406 OBSEEVATIONS ON THE GUEEENTS. 



was the warmest, the temperature falling rapidly inshore, and more slowly 

 outside. This was not only the case at the surface, but, with modifica- 

 tions easily understood, at considerable depths, and must be owing to the 

 meeting of the warm waters of the Stream with the cold water of the 

 Arctic Current, 



From observations taken under his direction, between 1854 — 1860, Pro- 

 fessor Bache, Director of the United States Coast Survey, drew up a 

 Table showing the relative distances off shore of these bands (three warm 

 and four cold, varying from 25 to 75 miles in width, within 300 miles 

 from Cape Hatteras) at ten sections between Cape Florida and Sandy 

 Hook. He was led to believe they were caused by irregularities in the 

 bed of the ocean, but by more improved methods of sounding it has since 

 been shown that the bottom is not divided into hills and valleys along 

 the United States Coast, 



Later investigation with the steamer Blake, on some occasions, has 

 shown an absence of these bands, and, in 1881, Commander Bartlett 

 found no warm or cold bands till he came off Hatteras, and he considered 

 that the work of the Blake seemed to show that the cold bands have no 

 regularity, and only represent the imceasing conflict going on between 

 layers of water of different velocities, and of different temperatures, as 

 reported by Lieutenants Craven and Maffit, U.S.N., and dilated on in the 

 previous edition of this work. In the seasons of 1883 and 1884, the tem- 

 perature of the surface water was taken every mile on the twelve sections 

 between Jupiter Inlet and Currituck, and in no case were any alternate 

 warm and cold bands found, nor was any layer of cold water found at the 

 bottom. 



The earlier observations on the Hatteras, Cape Fear, and Charleston 

 sections showed a counter-current where the cold streaks were found, but 

 as stated in (391) Lieutenant Pillsbury clearly proved that from his obser- 

 vations the temperature of these warm and cold bands gave no clue as 

 to the direction of their flow. 



(396.) The '• Cold Wall." — The separation between the warm, deep blue 

 "water of the Gulf Stream and the inner green water of the cold Arctic 

 Counter-Current is sometimes so well marked, that " one end of a ship is 

 seen in the one, and the other end in the other cmTent,"* Although it 

 does not follow that this line of demarcation is so distinct as Captain 

 Maury says, as above, yet a remarkable feature has been elucidated by the 

 United States Coast Survey, so often quoted here. It is, that between the 

 coast and the Gulf Stream there is a fall in temperature so abrupt that it 

 has aptly been called the "Cold "Wall ;" this extends, with varying dimen- 

 sions and changes of its peculiar features, along the coast from Cape Florida, 

 Northward, as far as examined. Professor Bache stated that inside this 

 " Wall " was another band of water of increased temperature, whilst out- 

 side the warmest band, which is next the " Cold "Wall," was another warm 

 and one other cold band. 



This " Cold Wall," from later investigations, cannot be considered as 



" H.M.S. 2^ile is reported to have once found a surface temperature of 46"^ F. at her 

 bow, while it was 70° at her stern. 



