142 National Geographic Magazine. 



since between Rebecca Shoal and Cuba, and between Yucatan 

 and Cape San Antonio (Cuba), and off Cape Hatteras, 



During the past year Lieut. Pillsbury extended the field of 

 operations to the passages between the islands encircling the 

 Caribbean Sea, and in order to study the Atlantic flow outside 

 the limits of the trade drift a station was to have been occupied 

 about 700 miles to the north-east of Barbados ; this, however, 

 was unfortunately prevented by bad weather. 



The deductions from the observations in Florida Strait showed 

 very clearly a daily and a nionthly variation in the velocity of the 

 stream, the former having a range of 2^ knots, and reaching a maxi- 

 mum on the average about 9*^ 9™ before and ^^ 37"" after the moon's 

 upper transit, and the monthly variation reaching its maximum 

 about two days after the maximum declination of the moon. 

 The variations in this section were found greater on the western 

 than on the eastern side of the strait, and the axis of the stream, 

 or position of strongest surface flow, was located by Lieutenant 

 Pillsbury \\^ miles east of Fowey Rocks, and, farther north, 

 about 17 miles east of Jupiter Light. The average surface cur- 

 rent at this section was Bf knots, the maximum b\ knots, and the 

 minimum If knots per hour. The results also indicate that 

 when the current is at its maximum the surface flow is faster 

 than at any depth below it, but when at its minimum the veloc- 

 ity at a depth of 15 fathoms or even down to 65 fathoms is 

 greater than at the surface, and that there is at times a current 

 running south along the bottom in all parts of the stream except 

 on the extreme eastern side. 



The results of the investigations in 1887 and 1888 have not yet 

 been published, but from information kindly furnished by the 

 authorities of the Coast Survey, I am able to give a brief outline 

 of the more prominent facts ascertained. 



In the section between Rebecca Shoal and Cuba the daily vari- 

 ation in velocity was found as prominent as in Florida Strait, the 

 mean time of eight maxima corresponding to G*" 18™ before, and 

 that of three maxima to 3^ 25™ after the moon's transit. The 

 axis of the stream in this section was found near the center of 

 the current prism, and the flow was easterly and inclined on 

 either side toward the axis. The axis seemed to occupy a higher 

 level than other parts of the sti'eam, and this appears to be borne 

 out by the fact that about half the number of the current bottles 

 thrown out in Florida Strait on the west side of the axis were re- 



