February, 1918. ] Annual Address. XXili 
piece of smoked glass. Analysis of the returns received from 
each of the three sources during the years 1914-1917—calling 
the sources A, B and C respectively, A being the seismoscope— 
shows that the following number of shocks were recorded :— 
by A (seismoscope) Ne oo ay 
>. - a AF alee 
woe z ; lpia sg 
of these only seven shocks are common to all three sets of re- 
turns ; fifteen are common to A and B only, ten to B and C only 
and one to Aand Conly. The seismoscope recorded during the 
four years 29 shocks not recorded by either of the human sources, 
while the two latter recorded, respectively, 27 and 23 not felt by 
the others. At first sight this would seem to point to the 
returns being very unreliable; but, in a place like Shillong, 
where slight shocks are common, one person frequently feels a 
shock not felt. by his neighbour, and in spite of the discrepancies 
in the three sets of returns, I should not be inclined to discard 
the system; but it cannot be regarded as more than a very 
rough indication of the relative frequency of shocks. A sum- 
mary of the records of the years 1909-1917 shows that the most 
active centres lie in the elbows where conflicting mountain 
trend-lines meet, in Assam on one side and in the North-West 
Frontier Province on the other, while the Peninsula has hardly 
been disturbed at all. The neighbourhood of the main boundary 
it originated in a faulted region to the east of Maymyo, in the 
Nothern Shan States, and appears to have resulted from sub- 
terranean disturbance along or near an old fault-plane, the 
Kyauktan fault. Other severe earthquakes have originated in 
the Irrawady valley, which follows another zone of instability. 
On the west a severe earthquake occurred at Bellpat between 
Jacobabad and Sibi in 1909; here, again, disturbance took place 
Opposite a sudden bend in the mountain trend-lines. 
r and intensity. A major shock is the result of relief of 
Strain which has been accumulating for a long time, and it is a 
