Review of Recent Geological Literature. i'27 
the two moraines at great length. Both kinds were observed by hmi 
in Greenland. There the ground moraine consists of a clay of bluish- 
gray color, carrying rounded, frequently striated boulders. The upper 
or inner moraine bears more angular boulders which are rarely striated, 
considerable gravel and its clay oxidized at the melting of the ice. 
The two moraines found in Germany and Sweden conform to 
these Greenland moraines. In Sweden they are found even far north- 
ward as well as nearer to the border of the glaciated area. The dif- 
ferences between the two moraines are summarized as follows. 
I. — In Germany as well as in Sweden the upper moraine has, as a 
rule, too insignificant and uniform a thickness to represent a distinct 
glacial period. It sometimes measures two meters, occasionally from 
three to four meters, but rarely exceeding the latter depth. 
2. — The upper moraine conforms closely to the surface upon which 
it rests, even though this consist of unconsolidated gravel or of osar 
and knolls with steep slopes fashioned from this material. It will 
therefore often reveal the exact form of the under-lying formation. 
A ground moraine cannot reproduce topographic features. 
3. — The upper moraine is not very compact since no inland ice 
has passed over it. It is frequently poor in boulders and often shows 
more or less distinct stratification, indicating that water played a 
part in its deposition. The few striated boulders are derived from the 
ground moraine. The differences referred to in the last two par- 
agraphs have often been stated by other speciali.«ts. James Geikie says : 
"One may note in many cases that the till which overlies inter-glacial 
deposits is not infrequently a somewhat looser clay than the generally 
excessively tough lower till that clings to the rocks underneath. Often 
too the stones and boulders of the overlying till are, as a whole, less 
well striated and smoother than those in the bowlder clay below." The 
latter is said to be "unstratified," the upper one "indistinctly bedded." 
Johnstrup also observed the same differences which he considered 
to indicate a dfferent source for the upper moraine and he attributed 
its origin to ice floes. 
4. — If the upper moraine were a distinct ground moraine, formed by 
a distinct inland ice then there should exist a definite boundary for this 
ice and its moraine. But such a boundary, though constantly searched 
for, has never been found, and it never will be found, because it has 
never existed. The great chains of terminal moraines represent the 
most striking feature of the ice age, but fihis feature interglacialists seek 
to obscure by directing attention to the two morainees as though they 
were of distinct origins widely removed in time. 
5. — If the upper moraine represented a distinct glacial period pre- 
ceded by an interglacial stage of long duration, its deposits would 
abound in vegetable remains and entire forests would be found in 
them now and then. It is far too thin for burying and covering up, 
as does the ground moraine, the trees which grew in front of the 
glacier to which the nmraine owes its existencf. The iiura morainic 
