174 



NA TURE 



[June 22, 1893 



The system works out in such a way that each element 

 in the first row of the periodic table becomes the parent 

 of all the elements in its own vertical series. 



Oxygen, for instance, is the root of the following genea- 

 ogical tree :^ 







/|\ 

 Cr I S 



/ Ni \ 



Mo 1 Se 



Prd 

 / 



/ 



U 



Pd 



\ 

 Te 



W Pt 



Er 



Chromium, nickel, and sulphur, in this way belong to 

 the second generation. Molybdenum, paladium, and 

 selenium to the third generation, and so on. The 

 constants of the elements, such as atomic weights, 

 densities, atomic volumes, specific heats, atomic heats, 

 and their electrical and magnetic properties, their 

 valency, &c., are then discussed with the view of 

 justifying the mode of treatment adopted. It is here 

 shown that on arranging the elements according to the 

 author's system, besides the well-known relations between 

 properties and atomic weights, additional simple nume- 

 rical relations are traceable between the magnitudes of 

 the atomic constants themselves, and also between these 

 magnitudes and the numbers denoting the degree of con- 

 densation of the groups to which the elements belong. 

 The use to which these may be put as a means of con- 

 trolling the values of atomic weights and predicting the 

 properties of undiscovered elements is indicated. 



The second and not the least useful part of the book 

 contains a collection of physical constants, from which 

 the data used in the first part were chosen. 



The book is a suggestive contribution to the literature 

 on a subject which since the time of Prout has been 

 prolific of speculation, but which even yet seems slow to 

 condense and take a form sufficiently definite to warrant 

 its being raised to the rank of a theory. J. W. R. 



The Future of British Agriculture. By Prof. Sheldon. 



(London : W. H. Allen and Co., Ltd., 1893.) 

 The opening chapters of this little book are devoted to 

 the solution of the questions, " Will wheat-raising pay in 

 Great Britain ? " and " Is wheat to be no longer king ? " 

 After indicating the reasons which led to the enormous 

 reduction of land under wheat^a decrease of something 

 like 42 per cent, within the last twenty-five years — Prof. 

 Sheldon comes to the conplusion, that, notwithstanding 

 the importation of foreign wheat, and the fact that an 

 ever-increasing demand for milk (of all farm products the 

 least suitable for importation) necessitates larger areas of 

 grass land, wheat-growing will not only continue, but 

 may soon reach its former position, an event which he 

 would not consider to be " a sign of unadulterated good." 

 In connection with the question of wheat-production in 

 the United States, there is one statement, made on the 

 authority of leading American statistical experts, which 

 we venture to think requires qualification, namely, " that 

 in less than twenty years from 10 to 15 per cent, of the 

 people's food will have to be imported into the United 

 States." This is a point on which there may well be 

 diversity of opinion, but, as pointed out by Messrs. Lawes 

 and Gilbert in their recent paper on "Allotments and 

 Small Holdings," the conditions will be quite changed 

 with increased population, rotation will gradually become 

 general, yielding various food products for home con- 

 sumption ; the soil will be better cultivated, yielding much 

 larger crops of wheat where it is grown ; straw and manure 

 will no longer be burnt or wasted ; and, lastly, there are 

 still considerable areas of rich prairie land to be brought 

 under the plough. So that it is probable that increased 

 density of population will less rapidly diminish the 



NO. 1234. VOL. 48] 



capability of production for export than may, at first 

 sight, be supposed. 



Perhaps the most interesting chapters are those on 

 dairy farming ; and it will afford a good deal of consolation 

 to the dairy farmers of this country to learn that Prof 

 Sheldon believes " the competition of the United States is 

 within measurable distance of its limit." 



The book concludes with a chapter on a most im- ' 

 portant subject — tenant farmers' interests. The author 

 states his view of the matter in his usual clear and for- 

 cible manner, and incidentally refers to what he terms ' 

 "exploded, impossible 'Protection'," and to "that new 

 economic craze, ' Bimetallism'." 



We welcome the book as a valuable contribution to our 

 agricultural literature, and as a useful guide to those 

 branches in which the author is especially qualified to 

 instruct. 



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 correstond with the writers of, rejected 

 manuscripts intended for this or any other part of Is ATURE, 

 No notice is taken of anonymous communications. ] 



Mr. H. O. Forbes's Discoveries in the Chatham Islands. 



I WRITE a final line on this subject to express my regret that 

 I should have misunderstood Prof. Newton and attributed to 

 him (Nature, p. 126 above) opinions in regard to the relation- 

 ship between Erythromachus and Aphanapteryx which he does 

 not hold. 



On a point of accuracy, however, in regard to the "slight 

 confusion of dates," allow me to say that I am sure no one will 

 admit more readily than he that this had occurred, when I 

 remind him ol his letter to me of December 22, i8c2 (now before 

 me), in reply to a note of mine requesting him to be so ^;ood as 

 to repeat his suggestion in regard to the name for the new genus, 

 which I was about to describe, as I had mislaid his former note. 

 "I have no memorandum," he says, "of what I suggested to 

 you, but only an indistinct recollection that it was Dla^'thorap- 

 teryx ... or something like that." This was, therefore, the 

 date of the re-suggestion, and not my visit to Cambridge on 

 February 23, 1893. Diaphorapteryx was described as a new 

 genus in the Bull. Brit. Ornith. CI., December 31, 1892. 



Henry O. Forbes. 



Tlie Fundamental Axioms of Dynamics. 



A VERY brief reply to such of your correspondents as have 

 favoured my paper with direct or indirect criticisms will at the 

 present stage of the discussion be sufficient. 



Referring first to Prof. Kucker's letter on p. 126, I acquiesce 

 in the greater part of it — especially in its concluding p.iragraph, 

 but it may clarify matters if I explain (i) that I do not contem- 

 plate parts of the ether, but regard it as an absolute continuum. 

 Not the slightest advantage is gained by pushing action and 

 distance back a step or two— it must be exterminated. (2) Th«t 

 I have no faith in "action at constant distance" other than 

 distance zero. The reason such a phrase ever appeared in my 

 papers is because that is all I am able to deduce from the as- 

 sumption of the conservation of energy. It requires identity of 

 energy to prove absolute contact. Hence I prefer to work 

 backwards, and, assuming universal contact action or the denial 

 of action at a distance, to deduce therefrom both the conserva- 

 tion and identity of energy. 



Prof. McGregor contradicts three statements in the Report of 

 the meeting of the Physical Society (p. 117), a report which is 

 usually admirably done, and which was well done in this case. 

 Though not responsible I reply to his three points categorically : 



(1) He was understood to object to the Newtonian statement 

 of the first law — not to the fact or law itself. 



(2) A reference to the first two pages of his paper m the 

 February Phil. Mag. will show him, I think, that he has now 

 partially forgotten what he said on the second head. 



(3) It is to be admitted at once that the phrase "equally 

 well," not "well," was employed. 



