Some of the materials for this grinding are brought down by the glaciers themselves, on which we commonly see, in the middle, or at the sides, or in both situations, sinuous lines of rock fragments, which, being traced up to their source, are always found to be furnished by rocks on the sides or at the junction of glaciers. These streams of stones are called moraine: the lateral streams are furnished by rocks on the side of the flow; a central stream may be formed by the union of two lateral moraines when two glaciers meet and unite, and thus, in the lower part of a glacier, which is formed of many confluent streams of ice, many lines of moraine may be traced. Arrived at the termination of the glacier, these streams lose their individuality for the most part, and constitute a great terminal moraine. Such remain, in many situations, many hundred yards, and even some miles, beyond the present range of the glacier which transported them.
In the diagram (p. 17.) several of the circumstances which have been mentioned are represented. It corresponds to a part of the Mer de glace above Montanvert. Three glacial streams are seen to unite, and three bands of moraine to run down the main glacier (marked m). The figures indicate the number of feet in a year which the glacier moves at the point where they are placed. (From Forbes's Travels in the Alps.)
Amongst the blocks brought down in this singular manner by glaciers, without attrition, are many of enormous magnitude; and, as each moraine band is only fed from certain rocks, it is easy to see that each has its own mineral character, and may bring detritus of a totally different quality from even its next in position. Much more, in this respect, may different glaciers disagree. If then, as in Spitzbergen, on the coast of Greenland, and in Tierra del Fuego, the glacier masses break off in icebergs, it is quite to be expected they should, after carrying their loads of rock to greater or lesser distances, deposit them in groups, each having a certain character and com-
