those cards returned many were found 

 water-soaked inside the polyethylene enve- 

 lope. The polyethylene envelope was in 

 some cases not sealed properly; and since 

 a number of cards were found on the bottom 

 off shore, it is possible that many of them 

 sank before they reached land. 



Bougis and Ruivo (1953) added 

 ballast to the polyethylene-envelope 

 type of float. Their "siphonophone" 

 consisted of three parts: a poleth- 

 ylene envelope of 0.004 inch thick- 

 ness that floats on the surface; the 

 reply card within the envelope; and 

 a drift with ballast. The drift was 

 a ribbon of polyethylene 1.2 meters 

 long and 8 centimeters wide attached 

 to the polyethylene float. About 20 

 grams of lead ballast were placed at 

 the lower extremity of the ribbon to 

 make the drift sink into the water. 

 Experiments on the Bay Banyuls, with 

 drift cards only and "siphonophore" 

 drifts, proved that the former fol- 

 lowed the course of the wind closely, 

 whereas the latter traveled at vari- 

 ous angles with the wind and also 

 moved much more slowly. 



Drift bottles released in 



Saginaw Bay and Lake Huron 



The drift bottle with metal 

 drag was the design chosen for the 

 Saginaw Bay-Lake Huron study in 1956 

 (fig. 2). It WcLS evident from work 

 by the Fish and Wildlife Service on 

 Lake Michigan in 1955 that bottles 

 with drags resisted direct effects 

 of wind and presumably gave a better 

 indication of water currents near 

 the surface than did the ballasted 

 bottles. Plastic envelopes were 

 rejected for reasons already noted. 

 A disadvantage of a bottle with the 

 drag suspended several feet below 

 the bottle is that the drag hits 

 bottom in the surf zone and resists 

 being washed ashore by the small 

 waves characteristics of the Great 

 Lakes. Observations have revealed 

 that these bottles can be carried 

 many miles in the surf, sometimes 

 against the prevailing offshore 

 current, before they are washed 

 ashore. This disadvantage was elim- 

 inated, for the most part, by 



suspending the drag only 1 foot beneath the 

 bottle instead of the usual 3 to 4 feet. 

 The change was made after repeated tests 

 with dye markers showed no discernable dif- 

 ference, under ordinary conditions, in 

 water movement between 1 and 4 feet below 

 the surface. 



Water level 

 Reply card 



Brass ring 



m. 



- P^^^ 



ron suspension 

 wire 



Metal drag 



Figure 2. — Drift bottle as it appeared at time 

 of release. 



