376 PART V WORKING STAGE. 



it follows that living substance can never be accumulated in 

 large masses, but can only exist in the form of small granules, 

 or of thin plates presenting relatively large surfaces to a cir- 

 cumambient fluid of some kind. . . . Since life is a fire, and 

 since this fire requires the constant diffusion of oxygen into 

 the living substance and of carbonic acid out of it, living sub- 

 stance must be a fluid, since only in fluids and gases can 

 diffusion exist." (Zoology, p. 20.) J. Arthur Thomson claims 

 that "if a portion of the germ plasma of a fertilised ovum is 

 preserved unchanged during development to form the rudiments 

 of the reproductive cells of the new organism, and if the germ- 

 plasma is as stable as Weismann makes out, then there is a 

 strong probability that no variations produced in the body by 

 use or disuse or by outside influences can be transmitted". 

 (Article "Heredity", in Chambers' Encyclopaedia, ed. 1908.) 

 Edison proceeds in the same manner: "If the indentations on 

 paper could be made to give forth again the click of the in- 

 strument, why could not the vibrations of a diaphragm be 

 recorded and similarly reproduced?" (Edison, as quoted in 

 Inventors at Work, by George lies, 1907, p. 311.) 



And here is an illustration courteously supplied to the author 

 by Dr. Cecil Desch: "The success which attended the appli- 

 cation of the undulatory hypothesis to the explanation of light 

 led its supporters to follow out its consequences to their furthest 

 limits. It was found deductively, by mathematical reasoning, 

 that light must exert a minute pressure on a surface on which 

 it falls. The calculated pressure was so small that its measure- 

 ment appeared almost hopeless, but two very skilled investi- 

 gators succeeded in devising means for measuring it, and their 

 results have been confirmed by others. There is an interesting 

 consequence of this. The pressure on a particle due to light 

 is proportional to its surface. Imagine small particles exposed 

 to the sun, in free space. They are attracted by the gravi- 

 tational force of the sun, and repelled by the pressure exerted 

 by its light. The smaller they are, the greater is their surface 

 in proportion to their volume (or mass, if they are all alike). 

 Hence, at a certain limit of size, attraction and repulsion will 

 just balance one another, and still smaller particles will actually 

 be repelled from the sun instead of being attracted by it. Now, 

 there are spectroscopic reasons for saying that comets' tails 

 are composed of fine dust. The repulsion of such fine particles 

 by light falling on them explains perfectly why comets' tails 

 always point away from the sun." 



Perhaps the most brilliant deductions recently made are those 

 by Einstein, resulting from his theory of relativity. From that 

 theory he inferred that the eccentric rotary movement of the 

 orbital ellipse of Mercury, which is 43 seconds of arc per cen- 

 tury, was not an exceptional, but an extreme case, the cor- 

 responding amount of rotation of the other planets being simply 



