•74 



NA TURE 



[June 2 i, 1906 



subject of immunity equally attracted tlie diligence of 

 the pupils whose work Nencki controlled and directed. 

 To attempt even an enumeration, still less a review, 

 of the papers contained within the book would be out 

 of place in a brief appreciation of its value. One can 

 only recommend those interested in such subjects as 

 have been indicated to procure this treasure-house of 

 information for themselves. 



W. D. H. 



OVR BOOK SHELF. 



Essais des MatMaux. By H. Bouasse. Pp. 150. 



(Grenoble : Gratier and Rey ; Paris : Gauthier- 



Villars, 1905.) Price 5 francs. 

 The ordinary mathematical theory of elasticity con- 

 sists mainly in the examination of the consequences 

 of the general principle involved in the statement of 

 Hooke's law, " ut tensio sic vis," or, in other words, 

 the proportionality of stress to strain. In many cases, 

 however, this assumption is far from being satisfied, 

 and the state of strain in a body at any instant de- 

 pends not only on the actual stresses, but on the 

 changes which have previously occurred in that body. 



Prof. Bouasse's treatise consists in large measure 

 of a classification of the various properties arising 

 from the study of strains and stresses, such as per- 

 manent deformations, perfectly elastic deformations, 

 viscosity, hysteresis, reversible and irreversible de- 

 formations and limits of elasticity. As the author 

 points out, many of the phenomena are of common 

 occurrence, and he instances the displacement of the 

 zero reading of the galvanometer as a simple ex- 

 ample. The various effects are illustrated by curves 

 showing the relations between strain and stress. The 

 ordinary- theory of elasticity is of course touched on. 



The printing of the preface in italics does not 

 favourably impress the English reader at the outset, 

 but evervone must agree with the conclusions at the 

 end, in which the author points out that the subject 

 has not received the attention it deserves, and this 

 at a time when rapid advances have been made in 

 most branches of physics. There is abundant evi- 

 dence that Prof. Bouasse has given much careful 

 thought and study to the subjects of which he treats, 

 and even if his book does no more than attract 

 attention to a neglected branch of physics it will 

 fill a useful purpose. 



The Scientific Roll and Magazine of Systematised 

 Notes. Conducted by Alexander Ramsay. Bac- 

 teria. Vol. i. Pp. 528. (Acton, London, W. : 

 R. T. Sharland.) Price 16s. 

 It is difficult to comprehend exactly what place this 

 work is designed to occupy. The author must have 

 expended an enormous amount of time and labour 

 upon it, but we regret to say we cannot help feeling 

 that much of his work is misapplied. For example, 

 the 200 pages or thereabouts occupied by the tables 

 of bacteria, arranged according to size, can be of 

 little or no value, because the size of bacteria is 

 extremely variable, and because the finer measure- 

 ments must be very rough. Had this space been 

 devoted to a summary of bacterial characters and re- 

 actions, abstracted from original papers, a great deal 

 of scattered material would have been gathered 

 together, and the result would have been most valu- 

 able. The bibliographv in the earlier parts should 

 be useful, but the summary of characters contained 

 in the later ones is too brief and scrappy to be of 

 much value. 



NO. I 91 2, VOL. 74I 



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 intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Another New Vesuvian Mineral. 



In Nature of May 31 I gave a preliminary note on a 

 new mineral species chlonnanganokalite, in speaking of 

 which I made reference to its association with iine crystals 

 of halite that I suggested were likely to prove rich in 

 I potash. The latter crystals occur as beautiful cubes often 

 more than a centimetre in diameter, and of a trans- 

 parent to a milky, opaline tint. They afford on analysis 

 the following results as to their composition : — 



KCI ... §7-57 KCl S7 93 



NaCI . . I2-02 equal to NaCl 12-07 

 M.pi-.,lure 0-412 — 



If we adopt the formula (KC^jNaCl, we should 

 theoretically e.\pect the following composition : — KCl 885. 

 NaCl 11-5, which is sensibly the composition found by 

 analysis as above, especially when we consider the errors 

 inherent to the estimation of these substances. 



I think, therefore, we are justified in considering this 

 mineral as a definite double chloride, which I propose 

 provisionally to call chlornatrokalite. It is my intention 

 to submit to analysis a number of similar minerals that 

 I have collected at Vesuvius during the last twenty-six 

 years to see if we have to deal simply with mixtures or 

 definite chemical compounds. Spectrum analysis failed to 

 show even traces of calcium, caesium, rubidium, or lithium. 



The great amount of potassium compared to sodium is 

 not astonishing when we consider that potash is the 

 dominant alkali in the paste from which Vesuvian lava 

 and its other products are derived. 



June 13. H. J. Joiinston-Lavis. 



The Discovery of Logarithms. 



In the review of a book, " Letters from the Dead to the 

 Dead," which appeared in your number of May 31, your 

 reviewer says : — " As another example we may take the 

 notes to Henry Briggs's letter, in particular the supposed 

 proof (p. 75) that Napier's true base is the reciprocal of 

 e and not e itself. As the difference depends entirely on 

 whether log sin 45° has a plus or a minus sign attached 

 to it, it is interesting to speculate on how many readers 

 will be deceived by what is after all a somewhat clever 

 hoax." (The italics in the above extract are mine.) 



I take it by the use of the words supposed, deceived, 

 and hoax, your reviewer intends to intimate that the 

 formula on p. 75 of " Letters from the Dead to the Dead " 

 is faked, or made by the author to suit his own purposes. 

 Nothing could be further from the truth. I have had the 

 curiosity to make the calculation de novo, and I venture 

 to submit that no fair or genuine criticism can be passed 

 upon it. The e.Kpression log 1/^/2 must have the minus 

 sign. Indeed, I almost wonder whether your reviewer 

 has read the book he is reviewing, because in that book 

 the author quotes from Macdonald's translation of Napier's 

 " Constructio " the statement that e-' is the base required 

 by Napier's reasoning. 



I am not concerned whether the book in question is a 

 hoax or not. For my part, I do not believe that it is. 

 On the contrary, I believe it will prove to be one of the 

 great books of history. It raises too many fascinating 

 questions to be non-suited in your summary manner, and 

 the reason why John Napier, knowing in 1614 that 

 logarfthms computed to base 10 must supersede all others, 

 went on computing his to the surd 1/2-7182818283 as base, 

 is an historical mystery that demands a solution. It is 

 ridiculous to suppose — nay, it is impossible to suppose — 

 that the inventor of logarithms did not know that they 

 must have a base. Cecil Seymour-Browne. 



