

TRANSACTIONS OF THE SECTIONS. 41 
“In the county of Sligo are two mountain ridges, the Ox mountains and the Curlew 
mountains, which have nearly parallel directions; the Curlew range being about 
twelve miles south of the other. The Curlew mountains consist of reddish-brown 
sandstone, connected with the Upper Silurian system, and the Ox mountains are 
composed of mica-slate and granite, the former predominating, and the country situ- 
ated to the north and south of both ranges is composed of rocks belonging to the 
Carboniferous system. 
In the limestone district south of the Curlew: mountains the gravel hills consist of 
limestone solely ; and ina northern direction the gravel banks extend up the southern 
slopes of the hills of brown sandstone, where numerous pits have been opened to 
raise the limestone for manure. 
Ascending the ridge of the Curlews, we find numerous boulders of yellowish-gray 
sandstone scattered on the surface. Passing over the summit, and descending to the 
northward, into the limestone valley of Ballymote and Tobercurry, the surface is 
thickly covered with boulders of reddish-brown sandstone, some of them weighing 
several tons, the largest being nearest to the Curlew range. On approaching the 
base of the Ox mountains the red boulders are still numerous, but diminish in size. 
Ascending the mica-slate ridge of the Ox mountains, we still find small boulders 
of the same sandstone, together with small eskers of limestone gravel in some of the 
valleys. These eskers are remarkable, owing to their forming ridges directly across 
the valleys. This is particularly the case in the valley of Lough Easky, situated in 
the middle of the mountain range. To the north and south of this lake the rock is 
mica-slate, but at the lake there has been an extensive protrusion of large-grained 
crystalline granite, composed of flesh-red felspar, white felspar, gray quartz and 
black mica, the mica-slate being metamorphic along the line of contact. 
_ In the line of the road to Easky Lough, two miles south of the lake, the valley is 
crossed at right angles by two eskers of rolled limestone, varying in size from two to 
three inches in diameter, mixed with small grains of limestone and a little clay. 
The declivities of these eskers are steep, as is usual, and their height may be about 
thirty feet; their elevation above the limestone plain to the south, whence the lime- 
stone of the eskers appears to have been derived, is 250 feet. It is remarkable that 
numerous large boulders of mica-slate, exactly similar to the rock of the district, are 
strewed over the surface of these eskers, but none of them are intermixed with the 
gravel. 
Approaching Lough Easky, there is an elongated sinuous esker, nearly parallel to 
the line of the valley. This differs in its composition as well as direction from those 
just described. It is composed of pebbles of quartz and mica-slate, intermixed with 
siliceous sand, the whole being evidently derived from the adjoining mountain. Here 
is a moraine which may be accounted for according to the hypothesis of Agassiz ; 
and so may also the boulders of mica-slate, which cover the eskers already mentioned, 
but not the eskers themselves. 
» Following the valley of Lough Easky in a northern direction to the sea-shore, be- 
yond the village of Easky, for ten miles, the surface of the limestone country, situated 
to the north of the Ox mountains, is thickly strewed over by large boulders of gra- 
nite, some of which (close to the sea-shore) are of enormous dimensions; and one, 
which is cleft through the centre, contains 1360 cubic feet, equal in weight to 100 
tons,—a mass which it is difficult to conceive could be moved by water, unless in 
the form of ice. 
The granite of these boulders is identical with that of Lough Easky, hence we must 
suppose that they were derived from that source. 
Similar granite boulders occur along the whole line of coast westward from Easky 
to Erris in Mayo. A few rolled blocks of metamorphic mica-slate may occasionally 
be observed, but not one boulder of limestone, though the entire district is composed 
of carboniferous strata. It may be observed that the whole of these granite boulders 
are precisely similar in composition to the granite of the Ox mountains, particularly 
of Lough Easky, Lough Talt, and Foxford. 
Taking all these facts together,—namely, the boulders of the brownish-red sand- 
stone covering the surface of the limestone valley between the Curlew and the Ox 
mountains, the Ox mountains containing eskers of limestone gravel evidently derived 
_ from the limestone valley of the south, and the granite boulders of Easky and of the 
