feveral of the articles, and think them executed, in general, with great accuracy and great impartiality. Mr. Keir keeps to the old eftablished religion of Stahl, without being drawn afide by new herefies. A few articles are, perhaps, rather too extenfive, and one or two fuch as are not strictly connected with a dictionary of chemistry, particularly that on aeromatic telescopes, in the first page; but it contains fo much interefting and ufeful information, that to have omitted it would have deprived the work of a confiderable ornament. Almoft the whole of this part relates to acids, and the confideration of thefe bodies is not yet concluded: the first article of the fecond part being, as we learn from the catch-word, the vitriolic. When it is confidered how important acids are in a chemical fyftem, and how many bodies refult from their union with other fubftances, we can form no proper estimate of the extent of the work from the copioufnefs of the articles on this fubject. Some of Mr. Keir's remarks on the nitrous acid, we have already had occafion to notice. This acid is now examined at a confiderable length, and many very important obfervations are added. Our author is fully of opinion, that the compofition of water has not been proved, and that nitrous acid is not owing, as the Hacrlem philofophers fuppofed, to the phlogisticated air. If the acid alfo is obtained from inflammable gaffes produced from different fubftances, it must neceffarily arife from fome principle in common to all, in other words, to phlogifton. Many inftances alfo occur of inflammable gas being converted into phlogifticated air, or into refpirable; fo that he thinks one principle is common to inflammable and phlogifticated airs, and that this principle is united to refpirable air. We fhall tranfcribe fome of our author's conclufions. One confequence is, that as the union of inflammable and pure airs, when effected by detonation, is always accompanied with a great production of water, whether that water be merely diffolved in thefe fluids, or actually be one of their conftituent "parts; fo it is highly probable, that when the union is flowly accompanied, without explofion, the fame effect should also follow, Another probable confequence is, that as the union of thefe two fluids, and confequent formation of atmospherical air, must be attended with a great diminution of bulk, on account of the rarity of the inflammable gas, comparatively with the denfity of the atmospherical air produced, partial vacuums must be formed. A third confequence feems to be, that as fo much time is required for the accomplishment of the union of these fluids, a great part of the lighter, or inflammable fluid will rife into the upper regions of the atmosphere, where this operation of nature will chiefly take place, and where its concomitant phenomena will be molt confpicuous. The vacuums there formed, and the chemical attraction of the two fluids to each other, may be the means by which the pure air may be gradually brought, notwithstanding it is a little heavier than the atmospherical, into these higher regions, and in contact with the inflammable gas. Probably alfo the pure air, having a greater affinity with water than the atmospherical, phlogifticated, or inflammable fluids, may unite with the aqueous vapours, which are continually afcending. The difference of temperature, and of various other circumftances will occafion diversity in the degrees, in which this union of airs will take place at different times and places; and when this operation proceeds in a comparatively great degree, the condenfation or precipitation of water may occafion the formation of clouds, and the vacuums left by the converfion of inflammable gas into a denfer fluid will produce currents of air.' This diminution is particularly and chiefly obfervable when these airs are in contact with water. M. de Luc found the vapour in the highest mountains not in a state to affect his hygrometer, which pointed to extreme dryness. "From hence he concluded that rain is not the immediate effect of the condensation by cold of the aqueous vapours, which rife from the furface of the earth, as thefe would always be indicated by the hygrometer; but that these vapours must pass into fome intermediate aerial state, from which state, and not from that of the aqueous vapours, they are principally, by fome unknown operation of nature, formed into rain. But M. de Luc, no lefs correct in his reafonings than in his physical obfervations, found that he could not apply the experiments which proved the production of water by explofion of airs, to explain the formation of rain, as no fuch quantity of inflammable gas exifted in those parts of the atmosphere, where clouds are formed, and as these clouds are actually formed without explofion. The conjecture that I have fuggefted of the poffibility of the formation of clouds from the aqueous vapours that must be precipitated, when the inflammable and pure airs unite, and are confequently reduced in bulk, without explofion, is not liable to the fame objection. But it must be confeffed, that unlefs circumstances were difcovered by which the union of these fluids could be occafionally accelerated, without explosion, that conjecture is inadequate to the explanation of the fudden formation of clouds, when the neighbouring atmosphere is dry.' We have followed our author on this fubject, because it is one