422 



NA rURE 



[June io, 1909 



that the slackening of the speed of the earth's rota- 

 tion, due to tidal friction, more than counterbalances 

 the quickening- due to contraction of the earth as a 

 cooling body. On the other hand, it is shown that the 

 heat that has been generated in the earth by tidal 

 friction, although very great in absolute amount, 

 hardly affects at all the temperature gradient near the 

 surface. All these conclusions are nearly independent 

 of the special hypotheses adopted in order to render 

 the mathematical problem definite and comparatively 

 tractable, and this independence is brought out in a 

 highly instructive graphic method of discussing the 

 problem by the aid of the general principles of energy 

 and momentum, a method which was developed by 

 Hie author after discussing the theory with Lord 

 Kelvin. 



A subsidiary effect of the viscosity of the earth's 

 substance is found in a tendency for any elevation on 

 the surface to be displaced gradually westwards by an 

 amount which is greatest at the Equator. This result 

 suggests that equatorial lands may tend to be dis- 

 placed westwards relatively to polar lands, and it is 

 therefore a step towards a solution of the dynamical 

 problem of the distribution of land and water. The 

 existence of the continental elevations and oceanic 

 depressions shows conclusively that the earth behaves 

 in some respects as a solid body of considerable 

 rigidity. The last paper in the volume is a discussion 

 of the strength and solidity which the materials of the 

 earth must possess in order that such continents as 

 actually exist may be supported without interior com- 

 pensation. This paper is the only one which has been 

 much altered from its original form, and in this 

 instance it is the mathematical theory that has been 

 re-written, the general argument being but slightly 

 affected. The author would seem, from a passage in 

 his preface, to have come to hold the view that the 

 continents are not actually supported in the manner 

 assumed in the paper as a basis of discussion, but his 

 investigation remains the most important contribution 

 that has ever been made to the problem. 



Workers in mathematical physics will be grateful 

 to the author for his careful revision, and to the 

 Syndics of the Cambridge University Press for their 

 public spirit in re-printing and re-publishing the 

 papers. The author's custom of summarising his 

 methods and results in language comparatively free 

 from technicalities should render his general argu- 

 ments and main conclusions accessible to all persons 

 interested in speculative astronomy. A. E. H. L. 



PAPER-MAKING. 

 The Manufacture of Paper. By R. W. .Sindall. Pp. 

 X + 27S. (London : A. Constable and Co., 1908.) 

 Price 6s. net. 



THE author is well known as a specialist and a 

 worker in this branch of technology, and, of 

 course, in a treatise of nearly 300 pages, could not fail 

 to deal, in an interesting way, with some critical 

 problems of the industry. But this contribution to the 

 subject, which is of deep, wide, and varied interest, 

 hardly commends itself as a spontaneous effort in rela- 

 tion to its literature. From our brief but " brotherly " 

 NO. 2067, "^'OL. 80] 



examination of its contents we are led to surmise that 

 it owes its origin to mixed motives, such as would 

 operate in the case of a publisher's " specification " 

 adopted by the author, not as a call or inspiration 

 illuminating as well as defining his task, but rather 

 as a condition of a contract to be fulfilled. This 

 somewhat artificial basis is already indicated in the 

 pointless preface, in which the author first records 

 some very obvious convictions, as to the complementary 

 relations of engineer and chemist in this industry. 

 But these are not applied as material to any purpose 

 or plan of the present work, which is otherwise intro- 

 duced in a paragraph of faint praise as follows :^ 



" In the present elementary text-book it is only 

 proposed to give an outline of the various stages of 

 manufacture and to indicate some of the improvements 

 made during recent years." 



The result is, as regards matter, a series of sec- 

 tional chapters dealing with aspects of the industry 

 and its processes, with no continuity or cohesion of 

 plan ; and as regards form there is not merely an 

 absence of style, but a disregard of accuracy of defini- 

 tion and precision of statement which, in an 

 elementary text-book, as it claims to be, is a usual 

 feature of distinction as of moral influence on 

 the mind of the student reader. It is a depressing 

 task for a reviewer thus to record a depreciative 

 estimate of a work which of course represents merit, 

 as well as effort, on the part of the author, and it is 

 equally thankless to have to justify such conclusions 

 in detail. We can only lighten the task ny 

 shortening it. 



The absence of plan is seen in the treatment of 

 fundamental processes and effects, such as bleaching, 

 beating, and sizing; matters of such general import 

 are introduced in successive chapters dealing with 

 different classes of papers without expository prepara- 

 tion. " Electrolytic bleaching " is treated in a 

 detailed expose of cost of production of the hypo- 

 chlorite analysed into its factors. This, on the other 

 hand, presumes a basis of critical knowledge on the 

 part of the reader out of all perspective. The paper 

 machine is introduced by way of photo-illustrations 

 and a paragraph or two of descriptive matter; the 

 reader is then rushed to the laboratory to test papers 

 for the presence of mechanical wood-pulp ; he is then 

 rushed back to the machine for the task of cal- 

 culating its output (pp. 119-25). The structural 

 features of paper-making fibres are introduced at 

 various points in the text by way of photomicrographs 

 and descriptive remarks; but if the author were asked 

 as to the educational effect intended, we think he 

 would reply by stating that that is " a question of 

 which he would require notice." 



As regards form and the defects of the text in 

 point of style and accuracy, examples might be taken 

 from almost every page. Note the opening sentence : — 

 " The art of paper making is undoubtedly one of the 

 most important industries of the present day." Of 

 course, we know what the author means, and in 

 English composition this is the popular touchstone of 

 language. A more typical example is the following 

 (p. 40) : — 



