into the canal. Mr. Sommering has sometimes adopted this plan in cases where the stricture was so narrow as not to admit the finest bougie. It is done by injecting olive or poppy oil into the canal, closing the orifice of the glans, and then by pressure with the fingers, attempting to propel the liquid through the obstacle. This manipulation is to be repeated until a bougie can be introduced.

M. Amussal affirms that this process is preferable to the use of bougies, at the commencement of the dilatation of a stricture; that it is applicable to cases of complete retention; and that it may also be had recourse to, to assist the action of flexible catheters; that is to say, when the stricture has been sufficiently dilated by injections to permit the introduction of a catheter, it will be advantageous to force the liquid between the instrument and the parietes of the urethra.”—pp. 218.

ART. III. On the Atomic Theory of Chemistry. By JOHN FINCH, M. C. S. &c.

2. Electro-Magnetism; being an arrangement of the principal facts hitherto discovered in that science. By JACOB GREEN, M.D. &c. Philadelphia, 1827.

THE paper of Mr. Finch under the foregoing imposing title, is published in the 29th number of the American Journal of Science and the Arts. We should not have noticed this production, did we not conceive that the author is completely at fault in his notions, and did we not fear, that from the wide circulation of the journal in question, he might mislead, or at least confuse some who are commencing chemical studies.

So far as we can understand this paper, the main object of the author is to point out the advantages which would result from considering water a compound of one atom of oxygen, and two atoms of hydrogen, a theory proposed several years since by Sir H. Davy, but which, with two or three exceptions, was not adopted by the best chemists.

The advantages which Mr. Finch promises from the adoption of this theory are,-1st, that the theory of volumes will then coincide with the theory of atoms; 2ndly, that the numbers representing the atoms or volumes of substances, will approach very near to their specific gravities.

But the author has omitted to mention the inconvenience attending this supposition, and which, in our judgment, is far

greater than the evil it is intended to remedy. To demonstrate this more clearly, we shall offer the following symbols, representing the composition of the several substances, in volume, according to the most approved chemical authors. Resulting volume.

Water.

Hydrogen

Oxygen

Muriatic acid.

Hydrogen Chlorine

Hydriodic acid.

Hydrogen Iodine

Phosphuretted hydrogen.

Hydrogen Phosphorus

Sulphuretted hydrogen.

Hydrogen Sulphur

Hydrocyanic acid.

Hydrogen Cyanogen

It will be observed, that in each of these compounds the volume of hydrogen is the same; that water consists of one volume of hydrogen, united with half a volume of oxygen; and that all the other compounds consist of one volume of each of the constituents. Now if we adopt Mr. Finch's theory, that water is a compound of one atom of oxygen, and two atoms of hydrogen, muriatic acid should be a compound of one atom of chlorine and two atoms of hydrogen, although formed of one volume of its constituents. Sulphuretted hydrogen should consist of one atom of sulphur, and two atoms of hydrogen, though composed of one volume of each of these elements. The same remark applies to hydriodic acid, hydrocyanic acid, phosphuretted hydrogen, and indeed to most of the compound gases containing hydrogen. How far then this supposition would effect the first object proposed by Mr. Finch, we need not stop to inquire.

This theory found a more able advocate in Dr. Ure, whose remarks at first sight have the appearance of great plausibility. "For aught we know," says he, "water may be a compound of two atoms of hydrogen and one of oxygen; in which case we should have the proportion of the weights of the atoms as given by equal volumes, namely, 1 to 16. There is no good reason for fixing on one compound of hydrogen more than on another, in the determination of the basis of the equivalent scales. If we deliberate on that combination of hydrogen in which its agency is apparently most energetic, namely, that with chlorine, we would surely never think of pitching on two volumes as its unity or least proportion of combination; for it is one volume of hydrogen which unites with one volume of chlorine producing two volumes of muriatic gas. Here, therefore, we see that one volume of hydrogen is quite adequate to effect, in an active gaseous body of equal bulk, and thirty-six times its weight, an entire change of properties. Should we assume in gaseous chemistry, two volumes of hydrogen as the combining unit, or as representing an atom, then it should never unite in three volumes, or an atom and a half with another gas. Ammonia however is a compound of three volumes of hydrogen with one of azote;

and if two volumes of hydrogen to one of oxygen be called an atom to an atom, surely three volumes of hydrogen to one of azote, should be called an atom to half an atom." Chemical Dictionary, 2d. Ed. 423.

To these suggestions, Dr. Turner in his excellent little treatise upon the laws of chemical combination, offers the following satisfactory reply.

1. Water is composed of one volume of oxygen to two volumes of hydrogen; euchlorine of one volume of oxygen to two volumes of chlorine; and both compounds are supposed to contain an atom of each constituent. An atom of hydrogen is therefore represented by two volumes of hydrogen, and an atom of chlorine by two volumes of chlorine. But muriatic gas is composed of one volume of hydrogen to one volume of . chlorine, or, what is the same thing, of two to two: hence it contains an atom of each. We see, therefore, that the same quantity of hydrogen which combines with an atom of chlorine, also combines with an atom of oxygen; and that the example adduced by Dr. Ure, is a most powerful and convincing argument in favour of the very doctrine against which he contends. 2. A similar argument applies to the constitution of ammonia. In fact, nitrous oxide gas is composed of one volume of oxygen and two volumes of nitrogen, but one atom of each element. An atom of nitrogen is therefore represented by two volumes of that gas, precisely as happens with respect to bydrogen and chlorine. But ammonia contains three volumes of hydrogen and one of nitrogen, which is the same ratio as 6 to 2; and hence it is composed of one atom of the one, to three atoms of the other.

Mr. Finch has attempted a table of chemical equivalents upon his plan, which at least deserves the credit of originality. For example, protoxide of chlorine is said to consist of two volumes of oxygen and one volume of chlorine; sulphuretted hydrogen, of two volumes of hydrogen and one of sulphur, &c. !!

In what is said by our author concerning the Daltonian formula, he has been combating a wind-mill of his own construction. Although unmeasured praise is due to Mr. Dalton for his researches, his formula has been greatly modified, and

is not at the present time, rigidly adhered to by a single chemist.

Upon the whole, we regret that Mr. Finch should have ventured upon a subject with which he has evidently so little acquaintance, especially, a subject where novelty can only be excused in the most profound philosophy.

Of the work of Dr. Green we have only a few words to say. It is but a few years since Electro-Magnetism has risen to the rank of a distinct science. The distinguished attention which it has received in various European countries has been followed by discoveries the most novel and interesting; and the facts connected with it have now become so numerous as to require for their due consideration distinct and by no means limited treatises. Several works of this description have been published or are now in the course of publication in England · and France; but if we except what is contained in the translation of Biot's Elementary Treatise, we have had nothing on the subject from the American press.

So far then as it regards the general diffusion of science among our citizens, we are greatly indebted to Dr. Green for the Manual before us, which, as its titlepage informs us, contains the "principal facts" in the science, although we cannot say much in favour of their arrangement.'

Dr. Green, in the composition of this work, has availed himself of the fragments which are scattered through the numerous scientific periodicals of the day. So far as we can judge from an attentive perusal, he is most largely indebted to the Historical Sketch of Electro-Magnetism in the 18th and 19th vols. of the Annals of Philosophy.

It would have been a great convenience to those who wish to pursue the science if Dr. G. had given more frequent references to the original papers from which his extracts are made. For example: "Note C. on electrical quantity and intensity," is copied without reference from an excellent article on Electro-Magnetism in the 35th volume of the Quarterly Review, a work within the reach of almost every American student.

We also regret that Dr. Green has not indulged his readers