396 



OBSERVATIONS ON THE CURRENTS. 



of 8i° W. 3. Rebecca Shoal to Havana. 4. Fowey Rocks to Gun Kay. 

 5. Jupiter Inlet to Memory Rock, Bahama Bank. 6. Cape Hatteras Shoals 

 towards the S.E. 



For those navigating the Gulf Stream, the most important questions to 

 be answered are : — What is the surface Strength of the Current, and the 

 Direction of the flow. It is well known that these vary at many if not at 

 all parts of the Stream. 



Section 4. Bekveen Fowey Bocks and Gun Kay. — As the labours of two 

 seasons, 1888 and 1889, were concentrated on this Section, the results are 

 more complete than at the others, and in studying these results carefully 

 we find the key to the solution of many of the apparent anomalies at points 

 where there are fewer observations on which to base conclusions. 



The whole width of the strait here is 43 miles, or 39 miles between the 

 100-fathoms lines. On the East side the bank is abrupt, 100 fathoms being 

 found within 1 mile of Gun Kay ; the current sometimes runs in as far as 

 the depth of 10 fathoms, but generally it is farther offshore. On the West 

 side the slope is more gradual, but the current is frequently found quite 

 close to Fowey Rocks. The bottom varies, coral, clay, and mud being 

 found. 



The following Table gives the observations, which were only taken down 

 to the depth of 130 fathoms : — 



From the above it will be seen that the greatest sm-face velocity was 

 found at 11| miles East of Fowey Rocks, and this is its average position, 

 but its flow is not at all times superior. The position of the maximum at 

 different times during the month is intimately associated with the changes 

 in the declination of the moon, and, indeed, not only the position, but the 

 velocity and width of the whole Stream as well. In mid-channel the 

 current appeared to flow to a depth of 325 fathoms. 



Monthly Variation. — Following the changes in the declination of the 

 moon, the velocity of the Stream at any given point in the Narrows is 

 accelerated or diminished, but while it is running faster at one place, at 

 another it is running slower. It is, in fact, a reduction in velocity at the 

 sides accompanying an increase in velocity at the axis, and the reverse ; 

 or, in effect, an alternate expansion and contraction of the Stream in 

 width. This is not marked on the East side of the Straits, but is very 

 marked on the West side of the Stream. 



It seems to be abundantly proved that the Monthly Variation in the 

 Straits of Florida consists of an expansion at high declination, and a con- 



