OF ARTS AND SCIENCES. 275 



nature of American storms, and their connection with the two great 

 aerial currents continually flowing over the temperate zone. He 

 considered that the great changes of the weather are principally due 

 to the gradual production of an unstable equilibrium in the two cur- 

 rents, by the accumulation of heat and moisture in the lower. 



He spoke in high terms of the importance of the labors of Mr. 

 Espy in developing the theory of the upward motion of air, and the 

 evolution of latent heat in the production of storms. 



In reply to a question as to the possibility of crossing the Atlantic 

 in a balloon, the Professor stated that? he had little doubt, if the bal- 

 loon could be made to retain the gas, and to ascend into the upper 

 current, it would be wafted across the ocean in the course of three or 

 four days. If it descended into the lower current, it would be carried 

 to the north of east ; and if it continued in the upper current, it would 

 reach Europe south of the same point. The course could be changed, 

 within certain limits, by ascending and descending from one current 

 to the other. The late balloon voyage from St. Louis to Jefferson 

 County, New York, was of interest in confirming the theoretical direc- 

 tion of the great lower current of this latitude. 



The Corresponding Secretary presented the following paper 

 upon the Mosses collected in Captain Rodgers's recent explor- 

 ing voyage ; which is published by permission of Captain 

 Rodgers. 



Characters of sortie new Musci collected hy Charles Wright in 

 the North Pacific Exploring Expedition* under the Command 



* Of the very interesting collection of Mosses brought home by the Expedition, 

 eighty-six were gathered in Japan and adjacent islands, and seven on the coast 

 of China. Of these ninety-three species, the fifty-four following are identical 

 with species occurring either in Europe or in North America, or in both coun- 

 tries : — 



Sphagnum squaiTOSum, Phascum crispum, Weisia viridula, Rhabloweisia fugax, 

 Dicranella curvata, Dicranum scoparium, Trematodon longicollis, Leucobryum 

 glaucum, Trichostomum pallidum, T. inflexum, Barbula unguiculata, Ceratodon 

 purpureus, Eustichium Norvegicum, Orthotrichum fastigiatum, Hedwigia ciliata, 

 Entosthodon acuminatum, E. ericetorura, Bryum pyriforme, B. nutans, B. torques- 

 cens, B. pallescens, Mnium punctatum, Bartramia pomiformis, B. fontana 1 Atri- 

 chum angustatum, Pogonatum aloides, P. alpinum, Polytrichum juniperinum, P. 

 commune, Hypnum scitum, H. minutulum, H. Starkii, H. crassinervium, H, popu- 



