president's address. 
13 
any earthquake in England within living memory, so that 
perhaps we are justified in making much of it. We have had 
the pleasure of seeing photographs of some of the effects of 
the earthquake, taken within a day or two of its occurrence, 
which clearly showed the direction of the wave which passed 
through the ground. I have only seen the record of one 
observation which gave any idea of the amount of vertical 
displacement. This was, that a man was enabled at the 
moment of the shock to see through opposite windows in his 
workshop from the ground outside, and measurements showed 
that he must have been lifted at least 2ft. 9in. Another man 
describes the appearance of the movement over the level salt 
marshes as like the wind passing over a field of corn, only 
quicker. A curious effect of the movement of the strata was 
the increase in the town water supply of Colchester. For some 
time previous the supply had been diminishing, so that the 
suction pipe, which had been already somewhat lengthened, 
was about to receive another addition, but immediately after 
the shock the water had risen seven feet in the wells, enabling 
about two hours more supply daily to be given, at the same 
cost of pumping. Whether this increased supply has continued 
to the present time I have not heard, but all the wells in the 
district seem to have been similarlv affected. If the failing of 
the supply was produced by the opening by subterranean 
movements of cracks which tended to drain the wells, the 
closing of these cracks by the settling down which produced 
the earth wave would very likely permanently increase the 
available supply. If, on the other hand, the earthquake 
opened cracks in the chalk so that the water flowed down 
more freely, as is suggested by Mr. de Eance, the increased 
flow would probably be only temporary. 
As to the limits over which the shock was felt, it is 
recorded from South Yorkshire, Boulogne, and Street, in 
Somersetshire. A rather curious suggestion has been made 
as to the relation of this shock to the floor of Palaeozoic 
rocks which is known to underlie not only the Midland 
district but the Thames valley and the Eastern Counties; 
deep borings having reached them in Harwich, near the 
centre of the disturbance, London, and at various points 
about due North and on to Northampton, while they come 
to the surface in the Mendip Hills south of Bristol, and in 
patches across the Midland and North Midland counties. 
Now it is almost certain that the shock originated far below 
the upper surface of these hard and compact rocks, and 
shocks of any kind are naturally much more readily propa¬ 
gated in such rocks than in the looser and softer strata of 
