of the 

 once supposedly indivisible atom, and since 

 the employment of the electric forces in 

 the analvsis and synthesis of substance in 



every form, even the production of a new 

 science, remains apparently among the op- 

 portunities and in the future^ perhaps, 

 many new sciences. The reduction to meas- 

 ure and to law of Thomson's 'corpuscles' 

 may prove to be the first step toward the 

 solution of many remaining problems other- 

 wise beyond our powers of analysis. This 

 new fact, if it so prove, may reveal to us the 

 real nature of the luminiferous ether, al- 

 ready studied by Herschel, by Wood and 

 others. 



The extraordinarily interesting and won- 

 derfully ingenious investigation of the 

 thermodynamics of the luminiferous ether, 

 made by De Volson Wood, in 1885 or ear- 

 lier, which study, however, seems to have 

 attracted little attention as yet, admirably 

 illustrates the fact that, given a certain 

 definitely known system of facts and prin- 

 ciples, a single thought of the man of 

 genius may open a new and wonderful 

 vista to the mind of man.* 



The essential properties of every 'per- 

 fect gas' had long been known. It was 

 known that two essential physical charac- 

 teristics of the ether had been determined 

 quantitatively— the velocity with which en- 

 ergy was transmitted by its vibrations and 

 the quantity of energy transmitted by it 

 from the sun to the earth per unit of its 

 section. It transmits energy at the rate of 

 186,300 miles, 982,000,000 feet per second 

 (299,838 kilometers per second), and de- 

 livers heat energy from the sun at the rate 

 of about 2.8 calories per square centimeter 

 of the section of the beam, 133 foot-pounds 

 per square foot, per second. 



Taking the evidence as wholly in favor 

 of the conclusion that the luminiferous 

 ether is a perfect gas, if a perfect gas in 

 the thermodynamic sense exists at all. Wood 



*'The Luminiferous Ether,' by De Volson Wood, 

 Philosophical Magazine, November, 188.5; Van 

 Nostrand's Magazine, January, 1886; Wood's 

 ' Thermodynamics,' Appendix I. 



