Jilt 31, 1903.] 



SCIENCE. 



143 



Sanderson is evidently not at one with Sir 

 William Thiselton-Dyer, though he reluc- 

 tantly supports the main contention of the 

 latter. Lord Kelvin says that the ether is 

 absolutely non-atomic, absolutely structure- 

 less, and homogeneous. Professor Osborne 

 Reynolds announced not long ago, as the 

 result of the latest investigations, that the 

 ether is atomic or molecular in structure, 

 gave the size of the molecules, calculated 

 their mean free path, and told us that the 

 ether is 500 times as dense as gold, that its 

 mean pressure is 750,000 tons to the square 

 inch, and so forth. 



'Whom shall my soul believe?' is the 

 question of the poet, which is echoed by 

 Your obedient servant, 



QtJE Sg^us-JE? 



London, May 11, 11103. 



I suppose I ought to bow my neck to 

 the rod now that it is wielded judicially 

 by the editor of the Times. I feel no in- 

 clination to do so. Nevertheless, I hope 

 I may be permitted to point out that 

 'directive power' is, as a matter of fact, 

 'the stroke of the pen' by which 'Lord 

 Kelvin, in effect, wipes out • * * the whole 

 position won for us by Darwin.' 



It is no use mincing matters. Students 

 of the Darwinian theory must be permitted 

 to know the strength and weakness of their 

 dialectic position. What that theory did 

 was to complete a mechanical theoiy of 

 the universe by including in it the organic 

 world. 



The attempt to introduce a directive 

 force into the Darwinian theory is no new 

 thing. It is, of course, only creative power 

 in disguise. The most notable are those of 

 Nageli in Germany, and Asa Gray and 

 Cope in America. Weismann has gen- 

 eralized them a.s an attempt to set up a 

 'phyletic vital force,' and he points out 

 that if we accept anything of the kind 'we 

 should at once cut ourselves off from all 



po.ssible mechanical explanation of organic 

 nature. ' 



I can hardly suppose that Lord Kelvin 

 was not perfectly aware of this. 



May I further add that the 'world of 

 spirit to which the world of matter is al- 

 together subordinate,' to which Dr. Alfred 

 Wallace would introduce us, is not, so far 

 as I know, a subject which biologists find 

 themselves in a position to investigate? 

 The 'ether' seems sufficiently perplexing. 

 W. T. Thiselton-Dyer. 



Kew, May 13, 1903. 



It seems to me that, were the discussion 

 excited by Lord Kelvin's statements to the 

 Christian Association at University College 

 allowed to close in its present phase, the 

 public would be misled and injustice done 

 to both Lord Kelvin and his critics. I 

 therefoi-e beg you to allow me to point out 

 what appear to me to be the significant 

 features of the matter under discussion. 



Lord Kelvin, whose eminence as a physi- 

 cist gives a special interest to his opinion 

 upon any subject, made at Univei-sity Col- 

 lege, or in his subsequent letter to you, 

 the following statements: 



1. That 'fortuitous concourse of atoms' 

 is not an inappropriate description of the 

 formation of a crystal. 



2. That 'fortuitous concourse of atoms' 

 is utterly absurd in respect to the coming 

 into existence, or the growth, or the con- 

 tinuation of the molecular combinations 

 presented in the bodies of living things. 



3. That, though inorganic phenomena do 

 not do so, yet the phenomena of such living 

 things as a sprig of mo.ss, a microbe, a 

 living animal— looked at and considered 

 as matters of scientific investigation — com- 

 pel us to conclude that there is scientific 

 reason for believing in the existence of a 

 creative and directive power. 



4. That modern biologists are coming 

 once more to a firm acceptance of some- 

 thing, and that is— a vital principle. 



