64 



NATURE 



[March 27. 1919 



LETTERS TO THE EDITOR. 



[The kditor does not hold himself responsible for opinions 

 expressed by his correspondents. Neither can he undertake to 

 return, or to correspond with the writers of, rejected manu- 

 scripts intended for this or any other part of Nature. No 

 notice is taken of anonymous communications.] 



Globular Clusters, Cepheid Variables, end Radiation. 



Dr. Shapley makes the suggestion (Nature, 

 March 13) that known supplies of energy become 

 adequate to maintain stellar and solar radiation 

 through astronomical time if we can suppose that 

 radiation is propagated only from matter to matter, 

 and is not radiated equally in all directions. In 

 brief, we see the sun because the sun has in some 

 way first seen us. Prof, Soddy points out (Nature, 

 March 20) that we have no direct evidence of loss of 

 radiation into space; "experiment and observation 

 justify only the conclusion that radiation is propa- 

 gated between portions of space occupied by matter, 

 . . . elsewhere it may not be propagated at all." 

 Prof, Soddy is, perhaps, on safe ground as regards 

 laboratory experiments, but it seems to me that astro- 

 nomical evidence is against him. 



We see star clusters by light which has journeyed 

 for 200,000 years to meet us; by what mechanism 

 could this light calculate 200,000 years ago that to- 

 day we should be where we are? There seem to be 

 only two possibilities open : the cones of light pro- 

 jected from matter to matter may be more than big 

 enough to catch the matter aimed at, or light may 

 not travel in straight lines, adjusting its course as it 

 proceeds on its voyage through space. 



Under the first possibility the whole advantage of 

 Dr, Shapley 's hypothesis disappears. We see, say, 

 10* stars, so that, presumably, 10* stars see our sun. 

 Suppose our sun sends out 10^ cones of light each big 

 enough to be fairly sure of catching. a star. Stellar 

 velocities being of the order of 10-* times that of 

 light, each cone must be of angle about 10- * radians, 

 and 10' such cones just about fill up the solid angle 

 of space. The hypothesis has lost its only advantage. 



Suppose, as an alternative, that the presence of a 

 star in some way guides the light from another star 

 towards it. The path of a ray of light is no longer a 

 straight line, but a sort of "curve of pursuit." To 

 catch the light from a star we ought no longer to 

 point our telescopes 20-4" x sin X forward along the . 

 earth's path in space, but an equal amount backwards. 

 The aberration-correction becomes reversed, and all 

 determinations of parallax, proper motions, etc., become 

 illusory. One puzzle might be solved, but at the cost 

 of shattering almost the whole fabric of astronomy. 



Thus if Dr. Shapley 's very strong case for a long 

 time-scale is accepted as proved, I think we must look 

 for a new mechanism of production of energy; the 

 problem is not solved by a mere rearrangement of the 

 expenditure. In looking for possible new sources of 

 energy, we ought to remember that our knowledge 

 of phvsics is derived wholly from experiments con- 

 ducted at the surface of a planet with the aid of light 

 emitted from the surfaces of sun and stars. Our whole 

 knowledge of phvsics is " surface-physics " ; it is the 

 special physics of conditions in which radiation is free 

 to scatter into space, so that radiation pressure is 

 negligible. There may be a more general physics 

 applicable inside a star, and this mav contain sources 

 of energy unknown to us. There is, for instance, a 

 possibility I suggested in 1005. which Dr. Shaplev 

 considers "bizarre." Conservation of mass and of 

 energy may be only phenomena of "surface-phvsics." 

 Inside a star, matter and energy may be interchange- 

 able. The intrinsic energy of an electron being mC'. 

 the transformation of i ner cent, of the sun's mass 

 into energy would yield up radiation enough for 

 150.000.000,000 vears. J. H. Jeans; 



March 22. 



The suggestion of Dr, Harlow Shapley and Prof^ 

 Soddy that radiation only occurs between portions of 

 space occupied by matter is difficult to reconcile with 

 the very considerable cooling by radiation that takes 

 place on a cloudless night, when, on the supposition 

 in question, it should be almost negligible — less,, 

 indeed, than with an overcast sky. 



Such a law of radiation would have other strange 

 results equally inconsistent with experience. 



John W. Evans. 



Imperial College of Science and Technology, 

 South Kensington, March 21. 



Scientific Research at St. Andrews University. 



The president of the Edinburgh Royal Society im 

 his address alluded to in Nature of March 13 has 

 done full justice to the St. Andrews University 

 Chemical Research Department, which owes its 

 prosperity to the munificence and the example of my 

 late colleague. Prof, Purdie, and also to his relatives. 

 It likewise throughout has had the unvarying support 

 of the University Court, which allocated a large sum 

 (more than 5000^.) from the Carnegie Trust Grant to^ 

 the University for its maintenance. 



But there is an older research department in the 

 University of St. Andrews which has been overlooked 

 by Dr. Home, viz. that for research in marine zoology 

 and the fisheries at the Gatty Marine Laboratory, the 

 oldest marine laboratory in Britain, and the scientific 

 work emanating from which will speak for itself. Its 

 trained workers hold, and have held, important posts 

 in the three centres of the kingdom and in the various 

 Colonies, as well as in foreign countries. That it 

 should have been severed from connection with the 

 Government by the Secretary for Scotland in 1896 

 (after twelve and a half years' labour), when the new 

 building was erected on University ground, seems a 

 paradox when the heavy expenditure (which still goes, 

 on) in subsidising the International Fisheries Council 

 is remembered. 



Chemistry research, adequately endowed, can be 

 carried out anywhere, whereas work in marine zoology 

 and the fisheries can nowhere be more successfully 

 pursued than in the bay and on the shores of St. 

 Andrews, where Prof. John Reid, the distinguished 

 physiologist, first dealt with its riches. There the 

 pulse of the North iSea is daily felt, and every student 

 of Nature is beckoned to engage in the elucidation of 

 the endless variety of its fauna and flora. It is to be 

 hoped that the University Court, which has closed the 

 laboratory at present from motives of economy, will' 

 soon reopen it. W. C. McIntosh. 



Maceration by Tryptic Digestion. 



With reference to the paragraph on the method of 

 maceration by tryptic digestion in Nature of March 6, 

 p. 9, it may be of interest to your readers to learn 

 that further work on the process has shown that 

 equallv good results are obtained by the use of Messrs. 

 Allen and Hanbury's Liquor Trypsini Co. This costs 

 onlv 3.'>. qd. a bottle, and the requisite strength is 

 obtained by adding i c.c. to a litre of water. The 

 procedure is in other respects identical with ^that 

 previously described. The trouble of dissolving the 

 powder is thus avoided, and the cost is reduced from 

 15. per litre to rather less than ^d., so that the method 

 becomes practicable for use on a large scale. 



On the whole, the optimum temperature is a higb 

 one, about 55° C., and this has the additional advan- 

 tage of somewhat reducing the unpleasant smell. 



Kathleen F, Lander. 



Zoological Societv of London, Regent's 

 Park, N.W.8, March 19. 



NO. 2578, VOL. 103] 



