August 6, 1908J 



NA TURE 



o^j 



A number of measurements showing the amount of 

 evaporation from the soil, or the amount of water 

 left behind in different circumstances, have already 

 been made, and Dr. Leather adds a further interesting 

 series. Water determinations were made in samples 

 taken to a depth of 7 feet from a plot of soil at Pusa 

 during the dry season. The results are as follows : — 



hhs. of water per Cubic Foot of Soil. 



The showers only seem to have affected the surface 

 layer. It will be observed that there is a considerable 

 break below the fourth foot ; this is due to a change in 

 the soil, which unfortunately was not uniform 

 throughout the entire depth. Taken as a whole, the 

 figures show that the rate of loss decreases as the 

 depth increases, but the want of uniformity of the soil 

 makes it impossible to get out any expression showing 

 the rate of loss. Dr. Leather argues that water 

 moves upwards from a limited depth only, and con- 

 siders that none has come from the seventh foot, but 

 he offers no evidence on this point. The results are 

 equally well explained on the supposition that the 

 upward movement takes place at all depths, since the 

 amount of water present in a particular layer depends 

 on the respective rates at which water is gained from 

 below and lost to the upper layers. If these measure- 

 ments could be repeated on a fairly uniform piece of 

 soil the results would furnish very valuable data for 

 a study of the movements of water in soil. 



E. J. Russell. 



LORD KELVIN.' 



THESE notices of the life and work of Sir William 

 Thomson, Lord Kelvin, are all true, and they 

 are all quite different from one another. Prof. 

 Larmor dwells upon the important mathematical 

 theorems -ftith which Lord Kelvin enriched natural 

 philosophy, and he is almost indignant that mere 

 inventions for the service of man sfiould have occu- 

 pied the best time in the life of the greatest of 

 naturalists. It is a masterly essay, and will be of 

 the greatest value to some future biographer or histo- 

 rian of science. As Stokes and Fitzgerald are dead, 

 there is nobody now living who could have done the 

 work so well as Larmor. Nobody ever could have 

 done it better. 



Prof. Gray's book gives a very straightforward and 

 interesting account of Kelvin's work; he does not 

 dwell so much upon that part which had the higher 



1 Proceedings of the Royal Society ; Obituary Notice of William Thomson , 

 Baron Kelvin. By J. L. Pp. i + lxxvi. 



" Lord Kelvin, an Account of his .Scientific Life and Work." By Dr. 

 Andrew Gray, F.R.S. (English Men of Science Series.) Pp. ix-l-3t8. 

 <London : J. M. Dent and Co., 1908.) Price 2S. 6d. net. 



" Kelvin in the Sixties." By Prof. W. E. Ayrton, F.R.S. An article in 

 the Tittus Engineering Supplement. January 8, 1908. 



"The Kelvin Lecture." By Prof Silvanus P. Thompson, F.R.S. Pro- 

 ceedings of the Institution of Electrical Engineers. 



mathematical aspects ; he writes as an old pupil, as 

 one who was Kelvin's secretary, and as the present 

 occupant of his professorial chair. Probably this 

 book will give most satisfaction to the general reader, 

 but the reader must be one who already knows some- 

 thing of what Kelvin did in electricity and magnetism, 

 and elasticity and light and thermodynamics. It 

 gives an interesting account of college life and 

 Kelvin's relations with his assistants and students. 



Prof. Ayrton's article, in spite of an obvious re- 

 straint, is intense w-ith affection and enthusiasm for 

 the memory of his master. He dwells on none of the 

 great theorems which are of fundamental importance 

 in all applications of mathematics, which indeed 

 created many parts of natural philosophy ; he only 

 casually mentions the discoveries and inventions of his 

 chief, for he assumes that they are all well known ; 

 he merely recalls his own experiences of forty years 

 ago, and his story is alive with interest, with remi- 

 niscences of a thousand acts of kindness and words of 

 sympathy from a man who never seemed to remember 

 his greatness when he was talking to a student, for 

 indeed he was always a fellow-student. 



Prof. Thompson's lecture, delivered to the members 

 of the Institution of Electrical Engineers, was per- 

 fect for its purpose. He touched on most of Kelvin's 

 work, but in particular he recalled to the leaders in 

 electrical engineering the history of their profession. 

 That history may be said to begin with Faraday and 

 with Thomson's papers when he was not yet twenty 

 jrears of age, papers in which he -recognised the inner 

 meaning of Faraday's work. Until he died he never 

 ceased to make electrical history, but the most wonder- 

 ful time was the time of his youth, when he was 

 developing the theories which were to educate Max- 

 well. The lecturer recalled the practical electrical 

 engineering work of the man who, when he died, was 

 j president of the institution for the third time. This 

 is not the place to speak of the many other tributes 

 which have lately been written to Thomson's genius 

 and ability. The real life of Lord Kelvin has yet to 

 be written, and the biographer will take account of 

 the notices now before us, as well as many others, and 

 he will especially use that masterly essay by Fitz- 

 gerald which was prepared for the Kelvin jubilee. 



To us. Prof. Larmor's notice is the most wonderful 

 of these productions. Was there ever so long an 

 obituary notice of a Fellow in the Proceedings of the 

 Ro}'al Society? And this notice is filled not only with 

 an enumeration of the contributions of Kelvin to 

 applied mathematics, with sufficient detail to keep the 

 reader intensely interested, but also with ungrudging 

 praise. To anyone who knows the severity of Prof. 

 Larmor's criticism, the almost impossibly high 

 standards which the modern Cato is in the habit of 

 applying to all scientific work involving mathematics, 

 this obituary notice will count as the greatest praise 

 ever given to any scientific man ! It is from another 

 point of view that we would ask students to read 

 particularly w-hat Prof. Larmor says about the 

 memoirs of Clausius of 1850 and Thomson's papers on 

 thermodynamics until 1851 and on to 1855. It is just 

 possible that the men who think they know the thermo- 

 dynamic events of that most interesting time may find 

 that Thomson's habits of self-effacement have made 

 it necessary now to re-write the history. We know 

 that it was all one to him ; he never made a claim for 

 priority except on behalf of somebody else than him- 

 self. We are sorry to say that we can make no more 

 comments on these essays ; when we try to write, 

 memory throngs too much with reminiscences and 

 power of expression fails us. He is still too close to 

 us; affection and emotion are overpowering. We have 



NO. 2023, VOL. 78] 



