THE

EDINBURGH NEW

PHILOSOPHICAL JOURNAL.

On the Mineral Water of the Baths of Nevis, in the West Indies; in a Letter addressed to Professor JAMESON, by JOHN Davy, M.D., F.R.S, London and Edinburgh, InspectorGeneral of Army Hospitals.

MY DEAR SIR,-In a visit which I made last year to Nevis, I paid some attention to the mineral water of which there is a spring at the baths of that island; and through the kindness of James Davoren, Esq., of Nevis, I obtained portions of the water for examination on my return to Barbadoes.

As, to the best of my knowledge, this water has not hitherto been analyzed ;-as its effects, when drank, are decidedly beneficial in many instances of derangements of function of the stomach and intestinal canal;—and, more especially, as some of the results I have obtained in the trials made on it bear on points interesting in relation to geology, and in which I know you take a lively interest, I would hope that a short account of the baths (avoiding minute detail, as unsuitable to the occasion), and of the analysis of the mineral water, with a few incidental remarks and inferences, may not be unacceptable to you and to the readers of the Philosophical Journal.

The Baths of Nevis are pleasantly situated on a rising ground, reputed healthy, about half a mile from the seashore. They are two in number. Each is sufficiently large to admit of swimming in it. One is warm, the other tepid; the former was 98° of Fahr. when I tried it; the latter 88°. Adjoining them is a well, or rather a little cistern, the water VOL. XLIII. NO. LXXXV.—JULY 1847.

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of which is used for drinking. This is the mineral water of Nevis. I found its temperature 110-5° immediately under the mouth of the pipe, through which it flows into the cistern. It was perfectly clear, and free from any appearance of effervescence or of disengagement of air. It had a just perceptible taste, not to me disagreeable, and by some persons liked. The water with which the baths are supplied, and this the drinking water, are, I believe, from the same source, and of the same quality; the temperature of cach depending on circumstances of an accidental nature: I say, I believe, for it may be otherwise, as I have examined only the water of highest temperature, that used for drinking.

The specific gravity of this water reduced to the temperature of 80°, I have ascertained to be 10-019. Though not sparkling, this water is nearly saturated with carbonic acid, and contains its own volume of the gas.

From 44 cubic inches, that is about 11.120 grains of the water, there were obtained, besides carbonic acid, 1.8 grains of saline matter, readily soluble in water, chiefly bicarbonate of potash, with a trace of muriate of magnesia, 1·3 of carbonate of lime, ·77 grain of carbonate of magnesia, 1·5 of silica, a trace of phosphate of lime, of sulphate of lime, and of vegetable matter. I sought in vain to detect in it either iodine or bromine.

The vegetable matter, a kind of mucor, was found in bottles of the water that had been kept many months, though confined with glass stoppers. It appeared in the form of minute delicate fibres, partly black, partly green, and when spread out colourless. Under the microscope it was seen as an irregular tissue of nucleated fibres, of an average width of about of an inch. Occasionally after long keeping, the water had a smell of sulphuretted hydrogen. This it may have derived from the decomposition by the vegetable matter of a little sulphuric acid in the minute portion of sulphate of lime present. In one instance that I perceived the odour of this gas, the water was confined by a common cork; and, in that instance, no sulphuric acid, after the sulphuretted hydrogen was perceptible, could be detected in the water by the test of muriate of barytes.

I need hardly remark, that the carbonate of lime which the water contains is deposited on the escape, or expulsion, or neutralization of the free carbonic acid. It is worthy of remark, that a little silica, with a trace of phosphate of lime, is deposited at the same time. It is also worthy of remark, that when the bicarbonate of potash (a rare ingredient in a mineral water), was obtained by evaporation to dryness, thus insuring the removal of the excess of carbonic acid,―on its being redissolved, almost the whole of the silica remained, forming a strongly adhering incrustation of a dead white colour.

These, and other facts on the direct action of carbonic acid on silica, some of which I have noticed in a paper lately communicated to the Royal Society of London, would seem to prove, that carbonic acid is capable of dissolving silica. As this is a matter of importance, it may perhaps be right to be more particular in describing some of the results. I shall notice two in particular.

