292 



NA TURE 



[July 28, li 



The book is well indexed and written in a clear style ; 

 it will doubtless occupy a prominent place amongst the 

 text-books of diseases of the lungs, and well deserves to 

 do so. F. W. T. 



An Elementary Course of Dtfiniiesimal Calculus. By 



Horace Lamb, M.A., F.R.S., Professor of Mathematics 



in the Owens College, formerly Fellow . of Trinity 



College. Pp. XX + 6i6. (Cambridge : University 



Press, 1897.) 



The author states that his aim in this book is to 



teach those portions of the Calculus which are most 



useful for a student of physics or engineering. We fear 



that many an engineering student would be disheartened 



at the start-off by such sections as those in the first 



chapter on the upper or lower limit of a sequence and 



of an assemblage. On the other hand, there is surely 



room to doubt the wisdom of the limitation implied 



rn the statement — " Imaginary quantities are nowhere 



employed in the book," seeing that this is a book of over 



600 pages, and includes chapters on differential equations 



in which symbols of operation are freely used. 



But although we think there is at once too much and 

 too little for the needs of engineering students, and that 

 it is to be regretted that the author has not permitted 

 himself to use illustrations from such subjects as heat or 

 electricity for the benefit of the students of physics he 

 has in view, we are glad to recognise in the work before 

 before us merits of a very high order. Thus immediately 

 after the rules for differentiation are established, we have 

 applications to maxima and minima and to geometrical 

 problems. The rules for integration are then introduced 

 with applications to areas, volumes, moments of inertia, 

 &c. The diagrams are numerous, always large and 

 clear, and often drawn to scale. There are a great many 

 easy, straightforward examples provided ; and care has 

 been taken not to admit examples or processes involving 

 difificult analysis or mere ingenious artifice. 



Teachers in secondary schools and colleges will be 

 well advised in using this as a text-book for beginners 

 in the Calculus, although it is not in our opinion what is 

 required in technical classes. 



Radiography and the "^" Rays. By S. R. Bottone. 



Pp. X -I- 176. (London : Whittaker and Co., 1898.) 

 This is another of the now considerable series of more 

 or less popular handbooks dealing with the applications 

 of the Rontgen rays. Medical men, amateur experi- 

 menters and others who may wish to put Rontgen 

 photography into practice will find it useful, lucid, and 

 trustworthy. Within the compass of 172 pages the book 

 contains many practical hints on the construction and 

 working of induction coils, influence machines, Crookes' 

 tubes, and fluorescent screens, and on general photo- 

 graphic and manipulatory details. 



Ackworth Birds, being a List of Birds in the District of 

 Ackworth, Yorkshire. By Major Walter B. Arundel. 

 Pp. viii -+- 105. (London : Gurney and Jackson, 1898.) 

 It may be well to remark at once that this is not merely 

 an enumeration of the birds observed in Ackworth and 

 the neighbourhood, but a collection of notes on the 

 habits of the species described. On this account, the 

 volume is not only of interest to local ornithologists, but 

 is also a worthy contribution to the literature of bird-life. 



Angling Days and an Angler's Books. By Jonathan 

 Dale (I. E. Page). Pp. 160. (London : Elliot Stock, 

 1898.) 

 A COLLECTION of stories concerning anglers and angling. 

 A few natural history notes are scattered through the 

 pages ; but in the main the book consists of more or less 

 commonplace remarks upon fishing experiences, and the 

 expression of the author's sentiments upon landscapes 

 and rural scenes in general. j 



NO. 1500, VOL. 58] 



• LETTERS TO THE EDITOR 

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

 pressed by his correspondents. Neither can he under-take 

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

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications. ^ 



Liquid Hydrogen, 



I SHOULD be inclined to let Prof. Dewar's manner of replying 

 to my statements speak for itself were it not that he makes in 

 his last letter imputations of an unwarrantable kind. He says, 

 "Mr. Hampson got at my assistant behind my back." This 

 expression is quite indefensible. I received an introduction to 

 Mr. Lennox from the senior partner of a large chemical firm in 

 London of the highest standing, who said that he had a familiar 

 acquaintance with Prof. Dewar's assistant. Had he been 

 sufficiently intimate with Prof. Dewar himself to offer me a 

 confident hope of gaining that gentleman's attention directly, I 

 should at that time have been still better pleased with an 

 introduction to him. As it was, I went openly to the Royal 

 Institution, in the busiest part of session, and between the hours 

 of eleven and twelve in the morning. Surely, nothing would 

 have been more natural under these circumstances than a chance 

 meeting with Prof. Dewar himself. Is this the conduct of one 

 who was plotting to " get at " his assistant "behind his back " ? 

 Whatever grounds Prof. Dewar may have for thinking his 

 assistant capable of improper action, he has no right to use 

 such abusive terms regarding the very simple and straight- 

 forward course that I took in the matter. Prof. Dewar says, 

 " I infer from the public correspondence that he (Mr. Lennox) 

 saw that they (the plans) would not work, and he told Mr. 

 Hampson why they were unworkable." This inference of- 

 Prof. Dewar's is altogether false, as is best proved by a study 

 of the correspondence itself. This correspondence took place 

 in Engineering last spring. I am myself so satisfied with the 

 conclusions to be drawn from it, that I have had the whole 

 series of letters reprinted, and I will send a copy with pleasure 

 to any one who desires to do me the justice of forming his own 

 opinion on the merits of the case. It is strange that Prof. 

 Dewar, having himself published his belief that his assistant is 

 capable of being "got at" by a complete stranger, should in 

 the very next line attach some importance to that gentleman's 

 account of the transaction as given in those letters. The identity 

 between the " unworkable " plan proposed by me to Mr. Lennox, 

 and that subsequently, or, as Prof. Dewar puts it, " in the 

 meantime," worked out with complete success by Dr. Linde, by 

 myself, and by Messrs. Lennox and Dewar, does not depend on 

 my statement only. All the points of the new combination were 

 put together in the drawings submitted by me to Mr. Lennox, 

 and an exact copy of these drawings was exhibited before the 

 Society of Chemical Industry on May 2 last, when Mr. Lennox 

 was present, as well as Prof. Dewar, and it appears with the 

 published report of my paper. The same combination is found 

 in no earlier drawings except some previous sketches of my own. 

 Prof. Dewar, in his last letter, admits an inventor's property in 

 " the particular combination to which he himself may give 

 concrete form " ; and I gave concrete form to this particular 

 combination in the drawings submitted to Mr. Lennox. Prof. 

 Dewar says that it took me "another year to perfect a pro- 

 visional specification," " which is totally devoid of any plan or 

 drawing of a workable apparatus." It only took five months, 

 of which time half was spent in waiting for Mr. Lennox to 

 fulfil his promise to experiment, and in trying to extract from 

 him some information as to what was being done. It was my 

 failure to obtain any satisfaction on this score that decided me 

 to apply for provisional protection, for which drawings are not 

 required, as Prof. Dewar well knows. My communications to 

 Mr. Lennox were made in November and December 1894, my 

 application for provisional protection in May 1895. 

 July 22. W. Hampson. 



The Distribution of Prepotency. 



Mr. Galton has raised under this heading a most important 

 point — or, rather, a series of most important points — in the 

 problem of evolution. Perhaps I maybe permitted to say a few 

 words with regard to his views on evolution by sports and by 

 normal variation. Mr. Galton's opinion, I think, is that sports 

 are inherited in a higher degree than improbable normal varia- 

 tions, and that evolution must accordingly take place very largely 



