considerable difference in recoveries of identical 

 drift units released oa different days and bring out 

 also the dissimilarities of returns from different kinds 

 of units released on the same date. As wUl be seen 

 later, generally similar variability characterized all 

 transects. 



The most obvious difference in the directions of 

 recovery of bottles released on August 3 and Septem- 

 ber 15 is from the four westernmost stations (fig. 4). 

 Recoveries from the August 3 releases at these stations 

 with the exception of 1 bottle, were from the Illinois 

 (west) shores, whereas all recoveries from the Septem- 

 ber releases were from the Michigan (east) shores. Al- 

 though the wind was decidedly variable in August 

 (fig. 3, table 3), for 5 days following the August 3 

 releases the Chicago Weather Bureau reported prevail- 

 ing east and northeast winds. Westerly winds prevail- 

 ed during September and October (fig. 3). The recov- 

 ery of most bottles released at the remaining stations 

 from the Michigan shores indicates a general west -to- 

 east drift in which the northerly movements {wedom- 

 inate;! slightly above those toward the south. Time- 

 areal distribution of recoveries from this transect sug- 

 gested no gyral motion of surface water in southern 

 Lake Michigan during the time the units were adrift. 



Recoveries of drift envelopes from releases along 

 the South Haven-Waukegan transect were low (fig. 4). 

 The location ofrecovery points of bottles and envelopes 

 released at the 4 westernmost stations were significantly 

 different; the envelopes exhibited a much greater ten- 

 dency to drift to the south than did the bottles. 



Grand Haven -Milwaukee transect. —Returns from 

 drift units released along the Grand Haven -Milwaukee 

 transect July 9 and July 29 had many similarities (figs. 

 5 and 6). Recoveries from the August 19 and Septem- 

 ber 9-11 (strong winds prevented completion of the 

 transect on September 9) transects resembled each other, 

 but differences between these two pairs of observations 

 were substantial. Discrepancies between results from 

 bottles and envelopes were less pronounced than those 

 of the South Haven-Waukegan transect. 



Recoveries from the releases made on July 9 sug- 

 gest that a littoral current was flowing inshore to the 

 north off Grand Haven, whereas surface -current move- 

 ments were toward the south farther offehore (fig. S). 

 Recoveries from releases along the western half of the 

 transect were obtained from several directions but those 

 from the 2 most westerly stations indicate a northward 



drift similar to that on the east shore. The more 

 definitely eastward drift between midlake and the 

 2 most westerly stations constituted a small differ- 

 ence between the July 9 and July 29 transects. The 

 littoral current to the north appeared again inshore 

 off Grand Haven following the July 29 releases, and 

 flow was to the south from the next 6 stations. The 

 recoveries from the releases along the western half 

 of the transect were widely scattered, and the north- 

 bound current was still present near the west shore. 

 Winds in July and August had slightly greater compo- 

 nents from the north than from any other direction al- 

 though variability was high in August (fig. 3). It is 

 apparent from the recoveries of the July 9 and July 

 29 releases that no clearly defined counterclockwise 

 whirl as posmlated by Harrington (1895) had develop- 

 ed in the southern portion of the lake. Rather, sur- 

 face water movenients tended to be clockwise as de- 

 scribed by Ayers et al. (1958). 



At the time the battles of the August 19 and 

 September 9-11 releases were adrift the littoral cur- 

 rent flowing to the ncxth off Grand Haven had broad- 

 ened to include the eastern 10 miles of the lake (Aug- 

 ust releases) and later the eastern half (September 

 transect). Recoveries from the midlake area between 

 inshore stations were made mostly from Michigan. 

 The north-bound current that existed along the Wis- 

 consin shore had disappeared; recoveries from the 2 

 inshore stations were scattered. 



The few drift envelopes recovered from re- 

 leases on the same dates at inshore stations on this 

 transect had followed courses generally similar to 

 those followed by bottles (fig, 6). 



Ludington -Manitowoc transect. --Recoveries 

 from bottles liberated on the Ludington -Manitowoc 

 transect cm? August 23-25 indicate movement of sur- 

 face water both to the north and south off Ludington 

 (fig. 7). A similar condition existed off Manitowoc 

 where there was evidence of a north-bound current 

 inshore and a south-bound one farther offshore. Di- 

 rection of recovery from the remaining stations was 

 extremely variable. 



Time distribution of recovery at the first sta- 

 tion off Ludington suggests the possibility that aU 

 bottles at first were carried to the north of the re- 

 lease station where four landed; subsequently, a 

 change of the current from north to south would ac- 

 count for the recovery of bottles to the south of the 



