156 ANNUAL EECORD OF SCIENCE AND INDUSTRY. 



He concludes that the highest proportion of heat reflected 

 from the lake was about seven tenths of the incident heat, 

 which amount is reflected when the solar rays make an angle 

 of about four degrees with the surface of the water. When 

 the sun is* thirty degrees above the water, the proportion of 

 heat reflected is inappreciable. The j^roportion of heat re- 

 flected is almost without exception greater as the lake is 

 calmer. The rays that after reflection strike upon the ad- 

 jacent shores of the lake have a decided influence in stimu- 

 lating: veo:etable crrowth. This action of reflected heat has 

 no probable connection with the absence of salt in the water, 

 and the same or very similar eflects will no doubt be observed 

 from the surface of the ocean. This reflected heat is not 

 without its influence on favorably situated plains, and ought 

 to afl*ect favorably the development of their vegetation. The 

 loss of heat passing out of tlie atmosphere into the celestial 

 spaces should by these experiments be considerable, and es- 

 pecially in the southern half of the hemisphere, where the 

 oceanic areas are wider than in the northern hemisphere. 

 4 i>, 1872, 218. 



A NEW METHOD OF ANALYSIS OF COMPOSITE SOUNDS. 



At the recent meeting of the National Academy of Scien- 

 ces, Professor Alfred M. Mayer read a paper entitled " A New 

 Method of Analysis of Composite Sounds." This analysis is 

 interesting, not alone by reason of its delicacy and perfec- 

 tion, but also on account of its being a complete experimental 

 confirmation of Fourier's celebrated theorem, as applied by 

 Ohm in liis propositions relating to the nature of a simple 

 sound, and to the ear's analysis of a composite sound into its 

 simple sonorous elements. The discoveries of Professor Mayer 

 led him directly into experimental researches on the organs 

 of hearing of different animals, and to the new and curious 

 discovery that the fibrils of the antenna? of certain insects 

 vibrate in sympathy to the notes which these same insects 

 emit, thus afiTording the only proof ever given that the an- 

 tennae must be the oro-ans of hearing:. 



The theorem of Fourier is the expression of a mathematical 

 possibility, and shows that if we represent any composite 

 sound by a periodic curve, then such curve can always be 

 reproduced by compounding harmonic curves (often infinite 



