Various other methods have been used 

 to reduce exposure of drift bottles to 

 winds. Gilson (Carruthers 1930) experi- 

 mented with coupled systems consisting of 

 pairs of bottles, one bottle of the pair 

 with positive buoyancy and the other of 

 negative buoyancy, linked together by cords 

 3 meters long. In his experiments in the 

 North Sea he noted a marked difference in 

 rate of travel between simple surface float- 

 ing bottles and his coupled systems. On 

 occasion simple floating bottles and coupled 

 bottles released at the same time traveled 

 significantly different routes and direc- 

 tions. A similar coupled system was 

 described by Sverdrup, Johnson, and Fleming 

 (1942) in which the lower of the two coupled 

 bottles contained a weak acid which in time 

 corrodes a metal stopper, thus permitting 

 sea water to fill the bottle and sink it. 

 Fishermen are depended upon to return reply 

 cards from bottles that become entangled in 

 their nets. 



(ballasted and unballasted) , drag-fitted 

 bottles, and coupled bottles systems. 

 Drag-fitted bottles were of two kinds: 

 those with a metal drag suspended from a 

 surface-floating bottle by a wire 3 feet 

 long; those with a 9- inch-high, 6- inch- 

 diameter toffee tin suspended by a 3-foot 

 wire from a surface-floating bottle. The 

 toffee tin contained a drift bottle and 

 both the surface-floating bottle and the 

 one in the tin contained reply cards. The 

 coupled system consisted of two bottles, 

 a bottle of negative buoyancy suspended 

 from a surface-floating bottle by a 3-foot 

 piece of stout sash cord. Carruthers found 

 that in some instances unballasted surface 

 floaters, ballasted surface floaters, and 

 drag-fitted bottles put out at the same 

 time and place showed significantly dif- 

 ferent movements. Only two replies were 

 received from the coupled system — not enough 

 to allow a valid compjirison with the other 

 returns . 



One of the most popular methods of 

 reducing direct influence of the wind is by 

 using a metal drag that is suspended from 

 the drift bottle by a length of wire. This 

 arrangement not only reduces the surface 

 area exposed to wind but also causes travels 

 of the bottle to be affected by currents 

 between the surface and the depth of the 

 drag. Length of suspending wire ceui vary 

 but most workers have used a wire in the 

 neighborhood of 3 feet long. Mavor (1922), 

 however, (Bay of Fundy) used drags suspended 

 by wire 5.5 meters long. Webster and Buller 

 (1950) in studying ocean currents off the 

 New Jersey coast used both free bottles and 

 bottles with drags suspended by a 4-foot 

 wire. Their bottles released with drags 

 attained a greater speed of transport than 

 those without; furthermore, prevailing winds 

 had little effect upon the direction of 

 drift. Deason (1932) who released bottles 

 with a drag suspended 3 feet below the bot- 

 tle (Lake Michigan) concluded that the 

 action of the prevailing westerly winds had 

 much to do with the rate of and direction 

 of surface currents. In Hudson Bay experi- 

 ments, Hachey (1935) used a 3-foot galva- 

 nized wire to suspend a metal drag. He made 

 no remarks concerning the circulation of 

 waters other than the general circulation 

 seemed to be counterclockwise. 



Carruthers (1930) experimented with 

 drift bottles on the North Sea to ascertain 

 difference in the travels of surface floaters 



In recent years drift cards in pis tic 

 envelopes, as developed by Olson (1951), 

 have been looked upon with favor by some as 

 a substitute for drift bottles. Olson used 

 a polyethylene envelope 0.004 inch thick 

 with the return card hermetically sealed 

 within. His Lake Erie experiments indicated 

 that the travels of these envelopes were not 

 at the complete mercy of the wind. Some 

 cards that were returned 18 months after 

 release were still in good condition. In 

 remarks on Olson's work, Verber (1953) wrote 

 that drift cards were better than drift 

 bottles since the cards are inexpensive and 

 give greater accuracy in interpreting the 

 surface flow because they are not exposed 

 to the wind. He concluded that Olson's 

 work proved a direct correlation between 

 wind and surface flow in western Lake Erie 

 and that the movements of surface water were 

 wind controlled. 



In Georgian Bay, Lake Huron, 3,000 

 drift cards similar to those developed by 

 Olson (1951) were dropped from an airplcuie 

 (Fry 1956). Polyethylene material, however, 

 was only 0.002 inch thick and proved to be 

 only moderately satisfactory because pin- 

 holes developed in the plastic from sand 

 abrasion. 



Drift cards were used by the Fish and 

 Wildlife Service on Lake Superior in 1953 

 Eind on Lake Michigan in 1954. Few returns 

 were obtained from these releases, and of 



