466 



NATURE 



[March 15. 1900 



With regard to this result, it should be noted that 

 (p. 323) the formula is treated as equivalent to 



2(/i„ - I )/3p = constant, 

 so that the experiments do not decide between the 

 simpler law due to Dr. Gladstone and that given by 

 Lorenz. 



In the second volume we have an important memoir, 

 on the solution of the equations of motion of a homo- 

 geneous elastic solid, published in i860 in Crelle's Journal, 

 and some interesting speculations on the relation of 

 thermal conductivity to electric conductivity in pure 

 metals ; but the papers which will attract most attention 

 are two on the absolute resistance of mercury {Pogg. 

 Ann. cxlix., and Wied. Ann. xxv.). The first of these 

 gives the original account of the now well-known Lorenz 

 method of measuring absolute resistance ; while the 

 second is a statement of the results of Prof. Lorenz's 

 own experiments made at the request of the International 

 Congress of Electricians in 1882. 



The first paper is most interesting ; the contrast be- 

 tween the original Lorenz apparatus, as figured on p. 88, 

 and the instrument designed by Professors Viriamu Jones 

 and Ayrton for the McGill University is most instructive. 

 Lorenz, from the beginning, was alive to the merits of 

 his method and to the difficulties of carrying it into 

 practice ; the first preliminary experiments, in which the 

 diameters of the tubes of mercury, used as resistances 

 to be measured, were 7 millimetres and 14 millimetres 

 respectively, led to the result that the length of a column 

 of mercury one square millimetre in cross-section, and 

 having a resistance of one ohm, is 107 centimetres, a 

 result surprisingly near the truth when all things are 

 considered ; while in his definitive paper the result ar- 

 rived at is io5"9 centimetres ; the value which has been 

 universally agreed upon as representing the result of all 

 the best experiments is, as is well known, io6'3 centi- 

 metres. 



Space compels only the briefest mention of another 

 interesting paper, " On the Propagation of Electricity " 

 {Wied. Ann. tome vii.) ; but enough has been written 

 to show the high value and real interest of these volumes. 

 Students of physics owe a debt of gratitude to Dr. 

 Valentiner for the care with which he has done his work 

 as editor, and for the labour he has spent in explaining 

 difficulties and in making Lorenz's meaning quite clear. 



OC//i BOOK SHELF. 

 Theory and Practice of Art Enamelling upon Metals. 

 By Henry Cunynghame. Pp. xvi + 135. (West- 

 minster : Archibald Constable and Co., 1899.) 

 This book treats of enamels and of their employment in 

 artistic work from several points of view. The intro- 

 ductory chapter, which extends to 33 pages out of the 

 133 which the volume contains, is mainly historical and 

 archgeological. The eight plates which illustrate this 

 section of the book are unsatisfactory, while the text is 

 Open to serious criticism. The author is mistaken when 

 he describes the Alfred Jewel in the Ashmolean Museum 

 at Oxford as a ring, and when he affirms that it contains 

 a " Byzantine enamel in a Saxon setting." A strange 

 passage, which is too funny to be missed, will be found 

 on p. 7, where the mosque of Santa Sophia at Constanti- 

 nople is stated to have suffered the destruction of many 



NO. 1585, VOL. 61] 



of its splendid enamels through the " fanaticism of the 

 followers of Dost Mahommed." The practical and 

 technological details of Chapters i. to iv., with the illus- 

 trations which explain the operations described in the 

 text, or represent the tools and apparatus employed, 

 constitute the valuable portion of this treatise. One can 

 discern throughout these pages the skilful and mtelligent 

 worker who has fought his way to success. We cannot 

 speak of the final chapter, " The Manufacture of 

 Enamels," with equal confidence. It would be wiser 

 to omit chemical formulae altogether rather than to give 

 Na02B03-f loAq. for borax, HOBOj for boric acid, 

 CugO for black oxide of copper, Cr.jOa for sesquioxide of 

 chromium, and KOCrOg for bichromate of potash. .\nd 

 what is the meaning of this sentence (p. 1 24), " Manganese 

 is called in German, brown-stone, and by the French, 

 peridot, after a town near Limoges where it was found " ? 



r oj 

 Job. 



Nature Sketches from the 

 Book of Job. By M. Cordelia Leigh. Pp. 167. 

 (London : Jarrold and Sons, 1900.) 

 We hope this book will be widely read by the Sunday- 

 school teachers and leaders of Bible classes, for whom 

 it is primarily intended ; for they will derive from it 

 many lessons which will create and foster a love of 

 nature in the members of their classes. The chapters 

 in the book originally appeared in The Sunday at Home., 

 each chapter being based on a passage in the Book of 

 Job or the eighth Psalm, in which some natural force 

 or object is referred to, such as the sun, snow, rain, wind, 

 ice, the lion, the wild ass, &c. 



The poem of Job is full of references to nature, and 

 Miss Leigh has interpreted these references in the light 

 of modern science. For instance, the words " foundations 

 of the earth " suggest remarks upon the earth's physical 

 structure ; " Hast thou entered into the springs of the 

 sea ? or hast thou walked in the recesses of the deep ? " 

 forms the text for a chapter on the sea ; and •" Canst 

 thou send forth lightnings, that they may go, and say unto 

 thee. Here we are ?" heads a short chapter on electricity. 

 This chapter, however, is a disappointing one, and a 

 writer with a real knowledge of what has been accom- 

 plished in electrical science could have given a brilliant 

 answer to the poet's inquiry. The texts dealing with 

 physical science are, as a rule, not so well expounded 

 as those referring to natural history objects. The idea 

 of viewing the sublime poem of the Book of Job from 

 the aspect of latter-day scientific knowledge is, however, 

 an excellent one, and we trust the book will be read by 

 priests as well as the laity ; for the contents will be 

 found a source of inspiration to all interpreters of Holy 

 Scripture. 



La Ceramique Ancienne et Moderne. Par E. Guignet et 



E. Gamier. Pp. 311. (Paris: F. Alcan, 1899.) 

 The author of the second section of this work, M. 

 Garnier, is already well known as a writer on ceramic 

 art. Filling the important post of Keeper of the Sevres 

 Museum, he . enjoys ample opportunities of becoming 

 familiar with the development of earthenwares and 

 porcelains and the characteristics of the several kinds. 

 But a couple of hundred pages illustrated by fifty poor 

 process-blocks have not afforded M. Garnier the chance 

 of treating his subject adequately. The essay by M. 

 Guignet on materials and manufacture, though far too 

 slight and unequal in treatment, is good so far as it goes. 

 Unfortunately, he omits much that one expected to find 

 in his pages, e.g. the process and rationale of salt- 

 glazing, while he repeats (p. 86) the exploded theory that 

 Josiah Spode, about the year 1800, first introduced bone- 

 ash into the body of English porcelain. Several other 

 Continental writers on ceramics, when they give any 

 account of English porcelain and earthenware, do not 



