in the Red Lead of b:Vcrla. 36/ 



with metallic oxydes, and of its oxyde with vitreous Jub- 

 ilances, will fumiih very beautiful and durable colours for 

 the art of painting and enamelling. This hope appears to 

 me fo much better founded, as I have already difcovered the 

 t>xvde of this metal in the emerald, in which it forms the 

 colouring principle. I have alio found it in the matrix of 

 the red lead, in the ftate of a green oxyde combined with 

 the lead; and I have no doubt that it may be found m 

 many other combinations, when minerals ihall be examined 

 with more care than they have hitherto been. 



It refults then that chrome is a peculiar metal before un- 

 known; that this metal, infufible and cryftallifable, has little 

 affinity with oxygen, from which it derives however two 

 thirds of its weight ; that this acid of a red colour diffolves 

 in water and combines with alkalies, earths and metals, to 

 which it communicates different colours, but more or left 

 analogous to its own; that it readily lofes a part of its oxygen 

 either by light, caloric, or the contact of certain metals, and 

 the greater part of combuftible fubiiances, by pafling through 

 all thefe circumffances to the ftate of a green oxyde ; and 

 hence it is that this acid and all its combinations yield, by 

 heat, .a certain quantity of oxygen, and communicate to glafs 

 a beautiful green colour. 



VI. Prcpofalfora new Hygrometer. By Mr. UuCEH£JMZR. 

 From Economifehe Hefte. 



VARIOUS hygrometers have been invented, but they 

 .are all in fome degree imperfect: ift, becaufe they do not 

 determine with accuracy in what proportion water isdiflblved 

 iu the atmofphere ; and 2dly, becaufe they do not fuller the 

 moifture they have imbibed to efcape from them in the fame 

 proportion as that in which they attracted it. I mall, there- 

 fore, mention in a brief manner only a few cf them, and then 

 propolea new method of conftruenng a hygrometer; though 

 1 mult, at the fame time, remark, that I by no means offer 



it 



