BAROMETRIC PRESSURES ON THE GREAT LAKES 



53 



one must expect to find the wind effects much smaller at these Lake Mich- 

 igan-Huron gages than at these Lake Erie gages. 



TABLE No. 10. Values of Zxfor use in formula (59) at the gages indicated. 



The average values of S* at the five gages stand in the order in which the 

 gages are given in table No. 10. Buffalo has the largest average value of 2*, 

 and hence the largest wind effects, among these stations, and Mackinaw has 

 the smallest. 



Buffalo is at the eastern end of Lake Erie, and Cleveland is to the westward 

 of the middle of the lake. Cleveland is on the south shore of the lake, and 

 Buffalo is near the most northerly point of the lake. From these facts 

 alone one would infer that in general the wind effects would be of opposite 

 signs at the two gages. Yet table No. 10 shows the wind effects to be the 

 same in sign at the two gages for six out of the eight directions tabulated. The 

 only values of 2* at the two gages which are of opposite signs are those for 

 the directions south and north. This apparently anomalous agreement in 

 signs arises from the crowding of the nodal lines into the western portion of 

 Lake Erie, in the region of shallow water, to which attention was called on 

 page 51, in such wise that for all directions of wind except north and south 

 Cleveland and Buffalo are on the same side of the nodal line. The effect of 

 southwest, west, and northwest winds is to raise the elevation of the water 

 surface at Cleveland rather than to lower it. One would naturally expect 

 the latter from consideration of the plan of the lake alone. 



There is a large change in x at Cleveland when the wind changes from 

 south to southwest, viz., from 1.72 to +3 . 89. Note by comparison with 

 plate 2 that this is due to the sudden shift of the nodal line from the leeward 

 of Cleveland to the windward when this change of wind occurs. The 

 corresponding statements are true for the shift of wind from north to north- 

 east. 



Milwaukee is much nearer the southern end of Lake Michigan than the 

 northern end. From this fact alone one would naturally infer that a south 

 wind would lower the elevation of the water surface at Milwaukee. But 

 table No. 10 shows that 2* for Milwaukee for a south wind is +0.36 and 

 that therefore the water surface is raised at Milwaukee by a south wind. 



