No. 1.] GEOLOGICAL SURVEY OF CANADA. 79 



erosion on the shores of Onondaga Lake. The limits of this val- 

 ley are nearly four miles from north to south, by two miles from 

 east to west. The shales belonging to the base of the formation 

 crop out to the northward, and are found in the various borings 

 beneath the ancient gravel deposit, which is itself covered by 

 thirty or forty feet of a more recent deposit of loam or sand. 

 The bottom of the basin is very irregular, the shales being met 

 with at depths of from 90 to 180 feet in some parts, and at 382 

 feet in the middle of the valley. According to Mr. Geddes, the 

 greatest depth of this ancient basin is not less than 414 feet 

 below the surface-level of Onondao-a Lake, and 50 feet below the 

 sea level. — (Trans. N. Y. State Agricultural Society, 1859.) 



Beds of the ancient gravel are occasionally found converted into 

 a hard concrete, the cementing material of which, in some cases 

 at least, is crystalline laminated gypsum. The wells are bored in 

 this gravel to various depths up to 350 feet ; brine is met with 

 at about 100 feet, but the brines of the deeper wells are stronger, 

 and less liable to variations in quality with the season of the 

 year." 



From the Report on Iron we extract as of much interest the 

 passages referring to Iron Sands : 



" The silicious sands of most regions contain a greater or less 

 proportion of heavy black grains, which consist chiefly of some 

 ore of iron. The source of these is easily traced to the crystal- 

 line rocks which, by their disintegration, have given rise to the 

 sands, and which, in addition to occasional beds or masses of iron 

 ores, generally hold disseminated grains of magnetite, hematite, 

 titanic iron (menaccanite or ilmenite of mineralogists) and more 

 rarely chromic iron ore. In the process of washing earth and 

 sand for gold, diamonds, or tin ore, considerable quantities of 

 these black iron sands are met with, and, from their high specific 

 gravity, remain when the iighter portions are washed away. The 

 chromic iron ore is comparatively rare, and confined to certain 

 districts ; the hematite, with the exception of some crystalline 

 varieties, is generally too soft to resist the abrading forces which 

 have reduced the solid rock to sand, so that the black grains, in 

 most districts, consist chiefly of magnetic and titanic iron ores. 

 In the gold-bearing alluvions of the Chaudiere region in Canada, 

 the sands obtained in washing for gold, when purified as much as 

 possible by washing, were found to hold eighteen per cent, of 



