52 



SCIENCE. 



[N. S. Vol. I. No. -2. 



ed as the key note to the more elaborate dis- 

 quisitions which followed at intervals up to 

 recent dates. These papers are so well 

 known, or ought to be so weU known, to all 

 geologists as to make it only necessarj^ to 

 say here that they will be found collected 

 iu this volume in convenient form and with 

 a few notes and occasional comments by the 

 distinguished author, made while the collec- 

 tion was being prepared for the press. The 

 most important of the earUer papers are the 

 address ' On Geological Time,'' given in Glas- 

 gow, early in 1868, and that on ' Geological 

 Dynamics ' at the same place about a year 

 later. In the first of these will be found 

 the somewhat severe strictures upon 'British 

 Popular Geology ' which brought forth the 

 interesting and pointed criticisms of Huxlej^ 

 in his address to the Geological Society of 

 London, and in the second the replies to 

 Huxley's criticisms and futher remarks upon 

 the subject. Nearlj' ten years later came a 

 'Jievieiv of the Evidence Regarding the Physical 

 Condition of the Earth,'' read at the British As- 

 sociation meeting at Glasgow ; two papers 

 read before the Geological Society of Glas- 

 gow, on. ' Geological Climate,' and on the 'In- 

 ternal Condition of the Earth;'' and after the 

 lapse of another ten j^ears a paper before the 

 same societj^ on 'Polar Ice Caps and their In- 

 fluence in Changing Sea Levels.' In these 

 much of the ground of the earlier addresses 

 is again gone over, in the light of later dis- 

 covery in geologjr, physics and astronomj'. 



Indeed these same topics recur again and 

 again, sometimes incidentally in other ad- 

 dresses in the volume, and Lord Kelvin 

 makes it entirely clear that in thus taking 

 up the discussion of geological problems 

 and applyiug to them the methods and 

 data of physics and astronomy, he does not 

 wish to be considered an interloper. In 

 his reply to Huxley, who had rather point- 

 edly intimated that view of the situation, 

 he good-naturedly remarks : " For myself 

 I am anxious to be regarded by geologists. 



not as a mere passer-by, but as one con- 

 stantly interested in their grand subject, 

 and anxious in any way, however slight, to 

 assist them iu their search for truth.'' 



It seems difficult to over-estimate the im- 

 portance of these geological addresses, not 

 only to the geologist, but to the phj^sicist as 

 well. They not only have a general interest 

 to both, but are of special importance to 

 each. To the one they open new possibili- 

 ties of a somewhat exact and satisfactory 

 treatment of a most important but hitherto 

 rather unmanageable department of his sub- 

 ject; and to the other they ofler a most in- 

 structive illustration of the power and scope 

 of the methods of exact science, when ap- 

 plied by one who may justly be called not a 

 master, but the master. 



Of the other addi-esses, none, of course, is 

 more important or interesting than the 

 British Association Presidential Address of 

 1871, so well known to all. One of the 

 earliest, on ' The Pate of a Clock or Chrono- 

 meter as Influenced by the Mode of Susj)ension,' 

 is most entertaining and suggestive as an ex- 

 ample of the many ' side-lights ' of a re- 

 markable intellectual activity. Of great 

 historical value is the Eoyal Institution lec- 

 ture of 1856 on the ' Origin and Transforma- 

 tion of Motive Power' — already republished in 

 Volume II. of the 'Mathematical and Physical 

 Papers ; ' and one of the most interesting is 

 that of late date (1892) on the 'Dissipation 

 of Energy.' In this much attention is given 

 to the principle of Carnot, and here also oc- 

 curs a remarkable statement which the au- 

 thor himself has thought worth while to 

 print in italics ; — it is : — " The fortuitous con- 

 course of atoms is the sole foundation in Philoso- 

 phy on ivhich can be founded the doctrine that it 

 is impossible to derive mechanical effect from heat 

 othenvise than by taking heat from a body at a 

 higher temperature, converting at most a definite 

 proportion of it into mechanical effect, and giving 

 out the whole residue to matter at a lower tem- 

 perature." 



