July i8, 1907] 



NA TURE 



269 



LETTERS TO THE EDITOR. 



[The Editor 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 

 manuscripts intended for this or any other part of Nature. 

 No notice is taken of anonymous communications.] 



Radium Emanation. 



In 1903, it was shown by Mr. Soddy and myself that the 

 spontaneous change of the emanation from radium results 

 in the formation of helium : this observation has been con- 

 firmed by Indrikson, by Debierne, by Giesel, by Curie and 

 Dewar, and by Himstedt and G. Meyer. Debierne has 

 shown that actinium chloride and fluoride also develop 

 helium. I have also once detected helium in the gases 

 evolved continuously from a solution of thorium nitrate, 

 and hope soon to confirm this observation. 



When the emanation is in contact with, and dissolved in 

 water, the inert gas which is produced by its change con- 

 sists mainly of neon ; only a trace of helium could be 

 detected. 



When a saturated solution of copper sulphate is substi- 

 tuted for water, no helium is produced ; the main product 

 is argon, possibly containing a trace of neon, for some of 

 the stronger of its lines appeared to be present. The 

 residue, after removal of tlic copper from this solution, 

 showed the spectra of sodium and of calcium ; the red 

 lithium line was also observed, but was very faint. This 

 last observation has been made four times, in two cases 

 with copper sulphate, and in two with copper nitrate ; all 

 possible precautions were taken ; and similar residues from 

 lead nitrate and from water gave no indication of the 

 presence of lithium ; nor was lithium detected in a solution 

 of copper nitrate, similarly treated in every respect except 

 in its not having been in contact with emanation. 



These remarkable results appear to indicate the following 

 line of thought : — From its inactivity it is probable that 

 radium emanation belongs to the helium series of elements. 

 During its spontaneous change, it parts with a relatively 

 enormous amount of energy. The direction in which that 

 energy is expended may be modified by circumstances. If 

 the emanation is alone, or in contact with hydrogen and 

 oxygen gases, a portion is " decomposed " or " disin- 

 tegrated " by the energy given off by the rest. The gaseous 

 substance produced is in this case helium. If, however, 

 the distribution of the energy is modified by the presence of 

 water, that portion of the emanation which is " decom- 

 posed " yields neon ; if in presence of copper sulphate, 

 argon. Similarly the copper, acted upon by the emanation, 

 is " degraded " to the first member of its group, namely, 

 lithium ; it is impossible to prove that sodium or potassium 

 are formed, seeing that they are constituents of the glass 

 vessel in which the solution is contained ; but from analogy 

 with the " decomposition-products " of the emanation, they 

 mav also be products of the " degradation " of copper. 



A full account of this research will shortly be communi- 

 cated to the Chemical Society. Willum R.imsay. 

 July II. 



Effect of Pressure on the Radiation from Radium. 



I HAVE, during the l.cst eighteen months, been engaged in 

 an investigation on the effects of pressure on radio-active 

 phenomena. In designing the apparatus necessary for the 

 purpose, it was necessary to consider that if any change in 

 the rate of production of the emanation occurs, through 

 pressure, effects would not be noticeable at once, as a new 

 ;tate of equilibrium would only be reached after sever.-il 

 days. Similar considerations hold if any of the slowly 

 decaying products is affected. A special pressure pump 

 was therefore constructed according to the designs of Mr. 

 J. E. Petavel, and this pump allowed me to keep up a 

 pressure of about 2000 atmospheres almost indefinitely 

 without sensible leak. The time of the experiments was 

 not, however, extended bevond four or five days. 1 he 

 results have been entirely negative, and I estimate that a 

 change in the activity of one-third per cent, would have 

 been noticed. . . . 



During the course of the investigation several fictitious 



effects made their appearance, and it was the elimination 

 of these which necessitated a gradual improvement in the 

 methods of observation and took up the greater part of the 

 time occupied in the experimental inquiry. 



In addition to the help of Mr. Petave) which has already 

 been mentioned, I have had the assistance of Mr. Makower 

 in the early stages of the work. The final experiments 

 were conducted by my assistant, Dr. Hans Geiger. 



Arthur Schuster. 



Victoria Park, Manchester, July 12. 



In order to ascertain if the rates of disintegration of 

 radium and its successive products (the emanation, A, B, 

 and C) are affected by high pressure, we have placed 

 about I gram of barium chloride, containing 104 mg. 

 of radium, completely sealed beneath lead, in a thick- 

 walled cylinder of nickel steel, and compressed the radium 

 by a tight-fitting chromium tungsten steel piston i cm. 

 in diameter. The greatest pressure applied has been 

 3-2x10^ lb. to the square inch, which is the estimated 

 pressure at a depth of fifty miles beneath the surface of 

 the earth. The penetrating radiation arising from 

 radium C was observed by two large electroscopes placed 

 on either side of the radium, and at a distance of about 

 30 cm. from it. The 7 rays produced a deflection of 

 about twenty-eight divisions a minute in an electroscope, 

 the natural leak of which was 04. The pressure on the 

 radium was gradually increased from zero to that at ten, 

 twenty, thirty, forty miles beneath the earth's surface, and 

 was maintained for four days at about the forty-mile value. 

 The pressure was then taken off, and observations were 

 continued for three days more. During all these variations 

 of pressure, no change v/as detected in the 7 radiation, 

 although a variation of i per cent, could have been observed 

 without difficulty. 



The pressure was then rapidly carried frorti zero to the 

 fifty-mile value and back, and also maintained at fifty 

 miles for two hours. Again there was no change, certainly 

 not I per cent. 



It is therefore clear that the transformation from radium 

 to radium C continues in a normal manner at pressures 

 equal to those at forty to fifty miles beneath the earth's 

 surface; and this important conclusion seems inevitably 

 to follow— that radium generates heat by disintegration 

 equally at the surface of the earth and at pressures which 

 obtain at debths forty to fifty miles beneath the surface. 



The Hon.'R. J. Strutt has proved that the quantity of 

 radium in rocks near the earth's surface is greatly in 

 excess of that required to compensate for the loss of heat 

 by conduction and radiation from the earth's surface. Dr. 

 Bronson has proved that the disintegration of radium is 

 unchanged by wide variation of temperature. It appears 

 from our experiments that the transformations take place 

 in the usual manner even under a pressure of 160 tons 

 to the square inch. If radium were distributed throughout 

 the earth in the same amount as at the surface, a 

 higher temperature gradient than that actually found 

 would be expected. A possible explanation of the 

 paradox has been put forward by Strutt and supported 

 by Milne. He supposes that the constituents of the earth 

 some twenty to forty miles beneath the surface are different 

 in character from those near the earth's surface, and that 

 they do not contain radium, or contain it to a smaller 

 extent This seems to carry with it the conclusion that 

 igneous rocks, which contain considerable quantities ot 

 radium, have their origin nearer the surface of the earth 

 than some geologists have supposed. 



A. S. Eve. 

 Frank D. Adams. 

 McGill University, Montreal, June 28. 



The .ffither and Absolute Motion. 

 The particular objection to identifying magnetic force 

 with velocity of the sther, which has been discussed 

 recently in ' the columns of Nature by Prof O. _ W. 

 Richardson, Sir Oliver Lodge and Prof. W. M. Hicks 

 Dr C V. Burton and Mr. E. Cunningham, must depend 

 on some point of view which is foreign to my ways of 

 thinking. Such a hypothesis involves, of course, that the 



NO. 1968, VOL. 76] 



