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XXXVI. — Description of two New Philosophic 

 col Instruments, 



By Alexander Adie, F. R. S. E. & M. W. S. 

 (Read 3d April 1819J 



In the following paper I propose to describe, first, 

 A new instrument under the name of Sympiesome- 

 ter, for ascertaining the changes in the pressure of 

 the atmosphere; and, %dly 9 A Hygrometer, in 

 which the smallest variation of moisture and dry- 

 ness are indicated. 



I. — Sympiesometer. 



My attention was first directed to the improve- 

 ment of the Barometer, with the view of rendering 

 it susceptible of indicating any of those minute 

 changes in the weight of the atmosphere, which 



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