Some Points in Geology. is, 
the great drainage-lines, but that for the most part the gorges of 
mountains, the rivers and fiords of rocky districts, and many smaller 
valleys and coombs, whether now occupied by water or not, indicate 
lines of fracture, and so assist in elucidating the structure of a 
country. And this is supported by the frequent coincidence of 
valleys with hitehes and curves of strata; the more so, as the broken 
arches of long undulations, or of elliptical or other domes, exhibit 
such branching and radiating drainage-systems as actually cor- 
respond more or less to geometrical rules. Some ignore faults in 
strata as productive of any line of weakness such as would tempt 
a trickling stream along their course; but the outcoming of springs 
along faults may certainly have marked out valley-lines; and in 
limestone, at least, and granite, fissures of dislocation or of contrac- 
.tion do carry the water-streams, and the smaller rills converge to 
feed them. 
In the history of the lower portions of river-valleys, we have 
been enlightened by the researches of Fergusson on the Bengal delta, 
Prestwich on some French and English rivers, Doyne on some 
rivers in New Zealand, Ellet on the Mississippi, and of other ob- 
servers. 
The origin of lakes is of great interest too. Many are merely 
dammed up valleys, like artificial reservoirs, always pressing against 
the gravel-heaps that hold them; some lie in expanded parts of 
valleys where soft rocks have been sapped-away; but some seem 
to have been neatly hollowed out of hard rock, with definite edges, 
like a saucer; such are many mountain-tarns, and such are the great 
Alpine lakes, according to Ramsay and others. The glacier, in its 
course, impinging on the ground where the slope is favourable and 
a check is received, can, it is said, scoop out a basin for a tarn ; and 
why, it is asked, should not the larger ice-masses of the Glacial 
Period have ground out the larger, but not disproportionate lake- 
basins of Switzerland, even where neither fissures nor folds have 
weakened the rocky surface? Wind and sand may hollow out 
small rock-basins in rotting granite: a pebble, the plaything of the 
torrent or the tide, may worry out a pot-hole in the river-bed or on 
the sea-shore; but wind and water could not, it is thought, excavate 
such basins as the great lakes; and certainly they lie in the path of 
old glaciers. Their origin as glacier-beds has been denied, by say- 
ing that glaciers do not grind at all, and by other more forcible 
arguments, to all which Professor Ramsay has already given fair and 
powerful replies. The complete proof of his hypothesis may yet be 
wrung from the glacial phenomena of the greater mountains of the 
world. 
For our part, the GzotocicaL Macazine has already served as a 
channel for much valuable information on the vexed geological 
questions of the day; and amongst home and foreign news relating 
to the many topics that we have to deal with, our readers will con- 
tinue to find facts and inferences as to how granite has been formed, 
how river-valleys and lake-basins have been excavated, and how 
species have come and gone. 
