Gas from Crude Petroleum. — 503 
of the emanation from radium follows may be expressed by 
the equation 
L= Ta 
where I, is the value of the conductivity at any given time, 
I, the value after an interval of ¢ seconds, e the base of a 
logarithms, and X a constant. By using this equation the 
values of 1/X have been determined for a number of pairs of 
the readings given above, and the results are tabulated in 
column 1 of Table II. These values of 1/A, which give a 
mean of 557,000, show a marked increase with ie time, 
and cons sequently indicate that the rate of decay is slower 
than that required by the law given above. This departure 
from the law of decay is probably due to a slight trace of a 
more persistent radioactive substance in the gas than the 
emanation, and will be referred to later. 
In column 2 of Table IT. is given a set of Strutt’s readings 
for the ionization due to the radioactive gas in mercury, and 
in column 3 the values obtained by Adams with the active 
emanation in Cambridge tap-water. The calculated values 
of 1/X are inserted in both cases, but do not show the increase 
exhibited by the numbers in column 1. The averages of the 
three series of values of 1/A given in Table IIL., together 
with the mean values of the same constant obtained by 
Mme. Curie* and by Rutherfordt for the decay of the 
emanation from radium, as well as the mean value calculated 
from Himstedt’s results for the radioactive gas in water, are 
collected in Table II]. The values show a very close agree- 
ment, and lead to the conclusion that the active gases from 
petroleum, spring-water, and mercury are very probably 
identical with the emanation from radium. 
TaseE III. 
Experimenter. Source of Emanation. Value of 1/X. 
Pehime: Curie  2...4-..213 Radium. 497,000 
dep shut herford.5s...3.st.va.c. Radiun. 463,000 / 
PSD oan coeds hues cand Mercury. | 423,000 | 
De NCATE | cu. n'saniceitinn aden Tap-water. 425,000 
Pestimsted by Ol Ji6. 2508 a Water. | 491,000 
REMELUNLONS 26 .cc0 2. eater Petroleum. | 557,000 
| : | 
| 7 
ae his aaierineene eek rs water fr om re C araibridge 
mains, Professor J. J. Thomson found that when the water 
* Théses prés. a la Faculté des Sci. de Paris, 1905. 
' Phil. Mag. vol. v. (April 1903) p. 445. 
