July 2, 1903J 



NA TURE 



213 



as that of the lines from which they originated, namely, 

 that of the lines of the normal triplet. At all fields up to 

 13,000 the faint companion to the yellow helium line D^ 

 was not tripled, but only doubled. 



For the above lines observations were made also along 

 the lines of force, one of the magnet cores being replaced 

 by a core drilled from end to end with a hole about a 

 <entiiiietre in diameter. The following table gives the 

 numbers obtained : — 



With respect to the green mercury line of wave-length 

 5461 tenth-metres, the authors incidentally observed fully a 

 year ago, as they found afterwards had also been done a 

 little earlier by Zeeman, that the line appeared to have 

 three faint companions on the violet side, and two (they 

 seemed at times to see three) on the red side. The com- 

 panions are visible only under special conditions of the 

 discharge tube. The values of d\ for the first three are 

 — o'2o8, —0096, —0059, ^nd ^o'' the other two +0032, 

 + 0067. Though those values do not in every case agree 

 with those given by Perot and Fabry, it is possible that, 

 on account of hitherto unexpected complexity of the line, 

 both sets of observations are correct. 



It ought to be noticed here that Runge and Paschen have 

 obtained a resolution of the green mercury line into three 

 triplets in the magnetic field. This observation is entirely 

 confirmed as to the side triplets by those of the authors 

 (which were made before Messrs. Runge and Paschen 's 

 paper came to hand), but they have not been able to verify 

 Runge and Paschen 's result for the middle group, which 

 ;ippears to the authors to be a doublet. But the instru- 

 ment of Runge and Paschen was a large Rowland grating 

 of 65 metres diameter of circle, and the spectrum was 

 photographed, so that their observations were, no doubt, 

 more certain than the authors'. 



May 28. — " Note on the Effect of Extreme Cold on the 

 Emanations of Radium." By Sir William Crookesi 

 F.R.S., and Prof. James Dewar, F.R.S. 



The first endeavour was to ascertain whether the 

 scintillations produced by radium on a sensitive blende 

 screen were affected by cold. 



/\ small screen of blende with a morsel of radium salt 

 close in front was sealed in a glass tube, and a lens was 

 adjusted in front so that the scintillations could be seen. 

 On dipping the whole into liquid air they grew fainter and 

 soon stopped altogether. Some doubt was felt whether 

 this might not have been caused (i) by the presence of 

 liquid, (2) by the screen losing sensitiveness, or (3) by the 

 radium ceasing to emit the heavy positive ions. To test 

 this two tubes were made, in one of which the radium salt 

 could be cooled without the screen, and in the other the 

 screen could be cooled while the radium salt was at the 

 ordinary temperature. 



The results were as follows : — (i) Radium salt cooled by 

 liquid air. Screen at ordinary temperature. Scintillations 

 quite as vigorous as with radium at the ordinary tempera- 

 ture, the screen and radium being in vacuo. (2) Radium 

 at the ordinary temperature and screen cooled in liquid air. 

 As the screen cooled the scintillations became fainter and 

 at last could not be seen. On allowing the temperature to 

 rise the scintillations recommenced. (3) A screen with a 

 speck of radium salt in front of it was sealed in a tube. 

 The tube was sealed off when a few fine drops of water 

 were still remaining in the tube. The scintillations were 

 well seen in this saturated aqueous vapour. The lower end 

 of the tube was dipped in liquid air, which instantly con- 

 densed the aqueous vapour and left a very good vacuum. 

 On now examining the scintillations they were if anything 

 brighter and more vigorous than at first. When liquid 

 hydrogen cooling was used instead of liquid air, the action 

 was equally marked, showing that the highest vacuum that 



^^' 1757. VOL. 68] 



can be obtained by the action of cold does not diminish the 

 scintillations. 



In order to test the activity of radium in rendering air 

 electrically conductive some radium bromide was sealed up 

 in a glass tube and heated to the highest temperature the; 

 glass would stand, during the production of as high a 

 vacuum as the mercurial pump would give. The whole 

 tube was then immersed in liquid hydrogen contained in a 

 vacuum vessel. On bringing the radium in such a vessel 

 into a room in which a charged electroscope was placed it 

 began to leak when the tube of radium surrounded with 

 liquid hydrogen was some three feet away, and was very 

 rapid in its action when a foot away from the electrometer. 

