NEW DRIFT CARD DESIGN 



with experience in the manufacture and use 

 of the drift cards described above, it became 

 apparent that considerable Improvement in the 

 design was possible. Although none of the data 

 presented herein were obtained with the new type 

 of drift card, the new card will be illustrated and 

 its manufacture briefly described because it 

 represents a significant improvement in design 

 which may be of value to others who are consid- 

 ering the use of drift cards. 



which is inserted a length of soda straw cut to 

 fit the width of the bag. When the upper compart- 

 ment is sealed, the card is finished and ready 

 to be placed in its waxed-paper bag with 19 other 

 cards. All cards of this design floated upright 

 without tilting, with a waterllne at a level with 

 the soda straw, exposing a uniform half-inch of 

 the upper edge above water. The cost per card 

 Is 14 cents in quantity lots. 



DRIFT BOTTLE AND CARD 

 RELEASES AND RETURNS 





!! 



TA'J 

 till 



i 



Figure 3. — New drift card design. 



The important characteristics of the design 

 (fig. 3) are: 



1. A strip of metal ballast whose center of 

 gravity is always near the long axis of the card, 

 so that the card does not tend to float with one 

 corner higher than the other , presenting an unbal- 

 anced area to the wind. 



2. The absence of significant amounts of air 

 in the card's compartment, so that the buoyancy 

 can be concentrated at the end opposite the bal- 

 lasted edge. 



Drift bottles, and later drift cards or cards 

 and bottles together, were released whenever 

 feasible by the Laboratory's research ship, the 

 Charles H. Gilbert , beginning with cruise 51 in 

 January 1961. In addition, the U. S. Coast and 

 Geodetic Survey ship Surveyor released almost 

 3,000 cards during two cruises early in 1963, 

 when that ship was working to the north of Mid- 

 way Island, and a few bottles were released near 

 Oahu in September 1961 by the M/V Broadbill . 

 a fishing vessel then under charter to the Labora- 

 tory. 



The releases are listed in the Appendix, 

 which shows the cruise number (except In the 

 cases of the Surveyor and Broadbill releases), 

 the sequence number of the release, the number 

 of bottles and/or cards In each release, and the 

 date and location of the release. Initially there 

 were 10 bottles In each release, but this number 

 was later Increased to 20 to improve the chances 

 of multiple recoveries. On various occasions 

 the number of bottles or cards per release were 

 modified, and these exceptions are also noted in 

 the tables. 



The Appendix also shows the number of re- 

 coveries, if any, per release, as well as the date 

 of each reported return, and the location where 

 the bottle or card was found. 



3. A controlled volume of air in a separate 

 compartment of the plastic envelope, which vir- 

 tually eliminates the possibility of sinking or of 

 exposing too much area to the winds. 



These cards are manufactured by placing 

 the card and metal ballast strip in a polyethylene 

 bagof 6-mil thickness, squeezingthe card-filled 

 portion between spring-loaded metal plates to 

 remove the air, and sealing the upper edge of 

 the card compartment. This leaves a 1-inch 

 pocket at the upper end of the plastic bag, into 



No reward was offered for reporting returns. 

 The finder was sent a letter which thanked him 

 for his assistance and outlined the project objec- 

 tives, which told him when and where the bottle 

 or card which he found had been released, and 

 which also contained information on the minimum 

 speed and the distance covered. Enclosed with 

 each such letter was a chart showing the release 

 point and the presumed path of the bottle or card, 

 as well as the postcard mailed by the finder in 

 reporting the recovery. 



