444 



NA TURB 



[September io, 1891 



it thus covers the portions of electricity and magnetism 

 which, under the new regulations, are selected for ex- 

 amination in Part I. of the Mathematical Tripos, and we 

 have no doubt it will be found useful for that examina- 

 tion. The book is very well arranged, and the explana- 

 tions are generally clear and concise. Among some minor 

 points which, we think, might with advantage be altered 

 in subsequent editions are the following. When discuss- 

 ing the rapidly alternating currents produced by dis- 

 charging a Leyden jar, the author says : " We do not 

 know, for instance, whether we are right in supposing the 

 currents to be the same throughout the conducting wire." 

 This seems an unnecessary affectation of ignorance, for 

 •we do know that such a supposition is certainly wrong. 

 The method of determining " v " by repeatedly charging 

 and discharging a condenser placed on one arm of a 

 Wheatstone's bridge is not given, though several other 

 less accurate methods are described. This is the more 

 -singular as the method itself is given in another part of 

 the book as one for determining the capacity of a con- 

 denser, but no hint is given of its most important ap- 

 plication. The method of measuring the self-induction 

 of a coil, which is ascribed to Lord Rayleigh, is really 

 due to Maxwell, and, though not in the treatise on " Elec- 

 tricity and Magnetism," is given in the paper on the 

 •" Dynamical Theory of the Electro-magnetic Field." 



1^ Sommeil et le Systhne Nerveux : Physiologie de la 

 Veille et du Sommeil. Par S. Sergudyeff. (Paris : 

 Felix Alcan, 1 890.) 



'It is difficult to understand why a writer upon the higher 

 branches or outlying districts of neurology should assume 

 that his readers are totally ignorant of the rudiments of 

 that science, and should occupy nine-tenths of his book 



' with a description of the anatomy and physiology of the 

 nervous system. If, indeed, for the purpose of throwing 

 new light upon his subject, he presented his facts in a new 

 form, or taught them from a novel point of view, or 

 arranged them so as to bring out some new principle, then 

 there might be an excuse for restating the facts ; but even 

 then a brief summary would be enough for the pur- 

 pose, there would be no need for the rediscussion of 

 settled theories and the requotation of trite authorities. 

 Scarcely ever do we find a writer on neurology who is 

 content to assume that his readers are acquainted with the 

 alphabet of his subject, or who will refrain from inflicting 

 upon them the wearisome account of cells and fibres, of 

 corona and cortex, illustrated by the familiar engravings 

 that have done duty in so many previous books. The 

 vicious habit is common enough and bad enough, but very 

 rarely is it carried to such an extent as in the book before 

 us, in which only about three hundred out of the seventeen 

 hundred pages of which it is composed are devoted to the 

 subject of which it is said to treat ; the great bulk of the 

 book being occupied by anatomical and physiological 

 descriptions which are not in this case even relieved by 

 illustration. So far is this system of padding carried, that 

 the author has even inserted, in his book on waking and 

 sleeping, descriptions of the minute structure of the retina, 

 of the internal ear and the organ of Corti. When we have 

 at last waded through his pages of preliminary matter, 

 we do not find that he presents any fresh theory of sleep 

 that is worth considering, or that he has any new facts 

 to bring under our notice. It is a shame that a student 

 should be trapped by an enticing title into spending his 

 time in reading such stuff. 



Elementary Science Lessons. By W. Hewitt, B.Sc. 



(London: Longmans, Green, and Co., 1891.) 

 The thirty-six object-lessons contained in the present 

 volume form the third part of a scheme of lessons drawn 

 up by the author at the request of the Liverpool School 

 Board. They are designed for children of Standard III., 

 and are in continuation of others given in previously pub- 



NO- II4I, VOL. 44] 



lished volumes suitable for Standards I. and II. The 

 author's long experience in teaching science to children 

 in elementary schools gives him the ability which is 

 necessary properly to draw up such a course as the one 

 before us. For the most part the facts and principles 

 dealt with relate to the classification of bodies into solids, 

 liquids, and gases, and with the changes from one of 

 these states to another. The experiments described may 

 be performed with the simplest of apparatus, and the in- 

 ferences to be drawn from them must be manifest to all 

 children for whom the work is intended. Whenever pos- 

 sible, the principles considered in the lessons are applied 

 to explain physiographical phenomena, thus aiding the 

 development of that intelligent observation which is the 

 soul of science. The arrangement of the matter is 

 generally good, and elementary school teachers will 

 find in the work exactly what they require for their 

 pupils. 



Solutions of the Examples in Charles Smithes '''■Ele- 

 mentary Algebra." By A. G. Cracknell. (London : 

 Macmillan and Co., 1891.) 

 Mr. Smith's small " Algebra" has deservedly obtained 

 high favour in our schools for its lucidity. The 

 work before us aims at presenting the solutions, not 

 always necessarily in the shortest way, but rightly so as 

 to " follow naturally from the formulse and theorems with 

 which the student is acquainted at that stage." It has 

 Mr. Smith's imprimatur, for he has revised the sheets ; 

 and from our own examination of it we can commend it 

 to teachers and students. 



LETTERS TO THE EDITOR. 



[The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 manuscripts intended for this or any other part of '^ATXS KM. 

 No notice is taken of anonymous communications.'] 



The Anatomy of Heloderma, 



The number of Nature for July 30, which I have only just 

 seen, contains (p. 295) a criticism of a statement of mine, to 

 which I have to answer. It is stated in my paper on the 

 osteology of Heloderma that there are eight or nine pre- 

 maxillary teeth in IT. horridum, and only six in H. suspectiim, 

 because such is the number in the specimens examined by me. 

 As Dr. Shufeldt has, on re-examination, found eight teeth in a 

 specimen of the latter species, I admit that the distinction, as 

 a specific character, does not hold good. It is just because my 

 figures are not diagrammatic that they represent fewer teeth 

 than are mentioned in the text ; to anyone familiar with the 

 dentition of lizards and snakes, it is clear enough that some of the 

 teeth have been lost, and they were therefore not represented 

 in the figures, which are faithful representations (in outline) of 

 the objects from which they are drawn. I am much surprised 

 at Dr. Shufeldt's statement, that he "cannot conceive of any 

 lizard normally having but nine teeth in its premaxillary bone ; 

 it should at least be an even number." I could refer him to no 

 end of examples of premaxillary teeth normally in odd number 

 among lizards with single premaxillary ; perhaps the best known 

 is afforded by the family Amphisbcsnida;. I must again correct 

 Dr. Shufeldt on a matter of fact : my figure of 11. horridum 

 shows seven teeth, not six, as he states in his letter ; and that of 

 H. suspectum five, not four. G. A. BoULENGER. 



British Museum (Nat. Hist.), August 28. 



A Straight Hand. 

 Although my writing master, who was an Englishman, 

 taught me slanting letters which old habit still clings to, I 

 approve highly what you say against it (Nature, August 6, 

 p. 325). Allow me to add some remarks on another side of 

 that question. For many years pait I have had in succession 

 several amanuenses, and my first care has always been to require 

 a straight hand without any distinction between up and down, 



