240 Native Bitumens and the Pitch Lake of Trinidad. [April, 
glace. The asphalt becomes harder the longer it is exposed to 
the air and the sun, through loss of its volatile ingredients, and con- 
sequently the downward progress of the “black glaciers” must 
sooner or later be checked, if: not entirely stopped.. It seems 
impossible to determine the extent of the overflow, for although 
the entire slope from the lake to the sea appears as a continuous 
stratum of pitch, the soil being everywhere very thin or entirely 
wanting, yet it is probable, as pointed out by Messrs. Wall and 
Sawkins, that the most of this superficial sheet has exuded from 
the asphaltic sandstone—a sandrock supersaturated with asphal- 
tum—which forms the rocky basis of that portion of the ridge 
where the free asphalt is found. The area covered or underlaid 
by this mantle of pitch is estimated at 3009 acres. 
The bitumen is certainly not injurious to plant life, for the scanty 
soil covering the pitch, and consisting largely of that material 
in a pulverulent state, supports a luxuriant vegetation. The vil- 
lage of La Brea, on the shore, with the boiling houses where the 
asphalt is refined, rests on the pitch; and the inhabitants com- 
plain that their houses are liable to be thrown out of level by the 
rising or sinking of the tarry foundations. It seems as if every- 
thing superficial here, vegetation, houses, roads, etc., must be 
slowly but surely drifting toward the sea. 
“It is fortunate,” as one writer has remarked, “that the pitch 
when compact will not kindle, or in other words will not burn 
without a wick, for otherwise the entire region, npinding the 
village, might suffer the fate of Sodom and Gomorrah. 
The pitch not only forms the sea-shore for the greater part of a 
distance of four miles, but in front of the village it appears from 
beneath the sea as a solid barrier reef some hundred yards from 
the shore, which is a source of danger to unwary boatmen when 
the water is rough. It is probable that this peninsula of La Brea 
owes its existence to the protection afforded the land by the 
asphalt, which resists the action of the waves and running water 
far better than the unconsolidated clays and sands forming the 
coast to the north and south. 3 
We may now return to the fountain head, the lake. Of the 
various published descriptions of this remarkable phenomenon, 
there are very few that can justly lay any claim to accuracy, and 
strange to say these are not to be found in encyclopedias, nor 
even in our best text books of science. Probably no object in 
1 Report on the Geology of Trinidad. 
