205 
Great Britain and Ireland,” by Edward Hull, B.A., F.G.S., 
of the Geological Survey. [Abstract.] 
The Author commenced by describing the phsenomena 
which induced M. Venetz to announce his opinion of the 
former extension of the Alpine glaciers considerably beyond 
their present limits, and proceeded to state that the same 
appearances as roches moutonnees, perched blocks, polished, 
grooved, and striated rock-surfaces, together with moraines 
in the British Islands, authorized Dr. Buckland and Professor 
Agassiz, in 1842, to extend the glacial theory to the moun- 
tains of Kerry, North Wales, the Lake District, and the 
Scottish Highlands. 
Mr. Hull then passed these several centres of dispersion 
for erratic blocks under review, showing the extent of the 
investigations which their glacial history had received from 
various authors up to the present time, dwelling more particu- 
larly on the Lake District, where the details were principally 
from his own observations. The results at which he had 
arrived fully bore out the conclusion of Professor Ramsay, 
that there have been three distinct periods in the glacial 
history of these Islands. First, a period when the glaciers 
extended very far down the main valleys, as those of Co- 
niston, Windermere, and Borrowdale. Second, a period of 
submergence, when the sea reached an elevation of more than 
1,200 feet on the Westmoreland and Cumbrian mountains, 
and 2,300 on those of North Wales, clothing their flanks 
with marine Boulder Clay. Third, a period of re-elevation, 
when the glaciers descended the minor or secondary valleys, 
ploughing out the Drift, and leaving behind the perched 
blocks and moraines at present in existence. 
The Author concluded by remarking that the great object 
to be accomplished in reference to this subject was the pro- 
duction of maps, showing the position of the moraines both 
lateral and terminal, and also the direction of the strue along 
the flanks of the valleys of our mountain groups. 'Fhis had 
been partially done by Professor Ramsay for North Wales, 
