S. Ff. Peckham—Pitch Lake of Trinidad. 49 
Asphalt is very inert to changes of temperature. It isa 
very poor conductor cf heat, and even under a tropical sun, 
the daily surface changes of temperature and consequent 
expansions and contractions are wholly inadequate to produce 
conditions affecting such enormous masses of material as the 
crater contains. 
The frequent use of the term “volcanic” in connection 
with the supposed origin of this mass of bitumen is in my 
judgment misleading. With the term volcanic is usually asso- 
ciated streams of melted lava, scoria and pumice. The masses 
of porcellanite and jasper mentioned by all observers as found 
in the neighborhood of the lake, do not require for their origin 
any “subterranean fires.” It only requires that hot water, 
holding silica in solution under high pressure, shall percolate a 
bed of clay. The distillation of beds of lignite, requires noth- 
ing more. In one case the product is red or yellow jasper, in 
the other a deposit of bitumen. The less the pressure, the 
more dense will be the bitumen. Water will inevitably bring 
the bitumen to the surface, unless it is held down by impervi- 
ous strata. If the water accompanied by bitumen, encountered 
in its upward passage such strata, as have been described by 
Mr. Guppy, a mud voleano yielding bitumen would be the 
inevitable result. It appears to me that all of these conditions 
are present in and about the pitch lake. They are exactly the 
conditions that have produced enormous tar springs and asphalt 
beds in California, excepting that there the strata necessary to 
prodnce mud volcanoes are wanting, but the porcellanites, the 
hot springs, the sulphur springs, and the bitumen, are all there, 
and in some localities on a scale that vies with Trinidad. 
I looked in vain for specimens of wood in process of trans- 
formation into asphalt. I enquired of many intelligent men, 
and others connected with mining the pitch, if they had ever 
seen such specimens; they invariably answered “no.” Two 
or three remarked that the wood never decayed in the pitch, 
that it came out as it went in. One man replied that, “if it 
went in rotten it came out rotten.” I saw in several excava- 
tions along the tramway masses of vegetable matter that 
appeared to have been converted into humus, and was told by 
the workmen that in time these masses would become incor- 
porated with the pitch. Such masses account for the organic 
matter in solution in the lake water, and also for the amor- 
phous organic matter not bitumen, observed by Mr. Richard- 
son. 
so much silica, I would suggest that the hot water that distilled the bitumen, 
might have held silica in solution, which has been precipitated within the pitch as 
it has cooled. The fact, if it be a fact, that so much silica exists in the pitch as 
hydrate, may account for the large amount of water held in the pitch. 
Am. Jour. Sci.—THIRD SERIES, ‘Vo. L, No. 295.—Juty, 1895. 
4 
