484 



NATURE 



{April 20, 1876 



milk, mortar, nickel, photography, analysis (qualitative 

 and quantitative), nitric acid, nitrates, salts, oxygen, gun- 

 powder, sulphur, sulphuric acid, silver, specific gravity, 

 thermometer, porcelain, hyposulphites, water, wine, tar- 

 trates, tungstates, sugar, &c. The following subjects are 

 treated of in some detail : — Alcoholometry, aniline dyes, 

 areometer, iron, carbonates, light, mineral waters, common 

 salt, sulphates, heat. 



The value of the dictionary as a work of reference is 

 decidedly enhanced by the adoption of thick type for the 

 words heading the articles. In the case of recently dis- 

 covered compounds we are of opinion that a short biblio- 

 graphical reference to the paper wherein such compounds 

 are first made known would have greatly increased the 

 value of the articles without materially adding to their 

 length. The author has fallen into an error in treating 

 of thermo- and pyro-electricity under the same heading ; 

 the former term is employed by electricians in this country 

 to denote the electricity developed by heat in conductors^ 

 the latter to denote the electricity produced by heat in 

 non conductors. 



Bearing in mind the enormous range of subjects now 

 embraced by the science of chemistry, for a volume of 

 the present size the amount of information conveyed is 

 really very great. With the exception above pointed out, 

 the articles, though necessarily brief, are to be depended 

 on for accuracy, and we can safely recommend Dr. 

 Dammer's dictionary as a useful work of reference. 



R. M. 



Clouds hi the East. Travels and Advetttures on the 

 Perso-Twkoman Frojitier. By Valentine Baker. With 

 Maps and Illustrations. (London : Chatto and Windus, 

 1876.) 

 The author of this interesting volume had special facili- 

 ties for visiting the Russian outposts in Asia and the 

 Persian frontier ; he had powerful recommendations to 

 the highest Russian and Persian authorities. By various 

 causes, however, he was prevented from taking complete 

 advantage of these, so that the main part of his work 

 describes his journeys in the district to the south of the 

 Caspian, and from Teheran towards the north-east Per- 

 sian frontier. He reached the Caspian by Trebizond and 

 Tiflis, and gives some interesting particulars as to naviga- 

 tion on the inland sea. He was able to visit the mouth 

 of the much-talked-of Attrek, and found that the Gurgan, 

 to the south of the Attrek, is the real Russian frontier in 

 this region. He was unfortunately prevented from visiting 

 Merv and Herat, which he had intended to do, Mr. 

 Baker's main objects were sport and to ascertain the real 

 nature of the advances made by Russia in Central Asia. 

 Of the former he got a fair amount around Teheran, and 

 his work will be of very considerable importance to those 

 who are interested in the movements of Russia. He took 

 considerable pains to ascertain Persian feehng on the 

 question ; Persia cannot understand, or rather misun- 

 derstands, England's inaction. Mr. Baker gives many 

 valuable notes as to the nature of the country passed 

 over, its productions, antiquities, and inhabitants. Con- 

 cerning the Turkomans especially, and their wonder- 

 ful houses, many details will be found. Altogether the 

 work is an intelligent and interesting narrative of travel 

 in an important region, and a substantial contribution to 

 the Asian question. There are three good maps, but the 

 chromolithographs are very poor specimens of their 

 kind. 



LETTERS TO THE EDITOR 



The Editor does not hold himself responsible for opinions expressed 

 by his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous communications. '\ 

 The Use of the Words "Weight " and " Mass " 

