294 THE PHYSICAL GEOGRAPHY OF THE SEA. 



CHAPTER XV. 



CLEVIATES OF THE OCEAN. 



Milky Way of the Sea, <^ 848. — Contrasted with Climates Ashore, 852. — Movements 

 of Isotherms, 854. — Mean Temperature of Sea and Air, 860. — Rain in high Lati- 

 tudes at Sea, 863.— Climate of England aiFected by Coast Line of Brazil, 871. — 

 The Gulf of Guinea, 875. — Summer in the Northern Hemisphere hotter than in the 

 Southern, 883. — A Harbor for Icebergs, 884. — Course of the Isothermal Line across 

 the Atlantic, 887. 



\ 



848. Theemal charts, showing the temperature of the surface 

 of the Atlantic Ocean by actual observations made indiscrimin- 

 ately all over it, and at all times of the year, have been published 

 by the National Observatory. The isothermal lines which these 

 charts enable us to draw, and some of which are traced on Plate 

 IV., afford the navigator and the philosopher much valuable and 

 interesting information touching the circulation of the oceanic wa- 

 ters, including the phenomena of the cold and warm sea currents ; 

 they also cast light upon the climatology of the sea, its hyeto- 

 grapliic peculiarities, and the climatic conditions of various regions 

 of the earth ; they show that the profile of the coast-line of inter- 

 tropical America assists to give expression to the mild climate of 

 Southern Europe ; they also increase our knowledge concerning the 

 Gulf Stream, for it enables us to mark out, for the mariner's guid- 

 ance, that "Milky Way" in the ocean, the waters of which teem, 

 and sparkle, and glow with life and incipient organisms as they run 

 across the Atlantic. In them are found the clusters and nebulse 

 of the sea which stud and deck the great highway of ships on their 

 voyage between the Old World and the New ; and these lines as- 

 sist to point out for the navigator their limits and his way. They 

 show this via lactea to have a vibratory motion in the sea that calls 

 to mind the graceful wavings of a pennon as it floats gently to the 

 breeze. Indeed, if we imagine the head of the Gulf Stream to be 

 hemmed in by the land in the Straits of Bemini, and to be sta- 



