December 19, 1901] 



NA TURE 



151 



discharge from the liquid interior are fewer. Eruptions 

 come from local reservoirs in the generally solid crust, 

 which, however, may have a communication from beneath 

 with the inner mass. In the fourth stage, when the 

 crust layer approaches 50 kilometres, there is a further 

 decline in number, though an increase in violence, of 

 discharges from the liquid interior, but the activity of 

 the reservoirs is maintained, and henceforth these are 

 the main sources of vulcanicity. That is the age of 

 ■catastrophic eruption, and the photosphere is disappearing. 

 The next stage continues the cutting off of direct com- 

 munication with the interior, separation takes place in 

 the masses of magma, and local eruptions are still very 

 violent. This phase may correspond with that stereo- 

 typed in the moon. The sixth stage begins, the seventh 

 continues, the deposit of sediments, during which meta- 

 morphism is active in the lower beds, thus forming an 

 outer skin to the crust layer. Eruptions continue to 

 affect a plateau type in the earlier of these ; the volume 

 •of the reservoirs is gradually being reduced, as well as 

 the communications with the more distant interior of 

 the earth. The eighth, in which the liquid reservoirs are 

 few and small, and communication from within any part 

 of the thickened crust layer to the interior very rarely 

 exists, is the present period. 



Pho/oj^raphic Cameras and Accessories. Edited by Paul 

 N. Hasluck. Pp. 160. (London: Casselland Co., Ltd., 

 1901.) 

 It is not often that one meets with amateur photo- 

 graphers who possess cameras made with their own 

 hands, because at the present day instruments can be 

 obtained at such prices that the pocket of even the most 

 modest purchaser can be suited. This is, however, no 

 reason why a camera should not be home-made ; and, 

 in fact, besides affording the worker a very pleasant 

 occupation, especially anyone who is interested in 

 carpentry, it redounds to his credit if he turns out a good- 

 looking and serviceable camera and produces first- 

 class pictures with it. 



The contents of this little book will afford a very ready 

 and serviceable guide to anyone who wishes to try his 

 hand in this direction, and supply the reader with con- 

 cise information on the details of the subject of which it 

 treats. As we are told in the preface, the matter con- 

 sists essentially of a digest of material contributed by 

 a professional photographer to a weekly journal, so that 

 the instructions should be, and are, thoroughly practical. 

 The text is accompanied by a great many working 

 drawings, 241 in number, and deals, not only with the 

 construction of the bodies of cameras, but with dark 

 slides, shutters and stands. 



Trattato elemeniare di Fisica. Da Oreste Murani. 



\'ol. iii. Optics and Electricity. Second edition. 



Pp. xxi + 675. (Milan: Ulrico Hoepli, 1901.) 

 This is a descriptive treatise in which the experimental 

 phenomena in optics and electricity are described and 

 the apparatus used for exhibiting or applying them are 

 illustrated by no less than 593 woodcuts. It is essen- 

 tially non-mathematical in its treatment, the few formula; 

 included in the text in connection with such laws as the 

 law of refraction of light and Ohm's law involving no 

 calculus and merely the notation of trigonometry. In 

 regard to modern electrical discoveries and notions. Prof. 

 Murani has brought his treatise very much up-to-date, 

 and the experiments of Righi, Lenard, Hittorf and 

 Hertz, on electric discharges, the Rontgen and Becquerel 

 rays, Kerr's, Hall's and Zeeman's phenomena, Tesla's 

 expernnents, wireless telegraphy, the coherer and the 

 Wehnelt interrupter, afford instances of the many recent 

 innovations which are described at some length. In the 

 concluding sections the author expresses doubts as to 

 the efficacy of lightning conductors of the old style 

 NO. 1677, VOL. 65] 



when the effects of electromagnetic induction are taken 

 into account. The book should be useful both as a 

 class-book in technical colleges, for which purpose it is 

 especially written, and as a work of reference for general 

 readers who wish to acquire some notion of modern 

 electricity and optics without entering into abstruse 

 theories or technical minutire. G. H. B. 



A First Course of Practical Science. By J. H. Leonard, 

 B.Sc. Pp. xii + 138. (London : John Murray, 1901.) 

 Excellent courses of practical work in the rudiments 

 of mensuration and physics are now available in several 

 text-books, but there is still room for volumes like the 

 present one. The exercises described are suitable for 

 quite young beginners, and they will serve the double 

 purpose of applying the pupils' knowledge of arithmetic 

 and developing a scientific frame of mind. .Simple 

 measurements of length, area and volume, and calcula- 

 tions (particularly with decimals) referring to them, form 

 the subjects of the opening chapters. Following these 

 are laboratory e.xercises on weight and centre of gravity, 

 relative weight, atmospheric pressure, thermal expansion, 

 thermometers, latent heat, filtration, solution and 

 distillation. 



The experiments are described concisely and are well 

 arranged, so that a pupil of average capacity could per- 

 form them without much assistance, and at the same time 

 would acquire clear ideas on fundamental principles. 

 We do not like such expressions as " Have all liquids got 

 a latent heat.'' Have all gases got a latent heat?" but 

 that is a detail. As a whole the book is satisfactory, and, 

 with others of the same kind, will assist the movement in 

 favour of introducing scientific measurements in early 

 stages of instruction in schools. Dr. Gladstone con- 

 tributes a short preface. 



Coltivazione delle Miniere. By S. Bertolio. Pp. vii + 284, 

 with 96 figures. (Milan : Hoepli, 1902 \sic\ Price 

 L. 2-50.) 



Thls is one of the numerous manuals published by 

 Hoepli of Milan ; it contains a useful little epitome of 

 the art of mining. It is not fair to expect too much from 

 a book costing only is., and consequently one must not 

 carp too loudly at the absence of detailed descriptions 

 and figures of certain important mining appliances. Steam 

 shovels and dredges, which play so weighty a part now- 

 adays, are merely mentioned by name, and hydraulic 

 mining is dismissed in a couple of lines. This defect 

 should be remedied in a second edition, for it is well 

 even in a small manual to impress upon the student the 

 great importance of all mechanical methods of excava- 

 tion. 



On the other hand, the author deserves credit for his 

 picture of the well-marked projecting outcrops of three 

 parallel lodes at Montevecchio in Sardinia ; the student has 

 not always the opportunity of seeing such a fine example 

 in the field. Mistakes in foreign words are too frequent, 

 and when the simple name of the inventor of the safety- 

 lamp is spelt "Dawy,'' the Englishman feels aggrieved ; 

 however, all nations are treated alike, for the author is 

 not absolutely faultless in his own tongue. 



The Ballads and Shorter Poems of Frederick V. Schiller. 



Translated into English Verse by Gilbert Clark, M.A. 



Pp. xv-f 40S. (London: Williams and Norgate.) 

 Schiller's philosophical writings have admirers in the 

 world of science, and this translation will contribute to 

 the wider appreciation of his poems among people unable 

 to read them in the original. The series of poetical 

 parables and riddles referring to natural phenomena, 

 and the verses on astronomy, astronomers, nature know- 

 ledge and transcendental philosophy are of interest to 

 scientific minds. 



