ires, which raise or sublime
the more subtle parts of the bituminous matters contained in rocks. Many
springs in the territory of Modena and Parma, in Italy, produce
petroleum in abundance; but the most powerful, perhaps, yet known, are
those on the Irawadi, in the Burman empire. In one locality there are
said to be 520 wells, which yield annually 400,000 hogsheads of
petroleum.[332]

_Pitch lake of Trinidad._--Fluid bitumen is seen to ooze from the bottom
of the sea, on both sides of the island of Trinidad, and to rise up to
the surface of the water. Near Cape La Braye there is a vortex which, in
stormy weather, according to Captain Mallet, gushes out, raising the
water five or six feet, and covers the surface for a considerable space
with petroleum, or tar; and the same author quotes Gumilla, as stating,
in his "Description of the Orinoco," that about seventy years ago, a
spot of land on the western coast of Trinidad, near half-way between the
capital and an Indian village, sank suddenly, and was immediately
replaced by a small lake of pitch, to the great terror of the
inhabitants.[333]

It is probable that the great pitch lake of Trinidad owes its origin to
a similar cause; and Dr. Nugent has justly remarked, that in that
district all the circumstances are now combined from which deposits of
pitch may have originated. The Orinoco has for ages been rolling down
great quantities of woody and vegetable bodies into the surrounding sea,
where, by the influence of currents and eddies, they may be arrested and
accumulated in particular places. The frequent occurrence of earthquakes
and other indications of volcanic action in those parts lend countenance
to the opinion, that these vegetable substances may have undergone, by
the agency of subterranean fire, those transformations and chemical
changes which produce petroleum; and this may, by the same causes, be
forced up to the surface, where, by exposure to the air, it becomes
inspissated, and forms the different varieties of pure and earthy pitch,
or asphaltum, so abundant in the island.[334]

It may be stated generally, that a large portion of the finer particles
and the more crystalline substances, found in sedimentary rocks of
different ages, are composed of the same elements as are now held in
solution by springs, while the coarser materials bear an equally strong
resemblance to the pebbles and sedimentary matter carried down by
torrents and rivers. It should also be