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The first essay of the second volume contains some observations on the compofition 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 falt 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 Elay, 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 fo 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 trcats of Calcareous Earth, crude and calcined. As this subject is interesting both in a philosophical 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, itone, and other calcareous substances really contained so very large a quantity of fixed air, as has been inferred from the loss 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 fuppofed 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 number 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 couniries, the medium quantity of lime that might be procured from a ton E 3

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(or twenty hundred weight) of these subítances, was found to as mount to ricwt, 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 poflified 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 Mall 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 infance, 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 oblerved pieces of new burned lime daily increafing at the rate of one hundred weight per ton, for the first five or fix days.

One of the practical inferences which the Author deduces. from these last experiments is, that, as a ton of fresh lime will, on exposure to the atmosphere, acquire an increase of weigho 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 lofer 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 it 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 foil 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 Author'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 foil, by means of the

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substance attracted from the air, equal to above 30 tons in weight beyond the original weight of the lime. We shall 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 subftance which calcareous bodies lose on calcination, and which they recover on exposure to the air, confitt wholly of fixed air; or whether a considerable 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 fpar distilled in a glass retort, with a heat which at length melted the glass, did not furnish so much aqueous vapour as was even sufficient to tarnish the fides 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 furnith a drop. of water in the receiver ; the retort, however, appeared to be cracked at the end of the process.- But a similar result attended 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 method 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 fewn, no vapours will rise and be condensed, even from boiling water, in vefsels perfeitly clofe;' though the receiver be kept ever so cold, or even contain tube : stances that attract water with the greatelt avidity; such as dry salt of tårtar, and concentrated vitriolic acid : though we do not think that the Abbé has divined the true cause of the phenomenoa, which depends on other principles than the mere faturation of the confined air with humidity.

Accordingly, the most decisive proof, in our opinion, that the lofs of weight above mentioned is solely, or almost wholly, occafioned by the diffipation of the fixed air expelled from calcareous substances, is deduced from some experiments made by the Au-thor with the greatest care, and resembling those originaliy made by Dr. Black; with which they perfectly agree in the results. These clearly few that.calcareous substances lose as much weight

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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 Aafk, containing a small quan-
tity of diluted marine acid, and weighed the whole in a nice ba-
lance. 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 calca-
reous 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 flask with
its contents, he perceived a very considerable diminution of its
weight; no sensible part of which loss could reasonably be a-
scribed to the evaporation of any of the aqueous particles con-
tained in it. Six out of thirteen different calcareous earths or
ftones, treated in this manner, loft 8 parts in 20 during their
folution in the acid; which is the very proportion originally as-
figned 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 Staffordfire, and of the yellow, or queen's ware; which last is made of the fame materials as the former : though the proportions of clay and fint (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 Staffordshire about 80 years ago. The effect is produced solely by throwing into the furnace fome sea-falt, which instantly produces a thick vapour, that attaches itself to the fute face of the ware, and there forms that vitreous 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 Efray, are contained various observations on pit coal, particularly with regard to its analysis; from which it appears that its products, by diftillation, 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 same substance in England ; particularly at Bristol, where a person prepares it under the fanction of a patent. The Author suggests fome improvements of the process, which he thinks might be successfully 8

executed

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 dould not omit to observe, that (wo 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. III. 8vo. 5 s. Boards. Dodsley. 1781. N 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 appearance--this * covert and convenient seEMINGthe 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 fanctified 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 detest 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 bitherto 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 Thall say but one word to elude the accusation. We ad hered 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

• Shakspeare.

+ Pope.

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