of the few places where we difcover his own opinion. We shall turn to another paffage, which we shall select for the fame purpose: it is in the article on vegetable acids, and relates to the elements of organic matter both animal and v❤ getable. After After confidering the gene products in confequence of the analyses of different fubftans, Mr. Keir reduces the elements to air, phlogifton, calceous earth, and water; and, by varying the proportions of efe, a number of compounds much greater than the various nds of organic matter may be produced. The following feridhow the proportion of phlo gifton, water, and earth, in ea of the products obtained by chemical analyfis : A. Of (Nitrous acid, or nit gifton. Uninflammable Inflammable Acetous acid Distilled or empyreuatic acids Acid of citrons Acid of benzoin Phlogisticated air Volatile alkali Sugar Gum Spirit of wine Ether Effential and empyramatic oils Grease and tallow Inflammable gas B. Of Wa- Charcoal Liquid volatile alli C. Of Ear.h.Nitrous acid Phlogisticated air contain none Volatile alkali Ether Spirit of wine Fixed air Acetous and othe.iquid acids Effential oils Fat oils Grease Tallow Refin Sugar Gums Charcoal Fixed alkali Calcareous earth. Our author's opinion ofvolatile alkali is peculiar, and we fhall enlarge a little on it,from the illuftrations of the order of thefe feries. It confifts he thinks, of as much phlogiston and water as can be unitectogether by means of a little earth and pure air. The proportii of the two last appears, however, too small to render the conlination firm, fo that the changes which the alkali admits of Le frequent. It may be objected, that nitrous acid has been claged to volatile alkali, by acting on metals in which calcareos earth has not been discovered; but the only metals known o have this effect are iron, tin, and zinc, which produce fixd air when burnt, and confequently may be fuppofed to retain fome portion of the charcoal employed in their reducion.' We know little, Mr. Kei obferves, of the compofition of phofphorus: it is the laft poduct of diftillation; it requires the utmost force of fire to feprate the ingredients of phosphorated lime, and the acid is rmerkably fixed. It may be fuppofed, therefore, that it conains much earth, and the pho phoric acid may be, at laft, a compound of nitrous acid and lime. To this opinion Mr. Keir feems to lean, and it is remarkable, that a compound of calcareous earth and nitrous acid is phosphorescent; the plofphorus of Baldwin is no more. It does not feem improbable, adds Mr. Keir, that phosphoric acid may acquire its peculiar character by an intimate combipation of calcareous earth, with fome determinate proportion of of the elements which conftitute acids; and this union may fa weaken the cohefion of this acid or of the air, with the phlogifton of the phosphorus, as to occafion its rapid feparation in burning, After thefe premifes, Mr. Keir proceeds to explain the great operations of nature. He had formerly remarked, that these are principally produced by the union of phlogifton with air, water, and earths, or by its feparation: the union is principally effected, he thinks, in vegetation, while the feparation, followed by new combinations, occurs in combuftion, the vinous fermentation and animalization. In vegetation, the juices are at firft watery: by the addition of pure air, they become auftere and acid: as the leaves expand they lofe this air, and acquire phlogiston, becoming faccharine: with more phlogifton only, and with more earth, farinaceous. When farinaceous feeds are moiftened and excluded from the light, the procefs is different and oppofite, ending with acidity and water. In the vinous fermentation the pure air efcapes in the state of fixed air, leaving the phlogiston predominant, and depofiting the fuperfluous earth. The remaining earth is depofited in the progrefs to the acetous fermentation, at leaft a large proportion of it, while pure air is abforbed to give acidity. If the air is excluded, and the heat retained, the phlogifton is feparated, flies off, in part, in the form of gas; and, in part, with much water, fome earth, and lefs air, forms volatile alkali. What reunites with pure air from the atmosphere becomes, with the earth of the vegetable matter, nitre, or calcareous nitre: the production of nitre is confequently a fecondary procefs, for, in putrefaction, almoft all the pure air is expelled. Animalization is defined by Mr. Keir to be a continually commencing putrefaction, conftantly checked and fubdued. The obviating caufes are, in his opinion, the ingeftion of fresh food and the abforption of air by the lungs. The progreffive ftages of putrefaction feem, he fufpects, to form the fluids for the different fecretions. The whole of this fystem, however unchemical, muft be received with reserve; and the addition, fo far as refpects the animal body, of other circumftances drawn from a different fource. On the whole, therefore, vegetables feem to contain a larger portion of pure air, by which their products are more acefcent, their phlogifton more firmly united with the other elements, so as to tamp a peculiar and diftinguishing character: while, in animal matters, the phlogiston is in greater, the pure air in lefs proportion; the former is more eafily difengaged, and the earth more readily forms thofe combinations in which it is chiefly found to predominate. Vegetables are therefore ready |