Page:Popular Science Monthly Volume 58.djvu/242

234 between a range of mountains and the shore o tone of the estuaries that enter the northern part of the delta of the Orinoco from the Bay of Paria. The lake has an irregularly shaped surface, about one mile and a half by one mile in dimensions, giving an area of something less than 1,000 acres. This area is covered with rank grass and shrubs, from one to eight feet in height, with groves of large Moriche palms. There is no extended surface of clean pitch as at Trinidad; but instead, at certain points, soft pitch wells up as if from subterranean springs. As the general surface of the deposit is not more than two feet above the surrounding swamp, in the rainy season it is flooded, and at other times so low that any excavation will immediately fill with water.

Instead of being more than a hundred feet in depth as at Trinidad, this deposit is a shallow exudation from numerous springs, over a wide surface, from a mere coating to from seven to nine feet in depth, the average being perhaps four feet. The largest of the areas covered with soft pitch is not more than seven acres in extent. The soft material has become hardened in the sun at the edges, but at the center is too soft to walk upon, in this respect resembling many of the deposits of less extent in California. This pitch is also too soft to hold permanently the escaping gas, as at Trinidad, but when covered with water it ri>es in mushroom-like forms.

Some of these areas have been burned over, producing from the combustion of the vegetation and of the asphaltum itself an intense heat that has converted the bitumen into coke and glance pitch. When this crust of hardened material is removed, beneath it is found asphaltum that may be used for paving.

Under the classification that I have adopted, the bitumen of the Bermudez deposit is nearly pure asphaltum, which has been formed by. the heat of the sun and by fire, from an exudation of maltha, or mineral tar, over a wide expanse, beneath the coke and other products of combustion, while here and there are masses of glance pitch, which are the result of less violent action of heat.

Many of the West India islands, from Trinidad around to Cuba, contain deposits of asphaltum. The most noted among them are the Mumjack of Barbadoes and the asphaltum veins of Cuba. These, however, have not entered commerce, with the exception, perhaps, of the very pure asphaltum found in Cardenas harbor, which is obtained in limited quantities and is used in varnish-making. None of these are used in paving.

In Mexico there are very extensive deposits of asphaltum of great purity, but up to the present time they have not entered commerce.

In Texas, and extending into the Indian Territory, there axe large deposits of both siliceous and calcareous asphaltes. In Uralde county, Texas, near Cline, to the west of San Antonio, on the Southern Pacific