December 29, 1904] 



NA TURE 



197 



continuity. This conclusion is opposed to Riemann's 

 theory. H. Weber, in his recent edition of Riemann's 

 " Vorlesungen iiber die partiellen Differentialgleicli- 

 ungen der mathematischen Physik," has contended 

 that a complete calculation of the energy supports 

 Riemann's theory against Lord Rayleigh's objection, 

 but he did not refer to Hugoniot. In the book under 

 review no mention is made of Lord Rayleigh's objec- 

 tion or of H. Weber's contention, but Riemann's 

 theory and Hugoniot's are developed side by side, and 

 the results are compared both with each other and 

 with the results of certain experiments by Vieille. 

 Much of the analysis is worked out and interpreted 

 by the aid of geometrical constructions, but the reader 

 wishes often for a more physical interpretation. 



Chapters v. and vi. contain e.xtensions of the 

 theories of the preceding chapters to motion in three 

 dimensions and to waves in elastic solid media. The 

 physical value of a theory of rapid motions, accom- 

 panied by strains that are not " small," in an elastic 

 solid, supposed to have a strain-energy function, is 

 extremely doubtful ; but no exception can be taken to 

 the analytical methods by which the theory is de- 

 veloped. Chapter vii. brings the theory of waves that 

 do not involve discontinuities of velocity or strain into 

 relation with the theory of characteristics of partial 

 differential equations. The discovery of the relation;, 

 between these two theories has attracted a good deal 

 of attention recently, and we may be grateful to M. 

 Hadamard for his masterly exposition of the subject. 

 .\ few notes are appended to the volume. Of these the 

 most interesting is the one in which it is shown that 

 discontinuities of the first order mav give rise to vortex 

 motion, even when the pressure and density in the 

 undisturbed state are uniform throughout the fluid. 



It is a sign of the healthy state of mathematics in 

 France that the ablest analysts are bringing their 

 powerful methods to bear upon recondite physical 

 questions. The book under notice is a very valuable 

 contribution to a most important and, at the same 

 time, a most difficult subject. It breaks fresh ground, 

 and it cannot fail to stimulate inquiry. It may be 

 expected to conduce to the further advance of our 

 knowledge of aerodynamics .X. E. H. L. 



THE GREAT ST. BERNARD PASS. 

 Across the Great St. Bernard. The Modes of Nature 

 and the Man)iers of Man. By A. R. Sennett. Pp. 

 xvi + 444 and in; illustrated. (London: Bemrose 

 and Sons, 1904.) 



A FLUENT but not too accurate pen, and a general 

 knowledge of the more frequented districts of 

 the Alps appear to be Mr. A. R. Sennett's chief 

 qualifications for writing this book. It has a compre- 

 hensive title, and needs it, for the St. Bernard Pass 

 is hardly more than a thread to connect, if possible, 

 quotations in prose and verse, scraps of science and 

 history, descriptions of scenery, and moralisings on 

 things in general. The author has nothing new to 

 tell us about the St. Bernard, which is not sur- 

 prising, for the pass has been often described, and a 

 carriage road now goes the whole way from Martigny 



NO. 1^35, VOL. 71] 



to Aosta. Mr. Sennett, however, informs us that 

 Hannibal crossed it "with his vast army," of which 

 he proceeds to describe the sufferings. Notwithstand- 

 ing what has been written by Law, Ellis, Freshfield 

 and others, we are well aware that it is not easy to 

 determine what route Hannibal did follow, but thought 

 that the Great St. Bernard was no longer advocated 

 by anyone who had studied the question. 



Other statements are disputable. We are told the 

 soldanella flower protrudes through the edge of the 

 nevd (which does not mean the winter snow) ; that the 

 edelweiss dwells " in snow, owning a habitat where 

 no other flowering plant may survive," and as " its 

 haunt is far removed from all verdant vegetation and 

 in the most craggy and inaccessible positions," we 

 cannot expect to see it growing at the botanical station 

 in Bourg St. Pierre, and so forth. This village is 

 rather more than 5300 feet above sea-level, and the 

 plant is often found between this and 6000 feet ; indeed, 

 it can be cultivated in England. As for the craggy and 

 inaccessible positions, we had thought newspaper 

 correspondents now enjoyed a monopoly of this fiction. 

 Like any other Alpine plant, it may grow in a break- 

 neck place, but its favourite habitat is a rough slope 

 of grass and stone. It used to grow profusely on a 

 place of this kind, where it could be gathered in perfect 

 safety, on a mountain ridge about a thousand feet 

 above San Bernardino. 



But Mr. Sennett, though prone to discuss scientific 

 questions, does not always win our confidence. The 

 " Tertiary period of the London Clay " is an odd 

 phrase, and adamantine an inappropriate epithet for the 

 firn or upper basin of a glacier ; and in what respect the 

 Lago di Garda resembles a diadem we fail to perceive. 

 To his vision of a Europe the glacier fields of which 

 only just failed in reaching the Alps we are perhaps 

 accustomed, but think that most geologists at the pre- 

 sent day would speak less confidently of glaciers having 

 scooped out the Alpine lake basins, or having " cut out 

 gorges for themselves through the solid mountain, 

 divided enormous peaks in twain, planed down and 

 levelled great asperities." The Marjelen See does not 

 lie in a lake basin, but simply at the head of a glen, 

 blocked by the great Aletsch Glacier, and after seeing 

 it one day full and the next empty, we utterly disbelieve 

 Mr. Sennett's explanation that it is emptied on the 

 principle of a syphon. The name Morjelen, which he 

 prefers, may be patois, but the other form is more 

 usual ; so also is Gondo for Gonda, Guttannen for 

 Guttenen, Meiringen for Meyrengen, and, notwith- 

 standing Baedeker, Penninus for Poeninus (the title of 

 the Alpine Jupiter). The science is discursive and 

 commonplace, where not enriched by extracts from 

 Tyndall or Ruskin, or yet more ornamental writing. 

 Mr. Sennett may think in English, but is so 

 prone to translate into journalese that we sus- 

 pect he was trained in a certain Fleet Street 

 haunt of young lions. We cannot welcome the verb 

 " resurrect," the adjective " riverian " (of or belonging 

 to a river), or " lithic " (a favourite one) when plain 

 folks would say stony or rocky. The book, however, 

 contains numerous illustrations, often pretty, but it is 

 tiresome to have them (except in the appendix) only 



