her imperfect knowledge was afterwards much improved in confequence of her converfing on the fubject with fcientific and communicative friends.

"As, however," the fays, "there are but few women who have access to this mode of inftruction; and as the author was not acquainted with any book that could prove a fubftitute for it, fhe thought that it might be useful for beginners, as well as fatisfactory to herself, to trace the fteps by which fhe had acquired her little ftock of chemical knowledge, and to record, in the form of dialogue, thofe ideas which the had first derived from converfation."

The titles of the converfations are, 1. Of the general principles of chemistry. 11. Of light and heat. 111. Continuation of the fubject. IV. On specific heat, latent heat, and chemical heat. v. On oxygen and nitrogen. VI. On hydrogen. VII. On fulphur and phofphorus. VIII. On carbone. IX. On metals. x. On alkalies. XI. Ôn earths. VOL. II. XII. On the attraction of compofition. XIII. On compound bodies. XIV. On the combinations of oxygen with fulphur and with phofphorus; and of the fulphats and phosphats. xv. On the combinations of oxy. gen with nitrogen and with carbone; and of the nitrats and carbonats. XVI. On the muriatic and oxygenated muriatic acids; and on muriats. XVII. On the nature and compofition of vegetables. XVIII. On the decompofition of vegetables. XIX. Hiftory of vegetation. xx. On the compofition of animals. XXI. On the animal economy. XXII. On animalization, refpiration, and nutrition. XXIII. On animal heat and on various animal products.

In the perufal of thefe converfations, we have, upon the whole, found reafon to admire the peculiar perfpicuity of the explanations, the manner in which fome natural objections are introduced and an!wered; and likewife the mode of introducing the definitions, which are difperfed throughout the volumes in their proper places, without the formality of arranging them all in a long lift, which frequently affrightens the beginner. The only objection, which might be made to this mode of explaining the terms, is, that if the ftudent at any time forgets the meaning of any of them, he cannot easily find out the page wherein it is explained. This objection, however, in the prefent work, is removed by the index which is placed at the end of the fecond volume.

In the lift of primitive or elementary fubflances, this author omits both the electric and the magnetic fluids, or the caufes which produce the phenomena of electricity and

magnetiim;

magnetifm; nor does fhe affign any reafon for the omiffion. Does the fuppofe, that they are the effects of nothing, or that they are produced by any of the other elements mentioned in her lift? We are of opinion, that she will find it very difficult to fubftantiate either of those fuppofitions.

In the abovementioned lift, this author likewife omits the muriatic, the boracic, and the fluoric, acids; but these she afterwards places in the fecond volume, where the says,

"Analogy affords us fo ftrong a proof of the compound nature of the undecompounded acids, that I never could reconcile myfelf to claffing them with the fimple bodies, though this divifion has been adopted by feveral chemical writers. It is certainly the moft ftrictly regular; but, as a systematical ar rangement is of ufe only to aflift the memory in retaining facts, we may, I think, be allowed to deviate from it when there is danger of producing confufion by following it too clofely; and this, I believe, would be the cafe, if you were taught to confider the undecompounded acids as elementary bodies." P. 18.

In page thirty one of vol. 1, it is afferted that Reaumur's thermometer is generally preferred by the French. This was undoubtedly the cafe fome years ago; but we are informed, that at prefent the centigrade divifion of the thermometrical scale has been generally adopted in that nation.

In page fixty eight, this author expreffes herfelf with too much confidence concerning the nature of a phenomenon, which is far from being clearly comprehended or explained by the most acute philofophers of the prefent age. Confidering caloric as a folvent, fhe fays, "caloric diffolves water, and converts it into vapour, by the fame process as water diffolves falt; that is to fay, the particles of water are fo minutely divided by the caloric as to become invifible."

In page 175, a fuppofition is mentioned, which might as well have been omitted, in the prefent ftate of knowledge repecting electricity and the nature of gafes.

"It is fuppofed," this author fays, "that thunder and lightning frequently proceed from a fimilar caufe--but this requires fome further explanation. Nature abounds with hydrogen; it conftitutes a very confiderable portion of the whole mafs of wa. ter belonging to our globe, and from that fource, almost every other body obtains it. It enters into the compofition of all ani. mal fubftances, and of a great number of minerals; but it is moft abundant in vegetables. From this immenfe variety of bodies, it is often fpontaneously difengaged; its great levity makes it rife into the fuperior regions of the atmofphere, and when, either by an electric fpark, or any cafual elevation of temperature,

U u 3

it

it takes fire, it may produce thunder, lightning, and fuch other la minous meteors as are occafionally seen in the atmosphere." P. 175.

Speaking of fteel, this author fays, "the hardness of fteel is very much increafed by an operation which confifts in heating the fteel till it is red hot, and then plunging it into cold water, this is called tempering." She ought to have faid hardening; for the tempering of fleel is when from that hard ftate it is foftened more or lefs according to the uses to which it is to be applied.

Treating of metallic alloys, this author fays, that bronze confifts of copper and iron. We imagine the means copper and tin; for copper unites very imperfectly with iron.

In page 248 of vol. 11, we read, that "in general a perfon at reft and in health will breathe between twenty and thirty times in a minute." This is confiderably beyond the truth.

