190 
WILLIAM SMITH I HIS MAPS AND MEMOIRS 
encouraged them to proceed ; the channel under my direction was 
deepened four feet, when the discharge became for some time fifty or 
sixty hogsheads per hour. 
" Suspecting from an intermediate and subsequent diminution 
that we had drawn ofi a confined stock of water, and that the regular 
run of the spring at the end of a dry summer might not be found 
sufficient, I suggested the propriety of damming up the produce of this 
spring for summer use, as the previous supply was more than sufficient 
for the town in winter. 
" The circumstances were favourable for the purpose, as there 
was no other known issue of water from the rock in that hill, which is 
about a mile long, narrow on the top, and insulated in all the upper 
part of its stratification. The same rock is not opened or known 
anywhere else on these hill sides, but in a deep valley which separates 
the insular hill from the main and higher hill of Falsgrave Moor. In 
the upper end of that valley a spring was opened several years since 
in the same kind of rock, and was brought with a declivity of thirty 
or forty feet round the south end of the insulated hill, near to and high 
enough to run into the opening made to the new spring. This was- 
sufficient to prove the general rise of the rock westerly in the base of 
the insular hill, and beneath an isthmus connected with the main ridge 
of Falsgrave Moor and Seamer Beacon. The rock in which the spring 
was found is a yellowish fine grained crumbly sandstone, in thick beds, 
with open irony joints, the same as in the cliff south of Scarborough 
Spa. From the quantity of carbonaceous matter in it, it is here called 
' coaly grit.' This sandstone, with its overlying and alternating clays, 
is analogous in position to the clay and sand and sandstone between 
the cornbrash and great oolite rocks. At the depth of ten feet the rock 
was found covered with a regular clay about four feet thick ; on this a 
mark of coal, and a thin bed of hard stone full of imperfect vegetable 
impressions ; and up to the surface a very tenacious slidden clay. The 
rock was found, by boring through it, to be ten feet thick, lying on 
clay. The channel excavated up to the spring about thirty or forty 
yards long and fifteen feet deep, at the upper end was entirely in a very 
tenacious clay partly diluvial, with a few rounded stones in it deeply 
covered by slidden clay. Within four feet of the edge of the rock lay 
gravel (deeply covered also with slidden clay), consisting of large 
and small boulders of whinstone, granite, mountain-limestone, etc., 
