34 
MR. H. B. WOODWARD ON THE EARTHQUAKE OE 18S1. 
the district chiefly affected, the stream valleys, according to 
Mr. G. H. Kinahan,* have exercised some influence in arresting or 
modifying the course of the earthquake-Avave. 
Dr. H. C. Sorby, Avho examined the area where the disturbances 
had been greatest, an area of about eight miles long by six broad, 
has referred to the irregular nature of the destruction Avrought. 
He infers that the shock came up from beloAv soineAvhat obliquely 
from south-east under East Mersea, Avhere scarcely any damage has 
been done, and Avas most violent along the stroke of the Avave at a 
distance of about three miles to the north-Avest. This, and the 
general character of the area of chief disturbance, point (in his 
opinion) to some very irregular distribution of hard rocks at a 
considerable distance beloAV the surface.t 
It AA\as suggested by Mr. J. T. Barton, of Northampton,^ that 
the area affected by the earthquake Avas that beneath Avhich the 
Paheozoic rocks occur comparatively near the surface in the south- 
east of England. This may of course be an area of subterranean 
disturbance, but it must be remembered these same rocks come to 
the surface in the Avestern and midland counties (ChaniAvood 
Forest, etc.), and the area in question does not appear to be more 
subject to earthquakes than other portions of the British Isles. 
As Dr. Taylor has pointed out,§ the disturbance Avas distinct in 
character from the shocks AA'hich precede or attend Amlcanic eruptions, 
and AA'as probably of a kind Avhich produced many of our faults, of 
Avhich he instances examples in Suffolk and Essex. 
Some have likened faults to the crackings of old furniture due to 
changes of temperature, and no doubt many of our disturbances arc 
due to the drying, consolidation, and shrinkage of the rocks. 
[Mallet, indeed, thought that Amlcanic action resulted from the heat 
induced during the contraction of the earth’s mass : but his aucavs 
are not generally accepted. Probably Ave shall not be far Avrong if 
Ave attribute the recent earthquake in Essex to one or more 
subterranean rents produced by shrinkage, aa’IucIi led to no material 
shifting of the rocks, and Avhich, oAviilg to the tenacious nature of 
the sub.soil at Colchester, chiefly London Clay, did not manifest 
itself in any conspicuous manner at the surface. 
* ‘Nature,’ June 5th. J ‘Standard,’ April 24tli. 
t ‘Nature,’ May 2yth. § ‘East Anglian Times,’ April 23rd. 
