May 26, 1 9 10] 



NA TURE 



;65 



glad to note that the author pays a tribute to the 

 British Association Committee on Mathematical 

 Tables, the activity of which has, unfortunately, in 

 recent times somewhat slackened. The collection in- 

 cludes tables of the sine-integral, cosine-integral, and 

 exponential-integral, the Fresnel transcendents, the 

 gamma-function, the error-function, elliptic integrals, 

 spherical harmonics, and the Bessel's functions of 

 both kinds. Especially welcome are the tables of the 

 latter function in which the argument is complex. 



Every worker in applied mathematics will applaud 

 this publication, and will wish it such success that it 

 may be speedily followed by new and still more com- 

 prehensive editions. 



(5) A "philosophical" discussion of the nature of 

 centrifugal force is hardly suited for review in these 

 pages. Such di^cwssions are apt to resolve them- 

 selves into verbal questions, and we fear that the 

 present one is no exception. The author insists, for 

 example, on a distinction between "motive forces" 

 and "resistances." the tension of a string being 

 reckoned as belonging to the former category, the 

 pressure of a smooth surface to the latter ! The tract 

 is lengthy and diffuse. 



(6) A formal treatise on the theory of interpolation 

 from the former professor of astronomy at Copen- 

 hagen is sure of respect. The present work is care- 

 fully written, and apparently from an independent 

 standpoint. There is, indeed, hardly any explicit 

 reference to the work of previous writers other than 

 Newton and Lagrange, and novel notations are intro- 

 duced freely without any reference to accepted forms 

 which have long been in general U5ie, The author 

 claims for the subject an important place in schemes 

 of mathematical instruction. To this we can hardly 

 assent ; processes of interpolation are, of course, con- 

 stantly required, in one form or another, but a 

 systematic study of the subject as an independent 

 discipline would, in the case of most students, be an 

 unnecessary infliction. The case of those who are 

 training to become experts in certain special subjects 

 is, of course, different. H. L. 



OVR BOOK SHELF. 



An Introduction to Petrology. By F. P. Mennell. 



Second edition. Pp. viii + 204. (London: Gerrards, 



Limited, 19 10.) Price 85, net. 

 This is a plain and clearly written introduction to a 

 branch of geology that has assumed much importance 

 among students, and it has the merit of including a 

 short description of the minerals that go to make up 

 rocks. The author's personal studies, as is well 

 known, have been carried on mainly in Rhodesia, and 

 there i'^ something pleasant in finding familiar facts 

 illustrated from Bulawayo, Kimberley, or the Rand. 

 ! he palisade structure of basaltic flows is thus well 

 >een in the view of the Zambezi gorge on p. 92. In 

 addition, we gain by the introduction of the results 

 of tropical weathering on rocks ; and the remarkable 

 banded siliceous ironstones of South Africa (p. 180) 

 are referred to the concentration of mineral matter 

 in a stratified series near the surface. 



Theoretical questions are touched on sufficiently 

 to arouse interest, and a sane balance seems to be 

 preserved between what can be seen in the field and 

 «vhat may be variously inferred. The discussion of 



NO. 21 17, VOL. 83] 



the absorption of schists and sediments by the granite 

 of the Matopos and Mashonaland is sustained by evi- 

 dence that seems convincing, and it has been our good 

 fortune to go over something of this ground in the 

 company of the author. The arguments derived from 

 the amphibolites (p. 171) might have been supported 

 by work of earlier date than that quoted, such as that 

 done in Saxony and round Mont Blanc ; but the intro- 

 duction of matter of this kind, of chapter xiii. (on 

 the origin and variations of igneous rocks), and of the 

 well-reasoned chapter xix., on metamorphism, show 

 that the author regards petrolog}- as far more than 

 the mere description of rock-specimens. Enough is 

 said on each point to show what researches lie before 

 the worker in the open country-. 



Simple and descriptive as the book is, it will un- 

 doubtedly encourage thought in all who read it. The 

 illustrations are excellent, though we should like 

 fewer rock-sections, and more landscapes, such as that 

 on p. loi. Very few misprints — " Brux " for " Briix," 

 " Fougue " for " Fouque," and " entectic " for 

 "eutectic," twice on p. 89 — have been noted. The 

 formulae of the silicates might be modernised in the 

 next edition, since comparison is thus rendered more 

 easy. On p. 70 the resemblance between kaolin and 

 serpentine is unnecessarily obscured by a small differ- 

 ence of method. .\ comma is wanted in the dolomite 

 formula on p. 75 ; but is not this better written 

 MgCa(CO,), ? The change of appearance in a section 

 of calcite when the polariser is rotated beneath it 

 (p. 75) is due to differences in "relief" at the sur- 

 faces, and not to differences of absorption within the 

 section. This well-printed book, as a whole, is a very 

 pleasant one to read. G. A. J. C. 



Map of Eastern Turkey-in-Asia, Syria, and West 



Persia. Scale, 1/2,000,000, or i inch = 3 1"56 miles. 



(London : Royal Geographical Society, 1910.) 

 The issue of this map occurs at an opportune moment. 

 Public attention has been much directed lately to the 

 once fertile strip of country that lies between the 

 deserts of Arabia on the one hand, and the mountains 

 of Asia Minor on the other. It is needless to dwell 

 here on the visions of the past that a mere inspection 

 of the names on this map will call up in the mind of 

 the historian. Looking to the future alone, it is 

 obvious that we have before us the representation of 

 a piece of country destined once again to play an 

 important part in human history, and to be the scene 

 of a busy commerce and a thriving agriculture. What- 

 ever be the political difficulties now blocking the 

 wav, it is certain that before very long we 

 shall see the construction of the railway join- 

 ing the Mediterranean with the head of the 

 Persian Gulf, a route possibly extending through 

 southern Persia and Baluchistan to India itself. In 

 the more immediate future we shall see the rich land 

 that lies between and about the great twin rivers wake 

 from its sleep of four centuries and water again flow 

 through canals and irrigation channels long choked 

 with the desert sands. 



The report on the irrigation system recently pub- 

 lished by Sir \\". W'illcocks makes it clear that, with 

 no great engineering difficulties, and even with no 

 great expenditure of capital, some, at all events, of 

 the old irrigation works can be reopened and a large 

 area of land once more taken into cultivation. The 

 enterprise and energy with which this work is now 

 actually being taken up is the best evidence of the 

 change that has come over the spirit of Turkish 

 administration since the advent of constitutional 

 government. 



It is sincerely to be hoped that the prime importance 

 of carrying out an accurate survey in advance of agri- 

 cultural development will not be lost sight of. In 



