Notices respecting New Books. 541 



opens with the short paper on Vortex Atoms, which was commu- 

 nicated to the Eoyal Society of Edinburgh in 1867, and was 

 published both in the Proceedings of that Society and in the 

 Philosophical Magazine. Then follows the great memoir " On 

 Vortex Motion," published in the Transactions of the Eoyal 

 Society of Edinburgh, vol. xxv., which has been for many years 

 accessible only in the older scientific libraries of the world. 

 Probably the vast majority of students of hydrodynamics have 

 never had a good opportunity of reading this great paper. No 

 doubt the outstanding features of Kelvin's mode of presentation — 

 especially the conceptions of Flow and Circulation — are well 

 given in our standard treatises on the motion of fluids ; but Kelvin 

 had a method all his own, full of suggestiveness to the thoughtful 

 reader. It is of infinite value to the real student to have ready 

 access to the original work of a man like Kelvin, especially when, 

 as in the present instance, each series of papers forms a kind of 

 continuity. The arrangement is broadly by subject matter ; and 

 in each section a chrouological arrangement is made the basis. 

 Thus the Hydro-dynamic section includes the papers on vortex 

 motion, on the motion of solids through fluids, and on capillary 

 waves. Then come three papers on the Tides ; and under the 

 heading Waves on "Water are grouped a number of connected 

 investigations on stationary waves, ship waves, the front and rear 

 of a free procession of waves, and so on. Several of these papers 

 deal with difficult subjects, and constitute some of the latest of 

 Kelvin's most characteristic contributions to the theory of certain 

 types of water waves. The five papers communicated to the 

 Eoyal Society of Edinburgh at intervals from 1904 to 1906 form a 

 continuous series, the paragraphs being numbered consecutively. 

 These portions occupy about four-fifths of the volume. The 

 remaining fifth is concerned with General Dynamics and Elastic 

 Propagation ; but many of the papers enumerated in the Table of 

 Contents are represented only by their titles, the papers having 

 being already reprinted in the Baltimore Lectures, or in the 

 earlier volumes of ' Mathematical and Physical Papers.' The last 

 paper printed in extenso is on a new method for specifying stress 

 and strain in an elastic solid. In place of the usual Cartesian 

 specification, Kelvin uses a tetrahedron of reference, and is thus 

 able to obtain a symmetrical specification of stress and strain for 

 finite as well as for infinitesimal strains. It need hardly be said 

 that the editorial work has been well and faithfully done, the 

 annotations, brief though they are, being always to the point and 

 full of instructive allusions. The final volume (V.), we are told, 

 is almost ready for press, and will contain papers on Thermo- 

 dynamics, Cosmical and Geological Physics, Electrodynamics and 

 Electrolysis, Molecular and Crystalline Theory, Eadioactivity and 

 Electrionic Theory, and other miscellaneous matter. 



