430 Hidden — Mineral Research in Llano County, Texas. 



of the ignited powder agreed with the sum of the C0 2 and H 2 

 found. Approximate molecular weight determinations of the 

 earths, separated into two portions by potassium sulphate, gave 

 335 for the cerium group and 226 for the yttrium group, the last 

 being the molecular weight of yttria itself. It is certain that 

 some, if not all, of the ferric oxide reported is foreign to the car- 

 bonate, but how much it is impossible to say. The calculated 

 ratios lead to nothing definite, except that the white mineral 

 appears to be a hydrous basic carbonate, but whether a double 

 carbonate of the rare earth metals and glucina, or a mixture, there 

 are no present means of deciding." 



Radio-activity. — All the minerals of Barringer-Hill have 

 been experimented with to ascertain the extent of this form of 

 energy present. As early as September, 1902, the writer was 

 at work upon it and had then made successful radiographs 

 from specimens mined at this locality as far back as 1889. In 

 the order of their activity, as shown by their own radiographs, 

 I here mention the species in which the phenomena were 

 observed. 



Nivenite (which is a very soluble variety of nraninite) 

 exhibited the most pronounced radio-activity, and beautiful 

 radiographs were made by placing the mineral outside of a 

 photograph plate-holder. Better ones were procured by plac- 

 ing the mineral in direct contact with the sensitive plate — 

 " Cramer's X-ray." Twelve hours exposure, in the dark, 

 developed very good interference figures ; but with forty-eight 

 hours, and np to live days exposure, the outlines became as 

 sharp almost as are shown in photographs by sunlight. 



Machintoshite (which is the parent mineral of thoro-gum- 

 mite) was next in the amount of radio-activity exhibited. Jt 

 showed about half the intensity of nivenite when compared 

 with equal exposures of the two minerals, side by side, on the 

 same plate. 



Positive evidence of the occurrence, within mackintoshite, 

 of little crystals having even a higher radio-activity than that 

 shown by the nivenite, was proven by developing the plates 

 used with direct contact. Little bright spots appeared in 

 the field where the less energetic mackintoshite had touched it, 

 and a dull gray border (made by the thoro-gummite coating) 

 united to make a radiograph having three degrees of intensity 

 from one mineral specimen. With a strong lens these bright 

 spots, possibly due to a new species, could be identified upon 

 the flattened surface and they were noticed to be very unlike 

 the surrounding mackintoshite. They resembled galena in 

 color and in metallic luster and were quite evenly distributed 

 over the several flat sections examined. Mackintoshite has 

 given evidence, in thin sections, of being translucent, and of 

 a very dull green color by transmitted light, but as the purest 



