ART. IV. On the Pitch Lake of Trinidad; by S. F.
PECKHAM.

AT the risk of saying a superfluous word, I am led after a recent visit to Trinidad, to add my testimony to that of the numerous observers, who for more than a hundred years have written concerning this remarkable phenomenon.

The earliest account of a visit to Trinidad, accessible to English readers, was published in the Transactions of the Royal Society of London in 1789, by Alexander Anderson.* He describes point La Brea as a promontory fifty feet high jutting into the Gulf of Paria. Ascending to the Lake he describes it as three miles in circumference divided into "areola" resembling those upon a turtle's back, the surface of each being. "horizontal and smooth." He was there in the rainy season, and concluded that evaporation on the clear afternoons removed the torrents of water that fell in other parts of the day, as there was no other outlet. He further states that the soil around La Brea consists of cinders and burnt earth, being evidently the product of subterranean fires, as there were hot springs in the neighboring woods.

The next visitor is Dr. Nicholas Nugent, who published an account of a visit made in October, 1807.† He landed on the south side of La Brea point which he describes as consisting of a bluff of porcelain jasper, "generally of a red color." Ascending to the Lake he perceived a strong sulphurous and pitchy smell, like that of burning coal, and soon after had a view of the Lake, which at first sight, appeared to be an expanse of still water, frequently interrupted by clumps of trees and shrubs, but on a nearer approach it was found to be a plain of mineral pitch with frequent crevices filled with water. "The surface of the lake was not polished or smooth so as to be slippery; the consistence was such as to bear any weight, and it was not adhesive; though it partially received the impression of the foot, it bore us without any tremulous motion whatever, and several head of cattle were browsing on it in perfect security. The interstices or chasms are very numerous, and being filled with water, present the only obstacle to walking over the surface. The arrangement of the chasms is very singular, the sides are invariably shelving from the surface, so as to nearly meet at the bottom, but there they bulge out towards each other with a considerable degree of convexity. These crevices are known occasionally to close up entirely, and we saw many marks or seams from this cause. The lake contains

*Philosophical Transactions, lxxix, 65, 1789.

+ Transactions of the Geological Society of London, i, 63, 1811. AM. JOUR. SCI.-THIRD SERIES, VOL. L, No. 295.-JULY, 1895.

many islets covered with long grass and shrubs. It is not easy to state precisely the extent of this great collection of pitch; the line between it and the neighboring soil is not always well defined. The main body may perhaps be estimated at three miles in circumference; the depth cannot be ascertained, and no subjacent rock or soil can be discovered. The negro houses in the vicinage, built by driving posts into the earth, frequently are twisted or sunk on one side. In many places it seems to have actually overflowed like lava, and presents the wrinkled appearance which a sluggish substance would exhibit in motion. In some parts it is black, with a splintery or conchoidal fracture; in other parts so much softer, as to allow one to cut out a piece in any form with a spade or hatchet, and in the interior it is vesicular or oily; this is the character of by far the greater portion of the whole mass: in one place it bubbles up in a perfectly fluid state, so that you may take it up in a cup."

"In the southeastern part of the island there is a similar collection of this bitumen, though of less extent, and many small detached spots of it are to be met with in the woods; it is even said that an evident line of communication may thus be traced between the two great receptacles."

Dr. Nugent devotes considerable space to a discussion of the geology and origin of the bitumen. As his opinions are based on theories no longer accepted by geologists I will only remark en passant, that he associates the mud volcanoes of Cedros Point with the agencies that have been active in bringing the bitumen to the surface.

The next notice that appeared, was written in September, 1832 by Capt. J. E. Alexander, 42a Royal Highlanders.* He says, "at the small hamlet of La Braye, a considerable extent of coast is covered with the pitch, which runs a long way out to sea, and forms a bank under the water. The Pitch Lake is situated on the side of a hill, a gradual ascent leads to it, which is covered with pitch in a hardened state, and trees and vegetation flourish upon it. The pitch at the sides of the lake is perfectly hard and cold, but as one walks off towards the middle with shoes off, in order to wade through the water, the heat gradually increases, the pitch becomes softer and softer, until at last it is seen boiling up in a liquid state, and the soles of the foot become offensively warm. During the rainy season, it is possible to walk over the whole lake, nearly, but in the hot season a greater part is not to be approached. The Lake is about a mile and one-half in circumference; and not the least extraordinary circumstance is, that it should contain eight or ten small islands, on which trees are growing close to the

*Journal of the Franklin Institute, 1833, xv, 337. New Edinburgh Philos. Magazine.

boiling pitch. In standing for some time on the lake near the center, the surface gradually sinks until it forms a great bowl, as it were; and when the shoulders are level with the general surface of the lake, it is high time to get out. The flow of pitch from the lake has been immense, the whole country round, except near the Bay of Guapo, being covered with it; and it seems singular that no eruption has taken place within the memory of man, although the principle of motion still exists in the center of the lake."

Speaking of Point Cedros, he says, "what renders this point so interesting to the stranger is an assemblage of mud volcanoes, of which the largest may be about one hundred and fifty feet in diameter. At times the old craters cease to act, but when that is the case new ones invariably appear in the vicinity. The mud is fathomless, yet does not overflow, but remains within the circumference of the crater. From what I recollect of the Crimea, I should say that there is a remarkable similarity between it and Trinidad;-geologically speaking, in both there are mud volcanoes, in both there are bituminous lakes, and both have been frequently visited with earthquakes."

