10 LOWER COAL MEASURES BETWEEN 
observed here by me. (I may mention, by the way, that 
there is here a fine section on the top of the sandstone of 
boulder clay, with eroded hollows filled up with gravel, and 
with large angular fragments of sandstone, similar to that 
(in situ) beneath it, resting on the clay under the gravel.) 
Leaving this and returning to the Holywell Road, we come, 
soon after passing Glyn Abbot, to a thick mass of thin shales ; 
and here a level has been driven into the hill-side for the 
purpose of getting the aluminous limestone, locally known as 
cement stone. As these workings have not proved so profitable 
as those further on, and there is less material for examination, 
it will be well to leave them and go on till we come to a road 
turning to the left down a steep hill’ At the bottom of the 
valley, to the right of the road, the cement beds are being 
worked vigorously, and a large quantity of shale has been thrown 
out in the course of the operations, which will well repay a 
careful examination. These beds, though apparently much 
lower, are really at almost exactly the same level as those on the 
Holywell Road. The dip in both cases is difficult to make out, 
but seems to be S. E. at 18° or 14°. 
The cement stone itself occurs in two beds, about 1din. 
and 18in. thick respectively, and separated by a bed of shale. 
They are worked by means of a level or gallery driven along 
their course. The stone, which contains a large proportion 
of alumina and comparatively little carbonate of lime, is burnt, 
and produces a lime similar in its properties—though by no 
means equal in quality—to the celebrated Portland cement, 
and must not be confounded with the so-called Aberdo lime, — 
which is obtained from the quarries on the slope of the hill, 
above the Holway Mine, on the other side of Holywell. These 
last belong to the upper measures of the carboniferous lime- 
stone, and produce a hydraulic lime which is extensively used 
for building in water, but is only worth about 25/- a ton; 
while the cement, when burnt and ground, is worth about 42/-. 
The cement beds appear, from their fauna and flora, to belong 
rather to the coal-measures proper than even to the millstone- 
