July 14, 1892] 



NATURE 



247 



On the Line Spectra of the Elements. 



Prof. Stoney seems to agree with me that \ have given an 

 ■obvious example of a motion for which the theorems in chapter iv. 

 of his memoir do not hold good. Theorem B, page 591, runs 

 thus : " Any motion of a point in space may be regarded as the 

 co-existence and superposition of one definite set of partials 

 which are the pendulous elliptic motions determined as above, 

 Ac." It is indeed obvious that a uniform motion in a straight 

 line cannot be regarded in this manner, not even approximately 

 for any length of time, if the set of partials are required to be 

 definite, i might have given an example of a limited motion, 

 e.g. X = sin /-, which equally contradicts the theorem, but I 

 thought a more obvious example would convince Prof. Stoney 

 more easily. I think, indeed, that the reasoning in chapter iv. 

 of his memoir is erroneous. But I do not say that therefore 

 Prof. Stoney's views on the cause of the line-spectra are wrong. 

 They may be right, although the argument in chapter iv. is not. 

 Why this criticism is not legitimate I do not see. For no slight 

 alterations or additions would set those theorems right, as there 

 is a palpable mathematical error at the bottom of it. 



Technische Hochschule, Hanover, July 9. C. RUNGE. 



The Grammar of Science. 



The exposition of the Newtonian laws as given by Thomson 

 and Tait has unfortunately been taken as the basis for the treat- 

 ment of the laws of motion by all elementary text-book writers 

 in the English tongue since the publication of the great " Treatise 

 on Natural Philosophy." When that exposition is attacked we 

 are told that Newton introduced a qualifying context which has 

 been omitted from the exposition. In other words the current 

 statement of elementary dynamical principles is thrown over- 

 board in favour of Newton pure and simple. On the other hand 

 when Prof. Tait uses an expression which is totally opposed to 

 that principle of the "subjectivity of force" which C.G.K. 

 claims that Prof. Tait was the first, or among the first, to pro- 

 pound, we are told that this expression was obviously suggested 

 by "Newton's own anthropomorphic language." C.G.K., I 

 take it, admits that the Newtonian Laws of Motion are illogical 

 and unphilosophical when stated by Thomson and Tait without 

 Newton's modifying context. I propose therefore to shortly 

 publish a criticism of the laws of motion as accompanied by that 

 context of Newton's which does not appear in Prof. Tait's text- 

 books. I trust C. G. K. will not then turn round on me and 

 say, " Oh, yes, but this has nothing to do with Prof. Tait ; it is 

 Newton's own anthropomorphic language." 



Lastly, as to the origin of the doctrine of the " subjectivity of 

 force," which to my mind is just as much or as little valid as the 

 "subjectivity of matter," I would remind C. G. K. that the first 

 two parts of KirchhofTs " Mechanik " were published in 1874, 

 and were then only the publication of lectures of an earlier date. 

 Philosophers before Kirchhoff taught the doctrine of subjectivity, 

 tut he, and not the author of the "Dynamics of a Particle," 

 was the physicist who first helped many of us out of the mental 

 obscurity as to dynamical principles produced by our study of 

 the expositions of the laws of motion due to the Edinburgh 

 school. Karl Pearson. 



"Are the Solpugidae Poisonous.'" 

 In reference to this question, propounded by Mr. Bernard 

 in your last issue, I should be inclined to answer in the negative. 

 I captured several specimens of Solptiga chelicornis in the 

 Transvaal, and on one occasion witnessed a persistent attack 

 made on this "spider" by a bird which appeared to be the 

 Cape wagtail {Motacilla capettns). Had the Solpuga possessed 

 poisonous qualities the attack would probably not have been 

 made. 



The specimens taken by myself exhibhed no =igns of pug- 

 nacity, but always sought refuge in headlong flight to the nearest 

 cover. W. L. Distant. 



Russell Hill, Purley, Surrey, July 8. 



Hairlessness of Terminal Phalanges in Primates. 

 I observe that, in your report of the proceedings of the 

 Zoological Society, you allude to my paper on "a seemingly new 

 <liagnostic feature of the order Primates," viz. that the terminal 

 phalanges are destitute of hair. 



NO. II 85, VOL. 46] 



Since the paper was read I have found that this feature is 

 not of ordinal value. But it is of sufficiently general occurrence 

 to merit inquiry touching its distribution in different species. 



Therefore I have withdrawn publication of the paper for the 

 present. George J. Romanes. 



Oxford, July i. 



Mental Arithmetic. 



Referring to the articles on " Mental Arithmetic " in 

 Nature, vol. xlv. p. 78 and 198, I beg to state that there also 

 exists a very clearly written little text-book on arithmetic 

 founded entirely on the principles mentioned by Mr. Olive 

 Cuthbertstone. The title is " Neuer Unterricht in der Schnell- 

 rechen-Kunst," by C. Jul. Giesing, Editor, Carl Schmidt, in 

 Doebeln (Saxony). Price i mark 80 pf. G. Daehne. 



Dresden-Blasewitz, " Isis," July 9. 



Jackals. 



The incident of the jackals entering Howrah brings to my 

 memory that this winter jackals entered the suburban town of 

 Bournabal, in the Smyrna district of Western Asia Minor. 

 This last winter being severe, it was noticed in the papers that 

 rabies had extended to wolves and jackals, and to this circum- 

 stance was attributed their entering the villages and attacking 

 people, and also their attacking the domestic animals. 



Hyde Clarke. 



WEIGHT. 



THE following remarks are presented with the object 

 of reducing the increasing gap which is growing 

 between the treatment of the fundamental ideas of Dyna- 

 mics, as taught in our academical text-books from the 

 standpoint of verbal abstraction, and the ideas and 

 language of those who have to deal with the actual 

 phenomena of Nature as a reality. 



I. According to the precise legal definitions of all 

 our successive Acts of Parliament on " Weights and 

 Measures," the weight of a body is the quantity of 

 matter in the body, as measured out by the operation 

 of weighing it in the scales of a correct balance. 



The body to be weighed is placed in one of the scales, 

 and is equilibrated by standard lumps of metal, stamped 

 as pound weights, or kilogramme weights, or hundred 

 weights, or ton weights, and the sum of these weights is 

 called the weight of the body. 



In the words of the Act of Parliament, 18 and 19 Vic- 

 toria, c. 72, July 30, 1855, the British pound weight is de- 

 fined as a weight of platinum, marked P.S., 1844, i lb., 

 deposited in the Office of the Exchequer ; and the Act 

 goes on to say that this lump of metal " shall be the legal 

 and genuine standard measure of weight, and shall be 

 and be denominated the Imperial Standard Avoirdupois 

 Pound, and shall be deemed to be the only standard of 

 weight from which all other weights and all other 

 measures having reference to weight shall be derived, 

 computed, and ascertained, and one equal seven 

 thousandth part of such pound avoirdupois shall be a 

 grain, and five thousand seven hundred and sixty such 

 grains shall be and be deemed a pound troy." 



In defining the unit of length, the standard yard, the 

 temperature must be defined, 62° F. in the Act of Par- 

 liament ; but in defining the pound weight, there is in 

 the Act no mention of temperature, height of barometer, 

 height above sea-level, latitude, longitude, date and time 

 of day, establishment of the port, &c., or of any other 

 cause tending to alter the local value of^. 



Details of the temperature and density of the air are 

 only required when defining the volume of the gallon of 

 10 lbs. of water, or when making accurate copies of the 

 standard platinum pound weight in some other metal — 

 brass or iron, for instance — when a correction for the 

 buoyancy of the air must be made ; and it is to cover 



