in the Island of Trinidad. 255 
ture naturalists of examining so remarkable and interesting a 
place, with proper leisure and attention, 
I remain, dearsir, your most obedient servant, 
P J. Tonrx. 
Charles Hatchett, Esq. ae 
Observations by Mr. Hatchett. 
From the BRE letters, as well as from the account pub- 
lished by Dr. Anderson in the Philosophical Transactions for 
1789, we learn, that the lake of bitumen in the island of Trini- 
dad. (known by the name of the Pitch- or Tar-lake, and called 
by the French: La Bray) is of considerable extent, and of an 
unknown depth *. Moreover, it appears that the general mass 
which forms this lake has been hitherto considered as simple bi- 
tumen more or less indurated. Dr. Anderson, however, observes, 
that he “ could make no impression on its surface without an 
axe, although at the depth of a foot he found it a little softer, 
with an oily appearance, in small cells." This degree of hard- 
ness certainly seems much more considerable than that of the 
unmixed indurated bitumens, and naturally leads toa suspicion, 
that the greater part of the bituminous mass in Trinidad is not 
(as has been supposed) simple mineral pitch | or asphaltum. 
Upon examining the specimens which Mr. Tobin had obliging- 
: ly sent to me, I found many of them very hard and difficult to 
- break; and when broken, they did not exhibit the lustre nor the 
conchoidal fracture of the simple bitumens. "The remaining spe- 
| cimens also, although easily broken, possessed still less of. the 
— —- # Philosophical Transactions, 1789, p. 67. t Ibid. di. 3b 
| puse 
= 
