138 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
a low cone. Down valley the cone becomes more flat as the internal 
structure becomes more regularly stratified. This is the fluvio-glacial 
region proper. The transition cone often presents alternations of 
glacial and fluvio-glacial material, which may appear at the base, 
within the mass or near the surface of the alluvium (ibid., p. 9). 
From these examples it will be seen that there is considerable simi- 
larity in the shape and character of some of the individual particles 
and masses produced by each process. The effects produced by one 
process alone may differ in a notable degree from those produced by 
another, but when they are combined, a gradation occurs, so that no 
sharp line of distinction can be drawn; and it is difficult or impossible 
to determine to which of the processes some of the materials deposited 
should be assigned. Accumulations produced by such combinations 
of processes are probably more common than those formed by the 
separate action of a single process. River-borne waste is rehandled 
by the sea. Even in the formation of what might be called truly 
glacial material washed gravels are apt to be interstratified to some 
extent with the till in consequence of the minor variations in the posi- 
tion of the ice front. Recognizing, then, the fact that many combina- 
tions are both possible and probable, it is best for the purposes of this 
paper to confine the discussion to those features which may serve to 
identify the several processes. 
ANALYTICAL Discussion.—In the previous pages the details of vari- 
ous occurrences of conglomerates and associated rocks have been set 
forth at some length, together with the opinions of numerous writers 
concerning some of the characteristics of conglomerates formed by 
the different processes. It now remains to gather from this material 
the typical features of each kind of conglomerate and to arrange 
them in some order for comparison. For this purpose the following 
scheme has been adopted: — 
Matrix: — kind of material; size of grains (coarse or fine, uniform 
or varied); shape of grains (angular, subangular, or rounded); 
arrangement of grains (orderly or disorderly; well stratified, 
rudely stratified, or unstratified); cement (argillaceous, silicious, 
calcareous, or ferruginous). 
Pebbles: — kind of material; size of pebbles (large or small, uni- 
form or varied, gradation in any particular direction); shape 
of pebbles (angular, subangular, or rounded); markings (facets, 
polish, striation) ; deformation (distortion, tension cracks, 
fracture); arrangement (well stratified, rudely stratified, un- 
stratified). 
