Drift cards released at station 55 (fig. 10) be- 

 tween Isle Royale and Ontario were recovered on 

 both the north and soutfi shores of the Island, and a 

 good number (12 cards) were recovered 9 days after 

 release on Passage Island just off the northeast tip 

 of Isle Royale. This recovery pattern indicates that 

 the cards moved northeast along the shore of Isle 

 Royale after release. Returns from shore near the 

 point of release can be termed relatively prompt 

 when we consider that the island is only sparsely in- 

 habited by fishermen and tourists during the summer. 

 Recoveries on the southeast shore indicate that at 

 least some of the cards moved around the island in 

 a clockwise direction. Cards that landed on the 

 north shore of Lake Superior adjacent to the south- 

 west end of Isle Royale may have been among those 

 that moved around the island. The cards recovered 

 along the north shore of Lake Superior east of the 

 eastern tip of Isle Royale could have moved around 

 the island or they could have separated from the 

 group circling the island and entered the open-lake 

 circulation before coming to shore. The earliest 

 dates of recovery of these cards from different areas 

 along the north shore suggest a west-to-east drift; 

 the direction of movement indicates that they may 

 have circled the island. This last indication is op- 

 posed to that suggested by recoveries of cards re- 

 leased with BT cast IV- 34. The areas of recovery 

 do not overlap broadly, however, and recoveries of 

 cards released with BT cast IV-34 were mostly made 

 2 to 3 weeks later than those of cards released 

 at station 55. The counterclockwise movement of 

 water around Isle Royale is exactly opposite water 

 movements suggested by Harrington (1895). 



The known limitations of drift cards as current 

 indicators prohibit their use in speculating too ex- 

 tensively about general patterns of circulation. In 

 fact, some recent work has demonstrated that sur- 

 face circulation systems of the Great Lakes can 

 change markedly in a relatively short time (Johnson, 

 in press). 



Values which were obviously incorrect because of in- 

 strument failure or human error have been omitted. 



Physical 



Cruise number . Cruises are indicated by roman 

 numerals (Cruise VI of 1952 and Cruises I-IX of 

 1953). 



Station number . Stations are numbered consecu- 

 tively (arable numerals), starting with one at the 

 beginning of the season's operations. The majority 

 of the 1952 stations were not visited in 1953. When 

 a 1952 station was visited in 1953, it was given a 

 new number. 



Date . Month, day, and year are given in each 

 table. 



Location . The position of any activity is given in 

 degrees, minutes, and seconds of Latitude (north) 

 and Longitude (west) for Cisco records and in de- 

 grees and minutes for WiUiams records. 



Time . Eastern standard time at the initiation of 

 bathythermograph cast; when the Cisco stopped 

 for a hydrographic station; or at the beginning of 

 a plankton tow. 



Depth . AU depths, except those recorded In fath- 

 oms by a sonic fathometer, are recorded in meters. 



Wind. Cisco records: approximate force is given 

 in descriptive terms; calm, light, ■ • • . Direction 

 is recorded for 8 compass points (table 1). Williams 

 records: force is given in descriptive terms; direc- 

 tion is given for 32 points of ihe compass; if wind 

 direction changed frequently, it was listed as 

 variable. 



Barometer. The barometric pressure, corrected to 

 sea level, is given in inches to two decimal places. 



EXPLANATION OF TABLES 



All data presented in this report are actual 

 measurements — no interpolated values are included. 



Sky . Cisco records: amount of cloud cover is re- 

 corded in descriptive terms; clear, overcast 1/4, 

 overcast 1/2, overcast 3/4, and overcast 1. Cloud 

 type is also recorded. Williams records: coded as 

 as indicated in table 16. 



22 



