תמונות בעמוד

The first essay of the second volume contains some observations on the composition and analysis of gunpowder. In the next, On common Salt,' the Author relates fome experiments made by him, to discover the quantity of water evaporated from a wet cloth, of a given fize, in a certain time; with a view to furnish hints which may be useful to those who may attempt the making of bay salt in this country. The third contains a few observations on common salt and nitre, considered as manures; and on the fertilizing quality ascribed to snow, which cannot juftly be attributed to any nitre contained in it. In the fourth, the Author has collected, from various writers, several observations relative to the temperature and faltness of the sea, and reasons upon them. .

In the fifth Essay, the Author treats of fresh water procured from that of the sea, by the means either of congelation, or distillation. In the manufacturing of sea salt, he proposes the freezing of sea-water ; by which he estimates that one third of the water at least may be converted into ice ; so that one third of the fuel may be saved, in boiling down the remaining brine into falt. An analysis is likewise given of some water distilled by Dr. Irvine from sea water; from which it appears that though the distilled sea water is not wholly free from saline particles, yet it probably contains them in so small a proportion, as not to render it unwholesome.

In the next Effay, which is more of an experimental nature than most of the others, the Author treats of Calcareous Earth, crude and calcined.' As this subject is interesting both in a phi. losophical and economical light; and as we not long ago [in our Review for May, 1780, p. 361] gave the results of Dr. Higgins's experiments relating to it; we shall abridge the account which the Author gives of some of his trials respecting it.

Some philosophers have doubted whether lime, stone, and other calcareous substances really contained so very large a quantity of fixed air, as has been inferred from the lots of weight which they sustain on calcining them ; or on applying acids to them, as in the original experiments on this subject made by Dr. Black. Some have supposed that a considerable part of the loss observed in these cases ought to be ascribed to the expulsion of the water which enters into the composition of these bodies. The Author appears to have made a considerable nuinber of experiments, with the greatest accuracy, on a great variety of marbles, calcareous earths, and spars ; the results of which confirm what had been affirmed by Dr, Black, and by others who have repeated his experiments.

In the course of thirty-two trials, in which were calcined a great number of calcareous substances of different kinds and countries, the medium quantity of lime that might be procured from a lon E 3

(or (or twenty hundred weight) of these substances, was found to a mount to ii cwt, 25 pounds. Consequently they had sustained a loss of weight amounting to somewhat above 8 cwt. 3 quarters,

That the whole, or nearly the whole of the substance thus lost was fixed air, seems to be satisfactorily evinced by some fublequent experiments, to be related hereafter.

It is well known that the calcareous stones thus converted into lime, on being exposed for a fufficient time to the atmosphere, attract from thence a considerable part of the same kind or kinds of matter which they had lost during their calcination ; and that they are then found to be posicfied of their former qualities, so as not to be fenfibly distinguished from crude limestone, marble, &c. We have, in the article above referred to, given the results of some of Dr. Higgins's experiments relative to this subject; and fall here relate some of the Author's.

On February 10, 1779, he converted a piece of statuary. marble, weighing 540 grains, into lime. : While still warm, it was found to weigh only 304 grains. It was then laid on a piece of white paper, and put into the drawer of a table. On the 4th of next month, it weighed 515 grains; having then acquired its greatest increase of weight, as appeared from the weighing it two months afterwards. Another quantity of lime from ftatuary marble was examined in the same way; and it acquired its greatest increase of weight in 22 days. In one particular in-, stance, in which the Author calcined 204 grains of dove marble, it was reduced to the weight of 116 grains; and on November 5, following, it had nearly acquired its original weight, as it was then found to weigh 203! grains. Further, he has frequently obierved pieces of new burned lime daily increasing at the rate of one hundred weight per ton, for the first five or six days.

One of the practical inferences which the Author deduces. from these: Jast experiments is, that, as a ton of fresh lime will, on exposure to the atmosphere, acquire an increase of weight amounting, in some cases, to half, and in others, to more than three quarters of a ton; it is obvious, that the person who purchases it by weight, will be a considerable loser in the article of weight as well as that of quality, if he buy it even a few days after the kiln has been drawn. The farmer too, who proposes to lime his land, should carry the lime out as soon as possible after ir has been burned; as otherwise, for every ton, he may have the trouble of carrying a ton and a half, or more.

It follows likewise that the soil on which fresh lime spread acquires a very considerable increase of maiter, attracted by the lime from the air ; fo that, according to a calculation of the Aus thor's, founded on the actual trials of a gentleman in Derbyshire, each acre of land limed by him (at the rate of 1000 bushels per acre), would in time receive an increase of soil, by means of the


Softime will probably dime. We tal tons in weighie

substance attracted from the air, equal to above 30 tons in weight beyond the original weight of the lime. We thail observe, however, that the lime will probably derive some of its increase from the contents of the soil in which a part of it is immersed, or from matters fermenting in it. .

It now remains to examine whether the large quantity of sub- . Stance which calcareous bodies lose on calcination, and which they recover on exposure to the air, consist wholly of fixed air; or whether a confiderable part of it may not be water. The Author relates fome experiments that do not seem to favour this last fuppofition; which has, nevertheless, been adopted by writers of distinguished reputation.- Crystalized spar distilled in a glass retort, with a heat which at length melted the glass, did not fura nish so much aqueous vapour as was even sufficient to tarnish the i sides of the receiver. This experiment, however, is not quite satisfactory, as we are not informed what was the loss of weight sustained by the spar, by the heat given to it; nor indeed are we informed that it had been converted into lime. ---- Another portion contained in an earthen retort, and exposed to a strong fire, so as to lose one-third of its weight, did not furnish a drop : of water in the receiver; the retort, however, appeared to be cracked at the end of the process. But a fimilar result at-' tended a trial made with 720 grains of what the Author calls Derbyshire Watricle; though this substance was reduced, by means of the heat employed in the process, to 400 grains.

