and accordingly solicits accurate and faithful information on all the subjects connected with his plan from every quar

ter.

Werner on

Veins,

Werner's Theory of the Formation of Veins, with its Ap- Translation of plication to the Art of Working Mines, has been trauslated from the German, by Dr. Charles Anderson, of Edinburgh, member of the Wernerian Society, &c. It is accompanied with notes by the translator, some of which relate to mine districts in our island not noticed by Werner. It is unue. cessary to say more of a work published about twenty years ago, than that it exhibits the results of nearly thirty years investigation by a man, whose experience and sagacity as a mineralogist have long been acknowledged.

eye.

Dr. Joseph Reade, of Cork, has just issuing from the Treatises on press some Critical and Practical Observations on the Dis- diseases of the eases of the inner Corner of the human Eye, comprising the epiphora, tumour of the lachrymal sac, and fistula lachrymalis, with a new arrangement and method of cure.

The communicatious from Mrs. Ibbetson, Mr. Dalton, Mr. Murray, and Mr. Bowditch, were too late for the present month, but will be inserted in the next number.

Meteorological

For DECEMBER, 1810,

Kept by ROBERT BANCKS, Mathematical Instrument Maker, in the STRAND, London.

Rain in the night.

at 9 A. M.

and stormy night.

a lutervening fogs.

+ Stormy night.

Maximum of Heat

§ Stormy morning, hail at half past 4 P, M. ligh:ning in the evening,

OF

NATURAL PHILOSOPHY, CHEMISTRY,

AND

THE ARTS.

FEBRUARY, 1811.

ARTICLE I.

Inquiries concerning the Signification of the word Particle, as used by modern Chemical Writers, as well as concerning some other Terms and Phrases. By Mr. JOHN DALTON. In a Letter from the Author.

SIR.

To Mr. NICHOLSON.

IN perusing the modern books, which are edited under Meaning of

undefined.

the titles of Elements or Systems of Chemistry, I have been chemical terms greatly perplexed in endeavouring to understand the meaning, which the authors attach to certain words and phrases, which are of perpetual occurrence, particularly when treating of affinity, but which the authors no where define. I allude more especially to the word particle.

With respect to the article affinity itself it is somewhat Affinity. remarkable, that different authors should view it in such different lights. Lavoisier in his Elements of Chemistry does not say a word on the subject, except a few observations in his preface tending to show the difficulties of it, and its unfitness to be presented to a novice in chemistry. In VOL. XXVIII. No. 127-FEB. 1811. G speak

Chaptal.

speaking of the number and nature of elements, he says, "I shall therefore only add on this subject, that, if by the term elements we mean to express those simple and indivisible atoms of which matter is composed, it is extremely probable we know nothing at all about them." Chaptal employs about 20 pages on affinity, two on the affinity of aggregation, and the rest on the affinity of composition. In the third edition of your First Principles of Chemistry, I observe 10 pages on affinity. Berthollet has written a small volume on the subject. Fourcroy, Thomson, Murray, and Henry, have all expanded their views on this subject pretty extensively. From these observatious it should seem, that the article affinity in systems of chemistry has been of growing importance since the time of Lavoisier's publication. This may certainly be right; but as the subject is acknowledged to be one of the most difficult in the science, it is highly necessary, that authors should treat it with all the perspicuity of which it is capable; the terms used should be clear and well defined; metaphorical expressions should be avoided; and ambiguities should be guarded against with all possible care.

Chaptal has been very sparing in the use of the term particle when treating of affinity (I refer to your translation, 2d ed.); he only mentions it three times, twice unqualified, and once along with the epithet elementary; he seems to Integrant part. use integrant part, where others would use particle, and he defines it thus: "two drops of water, which unite together into one, form an aggregate, of which each drop is known by the name of an integrant part."

Nicholson's

ples.

On the subject of affinity I observe you use the term First Princi particles frequently, but only once in the singular number. No definition of it is ever given; but the last time it occurs is in a very judicious concluding remark, which I do not remember to have seen in any subsequent writer; namely,

it seems reasonable to iufer, that two compounded particles coming together by attraction, undisturbed by any other cause, should dispose themselves so as to apply such sides of each together, as are occupied by principles the most attractive of each other." In another part of the chapter you observe, that "the minutest parts, into which

an

parts.

an aggregate can be imagined to be divided without decomposition, are called integrant parts; but the parts into which Integrant and it is divided by decomposition are called component parts component or principles." These definitions would be clear and intelligible to me, if the words I have put in italics were omitted*; the sense affixed to integrant parts is better than that of Chaptal, and is the same as the most correct modern writers apply to integrant particles. But, after thus defining the terms integrant parts, I do not find, that you have again used them throughout the chapter.

chemical affi

nity.

From the high encomiums, which several modern writers Berthollet on pass on Berthollet's researches into the laws of chemical affinity, I was induced to hope, that in a volume written exclusively upon affinity by so able a hand, I should find the term particle clearly defined in the first page. I took up the English translation, and read 37 pages without once meeting with the word particle, or any other word of similar import. I was beginning to think, that the author intended to abolish the old doctrine of bodies consisting of extremely small parts bound together by a principle of cohesion, or affinity of aggregation, and to establish the one that bodies consist entirely of cohesion, when in the opening of the 5th article I read, "the cohesion of the mole- Molecuiz, cule of a body is due to the reciprocal affinity of these molecule;" the word moleculæ did not again occur in the volume to my cursory observation. In the same page I met with the phrase integral parts, and afterward in the space of 150 pages the words part and particle were observed in about a dozen places. Whatever obscurity may be found in Berthollet's researches then, they do not arise from the frequent use of the term particle.

* I do not know how Mr. Dalton would understand the passage, if the words in italics were omitted; but they appear necessary, to express the true meaning with precision, Suppose a single atom of sulphuric acid combines with a single atom of mineral alkali to form a particle of sulphate of soda, and a crystal to be formed by the aggregation of such particles: we cannot actually divide it into these component parts, though we can imagine it so divided. The word imagined may be here taken as synonimous with the word conceived of the geometers, and has no necessary relation to operative or human practicabily. N.