318 Tertiary. 



shores of Owen sound, at 120, 150 aud 200 feet above the present level 

 of Lake Huron, and some of the higher terraces continue with great 

 regularity for several miles. Terraces and ancient beaches are found 

 in many places upon Lake Superior. On the north side of the lake, the 

 ancient water margins are frequently marked hy the wearing of the 

 solid rock as well as by the loose materials. In a sandy ridge near the 

 western part of Lake Ontario, called Burlington heights, at the height 

 of 70 feet above the lake, several bones of the mammoth were discov 

 ered, and in the same excavation, seven feet higher, the horns of the 

 wapiti (Cervus canadensis), and the jaw of a beaver {Castor fiber), were 

 also found. 



The drift in Illinois* is divided into — 1st, blue plastic clay, with 

 small pebbles, often containing fragments of wood, and sometimes the 

 trunks of trees of considerable size, which form the lower division of 

 the mass; 2d, buff and yellow clays and gravel, and irregular beds of 

 sand, with bowlders of water-worn rock of various sizes interspersed 

 through the whole; and lastly, reddish-brown clays, generally free 

 from bowlders, and forming the subsoil in those portions of the State 

 remote from the streams, and where the loess is wanting. The 

 scratched and grooved surfaces presented by the underlying limestones, 

 at many localities, and the smoothly worn and polished surfaces that 

 may be seen at others, and the immense size and weight of many of 

 the transported bowlders, which have been carried for hundreds of 

 miles from the nearest outcrop of the metamorphic beds to which they 

 belong, alike preclude the idea that such results have been produced 

 hy the action of water alone. Huge masses of moving ice, like the 

 icebergs of the present day, loaded with the mineral detritus of the far 

 northern lands, with angular fragments of hard, metamorphic rock, 

 firmly imbedded in the solid ice to act as a graver upon whatever rock 

 surface the}- might come in contact, are the only known agencies that 

 seem adequate to the production of the phenomena, characteristic of the 

 drift deposits in this State. 



There is an area in the southern part of the State, and another in the 

 northwestern part of the State, over which the drift deposits do not 

 extend. The lead region of Illinois, Iowa and Wisconsin was not in- 

 vaded by the drift, and is, therefore, entirel}^ free from accumulations of 

 gravel, pebbles and bowlders, that characterize drift areas. The topo- 

 graphical features of the country have been produced b}' the quiet but 



* Geo. Sur. of Illinois, vol. i. 