The next observer was Mr. N. S. Manross, who visited the lake in 1855, and has been widely quoted. He says, "the vil lage of La Brea stands on a projecting tongue of land which owes its preservation from the inroads of the sea to the fact that it consists entirely of hardened pitch, which withstands the waves far better than the loose materials of the accompanying formations. The shore for miles, both north and south, consists mainly of the same material, and juts boldly out into the sea wherever it is thus pitch-bound. A road leads up from the landing to some sugar estates beyond the lake. It ascends a gentle slope of hardened pitch, which, where left to itself is covered with a dense growth of reeds and bushes. The road itself is a fine illustration of the adaptation of pitch to the purpose of paving. Where too much mixed with earth it has become pulverized to a depth of a few inches, but in many places it is still so pure and solid that the wheels of heavily loaded sugar wagons and the hoofs of horses make but a slight, and even that, a transient impression. In no part of the ascent to the shore of the lake does the stream of pitch appear to be covered by more than one or two feet of soil, while in most places it is entirely bare. In places where the surface is not protected by vegetation it becomes so far softened by the sun as to be still making progress downward.

"On nearing the lake the ascent becomes steeper. Here the pitch is bare, or but slightly covered with grass. Its appearance is not that of a sudden simultaneous overflow in a single

smooth stream, but that of a great number of streams each but a few yards or rods in breadth. Their surfaces are drawn out into all manner of contortions, and where the edges meet, small ridges have been thrown up and the pitch broken into fragments not unlike the scoria of lava currents. These fragments of pitch were on fire in several places, having been kindled by a fire that ran through the bush' a few weeks before."

"On ascending the last slope of this pitchy glacier a singular scene meets the eye. A black and circular plain of pitch onehalf mile in diameter lies flush with the edge of the stream. It is surrounded by a dense wall of forest in which various species of tall palm are most conspicuous. The lake itself is entirely bare of vegetation, except about twenty small clumps of trees which are arranged in a sort of broken circle about one-half way from the center to the circumference."

"The entire surface of this circular plain is seen to be interspersed by a network of water channels. Its appearance is exactly that of marbled paper. The pitch is divided into flat or slightly convex areas, mostly polygonal but sometimes cir cular. They vary from one to eight rods in diameter. The intervening spaces are full of water. These channels (or spaces) have heretofore been described as crevices or cracks in the pitch. This description however is incorrect, for the material, though apparently almost as hard as stone, is yet far too plastic to admit of anything like a fissure remaining open in it. The channels are produced and maintained by the following singular process. Each of the many areas into which the Lake is divided possesses an independent revolving motion in this wise at the center of the area the pitch is constantly rising up, not breaking out in streams, but rising en masse. It is thus constantly displacing that which previously occupied the center, and forcing it towards the circumference. The surface becomes covered with concentric wrinkles and the interior structure somewhat laminated. When the edge of such an expanding area meets that of the adjoining one the pitch rolls under, to be thrown up again at the center at some future period. The material is nearly soft enough to meet and form a close joint at the top but descends with a rounded edge and at a considerable angle. The conclusion then to which a close observation leads us in regard to the present condition of this singular lake is, not that it has suddenly cooled down from a boiling state, as heretofore described, but that, as the material is, it is still boiling although with an infinitely slow motion. As the descent of the glacier may be considered the slowest instance of flowing in nature, so the revolutions of the scarcely less solid bitumen of this lake may be set down as the slowest example of ebullition."

"Towards the center of the lake several detached areas are met with, the surfaces of which yield under the foot. On standing ten or fifteen minutes one may find himself ankle deep. A person standing long enough would undoubtedly sink and perhaps disappear in it; but in no place was it possible to form those bowl-like depressions around the observer as described by former travelers."

The

"The water which filled the crevices of the pitch is clear and very pure. It is the favorite resort of all the washerwomen for miles around. As the water is flowing now, the pitch has formerly flowed from the lake in all directions. The entire surface covered by it is estimated at 3000 acres. pores of the pitch are full of water which oozes out on the slightest pressure, and by moistening the skin prevents adhesion. Streams of gas issue, sometimes rising through the water, but more frequently from small openings in the pitch. above water level."

"In one of the star-shaped pools of water, a column of pitch had been forced up from the bottom, expanding into a sort of center-table about four feet in diameter. Pieces torn from the edge of this table sank readily, showing that it had been raised by pressure and not by buoyancy."

"About a mile and one-half south of the lake I observed numerous beds of indurated clay filled with the remains of leaves and vegetation. A little further on appears a bed of brown coal and lignite, about twelve feet thick. It has such a dip and direction that, if continuous, it would pass under the lake at a great depth. About a mile to the northwest of the lake another bed of brown coal crops out upon the shore. It is about twenty feet thick. From the occurrence of such considerable accumulations of vegetable matter, so situated as apparently to pass under the lake, it seems reasonable to regard them as the source of the pitchy matter. Indeed, many pieces of wood may be observed in the beds of brown coal, which differ in no respect in their appearance from many of the pieces thrown up in the lake itself."

Mr. Manross is completely at sea in his points of the compass.

The observations upon which the descriptions of this lake, from which I have made careful abstracts, were based, were made from forty to one hundred and six years ago. I have been able to verify them in almost every particular, and these descriptions clearly portray the appearance and condition of the lake at the time I visited it in March, 1895. In addition to these descriptions, other observations quite different in character and purpose have been made concerning the island

*This Journal II, xx, 153, 1855.