56 REPORTS ON THE STATE OF SCIENCE. 
acted as seismoscopes, they quickly fell into disuse. To record unfelt 
teleseismic motion where the periods varied from about five to thirty 
seconds, I last year made the following experiment :— 
A cylinder of lead 10 inches in length and % inch in diameter, 
weighing 45 lb., Was suspended as shown in the accompanying sketch. 
From one end of the cylinder a light deal rod projected upwards. At its 
; “ely RE IR eee aS 
upper end this engaged a light aluminium lever carrying a glass style 
resting on a drum covered with smoked paper. This multiplied the 
motion of the rod, which was 8 feet 2 inches in length, 83 times. By 
this arrangement the equivalent of a rod 27 feet in length was obtained. 
The period of this pendulum with the style resting on the smoked paper 
was 0°6 second, or from eight to thirty times the period of the ground. 
During twenty-two days commencing November 26, although there 
were several earthquakes, two of which were distinctly large, no record 
was obtained. Possibly the multiplication was too small. 
VI. On a possible Synchronism between Seismic Activity in 
Different Districts. 
In the Report for 1908, p. 64, I pointed out that since 1902 
seismic activity on the two sides of the North Pacific had fluctuated 
similarly. For example, registers show that when large earthquakes had 
been numerous on the East side of the Pacific they had also been 
numerous on the West side. To extend this inquiry, | have drawn up 
the following table giving the number of destructive earthquakes which 
have occurred between 4.p. 1000 and a.p. 1650. They are grouped in 
periods of fifty years. Columns A, B, C, and D respectively refer to 
Japanese, Chinese, European, and Italian records. The letter ‘ a ’ indi- 
