92 REPORT—1840. 
four to six or seven workable coals, measuring from 24 to seven feet 
thick each, a valuable black band ironstone, and a great many clay 
ironstones, the whole based upon marine limestones of great thickness. 
Mr. Craig’s paper was illustrated by large coloured maps, and by 
sections of the various coal-pits and borings which had been made 
through the extensive district, amounting to 3600 square miles, which 
he had surveyed. These were taken at various points in the stratifi- 
cation, and developed the whole in depth to the extent of above 1000 
yards. 
Notes taken during the Surveys for the Construction of the Geolo- 
gical Model Maps and Sections of the Island of Arran. By 
A. C. Ramsay. 
The interior of the northern and more mountainous district of Arran 
is a mass of granite, against which recline various stratified formations, 
ranging between the primary schist and slates, and the new red sand- 
stone. Immediately resting on the central mass of granite lie the 
schistose and slaty rocks, which are sometimes much contorted, and 
contain innumerable quartz veins minutely laminated and parallel to 
the plane of stratification, and in other instances penetrating the slate 
laterally, being sometimes two feet in thickness. On the slate repose 
the old red sandstone and conglomerate, containing pebbles of schist 
and slate quartz, &c. The fragments of quartz are of two kinds,— 
Ist, well-rolled and polished pebbles, probably originating in some 
ancient mass of quartz now totally destroyed ; 2nd, broken and angular 
fragments, which seem to have been imbedded in the conglomerate 
immediately after they were detached from the original mass. These 
last probably proceeded from the larger quartz veins already alluded 
to, the softer materials in which they occur forming part of the cement 
which binds the conglomerate together. The anticlinal line is in 
the centre of the old red sandstone at North Sannox, and at either 
extremity the coal measures dip to the north and south, being again 
succeeded by what is generally believed to be the new red sandstone. 
The southern district of the island is composed of irrupted masses of 
traps, porphyries, and syenites overlying the stratified sandstone forma- 
tions. In general it is only where the action of the streams has worn 
away the superincumbent igneous rocks that this sandstone is visible 
in the valleys; and in many of the deep gulleys dykes may be seen 
penetrating, and thence overflowing, the strata to a great depth. In 
such cases the trap usually assumes a semi-columnar form. 
Mr. Ramsay then proceeded to notice some of the phenomena which 
preceded and attended the elevation of Arran. 
The deposition of the various formations has generally taken place 
under a gradual change of circumstances. Thus, in North Sannox 
Water, we have first, slate; next, a slaty conglomerate, or pebbles 
of slate inclosed in slate; then the common pudding-stone ; again 
the slaty conglomerate, and so on, alternating several times. At 
