Analyses of 161 thermograms from vessels on the Boston-Bermuda route illustrate temporary migrations of Gulf Stream water during 1932–1938. A northern limit of Gulf Stream waters, determined by the position of the "cold wall", on this route varies between latitudes 36°41′N. and 40°23′N. Average monthly positions of the northern limit indicate that more southerly positions follow the equinoxes. These mean monthly positions, plotted on a lagging scale, are inversely correlated with average monthly differences in sea level between Bermuda and Charleston, S.C., which inverse correlation indicates that the position of the northern limit is related to current strength, decrease in strength being followed by northerly migrations, and increase by southerly migrations. Hydrographic observations off the Canadian Atlantic coast offer some evidence of the influence of these migrations on the waters of this area.