294 A. P. COLEMAN 



at the higher level is testified by the thorough oxidation of the 

 iron in the upper sandy beds, which are in some layers deep 

 brown in color, and completely cemented with limonite. The 

 blue layers (2, 4 and 7) have retained their color because of 

 the large amount of deoxidizing vegetable material present in 

 them. 



The change in the level of the interglacial lake effected a 

 great change in another respect. Where the valley of the Lau- 

 rentian river had existed there was now a broad and deep bay 

 running to the north, and the great river began to spread out 

 clay and silt derived from its upper reaches in this basin. The 

 upper bed of blue clay may have been formed by a shifting of 

 the current of the main river, which, however, shifted again while 

 the highest layer of sand was formed, bringing to a close the 

 beds belonging to the warm climate series. 



The extent of the Don beds, as indicated by the typical unio 

 sands and clays, is not known very thoroughly, owing to the 

 depth at which they are buried in most places. They occur a 

 few feet below Lake Ontario at Scarboro', four miles southwest of 

 Taylor's brickyard and at Price's brickyard about half way 

 between; and unios have been found in sandy beds of intergla- 

 cial age at Adare's sand pit on Shaw street, about three miles 

 west of Taylor's. As logs of wood have been found by well dig- 

 gers at points between, there is a strong probability that the Don 

 beds continue to that point, in which case they have a known 

 extent from east to west of more than six miles, with a breadth 

 from north to south of more than two miles. The real area is 

 probably much greater than this. 



THE SCARBORO' OR COOL CLIMATE BEDS 



After the close of the Don period the interglacial lake deepened 

 greatly, finally standing more than 150 feet above Lake Ontario, 

 and a great series of clays and sands were deposited by the Lau- 

 rentian river in the form of delta materials in the wide and deep 

 bay, at this time extending still farther to the north than before. 

 As seen at Taylor's brickyard, the clay beds, gray and finely 



