It may appear late, on my part, to offer these remarks, considering that the work which has called them forth has now been nearly four years before the public. My absence from England, in the West Indies, during the interval, and my want of knowledge, in consequence, of the arguments used against Mr Cavendish, require only to be noticed to account for it.

LESKETH HOW, AMBLESIDE,

April 24, 1849.

By T. S.

On the Acid Springs and Gypsum Deposits of the Upper Part of the Silurian System (Onondaga Salt Group). HUNT, of the Geological Survey of Canada.

That portion of the upper Silurian system of New York, which has been designated by the geologists of that state the Onondaga Salt Group, is characterised not only by the saline springs to which it owes its name, but also by numerous deposits of gypsum and springs, which are sour to the taste, and contain free sulphuric acid. The one at Byron, New York, has long been known, and several others have been observed more recently in the same geological district. The same region in Canada affords a remarkable spring of this kind, which, in the course of my official duties, I had occasion to examine in the month of October 1847. It is situated in the township of Tuscarora, in the Indian Reserve, about twenty miles north of Port Dover, which is the nearest point on Lake Erie. The water contains a large amount of free sulphuric acid, about 4 parts in 1000, besides sulphates of the alkalies, lime, magnesia, aluminum, and iron in small quantities. The proportion of these ingredients is however not constant, as is evident from an analysis made in April 1846, by Professor Croft of King's College, Toronto, which is confirmed by a partial examination by myself, of a specimen of water brought from the spring in June 1845.

The specific gravity of the water was much lower, and the amount of foreign ingredients much less, than in that col

lected by myself, but the proportion of bases to the acid was much greater. The proportion of the lime to the acid I found to be about 1.15, and that of the magnesia 1.90, while Professor Croft's determination gave about 1·6, and one to 1·15, respectively. That collected in 1845 is a nearly saturated solution of gypsum, while that of 1847 contains no more than about 7 parts in 10,000.

These facts indicate a rapid change in the constitution of the spring, and its situation shews it to be of comparatively recent origin; for although the powerful acid has destroyed all traces of vegetation for a distance of several yards around the source, the water issues from beneath the roots of an enormous pine-tree, whose decayed stump still stands several feet in height, while the crumbling mould, from its slow decay, forms the surface soil for some distance around. Without overlooking the antiseptic virtues of the mineral substances contained in this remarkable spring, this fact shews that its antiquity can scarcely be greater than a century, if indeed half that cycle may not extend beyond the time of its first development, while the rapid decrease in the quantity of the saline bases shew that its character remains constant scarcely for a twelvemonth. It should have been observed, that there are four or five basins within the distance of as many yards, and that they are situated on the summit of a low mound, which rises with a gradual slope from the marshy plain.

The probable cause of these changes will be seen by adverting to the character of the gypsum deposits of this formation, which I regard as having an intimate connection with this class of springs. The investigations of Mr Hall, in New York, and Mr Murray, in Canada, unite in shewing that the gypsum of these rocks always occurs in hillocks or domeshaped masses, varying in size from one foot to 300 or 400 feet in diameter, and always near the surface of the formation. Sections of these masses shew them resting upon undisturbed strata of limestone, while the superior strata are thrown up and rest upon the flanks of the intruded hillock, often very much broken, and, as Mr Hall has remarked, in part consumed, so that one is at a loss to account for the disappearance

of a large portion of the overlying strata. In one case observed by Mr Murray, a slender cylinder of gypsum passes through several beds of the limestone, and at last terminates in a cone of the usual form, which is entirely superior to the limestone formation and surrounded by the tertiary clay of the region. The comparatively recent origin which this assigns to the gypsum deposits, is confirmed by the common experience of the people of Western New York, where it is a well known fact that since the settlement of the country, walls have been disturbed and houses raised from their foundations by a gradual elevation of the surface, where subsequent examination has shewn the presence of domes of gypsum.

On comparing these facts with those observed in connection with the acid spring, it appears probable that the origin of the gypsum is to be ascribed to the action of such mineral waters upon the calcareous strata. How far the pressure at a great depth may operate in preventing chemical changes, we may not know, but it is easy to see that once coming to a situation where it could act upon the limestone, it would evolve carbonic acid gas, and form a calcareous sulphate which from its sparing solubility would be at once deposited in a crystalline form, while the water would pass off saturated with the sulphate, and at the same time carrying with it the soluble sulphates of magnesia, alumina, and iron, which would be formed from the other bases generally present in the limestones of this region. If the amount of acid were copious, or the supply of calcareous matter limited, the water might rise to the surface with free acid, as in the cases already noticed, and when the deposition of calcareous sulphate had extended so far as to protect the carbonate from farther action, the water would appear with a much smaller portion of basis than before, having only the sulphate of lime, which it could dissolve from the sides of its channels.

