The British Critic, and Quarterly Theological Review

may be objected, that the fame mode of arguing may be applied to the vices of Chriftianity." But foft-by regular degrees, not yet;" for it must be remembered, that it is not the nature of Christianity to give birth or countenance to a fingle vice. And though we were to admit this pofition (a pofition, by the way, palpably falfe) I should feel for the too refined fenfibility, for the over nice and too prudifh delicacy of that man, who would turn away with difguft from the majefty of a Gothic edifice, upon feeing a few paltry blemishes thinly fcattered on the exterior of the building; who could think that the fpots which float round the furface of the fun, would more than overbalance the magnificence of the whole, and the particular beauties that continually flow from that fountain of light." P. 70.

It was the fpirit of Chriftianity that, in England, put a stop to the dreadful animofities of the Barons; that checked the perpetual feuds of the darker ages; that fubdued the pride and fiercenefs which fo convulfed the government of our own and other nations; that gave rife to the fingular but beneficial inftitution of chivalry, which tempered the valour of its profeffors, by uniting in the fame perfons the various and useful virtues of courtesy, humanity, honour, and justice"; that has

"fecured amid the mild majelly of private life, that variety of gratifications and endearments, which we are formed to feel with the moft exquifite fenfibility; thofe winning and attractive graces; thofe amiable and fofter virtues; thofe ten thousand decencies, which smooth and beautify our path through this to a higher and nobler state of exiftence." P. 76.

And, above all, that

"has reared a monument as durable as the world, I mean, the inftitution of charitable houses; an inflitution, that has fecured the morals and existence of millions and millions of our fpecies." P. 77

From the whole, then, we may fafely conclude, that the Chriftian religion has guided, to their proper objects, the intellectual, moral, and focial powers of man, with a certainty infinitely fuperior to every other inftitution." P. 92.

We have analyzed this tract with fome attention, conceiving that it is calculated to produce the beft effects, at this juncture in particular; and we have produced from it so many creditable fpecimens of argument and of eloquence, that any further recommendation of it, on our part, would be altogether fuperfluous.

ART.

ART. IV. Tranfactions of the Royal Society of Edinburgh. Vol. V. Part 1.

(Concluded from our last, p. 411.)

III. Experiments on Whinftime and Lava. By Sir James Hall, Bart. F. R. S. and F. A. S. Edin.

THE fubject of this rather long paper is briefly as fol

lows:

It was fuppofed by Dr. Hutton, in his investigation of the ftructure of the earth, that granite, porphyry, and bafaltes, had originally been in a state of perfect fufion. But this fuppofition is rendered improbable by the obfervation, that the internal. ftructure of thofe minerals is generally rough and ftony; whereas the fusion of earthy fubftances, in common chemical operations, converts them into a more or less perfect vitreous fubftance.

It occurred, however, to this author, that by flow cooling, which must have been the case of those minerals in the bowels of the earth, they might affume a different appearance, from what they are wont to affume, when cooled fuddenly. And this conjecture was rendered more probable by fome accidental phænomena, which had been obferved in a glafs-house. He was therefore induced to put the matter to the test of actual experiments, and his experiments were attended with the defired fuccefs.

The fubftances tried are, 1. Whin of Bell's Mills Quarry; 2. Whin of the Rock of Edinburgh Caftle; 3. Whin of the bafaltic columns on Arthur's Seat, near Edinburgh; 4. Whin from the neighbourhood of Duddingftone Loch; 5. Whin of Salisbury Craig, near Edinburgh; 6. Whin from the water of Leith; and, 7. Whin of the bafaltic columns of Staffa.

Each of thofe fubftances was expofed in a crucible to a ftrong fire, and was afterwards fuffered to cool, either fuddenly or flowly. The general refults fhowed,

"that all the whins employed affume, after fufion, a ftony character, in confequence of flow cooling; and the fuccefs of the experiments, with fo many varieties, entitles us to afcribe the fame property to the whole clafs. The arguments, therefore, againft the fubterraneous fufion of whinstone, derived from its ftony character, feem now to be fully refuted."

The narration of thofe experiments contains alfo a variety of collateral obfervations, the principal of which are contained in the account of the experiments on the whin of Bell's Mills Quarry, which is as follows:

L17

" In

"In trying the fufibility of the lafs obtained from it, a curious circumftance occurred, which accounts for the unexpected results already mentioned. I had placed in the muffle a long and flender fragment of this glafs, with its extremities refting on two fupporters of clay, and its middle unfupported. Having then increased the temperature by flow degrees, I expected to difcover the lowest point of emollefcence, by obferving when the fragment funk by its own weight. The muffle having attained a moderate heat, I obferved the glafs to lofe its fhape a little. Withing to fee it completely melted, the fame heat was continued, but no further change took place. The heat was then raised feveral degrees, but without effect. At last, being urged ftill further, the glafs funk down completely between its fupporters. The pyrometer being then withdrawn, denoted a temperature above 30.