 I WILL supplement Mr. Bottomley's authorities for the mean- 

 ing of gravity by others which will be perhaps considered 



more relevant. Maupertuis, " Figure de la Terre," Paris, 1738, 

 writes : — " II faut bien distinguer ici la pesanteur d'un corps 

 d'avec son poids ... La pesanteur dans un grand corps, 

 n'est pas plusgrande que dans un petit. II n'en est pas ainsi du 

 poids ; il depend non-seulement de la pesanteur, mais encore de 

 la masse des corps . . . il est le produit de la pesanteur par la 

 masse "(p. 155). Subsequently, he lays down the distinction 

 between pesanteur and gravite which Clairaut adopted ; but 

 universally the English^rawVy has been used as synonymous with 

 the French pesanteur. Airy, "Gravitation," p. 3 : "To take 

 the ordinary force of gravity for an instance, we might measure 

 it by the pressure which is produced on the hand . . . or by the 

 number of inches through which the lump of lead would fall in 

 a second of time . . . But there is this difference between 

 the two measures ; if we adopted the first ... we should find a 

 different measure by the use of every different piece of lead ; 

 whereas if we adopt the second ... we shall get the same 

 measure for gravity whatever body we suppose subject to its 

 influence." Here the broad distinction between "weight "and 

 "gravity" is clearly laid down; the one is the "impressed 

 force" on the falling body, the other its " accelerative effect" 

 (Thomson and Tait, " Treatise on Nat. Phil,," 217-219), or the 

 more familiar " moving force " and "accelerating force," In the 

 "Treatise" the former is called the " force of gravity on the 

 mass of a body," 220; but "gravity" alone seems clearly 

 enough defined as acceleration, by the words " According to this 

 formula, therefore, polar gravity will be 



^"•- 32-088 X 1-005133 = 32 •2527." 



Again, § 226: "The augmentation of gravity per degree . . . 

 is, at most . . . The average , . . differs certainly \but little 

 from 32-2." 



I think it evident that gravity has not been " lying ready for 

 use, but left almost idle," as Mr. Bottomley supposes. 



To the restriction on the use of weight — which I feebly sup- 

 port, but which is certainly not mine — I do not conceive that the 

 "Act of Parliament" offers any bar ; as the weights of masses 

 are merely thereby defined in terms of the weight of the standard 

 mass. This restricted sense is clearly recognised in such passages 

 as the following, from Thomson and Tait's " Elements," § 366, 

 " The measurement of force whether in terms of the weight of 

 a stated mass in a stated locality . . ." 



As to the compounds '^ centivires," &c., I advisedly adopted 

 the Latin prefixes in their old etymological sense, so as to have 

 wholly Latin names and thereby prevent any confusion with the 

 C. G. S- kinetic measures. The employment in the metric 

 system being quite conventional and contrary to analogy, I feel 

 justified in following older precedents. J. J. Walker 



"The Recent Origin of Man" 



In Nature, vol. xiii. p. 245, a writer over the initials 

 " W. B. D." reviews in no very complimentary terms my book 

 entitled " The Recent Origin of Man." I am charged with 

 inconsistency, inaccuracy, incompetency, &c. When charges of 

 this sort are made they ought not to be made lightly, and the 

 writer making them ought to weigh his statements. 



My space is necessarily brief, but I beg permission to com- 

 ment on a few of the asserdons made by " W. B. D." in ren- 

 dering his judgment on the premises. 



I. He remarks : " The statement that no traces of a rude and 

 imperfect civilisation have been met with in the East is refuted 

 by the discovery of enormous quantities of flint implements in 

 Egypt and of neolithic axes in Asia Minor and in India. In the 

 river gravels of bath these regions paleolithic haches have been 

 found of the same type as those of Amiens and Abbeville." 



We all know that palaeolithic implements have been found in 

 the river-gravels of India ; I refer to this on p. 31 of my book ; 

 but I am not aware that palaeolithic implements have been 

 found in the river-gravels of Egypt or Asia Minor, As 

 " W. B. D," asserts it, I beg leave to ask for the particulars. 



As for the occurrence of flint implements in Egypt, I remark 

 on p. 478 : " Flint implements have been found in Egypt but 

 they belong to the Neolithic age, and occur on the surface, or 

 near the surface, or in the tombs." I mention that one imple- 

 ment of palaeolithic type had been found. I show that flint 

 arrow heads and flint knives have been frequently found in the 

 Egyptian tombs by the side of the mummies. 



That Sir John Lubbock found in the Nile valley a few imple- 

 ments resembling the palaeolithic types I am aware ; but imple- 

 ments of palaeolithic type were found at Cissbury by Col. A. 



