November 14, 1895] 



NATURE 



29 



Practical Proofs . of Chemical Laws : a Course of Ex- 

 periments upon the Combining Proportions of the 

 Chemical Elements. By Vaughan Cornish, M.Sc. 

 (London : Longmans, Green, and Co., 1895.) 



This small work is essentially a product of the modem 

 efforts to teach science by a scientific method. 



The author has endeavoured to give, in some ninety- 

 two pages, clear and sufficient instructions for the experi- 

 mental verification of the great quantitative laws upon 

 which chemistry is based, and he has fully succeeded. 



Nothing could be better calculated to lend interest to 

 the work than the author's plan of quoting the results 

 which were considered sufficient to establish these laws 

 in the early days of our science ; and the comparison of 

 experimental data, obtained by the student, with the 

 classical results of the great pioneers of chemistry, must 

 lend a reality and zest to his efforts. 



Used in its proper place, with students who have been 

 well trained in general experimental science, and under 

 the supervision of a capable teacher, there is no reason 

 to suppose that the somewhat dogmatic statement of 

 chemical laws will have any ill result. 



The statement of the law of constant proportion given 

 on p. 3 — " this proportion remains constant in compounds 

 which contain also other elements" — is so worded as to 

 convey a wrong impression. It might be thought, for 

 instance, that the proportion obtaining between potassium 

 and chlorine in potassium chloride would remain the 

 same in potassium chloroplatinate, which contains also 

 another element platinum, and a reference to chapter v. 

 would confirm this impression. It is evident that this 

 statement requires remodelling. 



Certain slips of a different type have found their way 

 into the text. Thus, ^'' hollow glass-rod" is mentioned on 

 p. 52 ; and on p. 62, it is advised to treat silver with 

 " pure strong hydrochloric acid " in order to convert it 

 into silver chloride. Notwithstanding these minor de- 

 fects, the book may be safely commended as embodying 

 a well-thought-out and feasible plan of work. T. 



Great Astronomers. By Sir Robert S. Ball, F.R.S- 



Pp. 372. (London : Isbister and Co., 1895.) 

 The greater part of this book consists of r^chauj^es 

 articles from Good Words and other publications. At 

 the present day there is a large public curious to know 

 biographical details, so no doubt the book will find many 

 appreciative readers. The astronomers whose lives are 

 portrayed are Ptolemy, Copernicus, Tycho Brahe, 

 Galileo, Kepler, Newton, Flamsteed, Halley, Bradley, 

 William and John Herschel, Laplace, Brinkley, the Earl 

 of Rosse, Airy, Hamilton, Le Verrier, and Adams. It 

 need hardly be said that the serious student of astronomy 

 will find little in this book not already familiar to him ; 

 the volume is intended for the popular mind, and there- 

 fore much of it is small talk of the kind in which the 

 general public revels. When the lives of eighteen 

 astronomers are described in a volume of less than four 

 hundred pages, as they are in this book, it is needless to 

 say that only a few of the features characteristic of each 

 can be presented. Sir Robert Ball has, however, selected 

 the chief features in the lives and works of the great men 

 who form his subjects, and his sketches, though verbose 

 in parts, bring to light a few new facts in which 

 astronomers generally will be interested. The book con- 

 tains numerous illustrations, many of them new. The 

 illustrations chiefly represent the astronomers described, 

 and their houses, observatories, and instruments. We 

 cannot understand, however, why some of them are 

 in the book at all ; for instance, with the sketch of 

 the Earl of Rosse we find pictures of Birr Castle ; The 

 Mall, Parsonstown ; and the Roman Catholic Church at 

 Parsonstown. The connection of these views with 

 " Great Astronomers " is much less reasonable than that 

 between cats and clover. 



NO. 1359, VOL. 53] 



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 Nature. 

 No notice is taken of anonymous communications. ] 



Sir Robert Ball and "The Cause of an Ice Age." 



