The firft effay of the fecond volume contains fome obfervations on the compofition and analysis of gunpowder. In the next,' On common Salt,' the Author relates fome experiments made by him, to difcover 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 thofe who may attempt the making of bay falt in this country. The third contains a few observations on common falt and nitre, confidered as ma-' nures; and on the fertilizing quality afcribed to fnow, which cannot justly be attributed to any nitre contained in it. In the fourth, the Author has collected, from various writers, feveral obfervations relative to the temperature and faltness of the fea, and reasons upon them.

In the fifth Effay, the Author treats of fresh water procured from that of the fea, by the means either of congelation, or diftillation. In the manufacturing of fea-falt, he propofes the freezing of fea-water; by which he estimates that one third of the water at least may be converted into ice; fo that one third of the fuel may be faved, in boiling down the remaining brine into falt. An analyfis is likewife given of fome water diftilled by Dr. Irvine from fea water; from which it appears that though the distilled fea water is not wholly free from faline particles, yet it probably contains them in so small a proportion, as not to render it unwholefome.

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

Some philofophers have doubted whether lime, ftone, and other calcareous fubftances really contained fo very large a quantity of fixed air, as has been inferred from the lofs of weight which they fuftain on calcining them; or on applying acids to them, as in the original experiments on this fubject made by Dr. Black. Some have fuppofed that a confiderable part of the lofs obferved in these cafes ought to be ascribed to the expulfion of the water which enters into the compofition of thefe bodies. The Author appears to have made a confiderable number of experiments, with the greatest accuracy, on a great variety of marbles, calcareous earths, and fpars; the refults 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 fubftances of different kinds and countries, the medium quantity of lime that might be procured from a ton E 3 (or

54

(or twenty hundred weight) of thefe fubftances, was found to a mount to Icwt. 25 pounds. Confequently they had sustained a lofs of weight amounting to fomewhat above 8 cwt. 3 quarters. That the whole, or nearly the whole of the fubftance thus loft was fixed air, feems to be fatisfactorily evinced by fome fubfequent experiments, to be related hereafter.

It is well known that the calcareous ftones thus converted into lime, on being expofed for a fufficient time to the atmosphere,. attract from thence a confiderable part of the fame kind or kinds of matter which they had loft during their calcination; and that they are then found to be poficfled of their former qualities, fo as not to be fenfibly diftinguifhed from crude limestone, marble, &c. We have, in the article above referred to, given the results of fome of Dr. Higgins's experiments relative to this fubject; and fhall here relate fome of the Author's.

On February 10, 1779, he converted a piece of ftatuary. marble, weighing 540 grains, into lime. While ftill 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 fame way; and it acquired its greatest increase of weight in 22 days. In one particular inftance, 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 thefe laft experiments is, that, as a ton of fresh lime will, on expofure to the atmofphere, acquire an increase of weight amounting, in fome cafes, to half, and in others, to more than three quarters of a ton; it is obvious, that, the perfon who purchafes it by weight, will be a confiderable lofer in the article of weight as well as that of quality, if he buy it even a few days after The farmer too, who propofes to the kiln has been drawn. lime his land, fhould carry the lime out as foon as poffible after it has been burned; as otherwife, for every ton, he may have the trouble of carrying a ton and a half, or more.

It follows likewife that the foil on which fresh lime fpread acquires a very confiderable increafe of matter, 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 increafe of foil, by means of the fubftance

fubftance attracted from the air, equal to above 30 tons in weight beyond the original weight of the lime. We fhall obferve, however, that the lime will probably derive fome of its increase from the contents of the foil in which a part of it is immerfed, or from matters fermenting in it.

It now remains to examine whether the large quantity of fubftance which calcareous bodies lofe on calcination, and which they recover on expofure to the air, confift wholly of fixed air; or whether a confiderable part of it may not be water. The Au-' thor relates fome experiments that do not feem to favour this laft fuppofition; which has, nevertheless, been adopted by writers of diftinguished reputation.Cryftalized fpar diftilled in a glafs retort, with a heat which at length melted the glafs, did not furnifh fo much aqueous vapour as was even fufficient to tarnish the fides of the receiver. This experiment, however, is not quite fatisfactory, as we are not informed what was the lofs of weight fuftained by the fpar, 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 expofed to a ftrong fire, fo as to lofe 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 procefs.- -But a fimilar result attended a trial made with 720 grains of what the Author calls Derbyshire Watricle; though this fubftance was reduced, by means of the heat employed in the procefs, to 400 grains.

