SOME PLANKTON STUDIES IN THE GREAT LAKES. 133 



A similar record was kept of the contents of the fish stomachs, but no special 

 blank was used for this purpose. It is desirable to use such a blank. 



Reports are now in preparation by the various members of the laboratory staff, 

 and as these are soon to be published as bulletins of the Michigan Fish Commission, 

 detailed statements will be reserved for such publication. The following statements 

 as to the biological conditions existing in the lake may prove of interest. 



As to the lake itself, it has nearly the form of an equilateral triangle with rounded 

 angles and with sides, each of which measures 25 to 30 miles. The southern and 

 shortest side of the triangle runs nearly east and west, its western side inclines toward 

 the east as it extends northward, while the third and longest side looks directly toward 

 the northeast, and may be called the northeastern shore. 



In the middle of this northeastern shore the lake receives the waters of the St. 

 Clair River, which carries the overflow of the three upper lakes. At its entrance into 

 Lake St. Clair the river breaks up into several channels, each of which again divides 

 once or twice, so that the water of the river euters the lake through nine well-defined 

 mouths of various sizes. These mouths are scattered for a distance of 20 miles along 

 the northeast shore and discharge their waters into the lake at a considerable velocity. 

 Between the channels which diverge from the main river to these mouths is swampy, 

 shifting ground, which forms an enormous delta overgrown with rushes and covered 

 usually by a foot or more of water. These are the celebrated St. Clair fiats. The 

 banks of the channels only are usually formed of moderately firm ground, and it is 

 upon them that numerous summer residences and hotels have been built. 



The northwest corner of the triangle receives the greater part of the discharge 

 of the northern fork of the river (North Channel) and is partly cut off by a projecting 

 point of the west shore, so that there is formed a bay, Anchor Bay, upon which is 

 situated the town of New Baltimore. From the southwest corner of the triangle the 

 Detroit River leaves the lake and flows at first toward the west. The water poured 

 into the triangular lake by numerous mouths along nearly the whole of one side, thus 

 converges to the angle opposite this side, where it flows out. The lake is but little 

 more than an enormous expansion of the river, so that almost everywhere there is 

 a current, usually slight, but in some places near the mouths of channels reaching 

 a velocity of 3 or 4 miles an hour. The lake is shallow. Over a large central area 

 the bottom is quite level and the water has a nearly uniform depth of 20 feet. 

 From this central area the depth diminishes toward the shores in every direction. 

 The shores, so far as we examined them, are made by a clay bluff, which varies in 

 height from 1 or 2 feet to perhaps 10 or 20 feet. Mixed with the blue clay which 

 forms the bluff, there is more or less gravel or sand, and the action of the waves has 

 in many places washed this free from the clay and left it in the form of little stretches 

 of gravelly or sandy beach. The bottom of the lake is everywhere composed of the 

 same mixture of blue clay with sand or gravel. On the bottom also the finer clay 

 particles have been washed away from the superficial 1 Iyer of the bottom, so that 

 there is left everywhere a thin layer of fine sand or gravel which separates the hard 

 clay bottom from the overlying water. This layer of sand is in some places so fine 

 that it is known popularly as mud. 



The water of the lake is not clear. No measure of its transparency has yet been 

 made, but it lacks the great transparency of the water of the northern lakes. The 



