52 The American Geologist, January, i899 
forests tower over and grow upon successive generations of 
fallen trees, which rest upon glacial debris. Still further 
north, and at the same general elevations above the sea, these 
forests grow upon a thinner layer of dead and rotting trunks 
and the humus is less thick. Still more northward yet, these 
forest trees are found in the prime and vigor of full growth — 
no aged and fallen trunks encumber the ground, the roots of 
the living trees are buried in the gravelly, rocky soil of mo- 
raines and a thin layer of decomposing vegetable matter 
covers the ground. Where there is no morainic material, 
the thin soil gives scant roothold, and an upturned root some- 
times uncovers fresh glacial scratches. From commanding 
{)Ositions, the glittering glacier can be seen, and as he nears 
its front, the observer is forced to note that the for- 
ests are of young and half grown trees, then sap- 
lings and finally the very seedlings sprout from the 
freshly uncovered gravel of the matchless glaciers of British 
Columbia and Alaska. 
Now and then these young forests are uprooted and 
plowed under by a temporary advance of the glacier, and 
its gradual retreat will sometimes reveal the crushed roots and 
trunks of a previous advance. But the integral of successive 
retreats is greater than the integral of successive advances, 
and the forest has for thousands of years kept an accurate re- 
cord of the fact, although successive generations of dead 
trunks, whose decay has been retarded by the moist climate of 
the locality, have been necessary to keep the records. In 
making the observations one has to traverse twenty degrees 
of latitude, but the observations are only typical of what can 
be observed in a few thousand feet of observation upon the 
slopes of Mt. Kenia, the Equadorian Andes, or other glacier- 
crowned peak of any latitude. Above the timber line, the 
physical evidences of glacial retreat present the same grad- 
uations of distinctness as we recede from the active glacier. 
The fact that the evidence of glacial retreat grows progres- 
sively fainter as we recede from the living glacier, either in lati- 
tude or elevation, marks a progressive retreat from the equator 
polewards and from sea level upwards; since it is progres- 
sive it must be accounted for by progressive laws now active, 
and suppositions of upheavel and depression and other hy- 
