HUDLESTON AND DAVIS : EXCUKSION. 
127 
represents the draiuage of a hollow originatiDg in the high ground 
towards Belmont. The ground is chiefly made up of the Middle 
Permian Marls, and it is to the salts in these marls that we must 
trace the impregnation of the Dropping Well Waters. 
The following is an old analysis of the waters of the stream : — 
Grains to the gallon. 
Carbonate of soda ... ... ... .,, .., G 
Carbonate of lime ... ... ... ... ... 23 
Sulphate of lime ... ... ... ... ... 132 
Sulphate of Magnesia ... ... ... .. ... 11 
Total 172 
The deposit upon the sponges and other substances which are 
placed at the well, consist almost wholly of carbonate of lime, the 
amount of sulphate of lime deposited being very small indeed, not- 
withstanding the very large quantity found in the water. Mr. 
* Simpson, the lessee of Long Walk and the " Mother Shipton Inn," 
recently possessed himself of some magnificent specimens of 
sponges, which, from their porous nature, show the action of the 
deposit remarkably well. Some time was spent by the party in 
examining the caves in the valley of the Nidd, and in Hstening to 
the stories of St. Robert and of Eugene Aram, after which they 
crossed the river at Grimbald Bridge and finally took leave of the 
magnesian limestone where the romantic Grimbald Crag is ter- 
minated by a small fault on its western side. Plumpton Rocks, a 
mile and a half distant, were next visited. These rocks are 
interesting to geologists as having been regarded in former days 
as forming a portion of the Permian series, equivalent to the 
German " Rothliegende." The researches of the Government 
surveyors in recent years have shown that these rocks are really 
nothing- more than the highest beds in this district of the mill- 
stone grit series, which are unconformably overlaid, as already 
noted in the Nidd Valley by the Permian Rocks, The extraor- 
dinary action of the weather upon these rocks afforded matter for 
endless speculation. In this respect the Plumpton Rocks, which 
are the same bed of grit which forms the Brimham Rocks at a 
