47§ 



NATURE 



[July io, 19 13 



through the earth passes in and out through the 

 receiving apparatus. The Admiralty slation is, of 

 course, comparatively near, and the signals are very 

 powerful. This explains why it is only Admiralty 

 signals that I am able to receive by this' method. 



I am unable to agree with Mr. Lander in his 

 remarks as regards tuning, as I find that with my 

 bedstead aerial it is just as easy to tune in and out 

 such signals as I am able to receive as it is with my 

 proper aerial, which is suspended on poles above the 

 roof of the house. The Eiffel Tower signals are 

 always difficult to tune out, for the reason, as I 

 suppose, that they are of irregular wave-length, while 

 I find it impossible to tune out the Admiralty by 

 reason of its power and proximity. Norddeich and 

 other unidentified signals that I obtain are, however, 

 tuned in and out both with the bedstead aerial and 

 with the other with equal facility. 



For time signals very accurately tuned waves, such 

 as are sent out by Norddeich, are perhaps not alto- 

 gether an advantage, as badly tuned waves, such as 

 are_ sent out by the Eiffel Tower, are much more 

 easily picked up by all and sundry. 



A. A. Campbell Swinton. 



66 Victoria Street, Westminster, S.W., July 7. 



A Mechanical Vacuum-Tube Regulator. 



May I supplement Mr. Campbell Swinton's letter 

 in Nature of June 26? The device of sliding a glass 

 sleeve over the kathode for the purpose of varying 

 the hardness of a discharge tube was also used and 

 fully described by Wehnelt in 1903 (Deutsch. Phys. 

 Gcsell. Verh., 5, 14, p. 259), some five vears after 

 Mr. Swinton. 



The important part that the electrification on the 

 walls plays in a discharge tube is not, I think, gener- 

 ally realised; and Mr. Swinton is not quite right in 

 assuming that Mr. Whiddington's explanation is 

 novel. 



The electrification on the glass walls adjoining the 

 kathode, and its concentrative effect on the beam of 

 kathode rays, were remarked by Goldstein in 190 1 

 ( ibi d- 3i '5. P- I9 2 )- 



I remember some half-dozen years ago, Sir J. J. 

 Thomson, in one of his lectures at Cambridge, gave a 

 similar explanation of the formation of the "fine pencil 

 of kathode rays which can be seen crossing the bulb 

 from .the centre of the kathode in a soft X-ray tube. 

 He attributed the effect entirely to the negative elec- 

 trification of the glass round the kathode. The 

 pencil of rays is as definite with a plane kathode as 

 with a concave one. 



But X-ray tube-makers have long been aware that, 

 by withdrawing the kathode from the bulb into a 

 side tube, the discharge can be hardened. In the 

 earliest X-ray bulbs, the kathode was always mounted 

 in the body of the bulb ; but the advantages of a 

 side tube had been realised by 1896, and the design 

 has since been universally adopted. 



Mr. Swinton was also responsible about 1897 f° r 

 another adjustable form of X-ray bulb, in which, 

 instead of a sliding sleeve, a movable kathode could 

 be advanced in or out of a side tube. The bulb is at 

 present in the Rontgen's Society's historical collec- 

 tion in the South Kensington Museum 



G. W. C. Kaye. 



June 28. 



In order to remove the possibility of any misunder- 

 standing that may arise from Mr. A. Campbell Swin- 

 ton's letter in Nature of June 26 (p. 425), may I state 

 that the mechanical vacuum-tube regulator is not 

 claimed by me as new in the paper referred to. If 

 Mr. Campbell Swinton will read the actual paper he 

 NO. 2 2 8o, VOL. 91] 



will find it clearly stated that the regulator was dis- 

 covered by him. Richard Whiddington. 

 St. John's College, Cambridge, July 7. 



The Humphrey Owen Jones Memorial Fund. 



The committee formed to carry out the generally 

 expressed desire that some suitable memorial of the 

 late Humphrey Owen Jones, F.R.S., should be estab- 

 lished, has received subscriptions amounting to about 

 3600L It is proposed to devote the sum collected to 

 the endowment of a teaching post in physical chem- 

 istry in the University of Cambridge. 



The committee desires to close the subscription list 

 at the end of this month, and requests further intend- 

 ing subscribers to send their contributions to the 

 account of the H. O. Jones Memorial Fund, Messrs. 

 Barclay and Co.'s Bank, Cambridge, before that date. 

 W. J. Pope 

 (Chairman of the Committee). 



The Chemical Laboratory, Cambridge, July 7. 



Smithsonian Physical Tables. 



Attention was directed by Mr. C. T. Whitmell 

 on p. 320 of Nature of May 29, to a "very awkward 

 error " in the Smithsonian Physical Tables (1896). 

 The institution is always glad to have attention 

 directed to errors for correction in subsequent editions, 

 but as this particular error does not appear in the 

 first revised, second, third, fourth, and fifth editions, 

 it seems rather unfortunate to have discredit thrown 

 on the tables through an error long since corrected. 

 C. D. Walcott, 



Secretary. 

 Smithsonian Institution, Washington, U.S.A., 

 June 21. 



MODERN VIEWS OF ELECTRO-THERA- 

 PEUTICS. 

 INURING the last few years our views upon 

 *-^ the true meaning- of the action of electricity 

 upon living subjects have been growing much 

 clearer. We begin to see the principles upon 

 which our practice should be based, and already, 

 as a consequence of this, our methods are changing 

 and our results are growing more valuable. 



There are two factors which have brought this 

 about. One is the recognition of the importance 

 of the theory of ions in all matters which concern 

 the movement of electric currents in living tissues, 

 and is due to the genius of Leduc, and the other 

 is the recognition of the thermal action of high- 

 frequency currents, an action which remained un- 

 appreciated, even if not unknown, until it was 

 insisted on and emphasised by Nagelschmidt. It 

 is upon these two basic facts, the chemical or 

 ionic effects and the thermal effects of electric 

 currents, that the electro-therapeutics of the future 

 will be established. 



First, as to the chemical aspect of the medical 

 applications of electric currents. To begin with, 

 all movements of current in the body, whether the 

 currents are direct, interrupted or alternating, are 

 ionic movements pure and simple, and their effects 

 are due to the chemical displacements produced. 

 We may not speak of effects which are additional 

 to or independent of the ionic movement, for such 

 effects do not exist. The current in the body is 

 the double ionic movement only. The treatment 



