492 A. W. G. T\'ILSON SHORELINE STUDIES ON ONTARIO AND ERIE 



that when they had their nets set in deep water during the prevalence 

 of strong easterly winds they would find in drawing the nets that any 

 floating submerged leaves or weeds would be caught on the opposite side 

 of the net, showing that the undercurrent was from the west. This 

 would indicate that the waters, being driven to the west, pile up at Bur- 

 lington beach, and the head of water thus raised forces a portion of the 

 water back as an undercurrent. The seiche oscillations on the lakes 

 must tend to generate local undercurrents at the ends of the lakes 

 whenever the water rises above the niean level. 



Out on the open lake the transitory movement of the water before the 

 wind takes the form of a drift, and because of the prevalence of west- 

 erly winds this drift is most frequently identified with the easterly 



Figure 7. — Drift Currents in Lake Erie 



flowing body currents of the lakes. The drift currents vary their direc- 

 tion with the wind that causes them, usually starting a short interval 

 after the wind has commenced to blow and continuing for some time, 

 often several hours and occasionally several days, after the winds that 

 caused them have ceased. Where this drifting surface water impinges on 

 a shore a longshore current is developed, the direction of the current 

 being dependent on the angle at which the drift impinges on the shore- 

 line. These currents, which for convenience may be designated wind 

 currents, are seen during wind storms and reach their maximum velocity 

 at times of the strongest storms. They are so intimately connected with 

 wave and surf movements that both must be considered together. It is 

 when they act in conjunction that active erosion, transportation, and 

 deposition take place. 



