DRAINAGE. 45 



the relationship of the distribution of the lakes to the various sti'uctural feat- 

 ures of the district; here only two Avill be mentioned. The lakes in sees. '^, 

 8, and 9, T. 65 N., R 6 W., are separated by barriers of glacial drift. The 

 depression in which they lie was eAndently determined by the structiu-e of 

 the slates, and is clearly of pre-Glacial origin. The existence of this string 

 of lakes is due to the low drift barriers in which the connecting streams are 

 now cutting. The most striking instance which the writer has observed of 

 this relationship of the lakes to the structure is seen in the string of lakes 

 just north of the international boundary known as That Mans, This Mans, 

 Agawa, and the Other Mans lakes. They lie in a great depression in a 

 syncline of slates, and, like those first mentioned, are separated by barriers 

 of di-ift. 



The lakes in the eastern part of the district have, with a few exceptions, 

 very small drainage areas, and but few swamps of any size are tributary 

 to them. Consequently the organic matter which colors the water of the 

 lakes west is wanting, and as a rule the water is beautifully clear and 

 transparent. 



A simple sounding apparatus was used for one season with a view to 

 getting the depths of the lake basins. This apparatus consisted of an oiled 

 silk fishing line, with knots 1 meter apart, wound on a large reel, with a 

 three-fourths pound lead plumb bob attached to the free end. The reel 

 was screwed to an arm of light wood. One end of this arm was fastened to 

 a crossbar in the bow of the canoe; the other end, on which the reel was 

 screwed, was free to swing. When the reel was not in use this arm lay 

 close to the left side of the canoe and was suspended from a hook, which 

 kept the reel in place and prevented it from unwinding. When the reel 

 was to be used the arm was swung in front and to the right of the man in 

 the bow, and rested on the gunwale of the canoe. The reel was thus sus- 

 pended over the water, and soundings could readily be taken and the 

 approximate -depths read by counting the knots and estimating the fractions 

 of meters. By this means soundings were taken in a number of the lakes. 

 These showed that the lakes in the western part were shallow. For 

 instance. Lake Vermilion, the largest body of water in the district, gave in 

 two places a depth of 10 meters. The average depth of the lake would be 

 much nearer 6 meters. In contrast to this the narrow, clear-water lakes in 

 the eastern portion of the district, those with high, rocky shores, were 



