i86 



NATURE 



[April 24, 1913 



them in their true relations. The dissected high- 

 land of fig". 116, with the broad cone of detritus 

 funning the only habitable region at its foot, will 

 remind the traveller of the valley of the Inn or of 

 the Drau. The volcanic relics in fig. 132 explain 

 Gergovia and Mont Dore. The eighth chapter, 

 on "Der aride Zyklus," appeals strongly to 

 pioneers on the edges of our colonised lands, and 

 would have edified the Roman senate, when it 

 republished the Carthaginian text-books and faced 

 the problems of the desert and the steppes. On 

 PP- 375~6 the evidence for a recent uplift of 

 central and southern Africa is well stated. A 

 characteristic discussion on the methods of pre- 

 senting geographical problems finds its way some- 

 how into this chapter. British geologists will 

 turn with interest to the chapters on glacial condi- 

 tions and marine erosion. The explanation of the 

 features of the coast of south Devon on p. 502, 

 which seems at first somewhat complex, is fully 

 justified when we realise that the " soft rocks " 

 postulated really exist in the form of Cretaceous 

 and perhaps Eocene limestones beneath the Eng- 

 lish Channel. 



The disguise of Prof. Davis as a Prussian is 

 a thin one. Who does not recognise him in the 

 brilliant description of the Roman area on 

 pp. 393-4, which is to occupy four minutes of 

 oral instruction; or in the terrifying discovery on 

 p. 39S that every land-form can be treated geo- 

 graphically in four-and-fifty different ways? 



Grenvii.le A. J. Cole. 



OUR BOOKSHELF. 



The Manufacture of Iron and Steel: a Handbook 



for Engineering Students, Merchants, and Users 



of Iron and Steel. By H. R. Hearson. Pp. 



xi+103. (London: E. and F. N. Spon, Ltd., 



1912.) Price 4i'. 6d. net. 



This small volume is obvioush primarily intended 



to give engineering students an outline of the 



manufacturing operations of iron and steel, and 



also an idea of the chemical characteristics and 



the mechanical properties of the finished products. 



The author has undoubtedly, to a great extent, 



produced a lucid and useful little text-book. 



After a preliminary chapter on elements, the 

 blast furnace is considered, being followed by a 

 short chapter on wrought iron. Steel is next dealt 

 with, including the Bessemer, Crucible, and 

 Siemens methods. The book has so much valu- 

 able and accurate information that it may be of 

 very great use to elementary students of iron and 

 steel metallurgy, but several remarkable errors 

 should be revised in any future edition. For 

 instance, on page 37, steel containing 0*3 per 

 cent, of carbon is classified as medium instead of 

 mild, and steel containing o'7 per cent, of carbon 

 is designated hard instead of medium. In describ- 

 NO. 2269, VOL. 91] 



ing the manufacture of " blister steel " by cementa- 

 tion, the author states, " None of the bars is car- 

 burised right through to the centre, so the centre 

 still remains as iron." This is true of, say, No. 2 

 bars, but high-number bars are always " steeL 

 through." Some of the paragraphs on crucible 

 steel also need serious revision; for instance, the 

 curious assertion that if kept too long in the 

 furnace the steel will become brittle by taking up 

 too much silicon from the crucible. Mr. Hearson 

 also revives the obsolete dictum that mild steel is 

 crystalline and wrought iron fibrous. On page 77 

 the somewhat astounding information is given that 

 the top of an ingot may be prevented from 

 rapidly solidifying by covering the top with sand. 

 The chapter on the mechanical testing of steel is 

 excellent, but in the brief final chapter dealing 

 with the heat treatment of steel many metal- 

 lurgists will be surprised to learn that steel con- 

 taining o"25 per cent, of carbon becomes " hard " 

 on quenching, and the paragraphs on hardening 

 are out of date. If carefully revised, however, the 

 book will become of distinct value. J. O. A. 



Photochemische Versuchstechnik. By Dr. 



Johannes Plotnikow. Pp. xv + 371. (Leipzig: 



Akademische Vcrlagsgesellschaft m.b.H.,. 



191 2.) Price 11 marks. 

 This book forms the complement of a previous 

 volume by Dr. Plotnikow on the theory of photo- 

 chemistry (" Photochemie," W. Knapp in Halle 

 a.S., 1910). In the present work he describes at 

 length the apparatus and the experimental 

 methods used in photochemical research. Part i. 

 contains a useful summary of the characteristics 

 of the various sources of light that may be em- 

 ployed. The mercury arc lamp, in which a steady 

 electric current is passed through the vapour of 

 mercury in a highly exhausted tube of Uviol glass 

 or of fused quartz, is recommended as providing^ 

 a constant and trustworthy source. Other sources 

 discussed are the arc and spark between metal 

 terminals, the carbon arc, the Nernst lamp, and 

 the Rontgen ray tube. In part ii. Dr. Plotnikow 

 describes the construction of the special forms of 

 thermostat which he has devised for photochemical 

 experiments, and enumerates a number of solu- 

 tions that may be employed as light fillers with 

 the mercury vapour lamp in order to give 

 approximately monochromatic light. 



Part iii. contains an account of the instru- 

 ments used in optical measurements, including 

 photometers, spectrophotometers, spectrometers, 

 refractometers, and polarimeters. 



In part iv. the author describes a number of 

 interesting lecture experiments for illustrating the 

 fundamental laws of photochemical reactions, the 

 various phenomena of luminescence, and the 

 principal facts of photoelectricitv. It is satis- 

 factory to find attention directed to the subject 

 last named, since the separation of negative elec- 

 trons under the influence of light probably forms 

 the clue to the understanding of the mechanism of 

 all photochemical processes. 



Part v. contains a collection of tables likelv 



