5 12 
Mr. Buckland on the 
unconformably strewed over it ; but, from the similarity of colour 
and substance in the beds composing these two formations, it is 
impossible to trace accurately the precise limits of each, the only 
sections being at a few quarries where the cornstone is extracted 
from the old red sandstone, to be burnt to lime.* 
* I have thought it expedient to apply the local term cornstone to a kind of breccia, 
known generally by that name in Herefordshire, where it is found perhaps more abun- 
dantly than in any other English county. It occurs in the form of subordinate strata in 
the old red sandstone, and its dip is always conformable to that of the marl or sandstone 
beds between which it lies. It is composed of marl and marlstone, filled with concre- 
tions of compact limestone, presenting the fracture and colour of mountain limestone, 
and varying in size from that of a pea to blocks of many tons, and sometimes spread- 
ing itself out into thick and compact beds, to the almost total exclusion of the marl. 
The knotted characters which these concretions assume resembles that of a conglo- 
merate animal gland, and the small acini or kernels of which they are composed 
usually separate under the blow of the hammer. The transfusion of their outer por- 
tions and projecting points into the substance of the marlstone, shows them not to be 
fragments resulting from the destruction of any older rocks of transition limestone, 
but concretions of contemporaneous origin with the marlstone, in which they are imbedded. 
The marlstone itself also has occasionally a similar tendency to form concretions, in 
which the sharpness of the angles shows it to be quite impossible they could ever have 
been submitted to the process of rolling ; and the appearance resulting from the union 
of the calcareous concretions with the marlstone, is that of an angular breccia, resembling 
in structure the vert antique, and some of the Sienna and African marbles ; in which 
the fragments have never been submitted to the process of rolling. 
From the tubercular knotted condition of these concretions, and the non-appearance 
in them of any traces of organic remains, we derive a character of high importance in 
distinguishing cornstone from a calcareous conglomerate which very nearly resembles it 
in the new red sandstone; the fragments in the latter case being most frequently 
rolled portions of transition and mountain limestone, which can be identified by their 
organic remains, and of which various truncated sections are presented on the circum- 
ference of the fragments. In those cases w here they have been rolled only to a short 
distance from their native bed, the angles of these fragments have undergone a propor- 
tionally small degree of attrition. They occur sometimes loosely mixed with other 
pebbles and sand, and sometimes united into a firm breccia by a calcareous cement which 
is highly charged with magnesia, and which in the absence of the pebbles often enlarges 
itself into extensive beds of dolomite. This calcareous conglomerate occurs subordinately 
among the mixed pebble beds of the new red sandstone, and like all its other members 
is disposed in horizontal strata lying unconformably on the basset edges of rocks more 
