106 
ISLAND LIFE. 
[part I. 
rocky peaks which rise above it. As the glacier slowly moves 
downward, this debris forms long lines on each side, or on the 
centre whenever two glacier-streams unite, and is deposited at 
its termination in a huge mound called the terminal moraine. 
The decrease of a glacier may often be traced by successive old 
moraines across the valley up which it has retreated. When 
once seen and examined, these moraines can always be distin- 
guished almost at a glance. Their position is most remarkable, 
having no apparent natural relation to the form of the valley or 
the surrounding slopes, so that they look like huge earthworks 
formed by man for purposes of defence. Their composition is 
equally peculiar, consisting of a mixture of earth and rocks of 
all sizes, usually without any arrangement, the rocks often 
being huge angular masses just as they had fallen from the sur- 
rounding precipices. Some of these rock masses often rest on the 
very top of the moraine in positions where no other natural 
force but that of ice could have placed them. Exactly similar 
mounds are found in the valleys of North Wales and Scotland, 
and always where the other evidences of ice-action occur 
abundantly. 
Travelled Blochs. — The phenomenon of travelled or perched 
blocks is also a common one in all glacier countries, marking out 
very clearly the former extent of the ice. When a glacier fills 
a lateral valley, its foot will sometimes cross over the main 
valley and abut against its opposite slope, and it will deposit 
there some portion of its terminal moraine. But in these cir- 
cumstances the end of the glacier not beiug confined laterally will 
spread out, and the moraine matter will be distributed over a 
large surface, so that the only well-marked token of its presence 
will be the larger masses of rock that may have been brought 
down. Such blocks are found abundantly in many of the 
districts of our own country where other marks of glaciation 
exist, and they often rest on ridges or hillocks over which the 
ice has passed, these elevations consisting sometimes of loose 
material and sometimes of rock different from that of ichich the 
blocks are composed. These are called travelled blocks, and can 
almost always be traced to their source in one of the higher 
valleys from which the glacier descended. Some of the most 
