66 
PROCEEDINGS OE SOCIETIES. 
rents took place. In this case the boulder history of the previous sub¬ 
mergence would refer only to the direction of the prevailing winds, and 
not to that of the currents. 
The granite boulders on the Barna and Aughinish cliffs, already 
noticed, are, probably, the representatives of a thick formation of over- 
lying “ boulder driftand they may have reached their present posi¬ 
tion, returning to the vicinity of their parent rocks, and at the same 
time sinking through the diminishing mass of smaller materials borne 
away by the escar currents. 
It would he idle to enter into any minute details of the various 
phenomena of the drifts. My object is, to explain the conclusions which 
the study of their principal features has suggested. These are sufficient 
to distinguish them from each other, and, as I believe, to show that 
the supposed agency of ice, as opposed to water, cannot simplify their 
formation in our eyes, hut, on the contrary, must render it more diffi¬ 
cult to he understood. It is to he remembered that, if parts of the drift 
show a confused arrangement of their materials, others are stratified; 
and, instead of arguing from the former that it must have been deposited 
from ice, it should rather he concluded from the latter, that stratifica¬ 
tion is not always the result of the action of water ; and that conditions 
may exist which would prevent water from giving the orthodox regu¬ 
larity of bedding, which preconceived notions would lead us to expect. 
Indeed, I have remarked, as a general rule, that where fine sand occurs, 
stratification is sure to he found ; and its absence is chiefly noticed in 
coarse gravel and tenacious clay, which often form the great hulk of 
the drifts. 
How, as a summing up , I may briefly state my belief that the clay 
drift was deposited during an emergence of the land; the boulder drift 
during a subsequent submergence; and the escar drift at its re-emer¬ 
gence. 
I think that the general contour of the country in the north of Gal¬ 
way and adjoining parts of Mayo shows the occurrence of great denuding 
action from the east at a period anterior to the drifts. The shapes of 
the hills are, in most cases, elongated in an easterly and westerly direc¬ 
tion ; steep on the north and south sides, and eastern end, and stretch¬ 
ing away to the west in a long declining ridge. The rock often appears, 
or nearly approaches the surface, at the eastern acclivity; and throughout 
all the district I have remarked that, generally, the rise of outcropping 
strata is towards the low lands, proving them to he valleys of denudation 
where the upheaval and disturbance of the beds rendered them liable 
to be carried away. A grand illustration of this phenomenon may be 
seen on the Burren Mountains, south of Galway Bay. Long lines of 
platforms ascend their sides like stairs of giants; and in these the geo¬ 
logist will not fail to recognise the beach-terraces of an ancient sea, made 
during pauses in the building process of man’s abode. Those terraces 
have a dip that corresponds with that of the strata; and this may be 
observed on the eastern and western sides of the hills. Its direction is 
southerly, towards the mountain group, so that the elevation is towards 
the valley of the bay, and the low country to the east. 