A bottle with a glass stopper, two-thirds full of Nevis water, after having been kept many months, was carefully observed. Corresponding to the surface margin of the water, a line of deposit was found of white matter without lustre, mixed with minute crystals, with which the inside of the vessel was studded below. The water was next poured out, and the incrustation examined. It consisted of silica and carbonate of lime chiefly; the former remaining after the action of dilute nitric acid on it, and washing with water, It was best seen when dry, for when wet it was scarcely visible. Under a high magnifying power, it appeared in part crystallinė, but more generally in delicate laminæ.

The water poured out of the bottle, on admixture with ammonia, became turbid. After standing some time a deposition took place from it on the sides of the glass vessel, and this deposit also had the properties of a mixture of carbonate of lime and of silica; thus, after having been dried, the carbonate of lime, on the application of an acid and water was removed, whilst the silica in the form of a most delicate incrustation, remained, having resisted the action of the nitric acid and water.

These two results (not to revert to others) seem to shew, and it appears to me in a satisfactory manner, that silica may be, and is kept in solution by carbonic acid. If this be admitted, may it not aid in the explanation of much that is obscure in regard to the structure of certain rocky strata, especially of aggregates, in which the cementing principle appears to be silica? May it not also aid us in explaining the manner in which certain fossils are formed, such as are, as it were, casts, the petrifying matter of which is silica?

Hitherto a fixed alkali has been received as the solvent of silica, in mineral waters. That it is a solvent in its caustic state, I apprehend, must be granted;-but I am not aware of any facts or analogies tending to prove that it is also such a solvent when saturated with carbonic acid. And as, in every instance in which I have had an opportunity of examining waters containing silica held in solution, I have found carbonic acid, it seems to me natural to infer, that it with water is the solvent. As regards this view, it is desirable that the waters, most remarkably siliceous, should be re-examined; especially the water of the Great Geyser in Iceland, the petrifying effect of which, as it falls on the plants in the neighbourhood of the fountain is so remarkable, and so obscure at present, but which would cease to be so should it be proved that the deposition of silica in this instance is connected not only with a great and sudden reduction of temperature, but also with the rapid escape of carbonic acid, -the generation and evolution of which may perhaps be concerned in the production of some of the peculiar phenomena of this extraordinary spring.

The island of Nevis, like Iceland, is volcanic. Some of its rocks are highly crystalline, and abound in felspar, or in what appears to be felspar. Clay, too, is abundant in the island. Probably the potash which occurs in the mineral water is derived from the decomposition of felspar, or of analogous minerals, aided by heat, which expels carbonic acid from compounds containing it; and this acting on the silica liberated from the decomposing minerals, may, with water, effect its solution:-I say liberated, because we know that certain substances, perhaps all, then most readily unite with others

for which they have a feeble affinity, when in that state, which has been designated their nascent state, in which we may suppose that they are in a condition of the subtlest division, perhaps no two particles yet cohering. Not only are crystalline rocks and clays found in Nevis, but also well formed crystals of quartz of perfect transparency, which, under the name of diamonds, are in no small estimation amongst the inhabitants for ornamental purposes, after having been cut and polished. They are found, I was informed, loose in the beds of torrents; but whether they are of aqueous or igneous origin, I could learn nothing on which to found even conjecture.

I have alluded to the beneficial effects of the mineral water of Nevis, used as a drink. Considering its composition, such an effect, is what perhaps might be expected. I may also notice, that the baths have proved very beneficial in obstinate cases of chronic rheumatism. Our great naval hero, Lord Nelson, it is likely used them; for, when in infirm health, we are informed, he recruited it in this island, residing at a spot about two miles distant from the baths, in a house the property of the uncle of Mrs Nesbit, a native of Nevis, whom he married at this time.

For invalids, to whom these waters are likely to be useful, these baths hold out many recommendations. There is a good lodging-house adjoining them, built specially for the accommodation of invalids, by a philanthropic individual ;— they are about half-a-mile only from James Town, where medical advice can be obtained, and where the steamers of the Royal West India Mail Company touch twice a-month.

In a former communication which appeared in the Philosophical Journal, I took occasion to notice defects of ventilation in the vessels of this Company. I regret to learn that these defects continue; and that others are added to them,' arising out of want of proper attention to the comforts of passengers. When the winter climate of the West Indies is considered, compared with our home winter climate, and the probable benefit that a numerous class of persons in feeble health might derive from a voyage to the West Indies, and a sojourn here for two or three of the coolest months,