1853.] 315 



there this banking up of the water before it reached the rock, but there was 

 also a depression above that is, up stream from this bank of water on the one 

 hand, and below or down stream from the rock on the other. 



*' In like manner it appears to me, that Herndon's observations have revealed 

 the fact that there is, at times at least, in the intertropical atmosphere of South 

 America, an air-cast mould of the Andes. 



" It is remarkable how clearly these observations indicate a piling up of the 

 atmosphere to the windward of the Andes, and a depression in the general at- 

 mospherical level to the windward again of this air bank. If this conjecture 

 afford the real explanation of the phenomena, we should look on the lea side of 

 the Andes for a low barometer, or a depression in the atmosphere, corresponding 

 to the hollow in the water below Pot Rock. 



"The mean height of the Bar in Lima, as far as I have been able to ascertain 

 it, indicates that such a depression is felt there. 



"If subsequent observations should confirm these indications and establish them 

 as realities, we should then be put in possession of important physical facts. 

 We should be led to infer that the height of mountains, and of mountain slopes 

 above the sea level, as determined by the barometer, would depend somewhat 

 upon which way the wind blows, and the only safe rule of admeasurement in such 

 cases, would be to establish a standard barometer at the foot of the mountains, 

 both in the windward and the lea side. 



"Another of the physical facts besides that of establishing the direction of the 

 wind, as a function in barometric determination is, that if this increased pressure 

 of the atmosphere at the eastern foot of the Andes be caused by the obstruction 

 which that range of mountains affords to the passage of the trade winds, then do 

 those mountains in the trade wind region become a nataral anamometer, which 

 will give us in terms of the barometer an expression for the whole amount of 

 force employed in giving motion and velocity to the trade winds of the earth." 



ELECTION. 



J. Dickinson Logan, M. D., and Mr.Trederick Schafhirt, of Philadel- 

 phia, and Mr. P. W. Sheafer, of Pottsville, were elected Members of 

 the Academy, and 



Dr. H. Schaum, of Berlin, Dr. G. Hartlaub, of Bremen, and Prof. A. 

 Wagner, of Munich, were elected Correspondents. 



April 12th. 

 Vice-President Bridges in the Chair. 



A communication was read from the Historical Society of Pennsyl- 

 vania, dated March 17th, 1853, acknowledging the receipt of the last 

 number of the Journal, and of a collection of Indian antiquities pre- 

 sented by the Academy. 



Mr. Conrad presented a paper for publication in the Journal, describ- 

 ing new species of Unio ; which was referred to Dr. Ruschenberger, 

 Dr Wilson and Dr. Zantzinger. 



A second paper from Mr. Conrad was also presented, intended for 

 publication in the Proceedings, entitled, *' Monograph of the genus 

 Fulgur.'' Beferred to same Committee. 



