94 
LOWEST CARBONIFEROUS BEDS— GREAT LIMESTONE. 
white felspathic quartzose conglomerate succeeds, covered by yellowish sandstone 
and shale with reddish and green shale. The whole of this red series is sur- 
mounted by carboniferous limestone of considerable thickness and forming fine 
cliffs, in which are several species of Producti. Among the fossils Colonel Oli- 
vieri assured us that he had found the large species (P. giganteus ) so common to 
the lower band. In our very rapid examination, however, we detected only the 
Productus antiquatus, Spirifer glaber, and some corals. The whole of these strata 
dip to north-north-east at angles varying from 12° to 15°. 
The composition of the red beds, and their infraposition to what we considered 
to be the lowest mass of the carboniferous limestone, at first disposed us to con- 
sider them as the uppermost member of the Old Red Sandstone ; for by their 
position and aspect they seemed to be the exact equivalents of the Old Red Con- 
glomerate of the South Welsh coal-field, which occupies so well-defined a place 
throughout the Silurian region of England. This comparison may, after all, prove 
to be correct, and the Upper Red Conglomerate of South Wales, notwithstanding 
its colour, may eventually be classed with the carboniferous limestone, since it is 
by no means an easy task, even in England, to separate the Devonian from the 
Carboniferous system, particularly when fossils are absent and mineral character 
is our only guide. Judging, however, from the analogies of Northern Russia and 
the Moscow basin, where carboniferous plants and seams of coal unquestionably 
underlie every trace of limestone, and repose upon beds with true Devonian fishes, 
we are now disposed to group these red strata of Karakuba with the base of the 
Carboniferous system, the more so as the Stigmaria which we found in them 
seemed to be a species common to both. A visit which we made to the Berwick- 
shire coal-field, subsequent to our return to Great Britain, has further induced us 
to adopt this opinion ; for we there found a great thickness of red sandstone and 
shale with coal, the upper beds of which only are interlaced with courses of car- 
boniferous limestone, and the lowest of which lie far beneath all traces of that 
limestone, the whole constituting one great, red-coloured coal-field of considerable 
value (containing seven workable seams) , which clearly overlies the Old Red Sand- 
stone properly so called. We shall revert to this subject in our general conclu- 
sions. In the mean time, whether coal-seams may or may not exist in the red 
rocks of Karakuba, it is evident, that as they underlie the lowest mass of car- 
boniferous limestone, they offer a distinct base-line for the section which we now 
continue to describe in ascending order. 
