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II. Description of an improved Hygrometer. By Mr. Thomas 

 Jones. Communicated by Captain Henry Kater, F. R. S. 



Read June 16, 1825. 



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Xhe attention of the scientific world has been lately so 



much occupied in experiments on atmospheric phenomena, 

 that it is hoped any simplification or improvement in the 

 instruments emplojed for that purpose, may not be unac- 

 ceptable. 



The principle of the hygrometer which I am about to 

 describe, is that of enabling the observer, readily and accu- 

 rately, to ascertain by direct and simple means, the degree of 

 temperature at which the moisture of the atmosphere is con- 

 densed, and the instant at which that operation commences. 



The hygrometer is composed of a mercurial thermometer, 

 the graduated scale of which is about four inches and a half 

 long ; at the lower part of the scale the glass tube is bent 

 to form a right angle, at the end of which the bulb of the 

 thermometer rises parallel to the scale, and about one inch 

 from it ; the bulb is about one inch long, and of a cylindrical 

 form, with a black convex top, the diameter of which is a little 

 more than that of the cylindrical part, which is covered with 

 silk. The scale is attached to a piece of cylindrical wire, 

 three inches long, and turns upon a joint screw passing into 

 its edge, the other end of which wire being placed in a 

 tubular foot fixed to the inside of one end of the case, forms 



