The currents of Lakes Michigan and Huron / John C. Ayers.

9

down the center of the lake and approaching the St. Clair River from the northeast. The small clockwise eddy normally off Lakeport was pushed up to the
offing of Lexington.
Drift Bottle Studies
Charts 15 and 16 and Tables 6 and 7 give the release and discovery data on
78 drift bottles recovered from releases in Lake Michigan on 9 and 10 August
1955. These releases accompanied the unusual current condition in the lake and
the movements of the bottles as well as their average speeds have been used
as checks on the current directions and speeds of Charts 11 and 12 which were
deduced primarily from the distribution of water density.
These drift bottles have been studied and used in the same way as were
those accompanying the normal currents. No additional comment is considered
necessary for the bottles of 9 August. The bottles released on 10 August fall
into two groups, on the basis of their movements. Those recovered in less
than four days (see Table 7) moved in directions that indicate they were carried
by the unusual current condition present on 10 August. Those found and reported
after four days or more moved in directions not like those of the unusual current pattern, but like those of the normal current pattern. They are believed
to have stayed adrift until after the unusual currents had ceased and the winds
and currents had returned to normal or nearly so.
Charts 17 and 18, and Tables 8 and 9, give the drift bottle data for the unusual current conditions in Lake Huron.
IN CLOSING
Abridgment such as has been made here is never completely successful.
The omissions and condensations that are necessary always result in the loss
of explanatory material, and sometimes result in ambiguities where the reader
obtains an idea quite different from that being presented. The author honestly
believes that he has been successful in avoiding ambiguities, but he also has a
healthy pessimism about the matter. The material presented here has been
abstracted from the surface temperature, drift bottle, and composite surface
currents sections of the two full-fledged works indicated earlier. The perplexed
reader is referred to them, they are not as difficult as they may look.