466 
THE GEOLOGIST. 
In no single locality do wo find a section in wliicli all the beds 
occur in regular and luiinteiTupted succession ; the absence of some, 
or the thinning-out of others, constitute local differences which should 
always be ex])ccted and duly considered. Thus, in Lanai'kshu'e 
generally, as well as in other parts of the Clydesdale coal-tield, the 
strata composing the Carboniferous system have been divided into 
four principal groups ; and I am indebted to a friend in Carluke for 
the section here given, and which we will describe in the descending 
order. 
I. The Upper Coal-series, mea- 
suring in some localities 
about one hundred and fifty- 
nine fathoms. It consists of 
eleven seams of workable 
coal and numerous smaller 
seams (among which we may 
name that which has been 
designated as the " Ell coal," _^ 
and which is situated to- 
wards the top of the group), 
of sandstones, for the most 
part white in colour, or white 
with dark streaks, of fire 
clay and shales, a bed of 
freshwater limestone, and a 
few important bands of iron- 
stone. 
II. The Upper Limestone-series, 
about one hundred and 
twenty-five fathoms in thick- 
ness, consisting of three 
limestone beds, but no work- 
able coal, although there are- 
several thin seams, several 
bands of ironstone, occasion- 
ally gTitty — and in the lower 
part sandstone of a yellow 
colour, fire clay, and shales. 
III. The Lower Coal-measures, 
about thirty-seven fathoms 
in thickness — consisting of 
four workable seams, the un- 
dermost being the " cannel"- 
or"gas-seam," so well known, <j Maggy ironstones 300 
and several other smaller 
seams ; sandstones white and 
sometimes yellow ; fire-clay, 
shale, &afew ironstone bands. 
Horizon of the " Ell Coal" 
(In this column are enumera- 
ted the fossiliferous strata where- 
in Bracliiopoda have been found 
in the parish of Carluke, and 
which will be hereafter referred to 
when we treat of the species. 
The position is given at so many 
fathoms below the horizon of the 
" Ell Coal," but it would be quite 
as easy to take the space from the 
horizon of the " Productus gigan- 
teus limestone" upwards.) 
Slaty-ironstone, 160 fathoms, 
below Ell Coal. 
Thomson's Balls 173 
Gare limestone 
239 
Belston Bum Lime- 265 
stone. 
Belston-limestone 283 
