CHAPTER VIII. 



THE GULF -STREAM. 



The Eange of the ' Porcupine ' Temperature Observations. — Low 

 Temperatures universal at great Depths. — The Difficulty of in- 

 vestigating Ocean Currents. — The Doctrine of a general Oceanic 

 Circulation advocated by Captain Maury and by Dr. Carpenter. — 

 Opinion expressed by Sir John Herschel. — The Origin and Exten- 

 sion of the Gulf-stream. — The Views of Captain Maury ; of Pro- 

 fessor Buif ; of Dr. Carpenter. — The Gulf-stream off the Coast of 

 North America. — Professor Bache's ' Sections.' — The Gulf-stream 

 traced by the Surface Temperatures of the North Atlantic. — Mr. 

 Findlay's Views. — Dr. Petermann's Temperature Charts. — Sources 

 of the underlying Cold Water. — The Arctic Eeturn Currents. — 

 Antarctic Indraught. — Vertical Distribution of Temperature in 

 the North Atlantic Basin. 



All the temperature investigations carried on in 

 H.M.S.S. 'Lightning' and 'Porcupine' during the 

 years 1868-69 and 1870, with the exception of a 

 series of observations already referred to taken in 

 the Mediterranean under Dr. Carpenter's direction 

 in the summer of 1870, were included within an area 

 nearly 2,000 English miles in length by 250 in 

 width, extending from a little beyond the Pseroe 

 Islands, lat. 62° 30' N., to the Strait of Gibraltar, 

 lat. 36° N. 



The greater part of this belt may be described as 



