30$ Extracts from ike third Volume of 



choucj possesses a remarkable property, from which it 

 derives its name, and which distinguishes it in an eminent 

 degree from all other com.bustible minerals. Messrs. Hat- 

 chett and Scherer have described fifteen varieties of it ; the 

 first of which are still impregnated in part with fluid oil of 

 petroleum, and the latter have a resemblance to asphaltum, 

 completely hard and brittle, \\ hile the inttrmediate varieties 

 possess more oT less the elastic property. We must still 

 distinguish a new kind, found a itw years ago in a small 

 river situated near that mine, which difters frona the pre- 

 ceding by a more spong)? elasticity, and by other proper- 

 ties. It approaches to the nature of cork, and Mr. 

 Hatchett found five varieties of it. 



]st, The fossil elastic resin, in compact fragments, 

 greenish brown olive, which, when looked through towards 

 the light, is transparent, and appears of a bright red hya- 

 cinth colour. This fossil is soft^ exceedingly elasticj and 

 adheres to the fingers. 



2d, Dark brown fossil elastic resin, ■<vhichhas for gangue 

 crystals of sparrv gray swinestone. 



3d, Yellow and red bright hyacinth, inclosed m small 

 jnas5!es in groups of sparrj^ calcareous fluor. 



4th, Dull reddish brown, of a spongy, or cork -like tex- 

 ♦urej containing blackish gray nuclei of impure caout- 

 ■ehouc. 



The caoutchouc subjected to experiment by M. Klaproth 

 was the first variety of this new species. This fossil is one 

 of those bodies the analysis of which can be effected only 

 in the dry way 5 and, consequently, the immediate princi- 

 ples of it cannot be extracted. 



Exp. I. Fossil caoutchouc resists, in general, the ac- 

 tion of all fluid solvents. The one which appears to have 

 any is rectified oil of petroleum. Fragments of fossil 

 caoutchouc, immersed in this oil, were at the end of some 

 days swelled up a little and more transparent. The oil, 

 vhich wa9 colourlcss>, had acquired a bright yellow colour. 



The red vapours of fuming nitric acid, poured over an- 

 other part of caoutchouc, heated in a sand bath, soon gave 

 place to white vapours of nitric acid, which were disen- 

 gaged till it was almost entirely evaporated ; which proves 

 that there was no reciprocal action between the fossil and 

 the acid. The resin, when washed^ showed no sensible 

 mark of alteration. 



The action of alkalies is as ineffectual as that of acids. 

 Sixteen parts of concentrated solution of potash, boiled for 

 sonic time with cue part of this elastic resin till it almost 



actpireJ 



