September 7, 1893] 



NA TURE 



435 



other reference to it which has come under our notice is 

 a somewhat vague allusion in the annual address on 

 geographical progress at the Paris Geographical Society. 

 Ekroll intended, says Prof. Heilprin, to start in June, and 

 travel northward from Cape Mohn in Spitzbsrgen (about 

 longitude 20° E), the feature of his expedition being the 

 use of a composite structure capable of use as boat or 

 sledge, according to the surface which has to be travelled 

 over. This project is shown to be at least unsatisfactory, 

 the risk of damage to the sledge (or boat) being too 

 great, although the route to the north is an extremely 

 suitable one. We do not know if Ekroll has set out. 

 The third e.xpedition is that of Peary, who is already 

 en route, and intends to work northward over the 

 frozen surface from the norili coast of Greenland, where 

 he did such brilliant service in 1892. Of the success 

 of. this enterprise Prof. Heilprin is confident ; whether 

 the Pole is reached or not he thinks that Peary has the 

 best chance of breaking the record, and attaining a 

 higher latitude than any of his predecessors. 



Against the common plea that polar exploration 

 having baffled the best endeavours of men whose 

 heroism is beyond praise, any future effort is only waste 

 of life. Prof. Heilprin urges the incontrovertible fact 

 that in travel the almost impossible of yesterday is the 

 easy accomplishment of to-morrow. He remarks that 

 the ascent of Mont Blanc, at first a feat that made a man's 

 reputation for life, is now a common tourist's pastime, 

 while he might have added that Spitzbergen, formerly 

 ranking as scarcely accessible Arctic land, is now within 

 the reach of excursion steamers. 



As to the best route to the Pole, he agrees that no 

 expedition need waste its strength again on Smith's 

 Sound, and he criticises with some severity the con- 

 clusions of the Royal Geographical Society twenty years 

 ago before the despatch of the Alert and Discovery. The 

 region north of Spitzbergen where Parry attained 82°45' 

 in 1827, only forty miles short of the point to which steam 

 and the scientific advance of half a century enabled the 

 best equipped expeditions to reach through Smith's 

 Sound, certainly appears the most hopeful, and it is 

 that in which any new expedition on a large scale that 

 may be planned should undoubtedly make an attempt. 



Without much novelty in argument or substance, Prof. 

 Heilprin has set forth clearly and convincingly the plain 

 issues involved in the Arctic problem, a problem which 

 promises to be much before the public mind for some 

 years to come. 



OUR BOOK SHELF. 



\ Vorlesung Uber Maxwell's Theorie der Electricitdt und 

 ties Ltchtes. By Dr. Ludwig Boltzmann. Part I. pp. 

 139. (Leipzig : Johann A. Barth.) 



I This is a most interesting introduction to Maxwell's 



theories about electromagnetic actions. The whole 



question of generalised coordinates is introduced by 



means of models that enable the student to make a 



, concrete picture to himself of a particular case of what 



I he is studying. Some people mayprefer to study subjects in 



t the most general form, but the majority find very great 



[ difficulty in working out any advance on what they are 



, taught by others without the assistance of some concrete 



, case. In the case of most students it certainly helps 



NO. 1245, VOL. 48] 



them very much indeed to be provided with simple ex- 

 amples. Models may often do even more than facilitate 

 the path of the student, they have before now pointed 

 the way for the discoverer. As the mathematical part 

 of Maxwell's theory is so largely an application of the 

 principles of generalised coordinates this introduction 

 to his theory is eminently interesting and suggestive. 

 It is perhaps more suited to the state of scientific de- 

 velopment on the Continent than in England. German 

 and French electrical ideas had been so bound up wiih 

 Coulomb and Ampere's laws of action at a distance that 

 even the formulae of Weber and Clausius which postu- 

 lated propagation in time did not shake their faith in 

 action at a distance, attracting and repelling electricities 

 and currents and poles. Even yet Poincari^ cannot get 

 over the Coulomb law foundation of electrostatics. To 

 such ideas a dynamical foundation such as Boltzmann 

 has given should give a new direction. The whole 

 process by which the electric current, the electrification, 

 the magnetic pole, appear as generalised coordinates is 

 brought out. The only objection that can be raised to 

 the method from a British point of view is that the 

 method is not drastic enough. It panders to the weak- 

 nesses of those who look upon the electric current as the 

 important thing. It almost neglects the medium. It 

 does not emphasise the connection of electric force and 

 displacement, magnetic force and induction. It does 

 not go even so far as Maxwell in formulating a theory 

 as to the nature of the medium. It is too content with 

 symbols. It introduces the propagation of the action 

 through the medium almost as indirectly as Maxwell 

 does. The forces and the displacements should be the 

 foundations of electromagnetic theory and not the equa- 

 tion in generalised coordinates 



2T = Li ji» -I- 2M12/1J/2 -I- L^j-o^ 



We must however be content to lead people gently. 

 Prof. Boltzmann's introduction is certainly a move in 

 the right direction, and there is every reason to think 

 that the exertions of him and of Prof. Hertz are rapidly 

 turning the current of continental study of electro- 

 magnetism into the right channel. In view of Prof. 

 Boltzmann's recent interesting remarks on the value of 

 dynamical models, it would be well worth while trans- 

 lating this work of his into English as an example for 

 us how models can be employed successfully to illustrate 

 a difficult subject. It is only of recent years that geo- 

 metrical curve plotting has been popularised as a method 

 of illustrating and facilitating mathematical investiga- 

 tions, and judiciously constructed models might perform a 

 large part of a corresponding service for dynamics in the 

 future. 



Geology: an Elementary Hand-book. By A. J. Jukes- 

 Browne. (London: Whittaker and Co., 1893.) 



Viewed as a rudimentary description of all branches of 

 geology, Mr. Jukes-Browne's latest treatise is highly 

 commendable. Its 248 pages contain something about 

 everything geological. In a few places the information 

 is rather disjointed, but that drawback is inseparable 

 from an elementary work of limited dimensions 

 which aims at giving students an idea as to the wide 

 scope of geology. Of all the branches of the science, 

 physical geology is given the most space, and rightly, for 

 It is the division which is most intelligible to the general 

 reader. The majority of the illustrations arc rather 

 coarse ; nevertheless, they are usually of a helpful 

 character. An objectiopal feature in the text is the 

 frequent quotations from Geikie, Agassiz, and others. 

 It seems to us that, in general, quotations should only be 

 permissible in matters upon which a difference of opinion 

 exists. But, on the whole, the book is a good one, and 

 will be useful to students of_elementary geology. 