After having noticed molt of thofe paffages, which feemed to us deferving of alteration, it is incumbent upon us to lay before our readers a few fpecimens of this author's ftyle and manner of treating the fubject. The following paragraph is an instance of a clear and familiar comparison.

"You have," fays the teacher to the pupil," mifconceived the idea of decompofition; it is very different from mere divifion: the latter fimply reduces a body into parts, but the former feparates it into the various ingredients, or materials, of which it is compofed. If we were to take a loaf of bread, and separate the feveral ingre. dients of which it is made, the flour, the yeaft, the falt, and the water, it would be very different from cutting the loaf into pieces, or crumbling it to atoms." P. 7.

In the twelfth converfation, the meaning of fimple and double elective attractions, are neatly explained in the following manner.

"The 7th law is, that bodies have amongst themselves different degrees of attraction, Upon this law (which you may have difcovered yourfelves long fince), the whole fcience of chemistry depends; for it is by means of the various degrees of affinity which bodies have for each other, that all the chemical compofitions and decompofitions are effected. Thus, if you pour fulphuric acid on foap, it will combine with the alkali to the exclufion of the oil, and form a fulphat of potafh. Every chemical fact or experiment is an inftance of the fame kind; and whenever the decompofition of a body is performed by the addition of any fingle new fub. ftance, it is faid to be effected by fimple elective attractions. But it often happens that no fimple fubftance will decompofe a body, and that, in order to effect this, you must offer to the compound a body which is itself compofed of two, or fometimes three prin

ciples,

ciples, which would not, each feparately, perform the decompofition. In this cafe there are two new compounds formed in confequence of a reciprocal decompofition and recompofition. All inftances of this kind are called double ele&rve attractions.

"Caroline. I confefs I do not understand this clearly,

"Mrs. B. You will eafily comprehend it by the affiftance of this diagram, in which the reciprocal forces of attraction are reprefented by numbers:

"We here fuppofe that we are to decompofe fulphat of foda; that is, to feparate the acid from the alkali; if, for this purpose we add fome lime, in order to make it combine with the acid, we fhall fail in our attempt, because the foda and the fulphuric acid attract each other by a force which is (by way of fuppofition) reprefented by the number 8; while the lime tends to unite with this acid by an affinity equal only to the number 6. It is plain, therefore, that the fulphat of foda will not be decompofed, fince a force equal to 8 cannot be overcome by a force cqual only to 6. Caroline. So far, this appears very clear.

"Mrs. B. If on the other hand, we endeavour to decompofe this falt by nitric acid, which tends to combine with foda, we fhall be equally unfuccefsful, as nitric acid tends to unite with the alkali by a force equal only to 7:

"In neither of these cafes of fimple elective attraction, therefore, can we accomplish our purpose. But let us previously combine together the lime and nitric acid, fo as to form a nitrat of lime, a compound falt, the conftituents of which are united by a power equal to 4. If then we prefent this compound to the fulphat of foda, a decompofition will enfue, becaufe the fum of the

U u 4

forces

forces which tend to preferve the two falts in their actual state, is not equal to that of the forces which tend to decompofe them, and to form new combinations. The nitric acid, therefore, will combine with the foda, and the fulphuric acid with the lime. Caroline. I understand you now very well. This double effect takes place becaufe the numbers 8 and 4, which represent the degrees of attraction of the constituents of the two original falts, make a fum lefs than the numbers 7 and 6, which represent the degrees of attraction of the two new compounds that will in confequence be formed.

"Mrs. B. Precifely fo.

"Caroline. But what is the meaning of quiefcent and divellent forces, which are written in the diagram?

"Mrs. B. Quiefcent forces are those which tend to preferve compounds in a state of reft, or fuch as they actually are: divel lent forces, thofe which tend to destroy that ftate of combination, and to form new compounds.

"Thefe are the principal circumftances relative to the doctrine of chemical attractions, which have been laid down as rules by modern chemifts: a few others might be mentioned refpecting the fame theory, but of lefs importance, and fuch as would take us too far from our plan." Vol. ii. p. 9.

The defcription of the manner of obtaining fugar from the fugar cane, is the laft fpecimen of this elegant publica, tion, which we fhall offer to our readers.

"Mrs. B. The juice of this plant is first expreffed by paf fing it between two cylinders of iron. It is then boiled with lime-water, which makes a thick fcum rife to the surface. The clarified liquor is let off below and evaporated to a very fmall quantity, after which it is fuffered to cryftallize by standing in a veffel, the bottom of which is perforated with holes, that are imperfectly stopped, in order that the fyrup may drain off. The fugar obtained by this process is a coarse brown powder, commonly called raw or moift fugar; it undergoes another operation to be refined and converted into loaf fugar. For this purpofe it is diffolved in water, and afterwards purified by an animal fluid called albumen. White of eggs chiefly confift of this fluid, which is alfo one of the conftituent parts of blood; and confequently eggs, or bullocks blood, are commonly used for this purpofe.

The albuminous fluid being diffufed through the fyrup, combines with all the folid impurities contained in it, and rifes with them to the furface, where it forms a thick fcum; the clear liquor is then again evaporated to a proper confiftence, and poured into moulds, in which, by a confufed cryftallization, it forms loaf fugar. But an additional procefs is required to whiten it; to