dence fo neceffary to enfure the free circulation of grain, and the conveyance of fupplies to every part of the kingdom, without which, even if the barns of the farmer fhould be full, the market will be empty; and without which we may experience the horrors of famine, though not with plenty in the land, yet with a fufficiency to fave us from actual want.

"I have avoided carefully giving any opinion upon the degree in which the crop of the prefent year falls fhort of the average produce; no accounts which have been yet received appear fufficiently general or correct, to warrant a pofitive ftatement of its precife amount. If the deficiency be overrated, it fpreads alarm unneceffarily and increafes the price; if it be underrated, it puts us off our guard, and encourages an improvident confumption. The farmers, from whom information upon this point muft chiefly be collected, are difpofed generally to reprefent the quantity in their poffeffion as lefs than it really is, and it is probable, therefore, that the estimated amount of the crop may be, in fome degree, underrated. There is no doubt, however, that there is a deficiency; there is as little doubt that the means of fupplying it, or of alleviating its effects, are completely within our reach. Large fupplies, it is known, may be obtained from foreign parts, and the measure of propofing to Parliament an encouraging bounty for the purpose of bringing them to this country is determined upon; the fame plan which was formerly adopted by the more opulent claffes, of limiting the ufe of wheat in their families, will undoubtedly be again readily reforted to; and the liberal encouragement held out by the East India Company to the importers of rice, will furnish a large fupply of provision before the next harveft. All thefe confiderations tend to relieve our apprehenfions: and, upon the whole, there appears to be not only no danger of famine; but from the difpofition to meet the difficulty, which feems to manifeft itself, there is reafon to hope, that when the causes of high price, which have been ftated to apply peculiarly to the prefent moment, cease to operate, the poorer claffes of fociety may be, in a great measure, relieved from the preffure of that calamity which they now endure.

"I am well aware that feveral of the points which I have noticed in these few remarks have been rather touched upon, than fully and completely argued. Erroneous and mischievous doctrines appeared to be gaining ground, and I have endeavoured fhortly and diftinctly to obferve upon them, without entering into minute difcuffion. Upon a queftion on which opinions are fo various, I am not prefumptuous or fanguine enough to fuppofe that many perfons will agree entirely in mine; but if, upon a fubject fo interefting to all, I should have induced any candid mind to investigate further the topics which I have ftated, removed one falfe notion, or fuggefted one ufeful hint, my object will be attained, and my endeavours molt amply rewarded." 41.

Thus we have conducted the reader, ftep by step, through this interefting publication; but he will ftill do well and wifely, to examine the whole deliberately by himself. As far as its object extends, we profefs ourselves to have been satisfied with its arguments, its perfpicuity, and its vigour.

ART.

ART. VI. Elements of the natural History and chymical Analyfts of Mineral Subflances, for the Ufe of the central Schools. Tranflated from the French of Mathurin James Briffon. 8vo. 149 PP. 45. Walker.

1800.

THE author of this work begins by defcribing the more fimple mineral fubftances, and then their compounds. Mineral fubftances are either of an earthy or ftony, or of a metallic nature. The more fimple earthy or ftony fubftances, are lime, magnesia, baryte, alumine, and filex. From thefe, varioufly combined or mixed with other bodies, all other earths and ftones appear to be formed. Combined with acids, they form faline ftones, or earthy falts.

The different fpecies of thefe are firft defcribed, then stones properly fo called, then volcanic productions, then metallic fubftances. A work of this kind, which is intended principally as a text book, does not admit of being analysed, its merit confifting in the correctness of the definitions and defcriptions, and in their being no material omiflions. Under these heads, we believe, there will be found little ground for cenfure. On the other hand, the author appears to have collected a more ample body of information, on the nature of mineral fubitances, than we have seen in the fame compafs.

The following fpecimens, taken from different parts, will give an idea of the work, as well as of the merit of the tranfIation.

"Of Alumine, or pure Clay.

"Alumine is found chiefly in clay, of which it forms the basis, and is very often mixed with filice. To obtain it pure, fulphate of alu mine (alum) is to be diffolved in water, and then decomposed by the alkaline carbonates: the alkali combines with the fulphuric acid, which feparates from the alumine, and this combines with the carbonic acid left by the alkali. The alumine is then freed from this acid by calci. nation, and is found pure.

