Defcriptlon of a nezv Hygrometer. 1 6"] 



it points to. Both thefe inventions are for the fame purpofe 

 as the winding hygrometer, which is to avoid the confufioa 

 occafioned by the oat-beard having more than one turn or 

 twift in its courfe from wet to dry. 1 remain, Sir, 



Your very humble Servant, 



B. M. FORSTER. 

 Dtfcripthn of the IVinding Oat-beard Hygrometer. 



■ The principal differences in this hygrameter from thofe 

 ufualiy made of oat-beards are the following: 

 . The graduated circle (i'iate V. lig. 2.) is numbered cow- 

 pletely round, inftead of half round each way, as ufual. On 

 tlie top of the oat-bc;ird * is cemented a circular piece of pa- 

 per A, on which is fixed a tubular piece of (iraw B, which is 

 capped with another piece of paper C. D is a fupport to 

 keep the beard upright, made of card paper. On the (traw 

 tube, or little cvlinder, is faften.ed a piece of fine filkcn ftring, 

 on which is hung a pea, to ferve as a weight to keep the 

 ilring liretched. "As the oat-beard untwilts with moiliure, 

 the index (made of draw) moves the fame way round as 

 the hand of a watch, and, thus moving, coils the firing round 

 the ftraw tube or axisj bv which means the number of rcvo- 

 kitions from anv lime oblerved may be known; and thus the 

 confufion will be avoided which is occafioned by the index 

 niovina more than once round, which it does in paffing from 

 extreme (.Irvnefs to wet. 



The firing may be fo placed as to wind up when the index 

 moves the contrary way, that is, from moifl to dry, if the 

 maker fo choofes ; and in this cafe, the circle mufl be num- 

 bered the contrary wav from the above. 



The oat-beard xhfxed, and the index is not to be turned 

 or let to a certain point, as is the caie with the common hy- 

 grometer, by a contrivance behind the cafe. 



The method of keeping a regifter of this hygrometer will 

 be thus: 



When on the upper part of the axis there is 

 One coil, and the index points at 6, fet down i — 6 

 Two coils - - 6 - 2 — 6, Sec. 



If the circle be divided into loo divifions, the reckoning will 

 be, No coil, and the hand at lO, fet down to 

 1 coil - - JO - 110 



a coils - - iQ - 2IO, Sec. 



which, if the circle be large enough, will be a very conve- 

 nient mode of regiltt-ring. 



• The beard of tiic <.v/),,.y/ir//.'/ (of I.inivTiusJ, whicli, on acccunt t.f 

 Ub (j/cc, IS preferable lu rhc bcar^i of tliu coiiunun oat. 



L4 XXXI. HIjIq- 



