36 THE POLAR GLACIERS. 



Another 5,000 years pass, and the perigee now coincides with 

 the summer solstice of the northern hemisphere. This is the 

 position there of greatest cold ; the winters are twenty-eight 

 days longer than the summers ; and the extra days are in great 

 part those of the briefest sunshine. Besides this, the earth is 

 10,500,000 miles further from the sun in winter than in summer. 

 According to the most careful calculations, the temperature of 

 extreme northern regions would be lowered 50, and the mean 

 annual range would be fully 60 below zero. This in all proba- 

 bility would carry the isothermal line of Labrador, South Green- 

 land, and Iceland (32 Falir.), down to Charleston and the Gulf 

 of Mexico. The late Prof. Agassiz found ice-marks as far south as 

 this, though it can hardly be supposed that the permanent glacier 

 extended so far. There are however abundant signs of the 

 permanent ice-layer all over the State of New York, and both 

 east and west of it. The same distinguished authority was wont 

 to claim in his lectures that all the beautiful north and south 

 lakes of Western New York the Cayuga, the Seneca, the Can- 

 andaigua were ploughed out of the solid rock and walled around 

 with their clay and gravel hills, by advancing and retreating 

 glaciers. The rocky summits of New England are found to be 

 grooved and scored all over their sides and tops with markings 

 always in nearly a north and south direction. They have been 

 traced on Mount Washington to within 300 feet of the highest 

 point. There can be no doubt that, at the time we are writing 

 of, about 200,000 years ago, there was one solid ice-stratum of 

 immense thickness Agassiz said from two to three miles slowly 

 being pushed from the northward by the power of freezing 

 water, over all of New England and the Lake States. 



Again the perigee proceeds to meet the autumnal equinox. 

 The winter and the summer seasons have again become equal in 

 length ; and the sun is just half its time on the north side of the 

 equator. The great ice-shroud is now being gradually withdrawn. 

 Where it abuts on deep waters, enormous icebergs are broken off 

 and float away to the south, carrying bowlders and soil and what- 

 ever it may have picked up in its slow course down to the sea. 

 Where it terminates in shallow waters or on the land, its effect is 