 On immersing the tube containing the liquid hydrogen with 

 submerged radium in another large vessel of liquid air 

 and bringing the combination near the electroscope, the 

 action was the same. 



Prof. Rutherford and Mr. Soddy have made the important 

 discovery that a condensable emanation is diffused into 

 gases from solutions of radium salts, which is capable of 

 condensation from the gas mixture at the temperature of 

 liquid air. As it was important to ascertain what was 

 taking place in this respect with the anhydrous radium 

 bromide when isolated in the highest vacuum, the follow- 

 ing experiment was arranged : — A glass apparatus was con- 

 structed consisting of a p-shaped tube having a bulb at one 

 end, and being drawn out to a capillary tube at the other. 

 Above the bulb was a plug of hard-pressed purified asbestos. 

 The radium salt was located at the bottom of the bulb, and 

 the whole was most carefully heated, exhausted to the limit 

 of the mercurial pump, and sealed off. In the dark no trace 

 of phosphorescence could be seen in any part of the 

 apparatus unless from the pieces of the radium bromide. 

 The capillary tube was now immersed in liquid air in a 

 large flask, so that distillation might proceed undisturbed 

 for days. After twenty-four hours of this operation, on 

 looking at the capillary tube while covered with the liquid 

 air, a marked phosphorescence was recognisable owing to 

 some condensed emanation. The luminosity became natur- 

 ally more marked the longer the time the action was 

 allowed to proceed, and it is the authors' intention to con- 

 tinue the experiments for a lengthened period of time, and 

 then seal off the fine capillary part so that the condensed 

 product may be thoroughly examined. 



Entomological Society, June 3.— Prof. E. B. Poulton, 

 F.R.S., president, in the chair. — Mr. G. C. Champion ex- 

 hibited numerous specimens of Coccinella distincta, taken in 

 the pine woods of Woking. They were found, as usual, 

 running about the ground in company with Formica rufa, 

 and were perhaps wanderers from some other locality. Mr. 

 Donisthorpe said the species was still common at Wey- 

 bridge in the nests of Formica rufa, and that he had 

 observed it also at Bexhill, while Mr. Chitty noted its 

 i former occurrence in Blean Woods in great numbers. — Mr. 

 H. St. J. Donisthorpe exhibited a very remarkable melanic 

 \ form of Halyzia iS-guttata, L., black with white spots, the 

 I type, which was also exhibited, being light brown with 

 white spots. The former was taken at Oxshott on May 22. 

 { Ha also exhibited Stilicus fragilis, Gr., a melanic form with 

 1 a black thorax instead of red as in the type, taken at 

 Shirley on May 15; and Staphylinus fulvipes. Scop., taken 

 by himself at Bamber Forest on June i, a new locality for 

 this rare beetle. — Dr. T. A. Chapman exhibited two' full- 

 grown larvae of Thestor hallus, sent by Mr. H. Powell, from 

 Hyeres, and read a description of them in their various 

 stages. He also exhibited a larva of Heterogyna paradoxa, 

 full fed, reared from the egg at Reigate, and a cocoon of 

 Orgyia auro-limbata, with parasite microgaster. The 

 microgaster and the moth both came from the same larva, 

 and the moth, though containing a few eggs, laid none. 

 An imago and a parasite from the same larva have not 

 infrequently been recorded, but there has been some doubt 

 on the occurrence. — The President exhibited the dry form 

 of Precis actio bred by Mr. Guy A. K. Marshall from an 

 egg laid by a female of the wet form. The parent was 

 captured by Mr. Marshall at Salisbury, Mashonaland (5000 

 feet), on February 14 ; the egg was laid on the following 

 day. It hatched February 20, the larva pupated March 16, 

 the perfect insect, a male, emerged March 28. The differ- 

 ences between these two forms are as astonishing as those 

 between the two phases of Precis antilope bred, the dry from 

 the wet, by Mr. Marshall last year. The president said this 



