434 THE CANADIAN NATURALIST. [DeC. 



Making the same supposition as in the case of our cannon-ball, the final 

 pressure would be that here statetl. 



15 Tyxdall, J , Heat considered as a mode of Motion, Am.cd., p. 57, 

 Xew York, 1863. 



16 Rankine (The Steam Engine and other prime Movers, London, 

 1866) gives the efficiency of Steam-engines as from l-15th to l-20thof the 

 heat of the fuel. 



Armstrong, Sir Wm., places this efficiency at 1-1 0th as the maximum 

 In practice, the average result is only l-30th. Rep. Brit. Assoc, 1863, 

 p. liv. 



Helmholtz, H. L. F., says; "The best expansive engines give back 

 as mechanical work only eighteen per cent, of the heat generated by 

 the fuel." Interaction of Natural Forces, in Correlation and Conserva- 

 tion of Forces, p. 227. 



17 Thomsen, Julius, PoggendorflPs Annalen, cxxv, 348, Also in 

 abstract in Am. J. Sci., II, xli, 396, May, 1866. 



18 American Journal of Science; II, xli. 214, March, 1866. 



19 In this calculation the annual evaporation from the ocean is assum- 

 ed to be about 9 feet. (See Dr. BuiST, quoted in Maury's Pays. Geo- 

 graphy of the Sea, Xew York, 1861, p. 11.) Calhng the water-area of 

 our globe ]50,000<000 square miles, the total evaporation in tons per 

 minute, would be that here given. Inasmuch as 30,000 pounds raised 

 one foot high is a horse-power, the number of horse-powers necessary to 

 raise this quantity of water 3^ miles in one minute is 2,757,000,000,000. 

 This amount of energy is precisely that set free again when this water 

 falls as rain. 



20 Compare Odling, "Wm., Lectures on Animal Chemistry, London, 

 1866, "In broad antagonism to the doctrines wbich only a few years 

 back were regarded as indisputable, we now find that the chemist, like 

 the plant, is capable of producing from carbonic acid and water a whole 

 host of organic bodies, and we see no reason to question his ultimate 

 ability to reproduce all animal and vegetable principles whatsoever." 

 (p.58.) 



"Already' hundreds of organic principles have been built up. from their 

 constituent elements, and there is now no reason to doubt our capability 

 of producing all organic principles whatsoever in a similar manner." 



(P, 52.) 



Dr. Odling is the successor of Faraday as Fullcrian Professor of Chemis- 

 try in the Rojal Institution of Great Britian, 



21 Marshall, John, Outhnes of Physiology, American Edition, 

 1868, p. 916. 



22 Fran KL AND, Edward, On the Source of Muscular Power, Proc, 

 Roy. Inst., June 8, 1866 ; Am. J. Science, II, xln, 393, Xov. 1866. 



23 LiEBiG, JusTUR VON, Die organische Chemie in ihrer Anwendung 

 auf Physiologie und Pathologic, Braunschweig. 1842. Also in his 



