April, 1915. 



KNOWLEDGE. 



127 



United States will be practically exhausted by the year 

 1950." 



This being so, it was clearly opportune that an up-to-date 

 textbook on the general subject should appear ; and the 

 present work is in marked contrast to Dr. Hough's book of 

 1882, in that it is the exposition of a complete system of 

 forestry of purely national growth and character. Al- 

 though, of course, the general principles of the physiology 

 of the tree, of what the authors term " silvics," and even of 

 sylvicultural management, forest protection, mensuration, 

 and technology, are the same everywhere, the application of 

 these principles to American species and American con- 

 ditions gives a thoroughly local colour to the entire work. 

 These principles, including also those of wood utilisation, 

 wood preservation, and forest finance, are so clearly set 

 forth as to render the book useful to anyone concerned with 

 timber or forestry in any land ; while the map and the 

 second half of the text give a more succinct and intelligible 

 account of the forest regions of the United States than we 

 remember to have met with anywhere else. A tolerably 

 full glossary of technical terms is given ; but the English 

 reader might be glad of an explanation of a good many 

 words, such as " burlap," " duff," " excelsior," " kerf," 

 " ross," and " tierce," which find no place in it. As, how- 

 ever, the title-page bears the (to us) unusual inscription, 

 " First Edition First Thousand," we r.iay well look forward 

 to seeing all such terms explained in some future reissue. 

 A bibliography — mainly of United States Government 

 publications — is added to each chapter ; and the apparent 

 ambiguity of such names as Yellow, Hard or Norway Pine, 

 Red Cedar, and so on, is obviated by an appendix in which 

 the scientific names are given. 



G. S. BOULGER. 



LOGIC. 



Logic : Deductive and Inductwe. — By Carveth Read, M.A. 

 417 pages. 7£-in. x 5-in. 



(Alexander Moring. Price 6 /-) 



This, the fourth edition of Mr. Read's " Logic," has been 

 completely revised, and some new sections have been added. 

 In the main, the author follows Mill, though not without 

 occasionally criticising his position. The first part of the 

 book, dealing with deductive logic, seems very satisfactory 

 on the whole, the author's presentation being straightforward 

 and clear, though the determination of the nineteen moods 

 of the syllogism and their reduction to the first figure 

 are treated rather briefly. 



The latter part of the book, dealing with inductive logic 

 and allied topics, is of more questionable value, the writer, 

 it seems to me, lacking something of Mill's precision. Some 

 of the sections are, indeed, excellent, such as those on " The 

 Canons of Direct Induction " and " Definition of Common 

 Terms." But the defects in the chapters on " Transition 

 to Induction " and " Causation," and elsewhere, are so 

 serious that one hesitates to recommend the book to 

 students. In metaphysics, " causation," and consequently 

 " explanation," has an entirely different connotation from 

 that with which it is used in logic and the natural sciences. 

 It is very necessary, therefore, in a treatise on logic to make 

 this difference quite plain, especially as the common use 

 of these words has a vague idea of their metaphysical 

 meanings behind it. Now, Mr. Read not only fails to 

 do this, but habitually writes of " physical " causes as 

 though they were " efficient " cm i a well. Great stress, 

 moreover, is laid upon the principles of conservation of 

 matter and conservation of energy. But to base logic on 

 the principles of physical science, which themselves must 

 seek their justification in logic, is surely to argue in a circle ; 

 and the danger of this particular circle is the more evident 

 now that the principle of the conservation of mattei has 

 been called in question. Moreover, such a fallacious 

 statement as "... all Times and all Spaces are com- 

 mensurable, although in certain relations of space (as «•) 



the unit of measurement must be infinitely small," is surely 

 remarkable in a book on logic, ^"hat, in fact, does the 

 necessity for an infinitely small unit imply but that the 

 things so needing to be measured are incommensurable ? 



In the chapter on " Hypotheses " the author appears to 

 be straining after an unattainable ideal. As Poincare has 

 pointed out, every phenomenon permits of infinite hypo- 

 theses valid in the scientific sense of the term. The 

 pragmatic criterion is the only one that offers us any escape 

 from this burden of infinity ; and using that criterion we 

 should adopt that hypothesis which is simplest, and there- 

 fore most useful. There is no hint, however, of anything 

 of this in Mr. Read's treatment of the subject. These 

 defects are the more regrettable because of the commend- 

 able quality of much else in the book. There are thirteen 

 pages of examination questions at the end, but no index. 



H. S. REDGROVE. 



PHYSICS. 



The Principle of Relativity. — By E. Cunningham, M.A. 

 221 pages. 8§-in. x5i-in. 



(Cambridge University Press. Price 9/- net.) 



The subject of this treatise has received a large degree 

 of attention since Einstein, ten years ago, brought the theory 

 of Relativity into prominence. The doctrine itself may be 

 regarded as teaching the futility of all experimentation with 

 a view to determining the motion of matter with respect 

 to the ether, if one is assumed to exist. If one does not 

 postulate any ether, then the principle resolves itself into 

 a denial of the possibility of determining absolute velocity 

 in a physical sense. Although beginning with a negative 

 hypothesis, the results are by no means limited to negations. 

 As the author unfolds the results of the theory, one is 

 reminded of the consequences flowing from the denial of 

 a perpetual motion, or of the statement that heat will not 

 of itself move from a place of lower to a place of higher 

 temperature. 



The author is a well-known mathematician, a fellow and 

 lecturer of St. John's College, Cambridge, and it is therefore 

 natural to expect a highly mathematical treatment of the 

 subject ; but the mathematical part has been compressed 

 so as to leave room for very clear accounts of the optical 

 and electrical experiments bearing on the subject. In fact, 

 a large portion of the work will be read with ease and pleasure 

 by the non-mathematical reader. The usual table of con- 

 tents is reinforced by a very lucid and well-written summary 

 of each chapter, which will be especially useful to serious 

 students. The references given to the chief original papers 

 will form a vers- welcome guide to the voluminous literature 



of the subject. 



J. H. V. 



Introduction to Physical Metallurgy. — By Walter Rosen- 

 hain, B.A., D.Sc, F.R.S. 368 pages, 53 figures in the 

 text. 88 figures on 32 plates. 8J-in. x5i-in. 



(Constable & Co. Price 10/6 net.) 



The arts of winning metals from their ores, and of fashion- 

 ing these mi't.ils into weapons and implements, have been 

 practised from prehistoric times, but the systematic study 



0l the internal constitution and physical properties of 



metals and alloys- the science oi Physical Metallurgy — 

 can l>r said to date only from 1864, when Sorby first noted 

 the striking similarity in the nature oi the microstructures 

 of steel and minerals in fact, nearly all the names uso- 

 ciated with tins branch oi science are those oi men suii 

 alive, and actively conducting investigations at the present 

 day. 



This state of things naturally implies a large output of 

 original work which only .i fortunate few have tune to 

 follow closely. It implies, moreover. special methods of 

 investigation, and even .i special nomenclature, which make 

 it difficult, or even impossible, for those not familiar with 



