776 



SCIENCE. 



[N. S. Vol. XVI II. No. 4G8. 



when glass, which is opaqiie to thef3e rays, 

 was interposed. 



The yellow mineral labeled ' greenockite, ' 

 from Franklin, N. J., fluoresced in an 

 identical manner, leading one to infer that 

 this is itself a uranium mineral, or else eon- 

 tains the same substance that causes the 

 autunites to fluoresce. 



A comparative table is appended. It is 

 self-explanatory and serves to illustrate the 

 conclusions apparently inevitable, namely, 

 the presence of something not previously 

 recognized. 



7. Hyalite (botryoidal), on a trachytic 

 rock, from San Luis Potosi, Mexico, as 

 colorless as the purest water, fluoresced 

 most intensely, with a rich British green 

 color; but these specimens did not phos- 

 phoresce. This green fluorescence could be 

 observed when the source of the ultra-violet 

 rays was five or six feet away. It did not 

 persist on the removal of the source, but 

 flashed in when the rays played upon it. 

 The sparker held near, but without the 

 rays playing upon the specimens, gave no 

 fluorescent effects. Therefore, no other 

 conclusion is tenable than that it is the 

 ultra-violet rays that produce this change. 

 The same remark may be made for many 

 of the experiments carried on with the 

 sparker as the source of the ultra-violet 

 light, in the examination of these mineral 

 substances. On the other hand, this hy- 

 alite neither fluoresced nor phosphoresced 

 when exposed to the magnesium light. 

 Roentgen rays or radium, in this respect 

 behaving like the minerals from Mono 

 Lake; no hyalites from other localities 

 responded to any of these activities. 



8. By the action of ultra-violet rays a 

 number of fluorites both phosphoresced and 

 fluoresced; some phosphoresced and did 

 not fluoresce; some fluoresced and did not 

 phosphoresce ; and some did neither. Fur- 

 ther, their color had apparently no influence 

 in determining this result; it can not be 



the fluorine or alkaline earth present that 

 accounts for this variation, as artificial 

 preparations gave negative i-esults. It is 

 more probably the presence of rare earths 

 like yttrium and ytterbium. (A paper on 

 this will appear.) 



9. Chlorophane has long been known as 

 a mineral very easily rendered luminous by 

 heat. By some authorities it is stated, 

 a century ago, that it was almost always 

 luminous. This variety of fluorspar is 

 found with other fluorspars— sometimes as 

 a vein of purple between veins of green 

 fluorspar. It proved very responsive to 

 the ultra-violet rays. A variety from 

 Amelia Court House, Virginia, became sud- 

 denly luminous from the heat of the hand. 



This luminosity was lost upon further 

 heating (about red heat) but the phosphor- 

 escent properties were restored in a mea- 

 sure by exposure to the Roentgen rays. 

 Trowbridge has observed this with other 

 fluorites (see above). The exquisite colored 

 fluorescent properties Avere not regenerated 

 however. Chlorophane is pyroelectric by 

 attrition, and this peculiarity distinguishes 

 it from the ordinary fluorites. 



10. It was noted that gypsum from 

 Sicily, when submitted to ultra-violet light, 

 was from two to five times as responsive as 

 specimens from Bavaria and other local- 

 ities. 



11. It was found that those topazes which 

 had lost the sherry color— the tint so fleet- 

 ing that some of the museums have been 

 led to protect them from the light— showed 

 no distinct phosphorescence with ultra- 

 violet rays, while the unfaded crystals of 

 that color responded, but no others. 



12. Wernerite from New York phosphor- 

 esced, while specimens from foreign sources 

 did not. Many apophyllites and calamines 

 gave no response whatever. 



13. Pectolite proved an exceptionally in- 

 teresting mineral. Every specimen that 

 was exposed to the ultra-violet rays showed 



