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PROCEEDINGS OF SOCIETIES. 
The intervening hill is also covered with similar boulders, hut larger, 
some of them far exceeding one hundred tons, and more angular; and it is 
worthy of remark that they seem inclined to cluster round the summits 
of the hills, rather than spread over the valleys between them. 
The country adjoining Slieve Dart to the south-east, near Dunmore 
(Galway, 0. S. 5), is full of its sandstones and conglomerates; and I think 
it unnecessary to cite any more of the various examples I have remarked 
of this drift, which I have characterized by the name of “ boulder 
driftas its distinctive remains consist of the larger blocks that resisted 
the subsequent force which removed its lighter materials. 
The escar drift in the greater part of my district is composed of 
limestone gravel of various degrees of fineness, mixed in a small propor¬ 
tion with the debris of other rocks. In its formation it is often amor¬ 
phous, and often shows stratification more or less perfect, in which the 
coarser gravel and boulders generally incline towards the upper parts,— 
a fact that I think deserves especial notice, as it appears at variance 
with recognised geological theory. It might, perhaps, be referred to 
the action of light currents on the mass of previously deposited drift, 
the fine sand being carried away to a certain depth, and the larger 
stones and gravel left behind by a kind of winnowing process, and set¬ 
tling in an accumulation on the surface of the parts undisturbed. 
The disposition of this drift would show a force moving towards the 
north-east, in the southern part of my district, and then assuming a 
northerly course, which it continued to the coasts of Mayo and Sligo. 
The lines of gravel hills are favourable in their direction to this hypo¬ 
thesis, which is also supported by their mineralogical evidence. The 
escars immediately to the south of the sandstone district of Slieve Dart 
contain little or no gravel of that formation, though its large boulders 
are scattered over other parts of the land. The southern slopes of Slieve 
Dart are swept pretty clear of small drift, which, on the northern side, 
covers, to a great depth, a large extent of country. A felstone dyke 
occurs at the north-eastern extremity of the sandstone, and its boulders 
are only found to the north. Its date may be posterior to the “ boulder 
drift,’’ and it may have been contemporaneous with the rise of the land 
during the escar period. 
In the yellow sandstone, Silurian, and porphyry districts about 
ITggool and Kilkelly (Mayo 0. SS. 72, 73, 81, 82), the ranges of escar 
hills, approaching from the south, contain but few specimens of rocks in 
situ to the north of them; and those were, probably, carried back from 
southern localities, whither they had previously been carried as “boulder 
drift.” This remark is illustrated by a fine escar formation at Kilkelly, 
and about a mile east of that town an escar range commences within the 
sandstone country, and runs for about two miles, rather west of north, 
to the borders of the porphyry district. It is composed of mixed lime¬ 
stone and sandstone gravel, without containing, as far as I could see, any 
traces of the porphyry. Within the porphyry district the sandstone 
drift abounds, and its great boulders are seen close to the summit of the 
highest hill, at an elevation of near 700 feet above the level of the 
