60 REPORTS ON THE STATE OF SCIENCE. 
Bidston, Shide, Kew, and Edinburgh. These stations are respectively 
situated on sandstone, chalk, alluvium, and volcanic rock. In the follow- 
ing table we reproduce records of frequency as given in the Report for 
1902 and 1903, together with records for 1908 :— 
Year Bidston Shide Kew | Edinburgh 
1901 (11 months)... 133 107 7 rt 94 
Set a 228 168 0 re i 
| 44 
| 
1908. : : : 105 114 49 
We may add that in 1908 Paisley recorded forty-eight shocks—i.e., its 
number of records closely accorded with those obtained at Kew and. 
Edinburgh. The subsoil at Paisley is clay (‘ B.A. Report,’ 1905, p. 89). 
At all these stations similar horizontal Milne pendulums are in use, 
but the adjustment of these have from time to time only been approxi- 
mately similar. In 1908 at Shide 1 mm. displacement of the outer end of 
the boom corresponded to a tilt of 0”-44. The corresponding values 
at Kew, Bidston, and Edinburgh were 0”°56, 0°53, and 0”°53, or 
0”54. The table shows that the Shide instrument, with the greatest 
sensitiveness in 1908, gave the greatest number of records. The differ- 
ence between it and Bidston, however, is only nine. If we consider 
the latter half of 1908 only, we find that Bidston had sixty-one records 
and Shide had fifty-seven—i.e., the result is reversed. In 1901 and 
1902, when the Bidston instrument had for twelve months greater sensi- 
tiveness than the one at Shide, the number of records at the former place 
greatly exceeded that at the latter. 
The very marked difference in the number of records obtained at 
Bidston and Kew, Edinburgh and Paisley, does not seem to depend upon 
differences in sensitiveness of the instrument, inasmuch as these differ- 
ences are very slight. If we except Edinburgh and Bidston, which are 
founded on hard rock, there is a great difference between this and the 
softer materials which act as foundations for other stations. 
IX. Luminous Effects obtained from Rock Surfaces. 
In the ‘ British Association Report ’ for 1907, pp. 87-91, a long series 
of experiments are described which apparently show that from time to 
time surfaces of chalk and killas affect a photographic surface in the 
same way it is affected when exposed to light. Several control experi- 
ments are described, and the conclusion arrived at was that the markings 
on the photographic films were not due to radio-activity, but they might 
be due to a very feeble brush or glowlike electrical discharge. Since 
the publication of the above an attempt has been made to determine 
whether micro-organisms play any part in the phenomena observed. 
With the assistance of my friend, Dr. R. C. Brown, M.D., of Parkhurst, 
cultures were made from scrapings from the surface of the chalk, in 
front of which the cylinder, covered with bromide, had been placed. 
This was underground. Cultures were also made from scrapings taken 
from the chalk outside. Micro-organisms were found in both. These 
have been exposed to a moving photographic surface similar to that 
used in the pit, but they gave no evidence of luminosity. Dr. M. H. 
Gordon, M.D., suggests that before excluding a biological factor special 
media should be tried. This we hope to do. 
