J. F. CAMPBELL ON GLACIAL PERIODS. TOL 
range of mountains by the crumpling-up of sedimentary beds. By 
seeking for worn glaciated surfaces, and for angular and scratched 
stones, transported. by ice, it has been ascertained with tolerable 
certainty how far ice travelled from the Alpine snowshed after 
the Alps had grown high enough to condense enough of snow to make 
glaciers. It took many able men many long years to map these 
glacial records of one Kuropean chain of hills. As with volcanic 
cones and mountain-chains, so it is with the globe. The record can 
be read by going round the point from which the radiating polar ice 
now floats toward the equator to known limits. By seeking gla- 
ciated rock-surfaces and glaciated stones all round the world, it may 
be ascertained how far polar ice has reached. But it will take more 
men and a longer time to map even this branch of superficial geo- 
logy. I have tried to do as much as I could systematically. 
17. Before going to India in September 1876, I had seen for myself 
that the shape of a glaciated country differs conspicuously from the 
shape of a country where fluid water, falling, flowing, or stagnant, 
in showers, streams, lakes, or in the sea, has been the chief wearing 
engine. Where “lakes” and “ firths” are conspicuous geographi- 
cal features, I have always seen rounded tops and wide hollows of 
curved section, ~ ~. Curved outlines are conspicuous features in 
every landscape in Scandinavia, in Scotland, in Finland, in the Alps, 
and in parts of North America. On the map and at siyht these are 
glaciated countries. On closer examination I have found glaciated 
rock-surfaces and scratched stones, and all marks characteristic of 
glacial erosion. Where I could find few marks of glacial action, or 
none at all, after careful search, as in California and in Japan, 
Ceylon, and Java, and on recent volcanic cones, straight lines and 
angles are marked features in every landscape (y A), and there 
lakes and firths are exceedingly rare. Maps by form suggest a 
probability ; the first sight of a country increases that-probability ; 
a careful search on a few chosen spots is enough to ground an opinion 
as to the fact of “glacial action ” or “‘ pluvial erosion” in a given 
region. The.lesson learned in travelling with a purpose was an 
alphabet of “‘ form ” by which to read a record of the action of various 
engines which have covered the world’s surface. Al] sedimentary 
geology is based upon the erosion of that surface. That was my 
lesson. Having learned it, | wanted to read the record carved on 
the Himalayas, to see India, and to test my own opinions about 
glacial periods there. So I took stock of knowledge previously 
gathered, and started. 
18. As appears in the papers referred to for facts, I had gradually 
advanced from Swiss glaciers and their old marks to ‘ Potar Gua- 
CIATION,” which does, in fact, extend from the North Cape of Europe 
down to Cape Clear, from Archangel down to Nijni Novgorod, and 
down to the neighbourhood of St. Louis on the Mississippi, in America. 
Having ascertained the fact of “ Polar Glaciation,” I had to consider 
the possibility of continental icc-shects and of polar ice-caps. Ac- 
cording to theories still supported by many able geologists, solid 
glaciers have covered continents; solid ice has extended from the 
