258 Mr. HaTcuzrTT's Observations on the Pitch-lake 
only partially impregnated with it: but, as a conjecture, I shall 
venture to say, that I suspect it to be of the nature of the 
stone which is found with bitumen in Auvergne, and which is 
called by Born “a grayish compact lava *." 
The analysis of the stone of Trinidad which remains after the 
separation of the bitumen, accords with the prevalent soil of the 
island; for Dr. Anderson states that * the soil in general, for 
some distance round La Bray, is cinders and burned earths ; and 
where not so, it is a strong argillaceous soil." p. 69. In the latter 
part of the same page he also says, “ From every examination I 
have made, I find the whole island formed of an argillaceous 
earth, either in its primitive state, (by which he probably means 
common clay,) or under its different metamorphoses. ‘The bases 
of the mountains are composed of Schistus argillaceus and Tal- 
cum lithomargo." In almost all the species of the argillaceous 
genus, silica is known to predominate; and the stone impregnated 
with bitumen, which has been mentioned, evidently appertains 
to that genus, so asin some measure to approach the nature, 
but not the texture, of the bituminous slates. It is, however, 
remarkable, that in the more compact specimens of this sub- 
stance the bitumen so completely disguises the character of the 
stone, that it may easily be, and indeed has been taken for a va- 
.riety of asphaltum. 
Ihave already stated, that I have seen specimens from Trini- 
dad which exhibited the various gradations of petroleum into 
real asphaltum ; and from Dr. Andersons account, the liquid 
bitumen: or petroleum i is occasionally found: But this, as well - 
* Cube. de la Collection des Fossiles de Mademoiselle de Raab, tome i li. p. 77- 
+ Besides this place (La Bray) where it is found in this solid state, it is found 
liquid in many parts of the woods; and at the distance of twenty miles from this, about 
` two inches thick, in round boles of Hiree. or four inches. quunt and often at cracks or 
coim Tents. 
