34 TRANSACTIONS OF WAGNER FREE INSTITUTE OF SCIENCE 
у A COMPARATIVE STUDY OF RADIOACTIVE MINERALS 
blurred, so that the anomalous result is simply due to the opportunity afforded 
the rays to penetrate the metal. The exposures varied аз indicated at the top 
of each column, and development was conducted as described above. If they 
serve no other purpose, they at least call attention to the photographic activity 
of quite a number of mineral species. 
SYNOPSIS OF DATA, 
COMPOSITION. | ELecrroscopic TESTS. | PHOTOGRAPHIC TESTS, 
МАМЕ, | LOCALITY. | | | 
| pu | n | Time. | Activity, Reading. Activity. 
| | | | 
Uraninite.......| North Carolina. | 80 | kaye 15.2 1.00 5.0 1.00 
Gummi North Carolina. | 75 | M 19.7 9077 4.0 о.8о 
Thorianite......| Ceylon. 10 70% 25.1 0.61 3.0 0.60 
Uranophane . ...| North Carolina. | 65 1 | Л 0.55 3-5 0.70 
ee Norway. К, КЛ 60.3 | 0.25 nl 0.30 
Fergusonite..... Norway, 2 i 81.5 0.17 1.5 0.30 
Carnotite (10 %)| Colorado. 5 | 92 99.1 0.16 1.0 0.20 
Samarskite...... | North Carolina. f^ NC D VEA IIO.O A Md Tue 0.20 
Sipylite | Virginia, 4 : 158.0 0.10 | 0.75 bits 
Xenotime | Norway. P 2 175.0 | 0.00 0.75 0.15 
Euxenite | Norway, 10 y 200.0 0.08 0.80 0.16 
Samarskite | Norway. 10 2 215.0 0.07 0.50 0.10 
Aeschynite...... Norway he i5 | 225.0 0.06 0.50 0.10 
Monazite....... Virginia. We e dies 0.2 0.05 
MOTOS... deseos | Virginia. | 2 «Jn 400.0 0.04 0.25 0.05 
Aue и | Virginia. MO NA I 1200.0 0.01 0.10 0.02 
BIBLIOGRAPHY. 
Crookes, W.: Radioactivity of uranium. Proc. Roy. Soc., 1900, 66, 409. 
PISANI, F.: Examen de plusiers minéraux au point de vue de leur radioactivité. Bull, 
Soc. Min. Franc., 1904, 27 58. 
BARDET: Essai de mesure de l'activité photographique de certains minéraux. Bull. 
Soc. Min. Franc., 1904, 27, 63. 
Wuerry, E. T.: Radioactive minerals found in Pennsylvania and their effect on the 
photographic plate. J. Frank. Inst., 1908, 165, 59. 
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