The Evobttiou of Climates. — Mansoti. 109 
cial dispersion (a) from belts of maximum precipitation and (b) 
from elevated lands down the slopes of which glaciers flowed. 
4. Striated and polished surfaces of either rock in place 
or of detached masses. 
5. A surface distribution of "erratics" or large and small 
masses of rock transported only by flowing ice, and marking 
the direction or limits of flow. 
Of these the first may properly be said to be the only abso- 
lute and confirmatory proof of an ice age. Any or all of the 
others might have been formed during any stage of the earth's 
geological history, provided land areas were sufficiently ele- 
vated to permit of the local formation of glaciers. The evi- 
dences mentioned under (4) and (5) have actually been ob- 
served at many localities,* and at widely separated latitudes, 
in which latitudes tropical forms of life were co-existent. The 
only period in geological history, in which all the distinctive 
and characteristic proofs of an ice age occur is in Quaternary 
times. One of the marked characteristics of these proofs is 
that everywhere they just ante-date the present era. The true 
meaning of these evidences was first developed in cold temper- 
ate latitudes.! The disputes on the subject were very ani- 
mated and sometimes bitter during the few decades subsequent 
to the announcements of Agassiz of his belief in the existence 
of an Ice age. 
The contests over the evidences of Quaternary glaciation 
were then shifted to that occurring in warm temperate lati- 
tudes J and are now confined to that in tropical latitudes. § 
It is gratifying to the searcher for truth that this gradual 
progress has been made and that each step has been contested, 
for the naked truth would at any of the earlier stages of 
scientific development have been received with incredulity. 
*OIdham, Geological Magarine, Vol. XXIII, 1896. 
White, Carboniferous Glaciation, Am. Geologist, Vol. Ill, 1889, 
pp. 229-330. 
See also Glacialists' Mag., Vol. I. No. 6, p. 143. and authorities 
there cited. Also the extensive lists of instances cited by Oldham & 
White. 
fSwitzerland, Germany, France, North American States. 
X Gibraltar, Palestine, North Africa, India, Chile, Australia, New- 
Zealand, etc. 
§South America, Central Africa, Tropical Islands. See Journal of 
Geol., Vol. I, No. 8, pp. 752-772. Glacialists' Mag. , Vol. II, Nos. 5 and 
6. pp. 90-114. 
