LITERARY NOTICES, 



Z77 



the Association, whose report we have be- 

 fore us, held at Atlanta, Georgia, April, 

 1873, Mr. W, Leconte Stevens, of the Boys' 

 High School of Savannah, delivered an ad- 

 dress on " Scientific School Studies,'' which 

 has in it the ring of the true metal. Scien- 

 tific education is justly prized, not only for 

 the practical knowledge that it imparts, but 

 also for the discipline it affbrds to the mind 

 in drawing out and strengthening the per- 

 ceptive faculties, and inducing clear and ac- 

 curate habits of thought. 



The Great Ice Age and its Relation to the 

 Antiquity of Man. By James Geikie, 

 F. R. S. E., etc. New York : D. Apple- 

 ton & Co. 8vo., 525 pp. Price $2.50. 



There are many persons who would lis- 

 ten with an air of scornful incredulity to the 

 statement that the hills and valleys of New 

 York and New England, which summer now 

 clothes with a mantle of luxuriant verdure, 

 were once a dreary, desolate waste, covered 

 up by a crust of ice many hundred feet 

 thick. Nevertheless, the fact is indisput- 

 able ; the mountains, the rocks, the config- 

 uration of the soil, even the fragmentary 

 stones that lie upon the surface, point si- 

 lently, eloquently, and immovably, to the 

 fact. Geologists had long noticed, in val- 

 leys adjoining mountainous districts, cer- 

 tain long, low ridges, called " sow-backs," 

 running parallel to each other and trending 

 down the valley. They had dug into these 

 ridges and picked out flat, oblong stones, 

 with strange scratches upon their surfaces. 

 They had noticed that, while the mountain- 

 sides looked jagged and rugged from below, 

 from above they presented a rounded and 

 undulating outline to the very base of the 

 mountain. It was also noticed that the 

 rocks on the mountain-sides displayed on 

 their undulating or upper surface the same 

 mysterious scratches or striae that were ob- 

 served on the stones embedded in the ridges 

 below. All of these signs greatly puzzled 

 the geologists, and various theories were in- 

 vented to account for them, but their true 

 significance was not dreamed of until the 

 late Prof Agassiz, from the study of Alpine 

 geology, announced that they were the re- 

 sults of one and the same cause — glacial ac- 

 tion ; that is, that the whole face of the coun- 

 try was covered to the depth of two or three 



thousand feet with solid ice, which, in grad- 

 ually creeping toward the ocean to shed its 

 bergs, had worn the mountain-sides into 

 waves ; broken, scratched, and transported 

 the rock to distant points, and furrowed 

 up the soil of the valleys through which 

 it continued to crawl seaward. Unmis- 

 takable evidence existed that this arctic 

 condition of climate prevailed all over 

 Europe, Asia, and America, northward of 

 45° north latitude; that is to say, that the 

 vast area comprehended within that circle 

 was once covered with ice as completely as 

 parts of Greenland and the rest of the coun- 

 try immediately around the north-pole is 

 now covered. Of course no life could exist 

 under such conditions, and it was therefore 

 supposed that the advent of man, within 

 that circle at least, must have occurred sub- 

 sequent to their passing away. It is on 

 this point that Mr. Geikie's book throws a 

 flood of light. He describes the evidences 

 of the glacial condition with admirable 

 skill and clearness, and then proceeds to 

 consider its bearing on the antiquity of 

 man. The earth and stones, or " rubbish," 

 that covers the rocky foundation of the 

 countries comprehended in the circle de- 

 scribed, is called the " Drift or Glacial For- 

 mation," to indicate that it was deposited 

 thereon by glacial action. The drift is di- 

 vided into two parts, the upper drift and 

 the lower drift. The lower is, of course, 

 the oldest formation. It is composed of a 

 " tough, stony clay," colored like the rocks 

 about which it lies, and small, fragmentary 

 stones, flattened and scratched. The mass 

 of clay and stones is called " till." The till 

 is not laminated, but pressed down in a con- 

 fused mass, and its coloring shows it to have 

 been produced by comminution of the rock 

 upon which it lies, while the rock itself cor- 

 roborates that testimony by being scratched 

 and polished like the stones in the till. 

 Thus the till was formed by the grinding 

 of the ice against the rock. Deeply em- 

 bedded within the till, occur at intervals 

 deposits of sand and gravel, such as we find 

 at the bottom of lakes and rivers. But 

 how could there be lakes and rivers to de- 

 posit sediment, while the whole country was 

 covered by a crust of ice more than a thou- 

 sand feet thick ? This is a question that has 

 long puzzled geologists. But only because 



