404 



NAT URL 



[February 13. 1919 



LETTERS TO THE EDITOR. 

 |7'/n; Edilur does not hold himself responsible for 



opinions expressed by his correspondents. Neithei 

 ,111 he undertake to return, or to correspond zi'ith 



the writers of, rejected manuscripts intended for 



llus or any other part of Nature. No notice is 



taken o) anonymous communications.] 



The Effect of Light on Long Ether Waves. 



1 [i curious and important observation made l>_\ 

 Mr. Marconi cm the basis oi experience in long- 

 distance wireless telegraph} exhibits a strange kind 

 of interference between ethei waves of verj different 

 lengths. I'll.- extremel) shori waves which ionise air 

 interfere with the easy transmission oi the long waves 

 which are originated b) alternating electric currents, 

 in. I ma) conceivably have something to do with the 

 optical opacit) oi drj haze. 



Since main scientific men besides physicists read 

 Nature, ii ma) be permissible iu explain that this is 

 an entirel) different effect from the purely localised 

 bands of interference which accompany the super- 

 position ol wave motions, and are a matter of simple 

 geometry. In this phenomenon <>f interference bands 

 there is no destruction, only redistribution, of energ) ; 

 and there is nothing akin to opacit), whether of the 

 ibsorbent or the reflective kind. It is, moreover, 

 pure!) an affair of the ether. Whereas opacity is 

 ilways an effect brought about by the presence oi 

 matter in the path of ether waves, the ions or elec- 

 trons which are liberated from matter by exceedingl) 

 short waves raise a barrier or act as a refiectoi to 

 extremely long ones. '1'hus the phenomenon depends 

 on the interaction between free ether and electrified 

 particles immersed in it. 



A stud\ of the details of this phenomenon cannot 

 fail to be instructive, and tin Radio-telegraphic Com- 

 mittee of the British Association had made prepara- 

 tion for getting facts recorded during the solar eclipse 

 of August, 1 1 1 1 4 - The war prevented anything being 

 done. Inn now, as Prof. Fleming— the father of tin 

 committee suggests in Nature of January 23, another 

 opportunity presents itself in the eclipse of the after- 

 noon iif Ma\ jo. when the line of totality passes 

 aiiuss the South Atlantic from South America to 

 Vfrica, crossing 1 eara, in Brazil, and Princes Island, 

 in the Gulf of Guinea. The astronomers going from 

 this country will have their hands full, but a special 

 group of wireless experts might accompany the 

 expedition if funds were available. It seems probable 

 that assistance might l»- rendered more readilv by 

 the United Slates than 1>\ this country. Prof. Eceles, 

 1 In secretary of the British Association Wireless Com- 

 mittee, is still too engaged at present with Admiralty 

 work to superintend operations, but the Astronomer 

 Royal has informed him that Dr. Bauer, the head of 

 In Carnegie Institution of Washington, has already 

 mail.- plans for observations on magnetism and atmo- 

 spherii electricity, and ma) bi planning to take charge 

 ill radio : legraphic observations also. Several months 

 ago Prof. Eceles sent to Dr. Bauer the documents 

 prepared for recording wireless phenomena on the 

 occasion ol thi previous solar eclipse in 1014, and is 

 again commi ting with him. And thus we trust 

 that Prof. 1-1. n ;'s admirable suggestion will be 

 carried out. Oliver J. Lodge, 



' man of the British Association 



February 4. Radio-telegraphic Committee. 



The Aggregate Recoil of Radio-active Substances 



Emitting a-Rays. 



. 'I'm-: November (191S) iss f the Philosophical 



Magazine has just reached US, and I have read with 



real interest the results of some remarkable experi- 

 NO. 2572, VOL. I02] 



in- nl i b] VIi v Ratni 1 " < >n Somi Propi rties of 

 iln Vctivi Dep isil ol Radium." 1 In- papi r in - - 



I- als with tie 



I from the surfaci ol 1 pi 1 w ith the 



i radium to 



This 1 ii. 1 1 ha been up- atedl) obsi 1 

 in radio-acti h been attributed (.1) in a 



slight volat il at 1.1. lii. .11 \ p ni- 



peratures, 01 (2) to tin 1 ei "il ol a 1 ompai 



ni atoms "i tin ai v] nut thi atoms 



contained in it disintegrates with ejection of in 

 a-particle. To iliis lattei phenomenon I reci 

 I In- nam. ol " aggi egaO 1 1 1 1 nl 



Mr. Ratnei deals with both possibilities, and arrives 

 at iln conclusion that neither of them ^aiisii.s the 

 requirements of his results, lie states that his experi- 

 ments " have failed to disclose the nature of tin- pheno- 

 menon. " 



During tin last four Mars I have been engaged at 



intervals mi experiments of a similar kind, performed 

 with tin object of explaining the almost inevitable 

 and unavoidable contamination with polonium of 

 electroscopes and ionisation vessels used in experi- 

 ments with this substance. In 1915 I made mention 

 of this phenomenon in a paper published in the Com- 

 munications of this institute (No. So), and suggested 

 the possibility mentioned under (2) above in explana- 

 tion ni it, although 1 had, unfortunately, overlooked 



II 1 that Makowcr and Kuss had made tin ■ 

 suggestion in i.iio until I read Mr. Ratner's paper 

 v esterda 1 



M\ subsequent experiments with polonium, doni 

 for the most part in the summer of 1017, lend strong 

 support In the idea .if aggregate recoil as tie- causi 

 of this "wanderiqg" ol tin- active matter. Inasmuch 

 as I obtained quite appreciabli effects with polonium, 

 m\ results disagree with thosi of Mr. Ratner; in 

 fact, 1 have not a single observation which is not 

 adequately explicable in this manner. In No. 113 of 

 iln- Communications of this institute, which was pub- 

 lish. .1 in July; 1918, I discussed this phenomet 

 and examined tin- part played by tin disintegration 

 of the active foil ("spluttering") due to tin- bom- 

 bardment of a-particles. It was found that, in 

 general, much less than t per cent, ol tin- total effect 

 is due I.' the latter cans.. A further paper on 

 aggregate recoil is at present in tin- piess, and the 

 w ink is -till in pro^i 1 SS. 



As I am returning home in tin coursi of a few- 

 weeks, I hop. hifiii.- long to publish the results of 



these experiments in tin- Philosophical Magazine, as 



well as others of a similar nature done last summer 

 with the active deposit of radium. I beg to mention, 

 however, that, in the light of my own work, I am of 

 the opinion that almost all, if not all. of Mr. Ratner's 

 results an- in harmony with the recoil of aggregates 

 ol atoms of active matter, as originally suggested 

 l.\ Makower and Russ in explanation of the pheno- 

 menon in question. 



Like Mr. Ratner, I regard iln- so-called j8-recoil 

 of radium-C from radium-B .1- a theoretical possibility, 

 which ii will In- impossible to realise in practice. My 

 reasons foi the latter conclusion are contained in my 

 July publication. Dr. Lise Meitner, to whom I men- 

 tioned mv results last summer, informed me that sh< 

 in, inn-. 1 believes in tin- practicability of achieving a 

 transference of active matter by /3-recoil. She agreed 

 thai Iln idea ol aggregate recoil in the manner above 

 suggested is much more in harmon) with the experi- 

 mental results, and she informed me that Prof. Hahn 

 and herself had never been able to obtain pure 

 radium-C by the postulated 0-recoil method. 



Befon closing this letter, 1 should Rke to mak< 



