and bursts, thus forcing the center up and causing a slow but irresistible movement from the center towards the circumference, where the pitch continually rolls under, exactly as Manross has described it. His suggestions concerning the ebullition of the mass within the lake were confirmed to the very letter. This action is explainable in this wise: Mr. Richardson's analysis of asphalt water shows it to be very rich in sulphates. As has been elsewhere shown, sulphates, especially those of the alkalies, when in solution are decomposed, when the water containing them flows through strata impregnated with organic matter, into hydrogen sulphide and a carbonate of the oxide present. When hydrogen sulphide infiltrates strata containing carbonate of lime, gypsum is formed and sulphur deposited, or converted into free sulphuric acid.*

The Miocene bituminous strata of Southern California are full of sulphur springs and numberless deposits of sulphur. One such deposit in the southern part of Kern County is sup. posed to contain several thousand tons of sulphur.

The reaction between sulphates present in the lake water and the bitumen or other organic material of the formation, furnishes a ready explanation of the presence of hydrogen sulphide; but I must confess that the odor of that gas was much less apparent about the lake than I had been led to expect. Analysis will alone show what the gases are that inflate the asphalt, but of their presence in enormous volume, there can be no question. At a rough estimate, I should say that from one-third to one-half the volume of the mass as it exists in the center of the lake, is gas. I also hazard the opinion that this gas makes the mass specifically lighter than water, else the tables described by Manross and Kingsley would not rise and spread on the surface of the water and further the masses of asphalt would coalesce, and the water would float upon the asphalt. Moreover it is without any doubt, that through this motion or ebullition which is produced, not by escape of vapor generated by heat, but by gases forced upward by their own specific gravity through a yielding mass, that the asphalt and mineral matter which forms the floors and sides of the crater, are mixed together until the asphalt is saturated; i. e. it reaches such a condition of plasticity and viscosity, that it will no longer absorb any more mineral matter in presence of water. I cannot account for the almost uniform character of the mixture of water, bitumen and mineral matter, on any other hypothesis.†

* Proc. Am. Philos. Soc., x, 445. Bischoff, Chem. and Phys. Geol., (Cav. Soc. Ed.) II. 28; Ibid., i, 15, 340. T. S. Hunt. Chem. and Geol. Essays, pp. 23, 87, 99, 111.

Mr. Richardson asserts that 90 per cent of the 80 per cent of insoluble mineral matter in the pitch is silica. As a possible explanation of the presence of

Asphalt is very inert to changes of temperature. It is a very poor conductor of 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 associated 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 nothing 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 impervious strata. If the water accompanied by bitumen, encountered in its upward. passage such strata, as have been described by Mr. Guppy, a mud volcano 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 produce 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 transformation 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 excavations 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 incorporated with the pitch. Such masses account for the organic matter in solution in the lake water, and also for the amorphous 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, VOL. L, No. 295.-JULY, 1895.

The concessionaires of the lake, have recently put in operation a tramway and pier by which the pitch can be very rapidly and easily removed from the lake to vessels lying at the pier. The tramway forms a loop, which in a general way may be said to pass just outside the circle of islets. (See map.) In building the tramway much of the vegetation on these islets has been destroyed. The laying of the tramway presented some peculiar engineering difficulties, that have been successfully overcome. The islands float on the pitch, and I believe that they represent portions of the edge of the crater broken off during violent irruptions and placed in, and maintained in their relative positions through their relations to the various centers of ebullition into which the surface of the lake is divided. These islets, which largely consist of vegetable matter, float, while logs of wood and palm-tree ties sink in the pitch; it therefore occurred to Mr. Freeman, the engineer in charge of the work, to support his tramway on palm leaves, of which many specimens are twenty-five feet in length. This expedient has proved a complete success, not only upon the summits of the "aroela" but in crossing the crevices that separate them. The tramway furnishes a succession of admirable points from which to view the lake, as no difficulty is experienced in walking upon the ties around the entire loop. The cars are run in groups of four, which when loaded have a gross weight of about six thousand pounds. I carefully watched the passage of successive groups of these cars and could not observe any change of level in the road bed, as they passed along; yet I am quite certain if a group had been allowed to stand for several hours, that both tramway and cars would have sunk in the pitch.

