CHAP. VHi.] THE GULF-STREAM. 357 



the eastern border of the North Atlantic fringing 

 Western Europe. A small but very interesting por- 

 tion of it forms the channel between the Egeroe 

 Islands and the North of Scotland, one of the chan- 

 nels of communication between the North Atlantic 

 and the North Sea ; and a few soundings in shallow 

 water to the east of Shetland are in the shallow 

 North Sea basin. It is evident, therefore, that the 

 greater part if not the whole of this belt must par- 

 ticipate in the general scheme of distribution of 

 temperature in the North Atlantic, and must owe 

 any peculiarities which its thermal conditions may 

 present to some very general cause. 



All our temperature observations, except the few 

 taken in the ' Lightning ' in 1868, were made with 

 thermometers protected from pressure on Professor 

 Miller's plan, and the thermometers were individually 

 tested by Captain Davis at pressures rising to about 

 three tons to the square inch before they were fur- 

 nished to the vessel ; they were also more than once 

 reduced to the freezing-point during the voyage to 

 ascertain that the glass had been in no way distorted. 

 The results may therefore be received with absolute 

 reliance within the limits of error of observation, 

 which were reduced to a minimum by the care of 

 Captain Calver. 



A large number of scattered observations, most 

 of which have unfortunately been made with instru- 

 ments which cannot thoroughly be depended upon 

 for accuracy of detail, — the error, however, being 

 probably in the direction of excess of heat,— esta- 

 blished the singular fact that although the tempera- 

 ture of the surface of the sea in equatorial regions 