If, on the contrary, the acid were entirely neutralized, the spring would present at the surface the character of an ordinary bitter saline, containing calcareous and magnesian sulphates; two springs of this character are indeed found in the same formation not far from here. The ferruginous and

argillaceous substance known as gypsiferous marl, which surrounds these deposits, seem to be due to the precipitation by the carbonate of lime, of the iron and alumina, which have been previously taken up by the water yielding a mixture of these oxides with carbonate and sulphate of lime. The fact that crystalline gypsum occupies nearly twice the space of an equivalent quantity of carbonate of lime, will at once explain the displacement of the superincumbent materials. The observation which is now required to confirm this theory, is to find the carbonic acid which should be evolved from the decomposition of the limestone actually disengaged from one of these springs; the small quantity of gas which rises from the Tuscarora spring was found to be principally carburetted hydrogen, which is copiously evolved by the salines of this region, but it was collected at a time, when, from the minute portion of gypsum in the water, the action seems to have been at an end. I shall not attempt to speculate upon the probable source of the sulphuric acid at present, but shall defer the consideration of the subject, until the publication of my report on the mineral springs of Canada, which will be accompanied with the analyses of this water as collected in different years. Hoping that my observations may resolve a hitherto unexplained problem in the geology of this region, I beg leave to submit them to the notice of the Association.-American Journal of Science and Arts, vol. vii., No. 20, New Series, p. 175.

An Account of Two Aërolites, and a Mass of Meteoric Iron, recently found in Western India. By HERBERT GIRAUD, M.D., Professor of Chemistry in the Grant Medical College, Bombay, Assistant-Surgeon in the Hon. E.I.C.'s Bombay Medical Establishment. Communicated by the Author.

Although the records of science have of late years abounded in descriptions of meteorites, yet, from their unearthly origin, and characteristic chemical composition, these curious bodies continue to claim the peculiar interest which, it is believed, may attach to two

specimens of aerolites, and one of meteoric iron, that have recently been found in Western India.

Aerolite from Dharwar.-About one o'clock P.M. of the 15th of February of last year, this aërolite fell in a field to the south of Negloor, a village situated within a few miles of the junction of the Wurda and Toomboodra rivers, and belonging to the Gootul division of the Ranee-Bednoor Talook of the Dharwar collectorate.

The fall of this aërolite is most satisfactorily established. A cultivator of Negloor, named Ninga, was driving his cattle out to graze close by where it fell; at the hour above mentioned, he suddenly heard a loud, whirring, rushing noise in the air, but on looking up could see nothing. An instant afterwards, however, he observed a cloud of dust rise from a spot in an adjoining field, as if something had struck the ground there with violence. At this time several other villagers were standing by a threshing-floor, close at hand; they also heard the noise, and called out to Ninga, asking whether he had done so. He replied, Yes, and that something had fallen in the next field, where he saw the dust rise; and on his pointing to the spot, the whole party proceeded thither. There they found a stone, broken into fragments, imbedded in a hole, which they compared to the print of a young elephant's foot. They were naturally much puzzled to account for the appearance of the stone, which altogether differed from any to be met with in their neighbourhood, and at length they were constrained to conclude that it had fallen from the heavens. The circumstance seemed so extraordinary, that one of them was immediately sent to summon the Patel of the village, who soon arrived, attended by a crowd of people, who had also heard the wonderful tidings. These, too, unanimously adopted the same conclusion regarding the fall of the stone, the fragments of which the Patel took into his charge, and wrote a report of the whole circumstances to the Mahulkarree of Gootul, who is the revenue and police officer of the district in which Negloor is situate. The Mahulkarree thought the Patel's report so extraordinary, that he determined at once to proceed to Negloor himself to inquire into its truth. After having examined the stone itself, and the hole in the ground made by its fall, and finding that all the accounts of the villagers agreed, he could not avoid concluding as they did, that it fell from the sky. He, moreover, took statements in writing from the cultivator Ninga and another, who had heard the rushing noise made by the stone in its passage through the air, and forwarded their depositions, with his own reports, and the fragments of the aërolite, to Mr Goldfinch, the the assistant-collector and magistrate in charge of the district, by whom they were given to Captain G. Wingate, of the Bombay Engineers, who presented them to the Bombay Geographical Society, and by the secretary to this institution the fragments of the stone were made over to me for examination and analysis.

The fragments of the stone being placed together, constituted a mass of an ovoidal figure, measuring 15 inches round the larger, and