May 25, 191 1] 



NATURE 



411 



for Irrigation to the Government of India. The 

 duties of that office, coming- after a career of prac- 

 tical work on irrigation schemes, would give that 

 breadth of view with which a lecturer on so wide a 

 subject as " Irrigation Works " should be endowed. 



The irrigation works described in this book include 

 more than the material works of irrigation, such as 

 channels for irrigation and drainage and works of 

 regulation. "Notes on Irrigation TForfe " would 

 seem to be a more appropriate title. For, besides 

 discussing weirs and irrigation channels — irrigation 

 works properly so-called — the author describes what 

 may be termed the embryonic growth of an irrigation 

 project — that is, the preliminary surveys, studies, and 

 calculations, which mark stages of deve'opment in 

 the incomplete project. The final chapter, moreover, 

 explains the revenue duties of the canal engineer of 

 India. The canal engineer of Egypt is fortunate in 

 escaping the harassing duties of revenue manage- 

 ment, which in India are part of an irrigation 

 officer's duties. 



A separate chapter deals with the development of 

 irrigation in Egypt since 1884 in a concise and com- 

 prehensive summary, and concludes with a short 

 reference to possible future schemes. With this ex- 

 ception and a few references to works in Egypt under 

 the head of weirs, the author has wiselv drawn his 

 illustrations from works in India with which he is 

 personally acquainted, and treats his subject generally 

 from the point of view of India. He thus avoids a 

 fruitful source of error. The "eminent authority" 

 whom he quotes as misconceiving the cause of the 

 failure of Xarora weir, leant too heavilv on the broken 

 reed of an official report, and fell into error for want 

 of first-hand knowledge of the subject which he was 

 usinc" as an illustration. Mr. Mackenzie, with more 

 caution, gives his opinion "with all reserve" as to 

 the cause and marjner of the accident. He may be 

 right, but, as he points out, the local engineers decline 

 to commit themselves to a positive opinion. There 

 is, at least, one more theory of the cause of the acci- 

 dent, which has not yet appeared in print. Whatever 

 the real cause may have been, the discussion, which 

 has followed on the accident to the Narora weir and 

 to which the author makes his contribution in his 

 book, has been fruitful in establishing sounder prin- 

 ciples upon which to base the design of weirs than 

 had been recognised before. 



.\ chapter on the design of irrigating channels is 

 chiofl'- concerned with the important matter of silt 

 deposit in the small distributing channels in the 

 delivery zone of an irrigation system ; but the method 

 of water distribution on the rotation system is also 

 described in general outline. An introductory chapter 

 refers to the performance in the distant past and the 

 j)romise in the near future of irrigation in Meso- 

 potamia ; also to the conditions which create a need 

 of irrigation and drainage, and to the good effects 

 ' f moderation and to the evil effects of excess in 



:her. 



The book is written in good, plain English, and 

 !> free from unnecessary technicalities, as lectures 

 addressed to students should be, and as, indeed, all 

 NO. 2169, VOL. 86] 



lectures might well be. The substance of the book is 

 sound instruction, and irrigation engineers, as well 

 as students, will find much useful knowledge in it, 

 clearlv expressed and convincingly demonstrated. A 

 careful perusal of it would be a valuable preparation 

 for a more detailed studv of irrigation works and 

 administration, either by books or by actual practice. 



THE CRYSTALLINE SCHISTS. 

 Die KristaTlinen Schiefer. Eine Darstellung der 

 Erscheinungen der Gesteinsmetatnorphose und 

 ihrer Produkte. By Prof. U. Grubenmann. 

 Zweite Auflage. Pp. xii + 298 + xii plates. (Ber- 

 lin : Gebriider Borntraeger, 1910.) Price 20 marks. 

 ORIGINATING in a course of lectures at Zurich, 

 based largely on the author's own researches 

 among the crystalline scHists of the Alps, Prof. 

 Grubenmann 's book has already made for itself 

 a place in petrographical literature. The two parts, 

 general and special, issued separately in 1904 and 

 1906 respectively, are in the new edition included 

 more conveniently in a single volume ; but the 

 general plan of the work remains unchanged, and 

 the additions found here result merely from the 

 growth of material during the last live years. Thus, 

 in the first part, there is .some revision of those 

 sections which deal with the application of physico- 

 chemical principles, and some interesting illustrations 

 of original sedimentation, mixed injection, &c., are 

 drawn from recent work in Finland and Scandinavia. 

 The additions made to the second part of the book 

 are perhaps more important, including a large number 

 of chemical analyses, and some simplification of the 

 classificatory scheme. 



The general principles of Prof. Grubenmann 's 

 treatment are already known to petrologists. His 

 classification is based primarily upon chemical com- 

 position. No distinction is made between metamor- 

 phosed sediments and metamorphosed igneous rocks, 

 for it is urged that, even if their original characters 

 are not wholly obliterated, metamorphism has set so 

 marked a stamp upon them that the new characters 

 supersede the old in significance. The author adopts 

 Osann's chemical classification, originally devised for 

 igneous rocks alone, and in this way arrives at twelve 

 groups of crystalline schists. In each group there 

 is made further a threefold division corresponding 

 with different zones of depth, where the conditions 

 as regards temperature and pressure are presumed 

 to differ in an important degree. This division, an 

 amplification of Van Hise's conception, is described 

 as a "physical-geological" one; but, since the actual 

 depths of the several zones are not \hr --aine in 

 different groups of rocks, the geologic;il significance 

 is merely of a limited scope. 



The distinction made between crystalline schists 

 and "contact-rocks," which latter are excluded from 

 consideration, seems to us an artificial one, and is 

 difficult to defend in a scheme professedly based on 

 the actual characters of the rocks. Barrow has 

 shown that the great metamorphic aureoles of the 

 Scottisli Highlands can be divided into three zones, 

 having sillimanite, cyanite, and staurolite as their 



