6i4 



NATURE 



[October 27, 1898 



of a great master of the art is laid bare for us ; and the 

 acquisition of a right method is a greater thing than a 

 mere knowledge of the results : irAeov r^iucrv navros. 



Take as an illustration the interesting indications of 

 the way in which Huxley's mind was feeling its way 

 towards a grasp of evolution. The comparison of the 

 results of philology and embryology in the lecture " On 

 the common plan of animal forms" is curiously sugges- 

 tive (p. 283). It throws light on what some of us thought 

 a hard saying in his last (as I suppose) public speech 

 made at Oxford, when he said that whether the Darwinian 

 theory, remained or fell, the fact of evolution would 

 survive. 



It has been said that Huxley made a "stalking-horse " 

 of Darwin, and there is just the amount of truth in this 

 as in every jest. It is evident that Huxley's morph- 

 ological studies had brought him to the precise point 

 where the " Origin of species " gave him the illumination 

 of which he stood in need. And he seized it with 

 characteristic ardour and enthusiasm. In the case of 

 the cell-theory his mind was not so receptive because not 

 so prepared. "Its value," he says, "is purely an- 

 atomical " (p. 220). He could not foresee, and perhaps 

 would not have been justified in foreseeing, that it would 

 supply the future key of our physiology. 



And here I must acquit myself of the task which I 

 have reluctantly undertaken. To do any adequate justice 

 to the wealth of accomplished work included in this 

 volume alone is, as I began by saying, wholly beyond my 

 powers. But no intelligent student can turn over these 

 records of Huxley's work without realising the truth of 

 the remark of the editors, that " the progress of biology 

 during the present century was largely due to labours of 

 his of which the public knew nothing." And whatever 

 else such a student may take away from their study, he 

 cannot at least fail to learn how to treat of the most 

 technical matters with the extremity of pregnant and lucid 

 expression. W. T, Thiselton-Dyer. 



T//E SCIENCE OF APPLIED ELECTRICITY. 



Mas^nets and Electric Currents. By Prof. J. A. Fleming. 

 Pp. XV -f- 408. (London : E. and F. N. Spon, Ltd., 

 1898.) 



THIS work, as Prof. Fleming explains in his preface, 

 has grown out of, and may be considered as taking 

 the place of, his well-known smaller work, " Short Lectures 

 to Electrical Artisans," published about twelve years ago. 



" In recasting the information in such a manner as to 

 conform more nearly to the present state of knowledge 

 the author still desired to fulfil the original aim of 

 supplying electrical artisans and engineering students 

 with a brief and elementary account of the scientific 

 principles underlying modern applications of electricity 

 in engineering. With this object in view the use of 

 mathematical symbols has as far as possible been 

 avoided, but at the same time an endeavour has been 

 made to give the reader clear notions on the quantita- 

 tive measurements which lie at the root of all applica- 

 tion of electrical facts in the arts." 



This endeavour is more than justified by the present 

 admirable volume. 



After two introductory chapters, one on magnets and 

 NO. 1 513, VOL. 58] 



magnetism describing the simpler properties of per- 

 manent and electro magnets, and the other on measure- 

 ment and units in which the bases of physical knowledge 

 and the principles of "absolute" measurement are 

 explained, the quantitative connection between currents 

 and their magnetic effects is discussed under the heading 

 " Magnetic force and magnetic flux." This discussion 

 might equally well have been entitled " the magnetic 

 circuit," as it virtually amounts to an explanation of that 

 useful conception ; and it is appropriately followed by a 

 comparison of the present system of measurement with 

 the " rational " system suggested many years ago by 

 Mr. Oliver Heaviside, the advantages of which are 

 particularly striking in magnetic circuit problems. 

 Chapters iv. to vii. deal with electric currents and 

 the theory of their measurement, electromagnetic in- 

 duction, and electromagnets, with a discussion under 

 the last head of magnetic curves, hysteresis, and the 

 molecular theory of magnetism; chapters viii.- and ix. 

 are on the theory of alternating currents and on measuring 

 instruments respectively ; and chapter x., a longer one 

 than the rest, is devoted to the various methods of 

 generating currents. The book concludes with an 

 appendix on the measurement of the earth's horizontal 

 magnetic field strength, a table of natural sines, cosines, 

 and tangents, and an index. 



From what has been said, it is plain that Dr. Fleming's 

 work is far more than a mere enlarged edition of the 

 " Lectures to Electrical Artisans." It may be best de- 

 scribed as a clear and brief— sometimes, we are tempted 

 to think, almost too brief— but always admirably clear 

 account of those parts of electrical theory which should 

 be grasped by the better class of junior student of prac- 

 tical electricity. Such an account has, we venture to 

 think, long been needed. Valuable as are descriptions 

 of such things as Coulomb's balances and Wimshurst 

 machines in the ordinary text-book, the importance of 

 early guiding the thoughts of the youthful electrician 

 into the channels which lead most directly to the regions 

 of his subsequent activity cannot be too strongly emphas- 

 ised. Life is too short, for all but the very gifted men, 

 to do more than make a distant acquaintance with what, 

 from the electrician's point of view, are the ornamental 

 parts of his science ; and it is largely because Dr. 

 Fleming recognises the truth of this, that his book cannot 

 fail to be of very great value to both teachers and students 

 of electrical technology. A. P. C. 



OUR BOOK SHELF. 

 Natural Hygiene or Healthy Blood, the Essential 

 Condition of Good Health and how to attain it. By 

 H. Lahmann, M.D. Translated from the German by 

 Dr. H. Buttner. Pp. v -t- 253 ; plates 5. (London : 

 Swan Sonnenschein and Co., Ltd., 1898.) 

 The book before us is a learned exposition which aims 

 at two very laudable objects— the reform of clothing 

 and diet, and the banishment of disease. With regard 

 to clothing little is said : the author's children are re- 

 presented in a state of nudity; this, together with the 

 prescription of constant air baths, and declamations 

 against the amount of clothing worn by man at the 

 present day, makes one think that in his heart of hearts 

 the author regards the entire disuse of all clothing as the 

 beau ideal. 



