186 PROCEEDINGS OF THE AMERICAN ACADEMY 



Professor Lovering read the following communication, 

 viz. : — 



" Remarks on the Aneroid Barometer, by Professor J. Lovering, 



of Harvard University, 



"Most of the scientific journals of Europe and America have pub- 

 lished descriptions of the new French barometer, as it is called. For 

 the construction of the instrument, and the history of its invention, I 

 may refer to them ; and particularly to that contained in Silliman's 

 Journal for September, 1849. 



"The two ordinary statical ways of measuring forces are, first, by 

 means of gravity, and, second, by means of elasticity. Our common 

 balances to measure weight employ, either the gravity of a known 

 counterpoise, or the elasticity of a spring. In like manner, the weight 

 of a column of the atmosphere is determined by ascertaining the 

 height of a similar column of some known fluid, which it is able to 

 support, or the elasticity of some familiar substance with which it is 

 in equilibrium. The barometer with which we are most familiar 

 employs the first method : the aneroid barometer, which, as its name 

 implies, contains no liquid, is based on the last principle, namely, that 

 of measuring weight by elasticity. 



" This new instrument is already manufactured, in large numbers, 

 in France and Great Britain ; and its adoption is recommended on the 

 ground of economy, as well as of its great compactness. The barome- 

 ter is now extensively used, not only for tracing out the grand laws of 

 meteorology, but also as a practical guide to the mariner to forewarn 

 him of approaching storms, and an indispensable auxiliary to the man 

 of science in studying the geography of the solid parts of our planet. 

 It is highly important that the meteorologist, the navigator, and the 

 student of general science, should know what degree of accuracy may 

 be claimed for the new barometer, and to what extent they are allowed 

 to trust themselves to its indications. With the hope of assisting those 

 who desire to form an opinion on this subject, I present the following 

 experiments and observations, undertaken originally at the suggestion 

 of Professor A. D. Bache, Superintendent of the United States Coast 

 Survey. The instrument employed in this research was furnished by 

 Professor Bache. It bears the number 1265, and came from the 

 establishment of Lerebours and Secretan, Paris. 



