20 



two miles to the south, and wood and shells have been ob- 

 tained from excavations and wells at many points in the 

 city to the west and below the level of the lake at Scarboro 

 also, so that the Don beds cover several square miles, though 

 the exact boundaries are not known. 



A deposit of sand and gravel containing wood and shells 

 has been found near Thornhill, fourteen miles north of lake 

 Ontario, while boring for water. It underlies 200 or 300 

 feet of clay, and is no doubt the northward extension of the 

 Don beds along the channel of the interglacial river which 

 formed the delta. 



THE SCARBORO BEDS. 



The upper interglacial beds at the Don valley brickyard, 

 consisting of laminated clay with no fossils except peaty 

 materials, are found at several outcrops to the north and 

 northwest, growing thicker in those directions and reach- 

 ing, north of Reservoir park, an elevation of about 150 feet 

 above lake Ontario. They are also found to the east of 

 the Don and at Scarboro heights, where they are best ex- 

 posed. In the brickyard 672 laminae were counted in a 

 height of 19 feet 9 inches, probably representing as many 

 years of deposition. Above this a foot or two were too 

 much broken up by the later ice advance to be counted. The 

 counting was done by Baron de Geer's method, devised for 

 the marine clays of Sweden, the limits of the layers being 

 marked on strips of paper. 



Since the Scarboro cliffs give the best opportunities for 

 the study of these beds, they will be described as typical. 

 The splendid Scarboro section was worked out by Dr. 

 George Jennings Hinde many years ago, demonstrating the 

 first series of interglacial beds recognized in America. His 

 work was so good as to require scarcely any change in later 

 times. At Scarboro the Don beds are not visible in the 

 cliffs, but wells sunk on the beach show that they exist a 

 few feet below the lake and have a thickness of 36 feet. 

 They consist of yellowish sand with some beds of clay, 

 containing unios and pieces of wood as in the Don sections. 



Above the water level, where the interglacial section is 

 most complete, there is not only laminated clay like that 

 referred to above, but also a great thickness of sand rest- 

 ing upon it. 