Objections may be made even to this laft procefs, which is not related with fufficient minutenefs. The only fatisfactory method of afcertaining this matter, by diftillation, would be that of receiving the products of the procefs in mercury. If, in the Author's proceffes, any vent was given to the fixed air let loofe during the calcination, the aqueous vapours might and would pafs through the fame opening. On the other hand, as the Abbé Fontana has lately fhewn, no vapours will rife and be condenfed, even from boiling water, in veffels perfectly close; ' though the receiver be kept ever fo cold, or even contain fubftances that attract water with the greateft avidity; fuch as dry falt of tartar, and concentrated vitriolic acid: though we do not think that the Abbé has divined the true caufe of the phenomenon, which depends on other principles than the mere faturation of the confined air with humidity.

Accordingly, the most decifive proof, in our opinion, that the lofs of weight above mentioned is folely, or almoft wholly, occafioned by the diffipation of the fixed air expelled from calcareous fubftances, is deduced from fome experiments made by the Author with the greateft care, and refembling thofe originally made by Dr. Black; with which they perfectly agree in the refults. Thefe clearly fhew that calcareous fubftances lofe as much weight

on the addition of acids, as by fire; and that therefore the matter expelled from them, in both cafes, is the fame, or fixed air.

The Author ufed a Florence flafk, containing a small quantity of diluted marine acid, and weighed the whole in a nice balance. He then at intervals flowly dropped into it 20 grains of a calcareous fubftance; gently stopping the mouth of the flafk with his finger. As the fixed air expelled from the calcareous matter is fpecifically heavier than the common air before contained in the flafk; he either extracted it, after the effervefcence had ceased, by fucking it through a tube, or blew it out by means of a pair of bellows. Then weighing the flafk with its contents, he perceived a very confiderable diminution of its weight; no fenfible part of which lofs could reasonably be afcribed to the evaporation of any of the aqueous particles contained 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 affigned by Dr. Black, in his experiments made with chalk. It appears from fome subsequent experiments made with the greatest attention, with fome other, and probably more pure, calcareous fubftances, treated in the fame manner, that they lost 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 gypfeous alabafter, or plaister-flone.' He gives a fhort account of the compofition of the flint or white ftone-ware made in Staffordshire, 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 ftone-ware receives its harmless glazing, by a very fimple procefs, which was formerly executed in fecret by two Dutchmen, who introduced the practice into Staffordshire about 80 years ago. The effect is produced folely by throwing into the furnace fome fea-falt, which inftantly produces a thick vapour, that attaches itself to the fur face of the ware, and there forms that vitreous coat which is called its glaze.This Effay likewise contains feveral obfervations relative to the component parts and nature of porcelane.

In the 8th and laft Effay, are contained various obfervations on pit coal, particularly with regard to its analyfis; from which it appears that its products, by diftillation, refemble thofe obtained from wood. In particular, tar has for feveral years past been procured from it, in fome parts of Germany; and confiderable quantities are now obtained from the fame fubftance in England; particularly at Briftol, where a perfon prepares it under the fanction of a patent. The Author fuggefts fome improvements of the procefs, which he thinks might be fuccefsfully

8

executed,

executed, not only by thofe who char pitcoal, or convert it into cinder; but by thofe likewife who burn wood into charcoal: in both which operations, the oil which is now wafted in flame, or otherwife diffipated, might be faved and collected; fo as to be manufactured into tar, at a trifling expence.

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

B...y.

ART. XI. THELYPHTHORA; or a Treatife on Female Ruin, &c.'
Vol. III. 8vo. 5 s. Boards. Dodfley. 1781.

N an undertaking fo novel and fingular as this, a more than common appearance of zeal for religion was requifite, in order to give the colour of fanctity to a fyftem of lewdnefs, and to make the tyranny of the stronger fex confiftent with the fhew of affection for the weaker. To preferve this equivocal appearance-this covert and convenient SEEMING-the Author had difficulties of a very ferious and formidable nature to struggle with and to do him juftice we must acknowledge his ingenuity; though fuch hath been his fate, that in spite of all the folemn profeffions he hath made-t wrapt round and fanctified with texts of Holy Writ!-there is fcarcely one reader in a hundred but hath had the fenfe to fee through his defign, and the virtue to deteft his principles.

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

Some have faid that, we have kept no terms of civility with the Author :—and he himself, veiling his mortification beneath the mafque of indifference, hath repeatedly infinuated, that his argument is hitherto fecure, becaufe, forfooth! it hath not hitherto had the good fortune to be understood.

As to the want of civility, with which we have been charged, we fhall fay but one word to elude the accufation. We adhered to TRUTH, as the main object of our criticifm; and in attempting to fecure that, we were not particularly follicitous about the forms and ceremonials of addrefs. We must acknowledge, that we abhorred Mr. M.'s principles; but, though we were apprehenfive of their pernicious tendency, yet we dreaded not the abilities which fupported them. We were willing to thew the Public our undisguised fentiments, by a direct attack of the firft and fundamental principles of his fyftem; unawed by

• Shakspeare.

† Pope.

the