IMPROVED HYGROMETER. £ \ \ 



tvith data from which to calculate the true, noting at the 

 same time the hygrometer, barometer, and thermometer , 

 perhaps some law might be discovered, which might enable 

 us to ascertain the quantity of the effect of moisture on re- 

 fraction. It was with this view the hygrometer above de- 

 scribed was constructed ; but not having yet had an oppor- 

 tunity of obtaining the requisite observations, it is to be 

 hoped they may be made by those, who are in possession 

 of time and instruments equal to the undertaking. 



X. 



Description of an improved Hygrometer. By Lieutenant 

 Henry Kater, of his Majesty's 12th Regiment*. 



s 



INCE I had the honour of laying before the Asiatic Improvement 

 Society " a description of a very sensible Hygrometer," I ° n f '£* p ™™^ 

 have attended much to the improvement of the instrument, ter. 

 and am induced to think that some farther account of it 

 may not be deemed wholly unacceptable. 



The principal objection to the hygrometer described in 

 my former paper arose from the necessity of shortening the 

 beard of the oobeena hooloo, in order to reduce the scale to 

 a convenient length ; this was to be obviated only by giving 

 . the instrument a circular form, and inventing some mode 

 of ascertaining without difficulty the numbpr of revolutions 

 made by the index. 



A 15 C D, (PI. VI, fig. 5) is a frame, made of small Decryption of 

 square bars of brass or silver ; this frame is soldered to a the imp 1 " *** 

 square plate B E, the edges of which are turned up, as m$trume 

 represented by the dotted lines, to secure the index from 

 injury : on the face of the plate is engraved a circle (see 

 fig. 8) which is divided into one hundred equal parts. Three 

 holes, a, b, c, are made through the frame and plate in the 

 same direction ; the holes a and b, are of a conical form as 

 represented by the dotted lines, and are highly polished to 

 lessen friction ; the hole at c receives a screw, one end of 

 which is tapered, and has a notch cut in it with a fine saw, 

 which may be closed by means of the sliding ring d. 

 * Ibid, p. 394. 



P2 The 



