Propofal for a ne<W Hygrometer* §69 



adheres to them. Such a thread will fuftain a weight of fix 

 pounds without breaking ; and may be ufed for an hygro- 

 meter in the fame manner as cat-gut. Paper, parchment, 

 wood, ivory, hair, and the beard of wild oats, &c. have 

 been employed for hygrometers on the fame principle. 



Another fort of hygrometer is founded ort the increafe of 

 Weight which certain bodies acquire by the moifture they 

 attract from the atmofphere. Thus, for example, if a fponge 

 which has been dipped in a folution of fal ammoniac, and 

 again dried, be fufpended in the open air at the end of a ba- 

 lance, the variation of its gravity marked by a weight placed 

 at the other end will fhew the temperature of the atmofphere 

 in regard to drought and moifture. 



Mr. Lowitz found at Dmitriewfsk in Aftracan, on the banks 

 of the Wolga, a thin blueifh kind of ilate which attracted 

 moifture remarkably foon, but again fuffered it as foon to 

 efcape. A plate of this fiate weighed, when brought to a red 

 heat, 175 grains, and, when faturated with water, 247: it 

 had therefore imbibed, between complete drynefs and the 

 point of complete moifture, 72 grains of water. Lowitz fuf- 

 pended a round thin plate of this ftate at the end of a very 

 delicate balance, faftened within a wooden frame, and fuf- 

 pended at the other arm a chain of filver wire, the end of 

 which was made faft to a Aiding nut that moved up and 

 down in a fmall groove on the edge of one fide of the frame* 

 lie determined, by trial, the pofition of the nut when the 

 balance was in equilibrio and when it had ten degrees of 

 over-weight, and divided the fpace between thefe two points 

 into ten equal parts, adding fuch a number more of thefe 

 parts as might be neceflary. When the ftone was fufpended 

 from the one arm of the balance, and at the other a weight 

 equal to 175 grains, or the weight of the ftone when per- 

 fectly dry, the nut in the groove (hewed the excefs of weight 

 in grains when it and the chain were fo adjuftcd that the 

 balance ftood in equilibrio. A particular apparatus on the 

 fame principles as a vernier, applied to the nut, {hewed the 



Vol. I. Bb excefs 



