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the parent rock, of which they form a part, lie the three isolated 
masses of Limestone which form the subject of the present paper. 
The first and smallest of the three, known as the Tor rock, 
rises abruptly from the edge of the Mells Lake at Lower Vobster, 
attaining a height of fifty feet, and presenting a striking feature 
in the charming scenery of Mells Park. In shape it is oval, 
measuring about 190 yards from north to south, and 130 yards 
from east to west, its distance from the nearest outcrop of the 
same strata in the Mendip range being 850 yards. It is closely 
surrounded by ordinary Coal Measures hales, and the relation 
between the two is, generally speaking, hidden by the soil. On 
the south side, that is towards the lake, the bedding of the Lime- 
stone can be distinctly seen, the dip being uniformly to the north- 
west at a high angle. On the opposite side, however, the dip is 
tothe 8.West, at an angle of 45 degrees, 
The second and by far the most extensive of these outliers 
occurs at Upper Vobster, 250 yards to the north of the Tor 
rock, and 1,300 yards from the nearest Limestone in the Men- 
dip range. It is an irregular oblong figure, extending from the 
Bilboa coal yard westward to near Page house, its extreme 
length being 1,150 yards, and the average width exposed about 
300 yards. It can be well examined in a quarry at the Bilboa 
cross-roads, but the finest section of it is obtained in a deep 
cutting on the Newbury mineral railway, which intersects it from 
East to West, terminating at the Upper Vobster Limekiln. The 
prevailing line of strike appears to be East and West, but at 
some points the beds dip North, and at others South; in fact, 
they dip in all directions and at all angles, presenting every 
appearance of confusion and disturbance. 
Here, as at Tor rock, the exact junction between the Lime- 
stone and the surrounding rocks is a little uncertain, but the 
outline shown on the diagram is approximately correct. On 
the South and West it is flanked by Coal Measure shales, but 
its northern margin is hidden by a thin covering of Inferior 
