August 8, 1S89] 



NATURE 



339 



Any one of these might well call for detailed remark 

 if space permitted. They show the author at his best, 

 finely observant of overlooked points, subtly ingenious 

 in devising new, quaint, and even startling possibilities. 

 But the reader must be referred to the volume itself for 

 a fuller appreciation of these qualities. 



When one has gained much pleasure and profit from 

 a work, it seems almost shabby to begin to find fault. 

 Yet no critical reader of Dr. Venn's treatise can fail 

 to perceive its defects. It is as if the author had boldly 

 set them before our very eyes challenging criticism. 

 The want of close connection has already been touched 

 on. There seems, indeed, a surprising lack of systematic 

 arrangement, as if the author had sat down to write 

 without a clear plan before him. Poor formal logic 

 gets badly treated. Thus we have an account of terms, 

 propositions, including hypotheticals and disjunctives, 

 but no account of the syllogism. Nor can it be said 

 that the writer has introduced just as much of the 

 <:ommon syllogistic logic as is needed for setting 

 forth the processes of induction. Much given us 

 under terms and propositions cannot well be regarded 

 as needed in a treatise on the logic of induction. Some- 

 times, indeed, the author wanders into the mystic region 

 of symbolic logic. Again and again he opens up in a 

 tantalizing way views which he does not stop to establish. 

 One may instance the point touched on (p. 43), whether 

 the converse of a particular proposition is in substance a 

 new proposition. This depends on our view of the im- 

 port of a proposition, which, as already pointed out, is not 

 adequately dealt with. Again, the author seems to deny 

 the existence of a negative disjunctive of the type " Either 

 A is not B or C is not D," but he does not trouble to 

 prove the point, or indeed to make clear what he precisely 

 means. It is surprising, again, to find Dr. Venn discuss- 

 ing the functions of the syllogism not only without giving 

 any preliminary sketch of it, but without the barest refer- 

 ence to the nature of the axiom which underlies it. On 

 the other hand, a good deal that is known to the general 

 student from previous works (including the author's own) 

 is needlessly repeated, and helps sadly to swell the size of 

 the volume. Another feature that will strike every careful 

 reader, and which is strongly suggestive of defective plan, 

 is the frequency of the forward reference, as " we shall 

 see by and by," and so forth. This is apt to be very con- 

 fusing. In noting this, together with the comparative 

 infrequency of the backward reference, one cannot help 

 thinking of the author's remark on the popular view of 

 •causation, that it looks forward rather than backward. 



A number of the author's statements seem to the 

 present writer open to dispute. It must be surely a 

 ■slip which makes him write of the classifications of 

 natural history as made up of collective terms (p. 170). 

 The Dicotyledons are surely not a collection in the sense 

 in which the House of Commons is a collection. The 

 limitation of the denotation of terms to present existences 

 ((p. 179) strikes one not only as highly capricious, but as 

 inconsistent with what is said about differences of time 

 in connection with predication. Once more, one would 

 like to challenge the strong statement that the only easily 

 •discoverable instance of a purely verbal dispute is that 

 about the " sameness " of a thing (p. 296). In one place, 

 at least, the writer's ingenuity seems to carry him too far. 



Writing of logical definition by genus and differentia 

 (p. 302, by a slip written genus and species). Dr. Venn 

 tries to show that this is perfectly rational on the supposi- 

 tion (which logic is bound to make) that we all know 

 the meaning of our terms, or, since the very need of 

 defining a term shows that there is one term of which 

 this cannot be supposed, of all terms but one. But it is 

 obvious that this consideration would equally suggest or 

 justify an inverse process of definition, viz. by naming a 

 lower species, and subducting its differentia. Such slight 

 blemishes as these are probably inseparable from Dr. 

 Venn's manner of work, and it can safely be said that 

 they detract but little from the general and lasting im- 

 pression of masterful competence which his volume is 

 certain to leave on the student's mind. 



James Sully. 



REMSEN'S "INORGANIC CHEMISTRY:' 

 Inorganic Chemistry. By Ira Remsen, Professor of Che- 

 mistry in the Johns Hopkins University. (London : 

 Macmillan and Co., 1889.) 



THIS book is of interest from the circumstance that it 

 is the first of its kind in the language of any preten- 

 sions which is based upon the periodic law. It is further 

 characterized by the fulness with which general relations 

 are discussed. The attempt is made to present the facts 

 of inorganic chemistry in such a manner as to bring out 

 their analogies and connections, with a view of elucidat- 

 ing the broad general principles of the science. Details 

 of experiments, either as showing the origin and modes 

 of preparation of products, or as illustrating their leading 

 properties, are for the most part omitted, or are relegated 

 to an appendix containing special directions for laboratory 

 work. The book is put together in a plain, straightforward 

 manner, with no attempt at any literary airs and graces ; 

 indeed, we may add that at times the style verges on a 

 simplicity which is perilously near being puerile. Having 

 said this much in commendation of the general plan of 

 the wor^c, we have said all we can say in its praise. For, 

 however excellent may be the plan of a treatise of che- 

 mistry, its main value, after all, must depend upon the 

 accuracy and completeness of its statements ; and, as we 

 proceed to show, there is much in this book which is both 

 inaccurate and incomplete. From the style in which it 

 is issued, and its price, we presume that the work is in- 

 tended for the benefit of comparatively advanced students 

 — at all events for a higher grade than that for which the 

 author's well-known smaller books were prepared. In- 

 deed, we are distinctly informed that the earlier works 

 were intended to form a series of which the present 

 volume is the most advanced member. Now, whilst it 

 may be convenient for the purpose of elementary teach- 

 ing not to tell the whole of what is known about a thing, 

 the advanced student, if he has any scientific instinct 

 at all, insists on knowing the truth, the whole truth, and 

 nothing but the truth. Unfortunately, he does not always 

 get that from this work. Prof. Remsen is admirable in 

 his introductory books. In these there is a reticence of 

 statement and a subordination of facts which make the 

 books excellent for the purposes of school-teaching. But 

 in the larger book it appears to us that the author suffers 

 from the defects of his excellencies : what is a merit in 



