ACADEMY OF SCIENCES. 185 



Survey, and the results obtained indicate very clearly that valuable assistance 

 will be derived from the completed series in the reduction of the copious ba- 

 rometric determinations of altitude made during the progress of the Survey. 



Regular Meeting, September 4th, 1871. 

 Professor Davidson in the Chair. 



Donations to the Cabinet : Mr. Stearns presented an egg case 

 of the Ephemera vulgata, (caddis-fly) England ; specimens of 

 Chinese coral ; two new species of shells, Florida ; fossil Inocer- 

 amvs, from Butte county. 



Professor Henry presented the result of the observations which 

 had I een made and collected by the Smithsonian Institution on the 

 rainfall of the country, an account of which is now in process of 

 publication. 



The rainfall of the United States comes from three different quarters, the 

 Atlantic, Gulf of Mexico and the Pacific. Perhaps the largest comes from 

 the Gulf of Mexico— the bottom, as he termed it, of the trade wind. Although 

 nothing appears more irregular than the rains in the Eastern States, a long se- 

 ries of observations establishes the fact that they are very regular. 



The speaker explained briefly the operation of the law by which rarified va- 

 pors are carried into upper and colder regions, and there precipitated. He ex- 

 hibited several charts, showing on what months the maximum and minimum 

 of rainfall was observed to occur in different localities. He also displayed a 

 number of tl.e latest compiled charts, showing by graduated colors the com- 

 parative amount of the rainfall in various localities. He explained the fact of 

 the rainfall being wholly absent in Oregon in summer, and heavy in winter, by 

 saying that in summer the return trade wind swept the country at the north- 

 ward, and in winter it swept over Oregon. In Florida the rainfall was light 

 in winter and heavy in summer, owing to the fact that in winter the trade 

 wind which brought the rain took its course more to the southward. The 

 temperature of Sitka was about seventeen degrees warmer than it would other, 

 wise be, from the fact that the summer trade wind does take its course 

 there. 



Mr. Stearns read the following article : 