The pitch is excavated along this tramway upon the summits of the "areola." Wherever the surface of the pitch is broken, the vesicles are uniformly smaller as the pitch is taken from points removed from the center of the lake. As the water dries out, the vesicles collapse and the color changes from brown to bluish black. If left long enough in the sun, any of the pitch, no matter from what spot it may be taken, will first melt upon the surface and finally flow into a more or less compact mass. The pitch being dug by the Trinidad Asphalt Company, both within and without the lake, was brown when freshly dug, changing to black on exposure. The same might be said of that dug farther down the slope from village lots by the Trinidad Bituminous Asphalt Company. It was quite evident that as the pitch was taken from points farther and farther from the center of the lake it had been subjected to more and more pressure, the gas being forced out as a consequence, the vesicles made smaller and the specific gravity thereby increased.

There are enormous masses of pitch within the lake that could not in my opinion be distinguished by the eye, from the pitch taken from village lots by either of the companies before mentioned. I am therefore quite at a loss to determine why Mr. Richardson alleges such a specific distinction between what he is pleased to term "lake" and "land" asphalt. It appears to me to be a distinction without a difference.

For further facts concerning the commercial and economic relations of Trinidad Asphalt, the reader is referred to the report of Consul Pierce, which I believe to be one of the most complete and impartial of all the valuable consular reports issued by the State Department.

It was my intention to include in this paper some statistics regarding the enormous amount of asphaltum of different varieties shipped from La Brea since January 1st, 1890.

When a friend applied to the custom house in Port of Spain for an official statement, he reported that such information had been refused, on the ground that such a statement would make public private interests, inasmuch as the Trinidad Asphalt Company had shipped several cargoes of "land pitch" to the United States since that date.

By referring to the maps the reader can clearly distinguish the relative positions of the lake and the adjacent portions of the island.

University of Michigan, Ann Arbor, Michigan, April 15th, 1895.

ART. V.-The Determination of Selenious Acid by Potassium Permanganate; by F. A. GOOCH and C. F. CLEMONS.

[Contributions from the Kent Chemical Laboratory of Yale College-XL.]

THE fact that sulphurous and tellurous acids may be oxidized quantitatively by a sufficient excess of potassium permanganate suggests naturally the application of the same general method to the determination of selenious acid. It is the object of this paper to record the results of experiments in this direction.

Brauner* found that in the action of the permanganate upon tellurous acid, whether in a solution acidified with sulphuric acid or made alkaline by caustic soda, the reduction of the permanganate does not proceed to the lowest degree of oxidation, the tellurous acid being unable to reduce the higher hydroxides of manganese which separate. In employing the reaction quantitatively it is necessary, therefore, to add the permanganate in distinct excess and then to destroy the surplus by means

*Jour. Chem. Soc., 1891, p. 238.

of standard oxalic acid added to the solution acidified with sulphuric acid, subsequently determining the excess of oxalic acid in the warmed solution by addition of more permanganate. The difference between the amount of permanganate actually used and that required to oxidize the known amount of oxalic acid introduced should naturally be the measure of the tellurous acid acted upon. Brauner found, however, an error in the process, by no means inconsiderable, due to the decomposition of the permanganate outside the main reaction. In a subsequent paper from this laboratory* it was shown that if the precaution is taken to restrict the amount of sulphuric acid present in the solution when the permanganate acts the secondary decomposition involving loss of unutilized oxygen is kept within narrow bounds. In our work upon the oxidation of selenious acid we have followed the suggestions gained in the treatment of tellurous acid by Brauner's method.

The selenium dioxide which we employed was prepared from so called pure selenium by dissolving the element in strong nitric acid, removing the nitric acid by evaporation, treating the aqueous solution with barium hydroxide to throw out any selenic acid formed in the oxidation, evaporating the solution to dryness, and subliming and re-subliming the residue in a current of dry air until the product was white. The oxide thus prepared was weighed out for individual experiments or was dissolved in a standard solution from which definite por tions were drawn for use.

In the first series of experiments, the results of which are recorded in Table I, the selenium dioxide was dissolved in 100 cm3 of water, 10 cm3 of sulphuric acid of half-strength were added, an approximately decinormal standardized solution of potassium permanganate was added until the characteristic color predominated over that of the brown hydroxide deposited during the oxidation, oxalic acid in solution of known strength was introduced until the excess of permanganate had been destroyed and the insoluble hydroxide dissolved, and, finally, after heating the solution to about 80° C., more of the permanganate was added to the color reaction. The final volume. varied from 250 cm3 to 350 cm3, so that the sulphuric acid (absolute) present varied from about five per cent at the start to from one and a half to two per cent at the end.

When the permanganate is first introduced into the acidified. solution the color vanishes, leaving a clear colorless liquid, but as more is added the solution becomes yellow and deepens gradually in color to a reddish brown, until turbidity due to the deposition of a brown hydroxide of manganese ensues, and finally the characteristic color of the permanganate is plainly

*Gooch and Danner, this Journal, xliv, 301.