396 A PLAN OF A RESEARCH UPON THE ATMOSPHERE. 



habits, generally hiding under stones, on walls, &c., during the day, and during 

 the night huriting their food, which consists of flies, gnats, and other small in- 

 sects. They do, however, sometimes hunt during even the brightest part of the 

 day. They should be collected during the latter part of the summer and the 

 early autumn, because at that time they are mature. The collector sliould look 

 for them on the walls, and about the eaves of barns and out-houses, along stone 

 and other fences, beneath stones in dry or even moist gravelly places, under 

 sticks, fence-rails, logs, and the like in dry, grassy groves. In catching them 

 care should be taken not to break their legs, and they should be dropped into a 

 bottle containing very strong whiskey or ordinary alcohol, or spirits of wine. 

 When practicable each species should be preserved separately in homoeopathic or 

 other small phials, and an accurate account be kept of the localities in which 

 they may be captured, and any observations on their habits will be especially 

 valuable. After they have been put in spirits, no further care is necessary, ex- 

 cept to see that the alcohol does not evaporate and leave them dry. 



Hoping that you will be able to obtain collections, I remain yours, respect- 

 fully, 



H. C. WOOD, Jr., M. D. 



Professor Henry. 



[The Institution will be pleased to receive from its correspondents the speci- 

 mens asked for by Dr. "Wood, to be placed in his hands for investigation. 



J. H.] 



A PLAN OF A RESEARCH UPON THE ATMOSPHERE. 



BY PROF. C. M. WETHERILL. 



Washington, D. C, July 24, 1865. 

 Dear Sir : I beg leave to submit to your consideration the accompanying 

 sketch of a plan for securing the advantages of a research upon the atmosphere 

 in our country, which would be not only new, but fruitful of important practical 

 results. The work upon which I was engaged last winter, viz., the ventilation 

 of the Capitol extension, has impressed me with the necessity of this research, 

 and I hope that it will meet your approval. 



I am, very respectfully, your obedient servant, 



CHARLES M. WETHERILL. 



Prof. Joseph Henry, Secretary Smithsonian Institution. 



The need of a researchufon the proportion of carhonic acid (and oxygen) in tJie 

 atmosphere of the United States. 



Plants require carbonic acid, animals oxygen, for their existence ; hence an 

 accurate determination of these constituents in the atmosphere is of vast im- 

 portance, and the knowledge gained from such a research is of great value, both 

 from a scientific and a practical point of view. The question has engaged the 

 attention of scientists (in Europe) from the earliest period of modern chemistry, 

 and its discussion has advanced step by step with the improvement of the 

 methods of analysis. Through the labors of Gay Lussac, Humboldt, De Saus- 

 sure, Dumas, Boussingault, Lewy, Schlagintweit, and others we are acquainted with 



