July 3, 1890] 



NATURE 



219 



" There was no change till about midnight," writes his 

 niece, " and then we saw the shadow of death come 

 softly over his face, and we knew that he had passed into 

 the dark valley, and that the end was near ; but there was 

 no pain ; only quiet sleep. His breathing again grew 

 more faint and soft ; and without a sigh, just as the clock 

 in the great court of Trinity chimed a quarter past one, 

 his spirit returned to God." 



Sedgwick's original scientific work will be sketched in 

 another notice. This may conclude with a word on the 

 man himself. A stalwart figure with rugged features and 

 brown complexion, a flashing eye, and a grand pose of 

 the head, which always reminde me of an eagle. He 

 called himself — men called him — ugly. This I never 

 could understand. Few were better tellers of a story : 

 his memory of striking details, his sense alike of humour 

 and of pathos, were so strong. As a lecturer he was dis- 

 cursive, but suggestive — one who stimulated and fertilized 

 rather than who trained. His speeches were marked by 

 a curious play of fancy, unexpected transitions from grave 

 to gay, and occasional bursts of eloquence, which our 

 greatest orators might have been glad to own. As a 

 writer he was often diffuse, sometimes laboured — the 

 results of hurried work or unsystematic arrangement ; yet 

 he broke out occasionally into passages of singular force 

 and vigour. For instance, the concluding paragraphs of 

 his preface to the " Catalogue of Cambrian and Silurian 

 Fossils " — his last contribution to literature — are worthy, 

 in my judgment, of a place among the best extracts from 

 English literature. He was sometimes strong and even 

 narrow in his prejudices, as will appear hereafter ; he was 

 impetuous in temper, fierce in the fray, positively ripping 

 up an incompetent antagonist ; yet he was commonly the 

 most genial and placable of men ; he was tender as a 

 woman to those who sorrowed and who suffered, and was 

 the idol of little children. 



We may close the present notice with the words with 

 which Mr. Clark concludes his own part of the biography 

 — the words of one of Sedgwick's intimate friends : — 



" He was transparent and straightforward — the very 

 soul of uprightness and honour — tender and affectionate — 

 most generous and kind. He had a hatred of all duplicity 

 and meanness. He was entirely unsuspicious of evil, 

 unless it was forced upon his notice ; and he expected 

 and believed everyone to be as straightforward and truth- 

 ful as he was himself. I do not think that any man was 

 so beloved by his friends as he was." 



T. G. BONNEY. 



{To be continued^ 



GERARD'S " ikLECTRICITEr 

 LeqoHS sur V Electricity, professies d VInstitut Electro- 

 technique Montejiore annexe d V Universite de Li^ge, 

 Par Eric Gerard, Directeur de cet Institut. (Paris : 

 Gauthier-Villars, 1890,) 



THE author of this book says in his preface that when 

 he took charge of the classes in electric technology 

 at Lidge he felt the want of a text-book which would give 

 a clear and definite account of electrical phenomena 

 without requiring more extensive mathematical knowledge 

 than his pupils might be expected to possess. We think 

 that in this respect the experience of most teachers of 

 NO. 1079, VOL. 42] 



electricity will coincide with that of M. Gdrard. There 

 are very few text-books on electricity in which the happy 

 mean between utter vagueness and methods requiring the 

 use of high mathematical knowledge has been hit ; this, 

 however, has been done so successfully in the book before 

 us, that we think the difficulty to which we have just 

 alluded will be almost removed. In this book we have 

 the main outlines of electricity explained in language at 

 once intelligible and precise, and without introducing 

 more mathematics than every student of the subject ought 

 to be competent to follow. In a subject like electricity, 

 where forces have to be compared, the geometrical 

 properties of bodies of various shapes utilized, &c., it is 

 evident that if any numerical results at all are to be 

 attained, some mathematics must be introduced ; the 

 question as to how much mathematical knowledge 

 should be expected of students who, as a working 

 hypothesis, may be assumed not to have any special 

 aptitude for that study is one on which opinions will 

 differ. For our part, we think that, even regarding it solely 

 from the point of view of the engineer or physicist, such 

 students ought to be advised to acquire an elementary 

 knowledge of the differential and integral calculus ; the 

 possession of this knowledge will make many parts of the 

 subject easy which without it would be difficult, and the 

 time spent in acquiring the mathematics will be much 

 more than saved in the time spent over the physics. In 

 the book before us the mathematics are as plain and 

 straightforward as possible. At the same time, M. Gdrard, 

 very wisely we think, does not scruple to use the elements 

 of the differential and integral calculus. 



The work contains more than 500 pages, of which about 

 200 are devoted to the theory of Dynamos. The re- 

 mainder consists of an exceedingly clear and accurate 

 description of electrical phenomena, the subject through- 

 out being treated from Maxwell's point of view. The 

 book is brought well up to date, and contains an account 

 of most of the recent researches in electricity and mag- 

 netism ; we think, however, it would have been improved 

 by references to the places of publication of the original 

 papers in which these researches are described, so that a 

 student who wishes for a more detailed description than 

 could be given in an elementary text-book might be able 

 to refer to the original authorities for himself. 



A most excellent feature of the book is that M. Gerard 

 does not treat the subject as if an investigation was com- 

 plete when it had led to a relation between a number of 

 symbols. He applies the equations he gets to actual cases, 

 and thus familiarizes the student with the magnitude of 

 the quantities with which he is dealing. He commences 

 the book with Sir William Thomson's maxim, which is so 

 excellent in physics, though its application to other 

 subjects might possibly cause consternation, that "we 

 cannot understand a phenomenon until we can express it 

 in numbers," and he acts up to the spirit of this maxim 

 all through the book. 



The book is well and clearly printed, and the author 

 has realized the fact that it is more important that the 

 diagrams in a text-book of physics should be explanatory 

 than that they should be elegant. 



There are one or two points which we think might be 

 corrected in a new edition, which we are sure will soon 

 be required. The deformation of dielectrics under elec- 



