INTRODUCTTON. 
5 
A natural result of thiff habit of keeping local timo in each place 
is that it is practically never kept correctly. There is generally 
no recognized public clock which keeps accurate local time. 
Owing to the fact that there are exceedingly few -pucca build- 
ings over the area which was seriously affected and to the fact that 
Such as do exist vary greatly in nature, and strength to resist shock, 
it was found to be impossible to jnap isoseists according to the 
Kossi-Forel scale. Most of the area where the earthquake was 
violent enough to damage all. or nearly all. brick buildings, con- 
sists either of jungle-covered hills such as the Hill Tippera area, 
or of low-lying land such as that seen in south Sylhet, practically 
all of which was under water at the date of the earthquake. Brick 
buildings are limited therefore almost entirely to railway buildings, 
and to those in isolated placef^ such as Sylhet, Maulvie Bazar, Habi- 
ganj, Kishorganj, Brahmanbaria, Agartala, etc., and the buildings 
and factories of the tea estates in the valleys of south Sylhet. Con- 
sequently I have mapped isoseists on the plan adopted by R. D. 
Oldham in his iiavestigation of the Great Indian Earthquake of 
1897. In that investigation he found it impossible to attempt to 
define more than seven degrees of intensity lying within their isoseists, 
which he defined as follows : — • 
(1) the first isoseist includes all places where the destruction 
of brick and stone buildings was practically universal ; 
(2) the second, those places where damage to masonry or 
brick buildings was universal, often serious, amounting 
in Some cases to destruction ; 
(3) the third, those places where the earthquake was violent 
enough to damage all or nearly all brick buildings ; 
(4) the fourth those places where the earthquake was universally 
felt, Severe enough to disturb furniture and loose objects 
but not severe enough to cause damage, except in a few 
instances, to brick buildings ; 
(5) the fifth, those places where the earthquake was Smart 
enough to be generally noticed, but not severe enough 
to cause any damage ; 
\6) the sixth, all those places where the earthquake was only 
noticed by a small proportion of people who happened to 
be sensitive, and being seated or lying down were favourably 
situated for observing it. 
