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, consistiDg 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 Blocks. — 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 being 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 ivMch 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 



