OF ARTS AND SCIENCES. 383 



the working piston, by exposing it at each stroke to the current of 

 entering cold air; and in the system of cranks, rockshafts, levers, and 

 their connecting-rods, by which the varied, complicated, but necessary 

 motions of the supply and working pistons are regulated and connected 

 with each other and the fly-wheel. 



The minority recommend that the Rumford Medal be awarded to 

 Mr. Ericsson for his improvements in the management of heat, particu- 

 larly as shown in his air engine of 1858. 



E. N. HORSFORD, 

 Cambridge, April 8, 1862. Daniel Treadwell. 



The two Reports being accepted, the subject was discussed 

 in detail by Professors Horsford, Lovering, Winlock, Peirce, 

 and Treadwell. 



And, on motion of Professor Horsford, an adjourned meet- 

 ing was voted to be held on the 22d instant, for the further 

 consideration of the subject. 



Five hundred and geTrenth meeting. 



April 22, 1862. — Adjourned Monthly Meeting. 



The Vice-President in the chair. 



The Corresponding Secretary read a letter from Professor 

 Trendelenburg, of Berlin, in acknowledgment of the notifi- 

 cation of his election as a Foreign Honorary Member of the 

 Academy. 



He presented, from the author, a paper entitled PlantcB 

 Wrightiance e Cuba Orientali, a A. Grisebach : Pars 11. 



Also the following communication from Professor Tucker- 

 man. 



Observations on North American and other Lichenes. By 

 Edward Tuckerman, A. M. (Continued from Vol. IV. 

 p. 407.) 



Omphalaria leptophylla, sp. nov. : thallo membranaceo-carti- 

 lagineo glabro atroviridi subtus subconcolore e centre in lobos undu- 

 lates apice latiori rotundatos repandos mox sinuato-Iobatos diviso; 



