Dec, 1845.] 295 



Proceedings of the American 'Philosophical Society, vol. 4, 

 No. 33. May to Aug., 1845. From the Society. 



Extraits d'une lettre de M. Fresnel a M. Jomardsur certains 

 quadrupedes reputes fabuleux. Paris, 1844. From Geo. 

 R. Gliddon, Esq. 



A letter was read from N. S. Benton, Esq., Secretary of 

 State of New York, dated Albany, Dec. 5, 1845, in answer 

 to one addressed to him by the Corresponding Secretary, in 

 accordance with a resolution of the Society, directing appli- 

 cation to be made for a complete copy of the Natural History 

 of that State for the Library. The Society was informed 

 that no copy was at present at the disposal of the Depart- 

 ment. 



A paper, by Alfred T. King, M.D., of Greensburg, Pennsyl- 

 vania, entitled, " Descriptions of fossil foot prints," was read 

 and referred to the following Committee, viz. : Prof. Johnson, 

 Dr. Morton and Mr. Cassin. 



Professor Johnson communicated some observations on the re- 

 lative evaporation from land and water surfaces, and stated the 

 means by which the question had been investigated, referring to 

 the report, a copy of which was presented to the Academy at the 

 last meeting, concerning the water sources near Boston, for a por- 

 tion of the details of experiments and observations, by which the 

 ratio in question had been established. 



The method of research was stated to have comprised, 1st, an 

 observation- of the quantity of water falling in rain ; — 2d, the 

 quantity flowing away by the outlet of the source ; — 3d, the 

 depth removed from the surface of water by evaporation ; and 

 4th, the relation between the area of ground covered by Avater, 

 and of that constituting the water shed or drainage, from which, 

 owing to the direction of its slope, the rain falling upon it, must 

 necessarily pass into the pond or lake, constituting the source of 

 immediate supply. The plan pursued required of course a de- 

 termination by actual surveys, of the total area of ground em- 

 braced within the district or hydrographic basin, and also that of 

 the water surface at several different stages of height correspond- 



36 