"It occurred to me, that, on this occafion, the glass, by the first application of heat, had foftened, and then had cryftalized, fo as to become hard again; that, in crystalizing, it had acquired fuch infufibility as to yield to no heat under 30. I immediately confirmed this conjecture by the following experiment:

A piece of the fame glafs, placed in a cup of clay, was introduced into the muffle, heated to 21. In one minute it became quite foft, fo as to yield readily to the preffure of an iron rod. After a fe cond minute had elapfed, the fragment, being touched by the rod, was found to be quite hard, though the temperature had remained stationary. The fubftance, thus hardened, had undergone a change. throughout; it had loft the vitreous character; when broken, it exhibited a fracture like that of porcelain, with little luftre; and its colour was changed from black to dark brown. Being expofed to heat, it was found to be fufible only at 31; that is, it was lefs fufible than the glass by 13 or 14 degrees.

Numerous and varied experiments have fince proved, in the cleareft manner, that, in any temperature, from 21 to 28 inclufive, the glafs of this whin paffes from a fott, or liquid ftate, to a folid, in confequence of cryftalization; which is differently performed at different points of this range. In the lower points, as at 23, it is rapid and imperfect; in higher points, flower and more complete, every intermediate temperature affording an intermediate refult. I likewife found, that cryf. talization takes place, not only when the heat is ftationary, but likewile when riding or finking, provided its progrefs through the range just mentioned is not too rapid. Thus, if the heat of the fubitance, after fufion, exceeds one minute in paffing from 21 to 23, or from 23 to 21, the mafs will infallibly cryftalize, and lofe its vitreous character. "Thefe facts enabled me to account for the production of the fubftance refembling the liver of an animal, which I obtained in my first attempt to cryftalize the melted ftone. Not being then aware of the temperature proper for complete cryftalization, I had allowed it to be paffed over rapidly by the defcending heat, and I had begun the flow cooling in thofe lower points, at which the formation of this interme diate fubftance takes place.

By the fame means I was enabled to explain the other unexpect'ed refult, which I obtained in endeavouring to convert the glafs of

this ftone into cryftalite. The fire applied to the crucible, containing fragments of the glass, had been raised very flowly, which I know to have been the cafe by fome circumftances of the experiment. The glafs had foftened by the firft application of heat, but had cryftalized again as the heat gradually rofe; fo that the fubftance confolidated, while ftill fo vifcid as to retain the original fhape of the fragments; at the fame time it acquired fuch infufibility as to refift the application of higher degrees of heat during the reft of the procefs." P. 49.

The fecond part of this paper contains an examination of various fpecimens of lava, from different volcanos; namely, 1. Lava of Catania; 2. Lava of Sta. Venere; 3. Lava of la Motta di Catania; 4. Lava of Iceland; 5. Lava of Torre del Greco ; and, 6. Lava of Vefuvius, eruption 1785. But the narration of the experiments is preceded by a statement, with quotations, of the opinions of Dolomieu and Kirwan, relatively to the formation of lavas. Thefe two gentlemen agree in believing, that lavas have never been acted upon by a heat of fufficient intenfity to produce complete fufion, and endeavour, each by an hypothefis peculiar to himself, to account for their fluidity.

Sir James Hall's experiments were performed upon fpecimens collected by himself; not from the fuperficial fcoria of lavas, but from their interior and more compact parts."

When," fays he, "thefe folid lavas are compared with our whin-ftones, the resemblance between the two claffes is not only striking at first fight, but bears the clofeft examination. They both confift of a ftony bafis, which frequently contains detached crystals of various fubftances, fuch as white felfpar and black hornblend. The analogy between the two claffes feems to hold through all their varieties; and I am confident that there is not a lava of Mount Etna to which a counterpart may not be produced from the whinstones of Scotland.

"This refemblance in external character is accompanied with an agreement no less complete in chemical properties." P. 57.

After the recital of the experiments, which we hope are accurately stated, this author proceeds to apply their refults to the explanation of various geological facts; and, laftly, concludes his paper with a table of the various degrees of futibibilty of different fpecimens of lava,

IV. A Chemical Analysis of Three Species of Whinstone, and Two of Lava. By Robert Kennedy, M. D. F. R. S. and F. A. S. Edin.

"On the 5th of Auguft laft," this author fays, " I announced to the fociety that I had discovered foda in feveral varieties of the whinftone of Scotland, and alfo in lava from Mount Etna; but did not defcribe the various experiments to which thefe fubftances had been fubjected in my examination of them."

The

The account of those experiments, with all the necessary particulars, forms the contents of the prefent paper. It appears from their results, that the contents of 100 parts of the bafalt of Staffa, are,