the figure. The curves for the other cruises are omit - 

 ted to avoid confusion. 



It seems apparent that these water movements 

 were caused or at least influenced by the wind effect 

 on the lake level. Figures 17 and 18 have been pre- 

 pared in an effort to establish this relation. The rel- 

 ative positions of the cold water on the various dates 

 of observation are shown with the graph of the lake 

 level at Buffalo. The daily means were used in 

 plotting the lake-level curve, and the comparative- 

 ly large and sudden fluctuations caused by high 

 winds of short duration are apparent only insofar as 

 they affected the means. 



Figure 17 shows the cold water to be in its nor- 

 mal position on August 1, 1928, and the lake level 

 to be uniform until the 10th, when easterly winds 

 caused a drop of 0. 7 ft. in the 2 following days 

 (minimum on August 12). Three days later, although 

 the lake level had risen 0. 6 ft. , the cold water was 

 eastward (see limit in fig. 16). Apparently the 

 great eastward movement was the result of the low- 

 ering lake level at Buffalo, but we do not know 

 when the movement started or when the maximum 

 eastward limit was reached. We do know, however, 

 that the cold water returned to the Deep Hole dur- 

 ing the latter part of the month, even though the 

 mean level at Buffalo had fallen slightly since the 

 observations of the 15th. 



Figure 18 shows that the cold water was to the 

 westward (see fig. 16, cruise 4) on July 6-10, 1929, 

 after the lake level had been raised by the strong 

 southwest winds of the preceding 8 days. The water 

 was probably in westward movement soon after the 

 40-m.p. h. southwest wind of June 28 and was held 

 to the westward by the week of strong winds. After 

 July 10, the wind was variable and moderate until 

 the 18th, and during this period the cold water un- 

 doubtedly returned to its normal position. On July 

 19 and 20, the wind at Buffalo was easterly and 

 there was a marked lowering of the level of the 

 eastern end of the lake. Three days after this low- 

 ering, the cold water was observed to be eastward 

 (fig. 16, cruise 5). By August 2, the cold water 

 had probably returned to its normal position and was 

 then set in motion to the westward by the strong 

 southwest winds of August 3-4, which raised the lake 

 level at Buffalo materially. On August 6 the wind 

 died down and on the 7th and 8th blew from the 

 east, causing the level at Buffalo to fall rapidly. 



This lowering of level apparently caused the cold 

 water to reverse its direction, for its position on 

 August 8-12 was once more nearly normal. It is be- 

 lieved that the cold water was moving from the west- 

 ward to the eastward between August 6 and 14, and 

 that the observations were taken when a nearly normal 

 position was reached. 



Unfortunately, the data are not sufficient to plot 

 the daily position of the cold water and we are forced 

 to interpolate between observations. The actual ob- 

 servations, however, seem to justify the following 

 conclusions. During the summer a cold-water mass 

 normally lies in the Deep Hole below the disconti- 

 nuity layer. Winds of short duration, even though 

 they have a high velocity and cause wide but tem- 

 porary fluctuations in the lake level at Buffalo, do 

 not alter the position of this cold water materially. 

 But when the lake level at Buffalo is raised over a 

 period of 2 or 3 days, even though the total rise does 

 not exceed 0. 5 foot, the cold water is depressed to the 

 westward, and remains westward so long as the surface 

 of the lake has an upward gradient to the eastward. 

 When the outside forces subside and the surface of the 

 lake returns to a horizontal position, the cold water 

 returns to its normal position and remains there until 

 the outside forces again build up a gradient on the lake. 

 An upward gradient to the westward causes a similar 

 but opposite movement of the cold water. Because 

 the movements are slow, a lag exists between the 

 maximum or minimum lake level and the maximum 

 limit of cold-water movement. The much colder 

 and therefore heavier waters below the discontinuity 

 layer are returned to the Deep Hole by gravity and, 

 as this is an actual movement of the water mass, it 

 is probably a source of the surface currents so often 

 witnessed during periods of comparatively calm 

 weather. A uniform period of oscillation is not evi- 

 dent in these movements, although it can not be 

 stated that an oscillatory movement does not exist. 



That the bottom water is often in motion is well 

 known to the fishermen. During the summer of 1929, 

 the fish tug George V raised whitefish nets from the 

 bottom in 19 fathoms near station 53 (midlake) and 

 found them to be foul with old paper, leaves, green 

 slime, and other drift material. A small sample of 

 this twine was later examined by John Van Oosten, 

 of the Bureau of Fisheries, and although it had com- 

 pletely dried out, particles of paper (printed matter) 

 and leaves were found in abundance. 



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