THE GULF STEEAM. 417 



40J^; at 1,174 fathoms, 37^°; at 1,500 fathoms, 36° to 36^°; and below 

 this, 36° and 35^°, the lowest found. 



Between Bermuda and Bahama, the surface temperature gradually 

 increased from 68° to 77°, the bottom temperature being about 36°. 



Series of temperatures, from the surface to the bottom, were taken 

 during the summer of 1884, between Block Island and Bermuda, and 

 thence to Hatteras. The isothermals showed the Labrador Current until 

 nearing the Stream, when they descended gradually, and in the Stream 

 itself abruptly, to the greatest depths. Instead of the warm Stream-water 

 thinning away as it was reported to do when spread out, it was not much 

 over 50 miles in width at the time of their crossing, as shown by the 

 current and high surface temperatures. 



The temperatures below the surface were much higher than at the same 

 depths off the coast. The ordinary temperature at the bottom off 

 Savannah and Charleston in 400 fathoms was 45° ; at the same depth in 

 the Stream, between Block Island and Bermuda, it was as high as 55°. 

 To the Southward, the isothermals remained at almost the same depth as 

 in the Stream, on the entire line to Bermuda. Just North of the Stream 

 the temperature at 400 fathoms was 39^° and 40°. At a point well in the 

 Labrador Current away from the Stream, the temperature at 400 fathoms 

 was 38i°. 



From Bermuda to Hatteras the isothermals were at the same depths as 

 South of the Stream on the previous line, but when in the current off 

 Hatteras, where the Stream trends to the Eastward, they rose to the same 

 depth as off Charleston and Savannah on the plateau. These (iempera- 

 tures below the surface seem to suggest that the Labrador Current under- 

 runs the Stream at Hatteras, but ac no other point. It probably keeps its 

 Western boundary along the 1,000-fathoms line, and thus around the 

 plateau towards the Equator. 



The Velocity of the Gulf Stream in the section now under consideration 

 is very various ; but, as a mean, has been placed at from 26 to 36 miles 

 per day. If this estimate is reduced to agree with those of the Meteoro- 

 logical Office Charts, 1872, as referred to in the main course of the Stream, 

 these figures must be placed at about 20 or 27 miles respectively, and it 

 would thus take about forty days to bring the Stream from off Nantucket 

 to 48° W., a distance of about 850 or 900 miles. This would make a 

 period of 72 days from Florida. But all such calculations must naturally 

 be very vague, owing to the constant changes in the surface velocity of 

 various parts of the Stream, and at various depths below the surface. 



From February 16th to 19th, 1889, Captain Wall, of the steamer 

 Montreal, in about lat. 37° N., Westward of long. 64° W., found the 

 Stream setting due East, nearly 2 knots an hour, in spite of strong South- 

 westerly winds. 



The Limits of the Stream have now become a subject of great difficulty. 

 Formerly it was thought that its waters flowed Eastward as far South as 

 lat. 36° or 87° between longitudes 65° and 55° W., but with a feeble 

 current. But in the Meteorological Office Monthly Charts, of 1872, there 

 is positively no evidence of an Easterly set to the Southward of lat. 39" 



N.A.O. 54 



