CHAMBERS'S INFORMATION FOR THE PEOPLE. 



the other from the Cape of Good Hope along the 

 west coast of Africa as far as the Gulf of Guinea. 

 When the equatorial current reaches the coast 

 of Brazil, it divides into two branches. One pro- 

 ceeds southwards, turning gradually eastwards 

 across the Atlantic until it falls in with the 

 northern in-draught from the Cape of Good Hope. 

 The other branch is deflected northwards into the 

 Caribbean Sea and the Gulf of Mexico. The 

 water thus driven into this pent-up sea now rushes 

 with accumulated momentum through the strait 

 or gulf between Florida and the Bahamas, and 

 forms the famous Gulf Stream. 



The Gulf Stream, after issuing from the Florida 

 Strait, proceeds at first northward, parallel to the 

 American coast ; but between the parallels of 35 

 and 37, it turns gradually eastward, passing over 

 the southern extremity of the Bank of Newfound- 

 land, and all the while expanding in breadth and 

 becoming shallower. The temperature of the 

 stream, when it starts, is from 83 in summer to 

 77 in winter, and even after travelling 3000 miles 

 to the north, as high as the Banks, there is a 

 difference in a winter day between its water and 

 that of the surrounding ocean of 20 to 30. Along 

 its whole course a cold arctic current underlies 

 it ; and this arctic current intervenes between the 

 western border of the stream and the coasts of 

 Florida, Georgia, and the Carolinas, the line of 

 demarcation between the two being so abrupt that 

 it is known as the ' cold wall.' At the bow of a 

 ship entering the Gulf Stream the temperature has 

 been found to be 70, while it was only 40 at the 

 stern. The velocity of the stream, at its outset, is 

 from 50 to 60 miles a day ; but this velocity becomes 

 greatly reduced as it proceeds. 



It has usually been held that the Gulf Stream 

 extends across the Atlantic to the shores of North- 

 ern Europe, and is the cause of the mild and 

 moist climate enjoyed by the western parts of that 

 continent. The opinion, however, is beginning to 

 prevail that, as a distinct current, the Gulf Stream 

 ceases in the middle of the North Atlantic, its 

 waters being by this time thinned out to a mere 

 film, and its initial velocity and distinctive heat 

 having been dissipated. That warm waters from 

 tropical seas are brought to the coasts of Britain, 

 and even into the polar seas beyond, is proved by 

 drift-wood, seeds, and fruits from the West Indies 

 being frequently cast ashore on the Hebrides, the 

 north of Norway, and Spitsbergen. But this is 

 accounted for by the general flow of the surface- 

 water towards the poles, forming part of the ver- 

 tical oceanic circulation ; a flow which receives 

 an eastward deflection as it proceeds northwards 

 in the way above explained. This general set 

 of the surface-water is further promoted by 

 the prevalence of south-westerly winds or re- 

 turn-trades, which maintain a pretty constant 

 north-east drift over the whole surface of the 

 north-eastern portion of the Atlantic. In this 

 way, although the Gulf Stream may have lost its 

 original impetus, a large portion of the super- 

 heated water which it brings into the centre of the 

 Atlantic, must be carried to the shores of Europe 

 and into the Arctic Sea. Before, however, the 

 Gulf Stream loses its force as a distinct current, 

 it sends off a branch southwards by the Azores j 

 which re-enters the equatorial current before 

 described. 



While the climate of the west of Europe is thus 



62 



ameliorated by having its shores washed by waters 

 from warm seas, and by the moist and warm south- 

 westerly winds that predominate, the corresponding 

 coast of America is, at least, as much depressed 

 by a current from the Greenland seas which flows 

 southward along the shores of Labrador, carrying 

 with it immense fields of polar ice, and accom- 

 panied by dry and piercing winds from the north 

 and north-west This arctic current intervenes 

 between the coast of America and the Gulf Stream, 

 as already mentioned, and flows under it into the 

 Gulf of Mexico. 



The currents of the Pacific Ocean are little 

 known ; but the Indian Ocean, exposed to a 

 tropical sun and hemmed in on the north, sends 

 out several large currents of warm water. One is 

 the Mozambique current ; another escapes through 

 the Strait of Malacca, and flows past China and 

 Japan into the Pacific, making for the north-west 

 coast of America. This current resembles in 

 many respects the Gulf Stream. 



Two currents of equal force, but of different 

 directions, meeting in a narrow passage or gut, 

 will cause a whirlpool, a phenomenon which has 

 ignorantly been said to be produced by subter- 

 ranean rivers, gulfs, chasms, &c., but essentially is 

 only an eddy. Charybdis, in the Strait of Sicily, 

 and the Maelstrom, on the coast of Norway, are 

 eddies of this kind, alternately absorbing and 

 casting up again whatever approaches them. 



Being an elastic and mobile fluid, water is 

 readily acted upon by winds ; and thus waves are 

 produced, varying in height and velocity according 

 to the force and continuity of the wind, extent of 

 uninterrupted surface, depth of the ocean, con- 

 tending currents, and the like. The common cause 

 of waves is the friction of the wind upon the 

 surface of the water. Little ridges or elevations 

 first appear, which, by continuance of the force, 

 gradually increase until they become the rolling 

 mountains seen where the winds sweep over a 

 great extent of water. The velocity of waves is in 

 proportion to the square root of their length. The 

 large waves just spoken of proceed at the rate 

 of from thirty to forty miles an hour. It is a 

 vulgar belief that the water itself advances with 

 the speed of the wave ; but in fact \heform only 

 advances, while the substance, except a little spray 

 above, remains rising and falling almost in the 

 same place with the regularity of a pendulum. A 

 wave of water, in this respect, is imitated by the 

 wave running along a stretched rope when one 

 end is shaken. But when a wave reaches a 

 shallow bank or beach, the water becomes really 

 progressive ; for then, as it cannot sink directly 

 downward, it falls over and forward, seeking the 

 level Sailors and others speak of waves running 

 ' mountains high ; ' but, according to Scoresby, 43 

 feet is about the utmost difference of level between 

 crest and trough in ocean-waves. 



LAKES AND RIVERS. 



Lakes are inland bodies of water not connected 

 with the ocean or any of its branches : they are 

 generally fresh, but are occasionally brackish, or 

 even decidedly salt They are classified according 

 as they are fresh or saline, and according to the 

 manner in which they receive and discharge their 

 waters namely, those that both receive and dis- 

 charge running water ; those that receive waters, 





