aH 
X THE GEELONG NATURALIST. 
meet him and spend a few days in his district. Accordingly 
having arrived on the scene we set to work scouring the 
country. But before describing the nature of the formations 
met with, it is well to notice the chief indications presented by 
ice action, and which are recognized in other parts of the world. 
If we refer to any text book on Geology, we find that wherever 
glacier or ice-sheets have spread and moved over rock surfaces, 
the rocks are left scratched and striated. ‘This striation is pro- 
duced both in the bed rocks and also in the stones imbedded in 
the ice, by the rubbing of the one set against the other as the 
ice sheet moves down the slope. Here and there projections of 
rock from the strata are smoothed and rounded into “hummocks”? 
* dolphin-backs,” or roches moutonnées as they are variously 
called. Again, the grinding of the rocks imbedded in the ice 
upon those in the underlying strata, causes an immense amount 
of fine silt. ‘Ihis silt, together with rocks of all sizes, from 
hundreds of tons to a few ounces in weight, is carried along 
with the glacier till the snow-line is passed. Then as the ice 
melts, the silt, boulders, pebbles, etc., are all deposited in a 
confused and unstratified mass. Now this jumbled-up condition 
of boulders, clay, mud, pebbles, etc., is never produced by any 
ordinary aqueous action, and, together with striation, forms the 
chief indication of glacial action, no other agency being known 
that will cause the same effect, Again, if an ice sheet should 
extend down a valley and out into the sea, parts of it break off 
and float away as icebergs, carrying imbedded in them the silt, 
rocks, etc. When the iceberg melts the rocks are deposited on 
the ground beneath. ‘Then, when this ground becomes dry land, 
the deposited rocks are found perched on hillsides, or lodged in 
strata which do not in any way correspond with them in litho- 
logical character. Thus, a granite boulder might be found on 
a hillside resting on a sandstone formation, and no other granite 
within a radius of hundreds of miles ‘Ihe “ perched” or 
“ erratic ” blocks, the confused conglomeration of debris, and 
the striated rocks are the chief indications of glacial action. 
Near Derrinal railway station, along the Wild Duck Creek, 
are to be found scattered about on the hillsides a number of 
blocks of granite, some of pink granite, others of the 
commoner grey character. ‘Ihese blocks rest on rocks of 
Silurian age, but no granite of the same kind as the rocks can 
be found Zn situ anywhere in the district. In fact, pink granite 
of similar character has not yet been found nearer than Queens- 
land. The largest of these blocks is the “Stranger,” a beautiful 
mass of pink granite weighing about 60 tons. The top is 
smoothed off, and striated, giving a polished surface, as if done 
‘artificially. Scattered all around can be found rocks of various 
composition, scored and scratched in well-marked lines. Going 
