558 PROCEEDINGS OF SCIENTIFIC SOCIETIES: 
changes of level, either of the land or the sea, or both, during the ice 
period, particularly towards its close. 
wish to consider principally the changes of sea-level resulting 
from the accumulation of continental ice. Such accumulations can only 
occur by depositions of moisture from the clouds, derived from the 
ocean by evaporation: The water-line, or surface of the sea, is con- 
stant, only because there is an equilibrium between evaporation and 
the water returned through the rivers. If depositions, in the form of 
rain, dew, and snow, remain perpetually congealed, they are not re- 
turned to the common reservoir, and to that extent its surface must 
settle away. If the limits of perpetual snow and ice should now be 
enlarged, these effects should follow. A decrease of temperature of 
eet per annum, and increase the area of snow nevé and ice, while 
evaporation would measurably cease; but over which deposition 
would continue. 
The area supposed to have been covered by the ice mantle in North 
America, Northern Asia, and Europe, is equal to about one-fifth of the 
northern hemisphere. The ice-field must also have encroached upon 
the bays, fiords, sounds, lakes, and minor sea spaces adjacent, which 
with the enlargement of the South Pole Continent, I assume to be as 
much more, or equal to one-fifth of the surface of the globe. 
icted, as 
surface of the land and the sea enlarged, and the ocean mass became 
diminished. 
‘In reference to dry land, the present ocean is determined to be as 
three to one; the earth presenting a surface three-fourths water and 
one-fourth land. Geographers estimate the water surface at 111,000,- 
000 of square miles, the land at 37,000,000. If both the extent and the 
thickness of the ice covering could be determined, its mass would be 
easily fixed, and also the increase or diminution it would cause in the 
waters of the sea. 
Dr. Hayes: penetrated seventy miles from the sea at Port Foulke, 
- Greenland, over the continental ice, which attained an elevation of 
5,000 feet. The ice-grooving in New England reaches a height vary- 
ntral part of British America. Its bulk is about one-tenth greater 
than water, and, dissolved on the same space, would fill a height of 
nine-tenths, or ninety feet in a hundred. 
Af it attained erage thickness of 2,000 feet in a solid state, it 