"Alumine eagerly imbibes water, and diffufes itfelf in it.

It strongly adheres to the tongue.

"Alumine expofed to the action of fire dries, contracts itself, cracks, and hardens to fuch a degree as to give fire with steel. In this state it no longer diffufes itself in water.

Alumine, even the pureft, is completely fufible by a fire blown, with oxygen gas, and melts into a very hard, vitreous, opaque fubftance, which fcratches glafs, as the precious ftones commonly do. "Borate of foda, and phofphates of urine, diffolve alumine.”

P. 5.

" ORDER

ORDER 1.-Saline Stones, or earthy Salts.

This order comprehends all thofe ftones, in which the primitive earths are combined with the several acids, and for this reafon are defcribed by the name of earthy falts, or faline ftones. The primitive earths being five in number, this order is compofed of five genera of ftones, each diftinguished by the peculiar carth which forms its bafis. "GENUS I.-Saline Stones with calcareous Bufis.

"This genus is compofed of fuch ftones as have Hime for their bafis. The different fpecies comprifed under this genus are distinguified by the different acids in combination with this bafis.

"SPECIES I.-Combination of Lime with carbonic Acid.

"The refults of this combination are the carbonates of lime, or calcareous ftones. This combination is the most frequent, and the principal characters of these ftones are, ift, to effervefce with acids, which expel from them the carbonic acid. 2ndly, to be converted into lime by calcination, because heat alfo expels from them the carbonic acid.

Some of the calcareous ftones cryftallize regularly; most commonly in rhomboids, as for inftance the calcareous fpars; and fome others in pyramids, or prifms. Their fpecific gravity is commonly little above 27000. Chymical analyfis has fhown, that in a hundred parts of thefe ftones there are from 34 to 36 parts of carbonic acid, from 53 to 56 parts of lime, and the remaining parts are water.

Other calcareous ftones cryftallize confufedly, for inftance the alabafter and the ftalactites. The fpecific gravity of the former is from 27000 to 28000, and the fpecific gravity of the latter is only from 23200 to 24700.

Others are found in fhapeless males; fome of which are capable of receiving a bright polish, as the marbles; and fome have a rough and coarfe texture, as freeftone and chalk. The fpecific gravity of the marbles is from 26500 to 28500; that of the freeftone, from 16000 to 24000. Whenever calcareous ftones are poffeffed of a degree of tranfparency, they occafion a double refraction of light.

"N. B. What occafions the fuperior hardness of many ancient buildings is the converfion of the lime contained in the cement into chalk, by the abforption of the carbonic acid of the air." P. 7.

"ORDER II-Of Stone properly fo called.

"The fimple and pure primitive earths are feldom found feparate on the furface of the globe. Commonly they are found mixed with one another, and form maffes of different volumes, and different hardnefs, according to the nature of the earths which are mixed together, and of the extrageous matters which are combined with them. Thefe mixtures are ftones properly fo called.

"In thefe mixtures generally one earth predominates over the others, either by its greater quantity, or by imparting its character to the mixture. This circumftance determines the genera, which are five, according to the number of the primitive earths. The fpecies are diftinguished by the different principles which conftitute them; and the different proportions of thefe form varieties." P. 19.

"Alumine,

"Alumine, Silice (Silex) pure Magnesia, and Iron.

"This mixture forms the micas. They feel foft, but not greafy, in which they differ from the tales; and are alfo more shining than thefe. They are fealy, lamellous, or ftriated, and all of them permeable to water. Their colours vary, but the most common are white and yellow. Their specific gravity is from 26546 to 29342. Powdered white and yellow micas are used to prevent writing from being blotted, and are called golden and filver fand. The micas are very often one of the ingredients of granite.

"According to Kirwan one hundred parts of white mica contain 28 of alumine, 38.of filice, 20 of magnesia, and 14 of oxide of iron." P. 25.