Objections may be made even to this last process, which is not related with fufficient minuteness. The only satisfactory me. thod of ascertaining this matter, by distillation, would be that: of receiving the products of the process in mercury. If, in the Author's processes, any vent was given to the fixed air let loose during the calcination, the aqueous vapours might and would pass through the same opening. On the other hand, as the Abbé Fontana has lately shewn, no vapours will rise and be condensed, even from boiling water, in veflels perfeilly close ;' though the receiver be kept ever so cold, or even contain tub-: ftances that attract water with the greatest avidity; such as dry salt of cartar, and concentrated vitriolic acid : though we do not think that the Abbé has divined the true cause of the phenomenon, which depends on other principles than the mere saturation of the confined air with humidity.

Accordingly, the most decisive proof, in our opinion, that the loss of weighe above mentioned is solely, or almost wholly, occa-'. fioned by tre diflipation of the fixed air expelled from calcarcous substances, is deduced from some experiments made by the Au-thor with the greatest care, and resembling those originally made by Dr. Black; with which they perfectly agree in the results, These clearly Inew that.calcareous substances lose as much weight

on the addition of acids, as by fire; and that therefore the mat. ter expelled from them, in both cases, is the same, or fixed air.

The Author used a Florence flask, containing a small quantity of diluted marine acid, and weighed the whole in a nice balance. He then at intervals slowly dropped into it 20 grains of a calcareous substance; gently stopping the mouth of the Alask with his finger. As the fixed air expelled from the calcareous matter is specifically heavier than the common air before contained in the flask; he either extracted it, after the efferves. cence had ceased, by fucking it through a tube, or blew it out by means of a pair of bellows. Then weighing the Aask with its contents, he perceived a very considerable diminution of its weight; no sensible part of which loss could reasonably be ascribed to the evaporation of any of the aqueous particles contained in it. Six out of thirteen different calcareous earths or fones, treated in this manner, loft 8 parts in 20 during their solution in the acid; which is the very proportion originally affigned by Dr. Black, in his experiments made with chalki It appears from some subsequent experiments made with the greatest attention, with some other, and probably more pure, calcareous substances, treated in the same manner, that they loft 54 parts in 120, that is, 9 parts in 20, of their former weight.

In the 7th Effay, the Author treats of clay, marle, and gypseous alabaster, or plaister-sone.' He gives a short account of the composition of the flint or white stone-ware made in Staffordfhire, and of the yellow, or queen's ware; which laft is made of the fame materials as the former : though the proportions of clay and flint (of which they both confift), as well as the glazing, are different. Lead is the principal ingredient in the glazing of the queen's ware; whereas the white stone-ware receives its harmless glazing, by a very simple process, which was formerly executed in secret by two Dutchmen, who introduced the practice into Stafforoshire about 80 years ago. The effect is produced solely by throwing into the furnace some sea-salt, which instantly produces a thick vapour, that attaches itself to the sure face of the ware, and there forms that yitreous coat which is called its glaze. This Essay likewise contains several observations relative to the component parts and nature of porcelane.

In the 8th and last Effay, are contained various observations on pit coal, particularly with regard to its analysis; from which it appears that its products, by distillation, resemble those obtained from wood. In particular, tar has for several years past been procured from it, in some parts of Germany; and confiderable quantities are now obtained from the lame substance in England ; particularly at Bristol, where a person prepares it una der the sanction of a patent. The Author suggests some improvements of the process, which he thinks might be successfully


executed, not only by those who char pitcoal, or convert it into cinder; but by those likewise who burn wood into charcoal : in bɔth which operations, the oil which is now wasted in flame, or otherwise diffipated, might be saved and collected ; so as to be manufactured into tar, at a trifling expence.

We Thould not omit to observe, that iwo other volumes, which include the whole of the Author's plan, are nearly ready for the press; but that the publication of them will in a great measure depend on the reception which the two present volumes may meet with from the Public.

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Art. XI. THELYPHTHORA; or a Treatise an Female Ruin, &c.'

Vol. IIl. 8vo. 5 s. Boards. Dodsley. 1781.
IN an undertaking so novel and fingular as this, a more than

( common appearance of zeal for religion was requisite, in or. der to give the colour of sandity to a system of lewdness, and to make the tyranny of the stronger sex consistent with the Thew of affection for the weaker. To preserve this equivocal appear. ance-this * covert and convenient seEMING-the Author had difficulties of a very serious and formidable nature to struggle with :—and to do bim justice we must acknowledge his ingenuity; though such hath been his fate, that in spite of all the solemn professions he hath made-t wrapt round and fan&tified with texts of Holy Writ!—there is scarcely one reader in a hundred but hath had the sense to see through his design, and the virtue to deteft his principles.

Against these principles we early entered our protest; and it was our object, by exposing the design, to guard against the fatal delusion of his book.

Some have said that, we have kept no terms of civility with the Author: and he himself, veiling his mortification beneath the masque of indifference, hath repeatedly insinuated, that his argument is hitherto secure, because, forsooth! it hath not hitherto had the good fortune to be understood.

As to the want of civility, with which we have been charged, we ihall say but one word to elude the accusation. We adhered to. TRUTH, as the main object of our criticism; and in attempting to secure that, we were not particularly follicitous about the forms and ceremonials of address. We must acknowledge, that we abhorred Mr. M.'s principles; but, though we were apprehensive of their pernicious tendency, yet we dreaded not the abilities which supported them. We were willing to thew the Public our undisguised sentiments, by a direct attack of the first and fundamental principles of his system ; unawed by


† Pope.


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