118 
HUDLESTON : EXCURSION. 
the drainage area of the river Nidd, appearing in moderate eleva- 
tions at Plompton, but rising to a height of nearly 1,000 feet 
above sea level in Brimham Rocks. 
It is these Plompton Grits which the older geologists were 
disposed to regard as the equivalent of the " Rothliegende," appa- 
rently from a general impression that the base of the Permian 
should be rei^ in order to correspond with the beds in Grermany. 
The Red Rock of Rotherham, now known to be a member of the 
Upper Coal Measures, was for a long time classed with the 
" Rothliegende," in deference probably to the opinions of Phillips 
and Sedgwick. It is hardly necessary to repeat that, throughout 
Yorkshire, the unconformity of the true Permian to all members 
of the Carboniferous is one of the most marked features in the 
stratigraphy of the country. This svas recognized by Phillips, and 
yet he persisted in regarding the Plompton Grits as " Rothlie- 
gende." Mr. Binney seems to have been the first to suspect, 
from the character of the few fossil plants occasionally found in 
these beds, that they were not of Permian age, whilst later on, 
Mr. Clifton Ward and the Government Surveyors succeeded in 
establishing their true strati graphical position as members of the 
Millstone Grit. 
The coloration of these beds has also been the subject of much 
controversy. The causes which have produced rock-stainiug in 
the underlying beds, at the junction of the Permian and Car- 
boniferous of these parts, may not be all of the same nature. Mr. 
Ward thought that the prevalence of a red colour in the under- 
lying rock might be due to some action exerted by the Magnesian 
Limestone on the percolations ; and this notion has attained a 
certain degree of acceptance, though it is difficult on chemical 
grounds to see exactly what the nature of such action can be. 
Moreover, it is quite an open question whether there really is any 
increase of red colour in the grits which lie beneath the Magnesian 
Limestone ; indeed, that there is any such increase is denied by 
Mr. Lucas, who, as before mentioned, was inclined to attribute 
