216 REPORTS ON THE STATE OF SCIENCE, ETC. 
During February, March, and April some 150 records were taken, but beyond 
the average amplitude and period there was no satisfactory agreement. 
In the case of 1920 experiments the outlying station was two miles distant 
in a direction 17° West of North. 
The Sutton position lies 8:2 miles distant and 66°°5 East of North. Solihull, 
10°6 miles, and 134° East of North. 
Sutton is 10°6 miles from, and precisely due North of, Solihull; only 17° from 
parallel to the two-mile line of 1920. 
It seems remarkable that the microseisms, so perfectly reproduced at a 
distance of two miles, should so completely change in eight to ten miles. 
it is worthy of note that the two near positions used in 1920 were situated 
upon a narrow outcrop of Permian Sandstone and Marls, whereas Sutton and 
Solihull are located upon a bed of Keuper Marls, and a geological fault divides 
them from this Permian strata. 
If this discontinuity in the underlying rocks is responsible for the change 
shown in the microseisms, it might be possible to locate fault lines in this way. 
The earthquake which occurred South of Mexico on March 28 was recorded 
on the West Bromwich and Sutton machines (Solihull not running). The 
seismograms were quite similar in all the main features, any differences were 
in the tiny superimposed waves (probably microseisms) and occasionally small 
differences in amplitude, the excess being sometimes on one machine and 
sometimes on the other, notwithstanding the damping ratio was 20:1 and the 
periods the same. 
er 
