291 
This is especially the case in the neighbourhood of Bilboa, where 
partly from its broken up condition, and partly, it may be, from 
its contact with the Inferior Oolite, the Limestone presents a very 
peculiar appearance. 
After carefully examining all the three patches, I have been 
unable to discern in situ either Millstone Grit, on the one hand, or 
‘Mountain Limestone Shales on the other; but, in a field to the 
north of Upper Vobster Limekiln, I have found on the surface 
numerous stray blocks of Millstone Grit, not distinguishable from 
the same beds in Mells Park; and it is quite possible, therefore, 
that there may be portions of the grit in situ not far distant. 
Historical Notes.—Although seldom treated of at any length, 
these Limestones have been noticed by geological writers from a 
very early date. In an able paper, on “the South Western Coal 
District of England,” contributed to the Geological Society, by 
Dr. Buckland and the Rev. W. Conybeare, in the year 1824, they 
were carefully shewn in both plans and sections ; their origin 
being attributed to upthrow faults. While differing from those 
writers on this particular point, I cannot pass on without expressing 
my admiration of the marvellous industry and general accuracy 
exhibited in the paper referred to; a paper full of useful infor- 
mation, and which foreshadowed much that has been written on 
the district since their day. 
Probably, next in order, came the Geologists of the Ordnance 
Survey, who mapped the Luckington and Upper Vobster Patches, 
but the Tor rock escaped their notice. In their map, and a 
corresponding section, they appear to have arrived at much the 
same conclusion as Messrs. Buckland and Conybeare, viz. : that 
these areas of Limestone have been lifted up through the coal 
measures by the agency of faults. 
About this time Mr. Sanders published his map, in which he 
added the Tor rock patch to the two previously observed, but he 
does not appear to have committed himself to any theory on the 
subject. 