"Diamonds. The diamond is unquestionably to be placed among the gems, but it differs fo widely from thofe of which we have been fpeaking, as to deferve a particular article. Its combuflibility is a property which peculiarly belongs to it. The diamond burns in the fame manner as phofphorus docs, and difappears without leaving any refiduum; but for this effect it requires the prefence of air, in the fame manner as it is required in the combuftion of any other inflammable fubftance. A cupel fire is fufficient to produce this phenomenon,

"The diamond is the hardeft of all bodies, and can only be wrought by itself, diamond powder being the only fubftance that can cut the diamond.

"The diamond has a great tranfparency. It is the finest and brightest of ftones. All diamonds occafion but a fingle refraction of the rays of light, but this refraction is stronger than in any other fubtance; they feparate colours more, and for this reafon they fhine fo eminently, particularly in the funfhine, or even by candle light. We know two forts of diamonds, the oriental diamond, and the Brazilian diamond." P. 40.

"Pebbles are hard and opaque ftones fufceptible of affuming a fine polifh, fhining in their fracture (when broken) and feemingly compofed of concentric ftrata. Pebbles are never found in quarries like other ftones, but loose and scattered over the ground. The atmospheric air decompofes them, and for this reafon they are almoft always covered with a cruft fofter than their interior. They are of a great variety of colours, fpotted, veined, streaked, and even herborised. When united by any cement whatever they form the pudding stones. Their fpecific gravities are from 22431 to 26644." P. 57.

"Platina-Platina is a white metal, but darker and not fo bright as filver. It is heavier than gold, confequently the heaviest of all known bodies. Its hardness is inferior only to that of iron; and its tenacity, which is more than thirteen times that of lead, to that of iron and copper alone. Expofed to the fire, it is very nearly as fixed as gold. Neither water nor air occafions any alteration in it.

"Platina is found in its ores in fmall grains or fpeckles of a blueifh white, and always combined with iron, and poffeffing the magnetic property. So mixed, its fpecific gravity is 156017. In this ftate it is ittle malleable, but when perfectly purified from any extraneous fub

ftances,

ftances, it is malleable enough to be worked in the flatter, or in the wire engine, and reduced to a very flender wire without breaking.

"Platina is by no means fufible in a common fire. Expofed to the focus of Mr. Trudaine's burning glafs, it has fhown only a beginning of fufion, by the conglutination of its grains; but Lavoifier has eafily melted platina, by blowing the fire with oxygen gas. By prooceding thus, Lavoifier melted purified platina ftill more eafily. In this ftate of purification its specific gravity is 195000, but when it has passed through the flatter its gravity is 220690.

"Platina is foluble only in nitro muriatic acid, or oxygenated muriate. The alkalies precipitate it from the folution.

"A folution of muriate of ammonia, poured on a folution of platina, forms a precipitate of an orange colour, which is a true faline fubftance, intirely foluble in water. This property of the muriate of ammonia of precipitating platina, affords an eafy and fimple means of afcertaining the alloy of platina with gold.

"Platina can be mixed with many metals, but they render it brittle. Copper, however, if mixed in the proportion of 3 or 4 to 1, forms with platina a very hard but malleable metal, capable of a high polish, and little liable to be tarnished.

Platina is a metal valuable for its great hardnefs, the high polif of which it is fufceptible, and its inalterability. Speculums of telef copes may be made from it, much preferable to thofe we ufe, because their polifh is incapable of being tarnished. It poffeffes another very valuable property, that of changing but little its dimenfions in different temperatures. For this reafon it was very advantageoufly employed in the measurement of the arc of the meridian betwixt Barcelona and Dunkirk." P. 70.

At the end, the author gives an account of two additional primitive earths. Stroothian, firft difcovered by Dr. Hope of Glasgow; and Iargonic, found by Klaproth in the ftone called Jargon, brought from Ceylon.

The tranflator, we should obferve, conftantly writes filex, filice; and the colour grey, gray. Other inaccuracies there are, but not fuch as to obfcure the fenfe of the original.

ART. VII. A complete Syftem of Aftronomy. By the Rev. S. Vince, Plumian Profeffor of Aftronomy, and experimental Philofophy in the University of Cambridge. Two Volumes. with Plates. 21. 8s. Deighton, Cambridge; Elmfly,

London.

4to.

KEPLER, in his celebrated work entitled de Motibus Stelle Martis, publifhed three great difcoveries, which are the foundation of all plane aftronomy; that the planets defcribe

about