047 
stone to the old red sandstone; and the thickest beds of limestone 
are at the bottom, and not (as in Scotland) at the ¢op of the calca- 
reous series. 
The author then notices the geological map of Scotland, and 
states that Dr. M‘Culloch has not merely introduced much con- 
fusion by givmg the mountain limestone series and the old red 
sandstone a common Colour; but that he has committed a great 
error in principle, by confounding, along a considerable part of the 
country bordering on the north shores of the Solway Firth, the new 
with the old red ‘Sandstone: 
Op Rep Sanpstonr.—The author, after briefly noticing the ex- 
traordinary irregularity in the development of this formation in the 
British Isles, compares the old red conglomerates of Cumberland 
with those on both sides of the Galloway chain. In these localities 
they often form unconnected masses resting on the edges of the 
greywacke; but in Galloway they are not only more largely de- 
veloped than in the north of England, but show, as above stated, 
many passages into the overlying carboniferous groups. 
Ireland.—He then briefly notices the sections which, in the south 
of Ireland, connect the old red sandstone with the overlying car- 
boniferous deposits, and form a good passage from one formation to 
the other. The sequence is complete, and there is nothing to mark 
any interruption of the deposits. He adopts Mr. Griffith’s classifi- 
cation, as most agreeable to the physical character of the groups and 
to their suites of fossils. . 
In the south of Ireland the lower carboniferous shales (of Mr. 
Griffith) pass into the state of roofing-slates with a transverse clea- 
vage, resembling the black slates at the base of the culm measures of 
Devonshire. ‘The great coal-field in the west of the island overlies 
the mountain limestone; but it puts on the form of the culm mea- 
sures of Devon, and was formerly considered as a great transition 
group. These facts appear to remove a difficulty in classification 
which was presented by the mineral structure of the Devon culm 
series. 
The author, by way of conclusion, affirms that the Scotch and 
Irish sections enable us to show that no new formations can be i in- 
terpolated between the old red sandstone and carboniferous series, 
inasmuch as the sequence is complete. In like manner, the sections 
in the Silurian country show that no member is wanting between. 
the old red sandstone and the Ludlow rock. Hence he concludes 
. that, from the lower divisions of the new red sandstone down to the. 
Llandeilo flagstone, there is one continuous unbroken sequence in 
which no term is wanting. Hence also the argument for the true 
place of the Devonian system is complete. For any formation, with 
fossils intermediate between the carboniferous and Silurian systems, 
must have an intermediate position,—must therefore be on the par- 
allel of some part of the old red sandstone, which fills that whole 
intermediate position. But allowing the above sequence to be com- 
plete, there may still be great difficulties in fixing the lines of de- 
222 