I SHOULD like to correct one statement in my long letter m, 

 Nature of October 17. I there said that Sir Robert Ball had 

 not withdrawn his claim to the discovery of the law of distribu- 

 tion of summer and winter temperature in each hemisphere, 

 which had in fact been previously published by Wiener. I am 

 reminded by Mr. Kendall that I had overlooked a second edition 

 of the book in which credit is duly assigned to Wiener. Thereby 

 hangs a tale. I have looked in vain through Low's well-known 

 list for any trace of a second edition. I also looked through the 

 British Museum Catalogue without any result, and inquired 

 in the Copyright Office in that establishment, and was told that 

 no such book had reached the Museum. Lastly, the Museum 

 people tell me they have applied to the publisher for the book, 

 and have received the reply that it is only a re-issue, and not a 

 new edition with new matter in it. 



I am further told by the Museum officials, that he has there- 

 by incurred a penalty of ^5 for non-compliance with the Copy- 

 right Act. It was by an oversight of his, therefore, that this 

 second edition has been overlooked by myself and, probably, by 

 others. 



In this second edition. Sir R. Ball, after unwittingly wear- 

 ing the nimbus for six years, gives up his oft-repeated claim 

 to be the discoverer of the law in question, and attributes it 

 to Wiener. As the publication of his discovery was the alleged 

 reason for writing the book, he had now to find another excuse, 

 and did so by reiterating the unjust accusation he had made 

 against Croll of having ignored the disparity between the sun- 

 heat of summer and winter, and thus necessitating the writing 

 of a work to set the world right on the matter. 



As long ago as 1891, Mr. Noble had called attention to this 

 injustice, and shown that Croll had nowhere made the mistake 

 attributed to him, and quoted passages from pages 55 and 86-7 of 

 " Climate and Time," to show that he was perfectly aware of the 

 real conditions. Although Croll nowhere cites the actual numbers 

 63 and 37, or 3'93768 and 2*34550 as Wiener gives them, it is 

 odd that in calculating the amount of sunshine received at Edin- 

 burgh in summer and winter respectively, he does give the num- 

 bers 7 to 4, that is, 63:36, and "Climate and Time" was 

 published four years before Wiener's " Memoir." 



It is quite true that Croll does not use these figures in his cal- 

 culations as Dr. Ball does. For him they would be mere 

 academic numbers, since he knew, as we know, that the 

 problem to be solved depends much on the proportions of the 

 differential temperature of different latitudes at different seasons, 

 and little or nothing on the proportions of the temperatures at 

 different seasons of a whole hemisphere lumped together. 



Since the above was written, Mr. Hobson has replied to- 

 my previous note, complaining that I have converged attention 

 upon the now famous law, which was supposed to be Sir R. 

 Ball's own child, and have not referred to the effects of varying; 

 eccentricity, which were everybody's property. He forgets that 

 I was criticising Dr. Ball, who habitually claims the law in 

 question as the causa causans of an Ice age, and especially refers, 

 to this invariable and constant factor as " the following theorem 

 which constitutes the essence of the astronomical theory of an Ice 

 age." 



The value of this essential factor of the problem being the 

 matter in dispute, I presume Mr. Hobson wrote his letter to 

 illuminate your readers, and not merely to engage in a profitless 

 polemic. If so, perhaps he will do me the favour of meeting 

 the following case. 



(1) Wiener's law is not disputed. It represents the propor- 

 tions between the sum of all the sun-heat received in either hemi- 

 sphere in summer and winter respectively. 



(2) Sir R. Ball makes it apply not only to the whole hemisphere, 

 but to different zones in the hemisphere, and notably to Britaia 

 (see "A Cause for an Ice Age," new edition, pp. I27-I3l)^ 

 Will Mr. Hobson support this astounding conclusion ? 



(3) In the zone between the tropics there is perpetual 

 summer, and it absorbs one-half of the sun's heat received on the 

 earth in equal proportions in the two seasons. Here, therefore, 

 the proportions of sun-heat are not 63 : 37, but 50 : 50. There- 



