METEOROLOGY. 73 



deepest interest in the Society and are impatiently waiting for its publi- 

 cation. 



The members of the Society have been honored with the notice of 

 learned associations, both at home and abroad. Nearly all are corre- 

 sponding members of the highest scientific Society in our country, and 

 two of them have been honored with diplomas from Europe. 



The libraries of several members are rich in Entomological works, 

 and valuable additions are annually made. These books are costly, but 

 they are always free to the use of the members, and are considered pret- 

 ty much as common property, so far as the unrestricted use of them is 

 concerned. 



It will be the next business of the Society to study and describe our 

 numerous nocturnal lepidoptercij which have not yet been noticed by 

 previous authors. Here a wide field is open for cultivation, but, we have 

 no doubt, the work will be thoroughly done. 



A monograph of the diurnal lepidoptera has been prepared by one 

 of the members, which was accepted by the National Institute at Wash- 

 ington, for publication in their Bulletin, but was subsequently withdrawn 

 by the author, for further investigation. It has also been requested for 

 publication, by the editor of a northern Scientific Journal of great cele- 

 brity, and may appear in the course of next summer. 



Thus has this Society labored. Though very few in number, yet 

 their operations have been extended and, hitherto, successful. We hope 

 that they will soon find many colaborators in the delightful science of 

 Entomology. Entomophilus. 



METEOROLOGY, NO. IV. 



BY PROF. JACOBS, OF PENNSYLVANIA COLLEGE. 



Of the existence of moisture in the atmosphere. 



Previous to the discussion of some other points in meteorology, 

 which we intend taking up, it is deemed best to make the following pre- 

 liminary statements : 



1. The extent of the atmosphere. It is found by observation, that the 

 density of the air diminishes by a regular law as we ascend from the 

 earth. Thus the barometer., which measures the pressure and conse- 

 quently the density of the air, gives notice of our elevation above the 

 sea-level, by the descent of the mercury in its tube. A depression of 

 one inch corresponds to an ascent of 922 feet when the air has a tem- 

 perature of 62^. At an elevation of about 2i miles, the barometric col- 

 umn will have sunk to one half of its original height ; consequently, near- 

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