78. REPORT-——1850. 
on the other from those of the east of Ayrshire, by ridges of Devonian rocks, amid 
which igneous products are variously intercalated. On the S,W, side this separation 
does not take place, as we should be inclined ἃ priori to expect, at the highest part 
of the ridges forming the watershed between the two systems of river drainage; on 
the contrary, the strata of the Muirkirk field in Ayrshire rise up over this ridge at 
the height of 1000 or 1200 feet, and pass down into the basin of the Clyde, where 
they rest upon a narrow band of Devonian rocks, The boundaries of the field on 
the east reach out to near the base of Tinto. There is no great body of carboniferous 
limestone at the base of the series, but several beds of limestone are interstratified 
with the coal, of great continuity, and containing a complete suite of fossils of true 
carboniferous types. The coal shales, sandstones and ironstones, afford similar re- 
mains in abundance; and there can be therefore no doubt that the coal of this field 
is of the same age as that of the Clyde basins. It is worthy of remark, that several 
species of Trilobites occur in the shales and limestones, far up in the series; that a 
white grit, resting on one of the lower limestones, contains a prodigious quantity of 
fish remains, and corresponds, apparently, with the great “ fish-bed ” of some English 
fields; and that from one of the middle shales a fossil has been obtained agreeing 
exactly with the Serpulites longissimus of the “ Silurian System,’ pl. y. fig. 1. The 
field contains fifteen seams of coal, whose thickness varies from 2 ft. to 15 ft., the 
aggregate amounting to about 65 feet of workable coal. There are black band and 
clay band ironstones, the principal seam of the former averaging 1] inches; but 
neither these nor the oak beds have yet been worked to any considerable extent, 
owing to the greater accessibility of the fields further down the Clyde, The im- 
portance of this field to the south-eastern districts of Scotland was pointed out, and 
the attention of capitalists invited to its more thorough examination, 
The author exhibited a coloured map, with numerous sections, showing the inter- 
nal structure of the field. 
On the Glacial Phenomena of the Neighbourhood of Edinburgh, with some 
Remarks on the General Subject. By Roserr Cuambers, F.R.S.E. 
This paper opened with a description of the local phenomena, partly with a view to 
the gratification of the strangers present at the meeting cf the Association. The Cor- 
storphine Hill is a stratum of trap resting on sandstone, and dipping to the west, with a 
cliff in aline north and south. In its crest, which rises to 470 feet above the sea, are 
four transverse clefts. On the west surface of the hill, the rock, wherever it is ex- 
posed, is found to be rounded (moutonnée), smoothed, and grooved. The grooves and 
the clefts in the crest of the hill all lie in one direction, viz. directed to a point north 
ofeast, There are also, to the east of the hill, long hollows with intervening swells, 
and these run in precisely the same direction. At various places, in this region east 
of the hill, are seen sandstone surfaces worn down to a remarkable flatness and 
smoothness, and in several instances marked with striz, all pointing in the same di- 
rection. 
Throughout the valley of the Forth, from the Pentlands to Fife, from Linlithgow to 
Dunbar, the sandstone surfaces, wherever they come up, are likewise smoothed, and in 
many instances striated, the striz all pointing to the E.N.E., or thereabout, such opts 
the general direction of the valley itself. The trap hills rising in this valley are al 
long and narrow, generally free from abruptness on the sides, often abraded on the 
west, and generally sloping away gently to the east; the direction here also is always 
E.N.E. Surfaces on the Pentlands and in Fife exhibit striation precisely conform- 
able. In short, if a deep ice-flow passed through this valley, it might be expected to 
produce precisely the phenomena which have been observed. 
The similar markings in other districts of Scotland were shown, for the most part, 
though not without striking exceptions, to be directed towards the east and south, 
Mr. Chambers adverted to the theory of debacles, which was started to account for 
the appearances, as now nearly given up. Ice was generally acknowledged as cons 
cerned in producing them, because the appearances were precisely those which exist~ 
ing glaciers produce. But there was great room for speculation as to the circum~ 
stances under which the presumed glacial agent was applied. Mr. Chambers declined 
theorizing on the subject, but pointed out various conditions which any theory on 
