7i 



escape under a pressure of 250 lbs., whereby a constant 



flow of brine is induced. 



The average Windsor brine contains about 26-5% 



of sol ds made up as follows : — 



Calcium sulphate I • 795 



Calcium chloride 0-377 



Magnesium chloride 0-124 



Potassium chloride tr. 



Sodium chloride 24-2 



The preparation of salt is effected by both the grainer 

 and vacuum pan processes. At the Sandwich plant of 

 the Canadian Salt Company, caustic soda is made by the 

 electrolytic method, and the liberated chlorine is utilized 

 for the manufacture of bleaching powder. This company 

 produces 350 bbls. of grainer salt, 1,400 bbls. of vacuum 

 salt, 2\ tons of caustic soda and 9 tons of bleaching powder 

 per diem. 



Thedford — Alt. 469-89 ft.; 142-84 m. The middle 

 Devonian strata (Hamilton formation) lie in a syncline on 

 the Onondaga limestones, and extend in a broad belt from 

 Lake Huron to Lake Erie. The country underlaid by this 

 formation is heavily covered with drift, so that exposures 

 are seen at a few places only. The most noted localities 

 are the vicinity of Thedford and the valley of the Aux 

 Sables river between Rock Glen and Marshall's Mills. 



For a full account of the geology of the Thedford 

 region, with lists of fossils, etc., see the section on Thedford 

 in the guide book to Excursion A12. 



Lake Huron — Lake Huron is 207 mi es (333 km.) 

 long, 100 miles (161 km.) wide and 

 has an area of 23,200 square miles (60,134 sq. km.) The 

 maximum depth is 750 feet (228-6 m.) and the elevation 

 579-86 feet (176 m.) At Kettle point near the southern 

 end of the lake is an exposure of the highest Devonian 

 strata in Ontario. The rocks consist of highly bituminous 

 shales supposed to be equivalent to the Genesee shales of 

 the New York geologists. Spherical concretions of brown 

 crystalline calcite occur in these shales and sometimes 

 reach a diameter of several feet. These concretions when 

 half exposed above the waters of the lake resemble inverted 

 kettles, and are responsible for the name of the point. 



