Extracts from the Minute Book of the Geological Society . 619 
1819, April 2. 
An account of the Limestone of Plymouth, by the Rev. Richard 
Hennah, Chaplain to the Garrison of Plymouth, was read. 
The bed of limestone which occupies that part of the vicinity of 
Plymouth that lies toward the sea, between the actuaries of the 
Plym and Tamar, rises to an elevation of about 100 feet above 
highwater mark, as appears from an accurate measurement of the 
Hoe, a hill sufficiently central to afford a fair criterion of the general 
height of the adjoining eminences. The limestone dips towards 
the south or south-west, and runs in a direction nearly east and 
west. Its breadth from north to south does not exceed the distance 
of from a half to a quarter of a mile. Its length from east to west 
extends to many miles. 
Towards its western extremity in the Dock-yard, and at the 
Devil’s Point, we perceive it sinking into the sea ; it re-appears, 
though only for a little space, below Mount Edgecombe, and behind 
the passage-house at Cremhill ferry ; after which I do not appre- 
hend that it is any where visible towards the west, except in a few 
confined patches or rocks. From the Dock-yard, eastward, its course 
may be observed uninterruptedly as far as the Plym, and across that 
river into the parish of Plymstock, from whence it may be traced, 
appearing occasionally, to a considerable distance. 
The limestone, wherever I have been able to observe its contact 
with the rock beneath it, rests upon clay-slate. The calcareous 
strata adjoining the north side of the road over Stonehouse-hill, 
immediately before arriving at the quarries and lime-kiln at Mill 
Bay, are interrupted in a remarkable manner by the clay-slate 
which is protruded upwards through the limestone. 
