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Page:Popular Science Monthly Volume 81.djvu/26

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THE POPULAR SCIENCE MONTHLY

PSM V81 D026 Trinidad pitch lake.png

Photo, C. R. Toothaker, Phila. Commercial Museum.

Trinidad Pitch Lake.
 

The shape and structure of the long promontories which have been mentioned reveal the fact that Trinidad is, structurally, intimately connected with the mainland. This is proved by the geology and fauna of the island, the latter corresponding closely to that of the mainland and the geological structure being a continuation of that of the continent. Its climate is entirely tropical and somewhat different from that of the remaining Antilles in this respect.

Trinidad was discovered by Columbus on his third voyage in 1498 and taken possession of in the name of Spain, which colonized it about ninety years after. In 1797 it was taken by Great Britain, and has remained since then one of her most important West Indian colonies, and the second in size.

The Island of Trinidad, while not directly connected with the chain of islands of volcanic origin known as the Windward or Caribbean Islands, is directly on the great line of volcanic disturbances running from these to the continent of South America and its volcanic regions. Many cf the Windward Islands are still possessed of active vents, so that Trinidad may be looked upon, with its thermal springs and pitch deposits, as being situated at the lowest point between the mountainous volcanic chains of the West Indies and those of South America. More than two thirds of the surface is of Tertiary or recent origin, including the entire southern portion, where the pitch deposits are located. The formations consist of clay, loose sand, shales, limestones, calcareous sandstones, indurated clays, porcelainites of brilliant colors, with pitch deposits here and there. The beds have been considerably disturbed and have at times a large dip. In a series of sands, clays and shales lies the pitch lake.

While there are deposits of pitch scattered all over the island, the only ones of commercial importance are those situated on La Brea Point,