426 



SCIENCE. 



[Vol. II., No. 34. 



tlae greater the attractive force, enables us to 

 enunciate the following law, the truth of which 

 I am at present unable to verify for want of 

 sufficient experimental data : those solids, 

 other things being equal, which evolve the 

 greater amounts of heat of chemical decompo- 

 sition in changing from simple mixtures to 

 compound solids, are those which have less 

 specific heat per atom. The phrase, ' other 

 things being equal,' in the above statement, 

 refers to the fact that similar compounds which 

 are chemically similar are in strictness com- 

 parable. Manj' other circumstances, more- 

 over, besides want of chemical similaritjs may, 

 in special cases, mask the experimental results ; 

 j-et the truth of the law should be clearly recog- 

 nizable in anj- general comparison of specific 

 heats with the heat of formation of compound 

 solids. 



Similar principles evidently apply to the 

 cases in which simple solids are permanently 

 decreased in volume bj- hammering or com- 

 pression ; for then greater cohesive forces are 

 brought into action, and the specific heat is 

 diminished. It remains to be shown, in con- 

 clusion, that thermal equilibrium, which has 

 been established by collisions of gaseous and 

 solid molecules, will continue to exist when its 

 continuance depends upon radiations between 

 equal and similar ultimate atoms which are 

 set in vibration bj' molecular collisions ; or, to 

 state it differently, it remains to be shown that 

 the ultimate atoms of a gas and a solid in 

 contact, each have the same mean vibratory 

 energy with respect to each of their degrees 

 of freedom with respect to each other. This 

 appears to be a direct consequence of the laws 

 of constrained motion which have been consid- 

 ered in this and previous papers. It is only 

 necessavj' that the impacts of a pair of solid 

 molecules with each other should be such as 

 to mutualh^ impart and receive the same mean 

 amounts of energy as would those of a gas- 

 eous and a solid molecule at the same tempera- 

 ture, to cause it to be a matter of indiflerence 

 whether a given solid molecule is struck by 

 another solid molecule or bj' a gaseous mole- 

 cule ; and, when so struck, each ultimate atom 

 will receive its proper proportion of energy, 

 whether it form part of a solid or of a gaseous 

 molecule. 



It is mj^ intention to return to this subject 

 hereafter, and to treat the vibrations of ulti- 

 mate atoms more at length, in the hope of 

 being able to show, more precisely than has 

 been done so far, how the characteristic differ- 

 ences in the spectra of solids and gases arise. 

 H. T. Eddy, Ph.D. 



CLIMATE IN THE CURE OF CONSUMP- 

 TION. —I. 



The prevalence of phthisis pulmonalis is 

 such a well-attested fact, that to adduce statis- 

 tics to prove it would seem to be labor thrown- 

 awa}^ Since the eradication of small-pox in 

 consequence of the introduction of vaccination, 

 l^hthisis heads 'the list as the prime cause of 

 the large mortalitj'. The insurance companies 

 recognize the fact, and the statistics of the 

 New- York mutual life-insurance company show, 

 that between the ages of twenty and thirt}- 

 years the mortality from phthisis is thirt}'- 

 three per cent of the whole mortalitj'. The 

 U. 8. census for 1870 shows that in the state 

 of Maine the mortalit}' from consumption was 

 fifty per cent for the same ages. 



Equally well known is the belief in climate 

 as a cure for the disease. There are certain 

 well-recognized climatic conditions known to 

 be favorable to the prophylaxis and cure of the 

 disease. This knowledge is largely empirical, 

 based upon trial and observation ; but there is, 

 underlying it, a substratum of conviction, that 

 is justified, on the one hand, hy careful clinical 

 observations, and, on the other, by facts ascer- 

 tained by carefully conducted experiments. 



The writer proposes, in the thoughts to be 

 presented, to make these various elements his 

 tests in searching out a desirable climate in 

 the United States for the cure of phthisis. He 

 offers, as his data for forming an opinion, 

 carefully compiled tables, furnished by the Sig- 

 nal-service bureau, U.S.A. ; and he wishes to 

 emphasize the fact, at the outset of his re- 

 marks, that a climate ra&y become desirable 

 quite as much by comparison as on account of 

 its intrinsic properties ; that even though it may 

 ■ not possess in itself all desirable qualities, j-etit 

 may contain so manj' as to be, bj' comparison 

 with others, the climate par excellence. With 

 this thought in view, the writer has prepared ta- 

 bles embracing all the chief resorts in this coun- 

 trj' for phthisical invalids, — tables embracing 

 a range of the whole countrj', from Jacksonville 

 to St. Paul, and from Boston to Los Angeles. 



He has given the data for Augusta, Ga. , as the 

 .best substitute for Aiken, S.C., at which place 

 there is no signal-station ; and in doing so he 

 thinks that he is presenting data which will fairly 

 repi'esent the chmatic conditions of Aiken. 



He wishes to gratefully acknowledge his in- 

 debtedness to the chief signal-officer, U.S.A., 

 to the observers at each of the stations in- 

 cluded in the tables, and especially to Sergeant 

 F. M. Neal of the Denver station, for their 

 kindness in furnishing him with the data from 

 which the tables are compiled. 



