THE LAKE-BORDER MORA.KSTIC SYSTEM. 399 



volume of the Indiana Survey, has a depth of 212 feet at the Michigan 

 Central Station, whose altitude is only 20 feet above the lake. 1 



At Sawyer a deep well made by Mr. Rough has the following section: 



Section at Sawyer, Michigan. 



Feet. 



Surface sand 3 



Blue till, with sand bed at 25 feet and at bottom 120 



Rock of bluish color, varying in hardness 208 



Total depth 331 



. An exposure in the south bluff of Galien River, at New Troy, where 

 the till ridge is undermined by the stream, shows a slightly pebbly blue 

 clay from the river's edge up to a height of about 40 feet, Above this clay 

 there is a brown till interbedded with calcareous sand, having a thickness 

 of 12 feet. A well in the village of New Troy may have struck rock at a 

 depth of 65 feet, though the owner of the well thinks that sand and gravel 

 was entered below the supposed rock ledge. In case the latter interpreta- 

 tion is correct the former is probably erroneous. 



At the point where the Galien River cuts through Covert Ridge, in 

 sec. 2, T. 8 S., R. 20 W., there is sand at the top of the bluff 12 feet in 

 depth, below which is a brown pebbly clay interbedded with sand which is 

 quite calcareous. Both the till and the sand are in beds which are in arch- 

 ing and oblique attitudes. On the north bluff of the river nearly opposite 

 this point a well 96 feet in depth entered blue till at 2 feet and continued 

 in it to the bottom. 



At Bridgman a boring 250 feet in depth entered rock at 140 feet, and 

 struck an inflammable gas at about 160 feet which would burn a jet several 

 feet in height, The rock is apparently a shale. The upper 80 feet of the 

 drift is mainly blue till, but the lower 60 feet is gray sand, yielding water. 



Along the St. Joseph River there are sxtensive exposures of blue-gray 

 till in the west bluff from St. Joseph southward to the mouth of Hickory 

 Creek, but in the east bluff exposures were found in which there is a blue 

 silt free from pebbles rising to a height of 30 feet or more above the stream. 

 This silt is usually capped with 15 or 20 feet of sandy gravel. A well near 

 the east bluff, 2£ miles south of Benton Harbor, reached a depth of 153 

 feet without entering rock, and is mainly in blue clay ; whether silt or till 



1 Op. cit., p. 431. 



