■72 



SCIENCE. 



[N. S. Vol. XVIII. No. 408. 



rays result, or the bombardment of elec- 

 tronic emanations produces such an effect. 

 The luminosity can not be attributed solely 

 to the a-rays, or helium, as thorium oxide 

 does not respond (at least visibly to the eye 

 unaided by magnifying lenses), unless it so 

 happens that the helium exists in one radio- 

 active body in a different form from that 

 in the other. Further, we have tested a 

 number of helium-bearing minerals and 

 none responded to the strong radium 

 bromide. It appears that the luminosity 

 of such substances, so variable in their con- 

 struction as those mentioned above, may be 

 accounted for in a measure by the physical 

 explanations adverted to; yet, the striking 

 fact that four zinc compounds of totally 

 different composition, willemite (zinc or- 

 thosilicate), zinc sulphide, zinc oxide and 

 kunzite (which contains a fraction of a 

 per cent, of zinc) all respond in the most 

 pronounced manner to radium emanations, 

 would indicate the presence of a new ele- 

 ment, a 'radium-foil,' as it were, or some 

 unusual combination of known chemical 

 integers, which synchronize with the ac- 

 tivities of this unique body, in fact radio- 

 active responsive bodies. One is immedi- 

 ately reminded of the actinium that Phip- 

 son announced in the eighties as being 

 present in zinc white. (This is not to be 

 confounded with Debierne's actinium, re- 

 sembling titanium, announced in 1898.) 



Becquerel, as is well known, first ob- 

 served that certain substances, without any 

 previous artificial excitation, emit rays 

 which affect a photographic plate in the 

 dark. Non-luminous radio-active bodies 

 readily give this evidence of the presence 

 of 'Becquerel rays.' We have made a 

 paint, composed of zinc sulphide and 

 radium barium carbonate in linseed oil, for 

 making prints directly upon sensitive pho- 

 tographic films. The exposures varied from 

 thirty-five minutes to an hour, some being 

 made through glass. This would indicate 



the production of actinic rays and, further- 

 more, rays differing from those of the 

 ultra-violet, the transmission of which are 

 interfered with by glass. 



Selected gems were mounted in paraffine 

 blocks, held in wooden frames, obtained by 

 pouring the hydrocarbon, after melting in 

 a water-bath, into especially constructed 

 boxes about 18 x 27 cm. and 1.5 cm. deep. 

 The wooden bottoms attached to the frames 

 by screws were readily removed. Each 

 'plate' was numbered by placing small hot 

 wire nails on the paraffine. Where gems of 

 the same species varied in color they were 

 arranged according to the spectrum as far 

 as practicable. Comparisons as to color 

 effects could thus be had, but of course 

 no comparison of penetrative effects, as the 

 stones were of variable thickness. They 

 were photographed in place. 



These plates admitted of a careful com- 

 parative examination of the gems when 

 subjected to the bombardment of the Roent- 

 gen rays produced by a Queen's self -regu- 

 lating Crookes' tube with a twelve-inch 

 spark coil. Many radiographs were also 

 obtained with variable exposures, the iron 

 markers adverted to, through their im- 

 penetrability, serving to identify the plates. 



Perhaps no such complete collection has 

 been studied in this manner, although 

 Doelter in 1896 published a most interest- 

 ing study of the conduct of some sixty-five 

 minerals and other precious stones when 

 subjected to the Roentgen rays. During 

 the same year J. B. Cochrane published a 

 very practical paper on the testing of 

 precious stones by Roentgen rays. Without 

 giving details, it may be said that their 

 observations were verified, and in general, 

 it was learned that the penetration of gem 

 material by these rays is a matter of degree 

 rather than kind, and sharper conti'asts 

 were obtained with certain precious stones 

 when they were surrounded by metals, like 

 gold or lead, than was had when they were 



