Jan. 7,1870.] ^^^ [C'liase. 



the Micliaux Fund, after satisfying the requirements of the preceding 

 resolution, shall be devoted to the cultivation of Oaks of every variety ca" 

 pable of cultivation in our climate, in the Park nursery, -which Oaks, to 

 the extent of two of each kind cultivated, be hereafter distributed to 

 other Public Parks in the United States, under proper regulations to be 

 hereafter prescribed. 



Attest, David F. Foley, Sec. Park Commission. 



On motion of Mr. Price, it was then 



Besohed, That this Society do agree to the terms contained in the pre- 

 amble and resolutions of the Fail mount Park Commissioners, adopted on 

 the 12th day of March, 1870, in the expectation and confidence that the 

 planting of the Michaux Grove of Oaks may be soon commenced, so that 

 the Grove shall early become one of the attractions of the Park. 



And the Society was adjourned. 



COMPAKISON OF MECHANICAL EQUIVALENTS. 

 Bt Pliny Eaele Chase. 



Bead January 7, 1870. 



The comparison of different mechanical equivalents will open a new 

 field for investigation, Avhich may prove to be fertile in vahiable results. 

 For example, recent determinations, by the different methods of Thom- 

 sen and Farmer, fix the mechanical equivalent of light, in a wax candle 

 burning 126^ grains per hour, at 13.1 foot-pounds per minute, the equiva- 

 lent of 1 grain being 6.213 foot-pounds. According to Dulong, the heat 

 evolved, during the combustion of 1 grain of olive oil in oxygen, is suffi- 

 cient to heat 9862 grains of Avater 1° C. According to Favre and Silber- 

 mann, 1 gi-aiii of oil of turpentine, burned in oxygen, would heat 10,853 

 grains of water 1° C. 



It may therefore be presumed that the total heat given out by the com- 

 bustion of 1 grain of wax, is about sufficient to raise 10,000 grains of 

 water 1° C, or 18,000 gr. 1° F. This represents a mechanical equivalence 

 of (18,000 X 772 - 7000 =) 1985.143 foot-pounds, which is 319.5 times as 

 great as the corresponding equivalent of the light given out during the 

 combustion. 



Tyndall, in his lecture on Kadiation, states that the visible rays of the 

 electric light contain about one-tenth of the total radiated heat. The re- 

 lative luminous intensity of an electric lamp would therefore appear to be 

 about 32 times as great as that of the Avax candle. This ratio so nearly 

 resembles that of solar to terresti'ial superficial attraction, and the con- 

 nection of electric and magnetic currents with solar radiation is so evi- 

 dent, that additional exi:)eriments, to furnish materials for a great variety 

 of similar comparisons, seem desirable. While it is possible that the re- 

 semblance, in the present instance, may be accidental, the numerous 

 harmonies between the manifestations of cosmical and moecular forces, 

 render it at least equally possible that it may have a weighty significance. 



