450 



NATURE 



[September 22, 1923 



in very small quantities, so that it is practically certain 

 that the chemical atomic weight 87*63 at present in use 

 is too low. " 



Cobalt also appears to be a simple element of mass- 

 number 59, as was to be expected from its atomic 

 weight, which has been determined with great care by 

 a number of observers. 



Scandium was successfully attacked by the use of 

 material kindly supi)lied by Prof. Urbain, of Paris. 

 The only line obtained was at 45. It may be taken 

 provisionally to be a simple element, but the effects 

 are not strong enough to disprove the presence of 

 small quantities of another constituent. 



Manganese; behaved surprisingly well, and yielded 

 unequivocal results indicating that it is a simple 

 element of mass-number 55. This result is in good 

 agreement with the chemical atomic weight, and is 

 particularly interesting, for 55 is a term in the numerical 

 series 2, 3, 5, 8, 13 — all of which had previously corre- 

 sponded to gaps in the list of weights of known species 

 of atoms. 



Gallium fluoride made from a specimen of the hydrate 

 kindly provided by Prof. Richards, of Harvard Uni- 

 versity, also gave satisfactory results. Gallium consists 

 of two isotopes, 69 and 71. The intensity relation 

 between the lines agrees much better with the atomic 

 weight 69-72 recently published by Richards than 

 that previously in use, 70-1. 



Vanadium and chromium give single mass-lines at 

 positions expected from their atomic weights 51 and 52. 



Titanium gives a strong line at 48. On one of the 

 spectra obtained there is a faint and doubtful indication 

 of a line at 50. Should this latter be confirmed it 

 would tend to support Honigschmid's value 48-1 for 

 the atomic weight rather than the lower figure 47-85 

 more recently obtained by Baxter. 



Silver in the form of the chloride worked unexpectedly 

 well, and gave two nearly equally intense lines at 

 107, 109. 



Yttrium gives a single strong line at 89, another 

 term of the numerical series already referred to, and 

 completes the analysis of the first 39 elements, 



A specimen of potassium hafnifluoride sent from 

 Copenhagen by Dr. Hevesy was experimented with, 

 but in no case were any lines visible in the region of 

 the expected atomic weight of hafnium. This sample 

 contained about 50 per cent, of zirconium, and an 

 extremely faint effect at 90 shown here and on other 

 plates taken with pure zirconium salts sugf;ests this as 

 the principal isotope of this element ; but further work 

 is necessary on this point. 



Niobium, molybdenum, cadmium, barium, and lead 

 have all been tried without any definite results, and it 

 is feared that difficulties may arise in finding suitable 

 compounds to use in the case of these and other elements 

 not yet analysed. On the other hand, success with 

 scandium and yttrium offers hope of obtaining the 

 mass-spectra of all the rare-earth group. 



The following is a list of the elements the composition 

 of which has been first indicated by the use of accelerated 

 anode rays. The mass-numbers were usually deter- 

 mined with reference to the lines of iron or iodine, and 

 no outstanding divergence from the whole-number rule 

 was observed. 



Miaimum Number Mass-numoers in 

 oi Isotc^>e3. Order o( Intensity. 



45 

 48 



^3, ^5 

 69,71 



74, 72, 70 

 88 



89 



lOT. lOQ 



Obit 



Sir Henry Hubert Hayden, F.R.S. 

 A LL who knew Sir Henry Hayden well enough must 

 ^^ recall a passing thought, more than once definitely 

 formulated, that some day his irrepressible keenness 

 for exploring new and little-known lands would lead 

 to accident. Those who had the inestimable privilege 

 of knowing him with real intimacy know well that, 

 if he had to choose a way of ending his career, it 

 would be on a mountain side and in a fight against 

 physical difficulties. He never revealed and probably 

 never entertained but one fear — that the medical 

 history of his family might repeat itself and render 

 him unfit for further exploratory work. It is appro- 

 priate that he should be laid to rest near the foot of a 

 great mountain, and appropriate too that it should 

 be the mountain which he had just conquered, for as 

 a mountaineer he was as efficient as he was daring. 



To accomplish a difficult task in exploration was in 

 itself his sufficient reward. Kindred spirits and but 

 very few others knew of his accomplishments ; for, 

 without being reticent, he never looked to the 

 " gallen,- " : his photographs, maps, sketches, and 

 collections were made readily available to specialists, 



NO. 2812, VOL. 112] 



uary. 

 but rarely, and only under pressure, were they turned 

 into lantern slides. The end of one task was to him 

 the beginning of the next : there never was an inter\al 

 for popular demonstrations, and little even for rest. 



Each geographical enterprise was invariably in a 

 new field, and Hayden's geological work was just as 

 varied — geotectonic problems in the Himalayas, 

 economic mineral questions in various parts of India, 

 pure palaeontology, the application of geolog\' to 

 engineering problems, and the microscopic petrology- 

 of igneous rocks formed the subjects of his papers, 

 each treated in turn with a thoroughness and sense of 

 relativity that revealed a wide and precise acquaintance 

 with literature, which was always surprising to those 

 who were impressed by his restless physical activity 

 in the field. 



Since January 3, 1895, when I met Hayden on his 

 landing at Calcutta to join the Geological Sur\ey of 

 India, I have been in closer and perhaps more constant 

 touch with him than most of his friends, and during 

 those twenty-eight years I never heard from him an 

 • ungenerous remark about a colleague, never heard him 

 grumble about the cUmate, at the work, or even at 

 the inequalities of treatment that seem to be the 



