Review of Recent Geological Literature. 121 
of floating ice a load greater than it can carry, and to underrate the ne- 
cessity for more than mere local glacieisto account for theglaciation of 
the midland states. It is not possible for a geologist residing and work- 
ing in that region to see in the ''terminal moraine" the marginal wash 
of a glacial lake, when he follows it mile after mile across the country 
and sees it adapting itself everywhere to all the unevenness of outline 
and contour, now crossing a high divide, and then plunging down into a 
river valley, from which anon it rises to continue its former course. To 
presuppose local elevations and depressions of the surface in order to 
remove the difficulty, would transcend the scepticism of the most thor- 
ough-going unbeliever in the stability of the earth, and would demand 
more faith than the ordinary geologist possesses. 
We cannot resist quoting, in conclusion, with a little condensation, 
some of Sir William's excellent remarks in his last chapter. He says: — 
"With reference to the life of the Pleistocene period, one can scarcely 
fail to observe that, whatever may have been the lapse of geological 
time from the period of the oldest boulder-clay to that in which we 
live, and great though the climatal and geographical changes may have 
been, we can not affirm that any change, even of varietal value, has 
taken place in any of the species of the above lists. This appears to 
me a fact of extreme significance with reference to theories of the 
modification of species in geological time The great elevations 
and depressions of the land, the extensive erosions, the wide and thick 
beds of sediment, all testify to the lapse of time. The changes which 
occurred were fruitful in modifications of depth and temperature. 
Deep waters were shallowed, and the sea overflowed areas of land. The 
temperature of the waters changed greatly, so that the geographical 
distribution of marine animals was materially affected Yet all 
the Pleistocene species survive, and this without change 
"A second leading thought to which I would direct attention is 
tbe relative value of land-ice and water-borne ice as causes of geolog- 
ical change in the Pleistocene. On this subject I have constantly 
maintained that moderate view which was that of Sir Roderick Murchi- 
son and Sir Charles Lyell, that the Pleistocene subsidence and refrig- 
eration produced a state of our continents in which the lower levels, 
and at certain periods even the tops of the higher hills, were submerged, 
under water filled every season with heavy field-ice formed on the 
surface of the sea, as at present in Smith's sound, and also with abun- 
dant ice-bergs derived from glaciers descending from unsubmerged 
mountain districts.'' 
As a parting word we read on the last page: "I shall not attempt to 
extend these generalizations to the country south of the Canadian bor- 
der, but must respectfully warn those of my geological friends who in- 
sist on portentous accumulations of land-ice in that quarter, that the 
material can not be supplied to them from Canada. They must estab- 
lish gathering grounds within their own territory." 
