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THE GEOLOGY OF THE FAROE ISLANDS. 227 
tion will sometimes reveal several lines of coarser granules alternating with 
the finer-grained sediment. Under the microscope, the red tuffs are seen to 
be made up essentially of so-called “ palagonite.” 
In the numerous exposures we visited I never was able to find any true 
lapilli. In a coarse-grained tuff that crops out on the eastern slope of Kvan- 
nafield a few small stones were detected, but none of these exceeded half-an- 
inch in diameter. Only in one place did we come upon what seemed to be a 
true agglomerate. On the shore at Qvalbde, the low cliffs, 10 to 12 feet 
high, are formed of an agglomeratic tuff resting upon anamesite. The matrix 
of comminuted gritty débris is crammed with angular and subangular stones 
and lapilli of ail shapes and sizes, from mere grit up to blocks more than one 
foot in diameter. The included fragments were all of basalt-rock, and the 
mass showed no trace of bedding. It is just possible, therefore, that it may 
be only the scoriform brecciated upper surface of an anamesite. 
4, Coal and Coal-bearing Beds.—The strata immediately associated with the 
coals of Suderée may be described as dark carbonaceous shales and clays, 
which frequently have a tufaceous aspect. But their general appearance will be 
gathered from the sections given in Plates XIII. and XIV. figs. 5-9, and described 
in the Explanation. The coal occurs as more or less lenticular layers in beds 
of dark indurated clay and shale. The seams, therefore, are very inconstant, 
and thicken and thin out in the most irregular manner. They appear mainly 
along one horizon, occupying a position about midway between the top and 
bottom of the trappean rocks of Suderde. This is the only horizon along which 
they have been worked to advantage, and it is doubtful whether they occur 
anywhere else ina workable condition. About 1100 feet lower down, however, 
another outcrop of coal occurs, but it appears to be very local. The section 
seen is shown in the illustration (Plate XIII. fig. 7). The whole thickness of 
the coal-bearing beds at this place was 10 to 15 feet. They consisted of fine- 
grained greenish mudstone and tufaceous shales, with some nodules of coarse 
ironstone. FoRCHHAMMER says that a layer of glance coal, 3 inches thick, was 
got here, but we saw ohly fragments of it lying about. This appears to be the 
lowest horizon at which coal has been met with. 
It is in the central and northern part of the island where coal has been 
principally worked, and there can be no doubt that all the workings are upon 
one and the same horizon (see Plate XIII. figs. 1 and 4). TreveLtyan knew 
this, and the section which accompanies his paper gives a correct generalised 
view of the geological structure of Suderée. 
The coal is of two kinds: one a bright lustrous coal, which does not soil 
the fingers, having a glassy fracture, and closely resembling in general appear- 
ance some of the glossy parrot coals of the Scottish coal-fields—the other, a 
dull lustreless coal, which soils the fingers, and in which one may readily detect. 
