194 



THE POPULAE EDUCATOR. 



in the equatorial regions, and the cold and more dense air flow- 

 ing in from the poles to supply its place. As this sweeps the 

 surface of the Antarctic Ocean it sets the water in motion, in 

 the direction of the wind, producing what is called a drift 

 current; but when once a large body of fluid is set in motion it 

 exhibits little disposition to return to its tranquil state, and if it 

 be acted upon by encouraging causes, a permanent current is 

 produced. When the great Antarctic drift current, which is 

 about 1,400 miles broad, abuts upon the west coast of South 

 America, its waters are divided : one branch bends southwards, 

 and sweeps round Cape Horn; the other flows northwards along 

 the coast, until the projecting shoulder of Peru gives it a 

 westerly direction, and it leaves the land and traverses the 

 Pacific along the equator as the equatorial current ; finally, it is 

 lost among the East India islands. 



A drift current appears off the west coast of Australia, going 

 northwards, until it reaches a latitude of 15 degrees south, 

 when it turns at right angles across the Indian Ocean. It is 

 separated by the island of Madagascar : one branch takes a 

 northerly direction, washing the coasts of Africa, Arabia, and 

 India ; the other branch, passing round the Cape of Good Hope, 

 sets in northward as the Atlantic current ; like the other two, 

 near the equator it takes a westerly bend, crossing the Atlantic 

 Ocean ; striking against the angle of South America, one stream 

 follows the coast of Brazil, the other sweeps round the Gulf of 

 Mexico, passes the south of Florida, follows the coast line of 

 the United States, re-crosses the Atlantic at 40 degrees north 

 latitude, and pours its warm waters on the coasts of the British 

 Islands and Norway. Besides these main systems of currents, 

 there are several smaller and less important branches. Yet we 

 have said enough to show that the waters of the ocean are in 

 continual circulation, carrying the material eroded on one 

 coast to distant areas of deposition. A remarkable proof of the 

 capability of the gulf-stream to transport material is related by 

 General Sabine. In 1822 he was on the coast of Africa, near 

 Cape Lopez, when a vessel was wrecked ; the following year he 

 visited Hammerfest, in Norway, near the North Cape, and while 

 he was there casks belonging to the same vessel were cast on 

 shore. They must have crossed the Atlantic south of the 

 equator, navigated the Gulf of Mexico, passed through the West 

 Indies, rounded Cape Sable, re-crossed the Atlantic, the North 

 Sea, and finally landed on the very north of Europe ! 



The great banks which exist and are carefully mapped are 

 due to the accumulation of drifted matter ; they are formed in 

 tranquil places where the burden carried by the waters can be 

 deposited. Off the Northumberland coast is the Dogger bank, 

 which is 200 miles long, and sometimes sixty broad. 



In many areas the trawling-nets of the fishermen bring up 

 broken shells and other similar debris, which have been brought 

 together by some current. There can be little doubt but these 

 materials arrange themselves according to certain circumstances, 

 and when a storm disturbs the bank and causes a new order of 

 deposition, an arrangement of strata would result, which, if 

 consolidated, would bear a great resemblance to a class of rocks 

 called the Norfolk and Suffolk Crags. 



Between the coasts of Suffolk and the Netherlands oysters 

 have been dragged up which were adhering to the bones of 

 extinct elephants ; and if these had been borne so far from the 

 land by the water, specimens of existing animals must also be 

 embedded in the strata in process of formation far out at sea. 

 Our knowledge of the depositions going on at the bottom of the 

 seas is necessarily very limited. All we can be sure of is, that 

 the matter with which the waters of the sea becomes charged is 

 deposited somewhere, and the deposition must be more or less 

 homogeneous that is, particles of the same specific gravity, and 

 of much the same size, will reach the bottom about the same 

 time. It has often been proved that near the shore the bottom 

 of a sea not swept by a current is covered with gravel or 

 shingle; further out the deposit gradually becomes finer; and 

 at last, in deep water, the sounding leads bring up fine mud. 

 Matter in a state of great sub-division, we know, requires a long 

 time before it sinks to the bottom ; for instance, barium sul- 

 phate is one of the heaviest of minerals, and yet when it is pre- 

 cipitated from a solution of baryta, some hours are required 

 before the water is perfectly free from particles of the salt, so 

 that the very fine particles may not reach the ocean-bed until 

 they have been carried a great distance from the place where 

 they entered the water. 



We have thus rapidly reviewed the part which water plays in 

 the degrading of existing land and the re-distribution of material 

 upon the ocean-bed. The power thus employed is never-ceasing, 

 and it is universal, and is capable of producing any alteration in 

 the shape of continents and islands if sufficient time be allowed 

 for its action. When we remember that our records of actual 

 facts, sufficiently surprising in themselves, only extend back a 

 few hundred years, what may we not ascribe to aqueous action 

 in time not measured by years, but by ages ? 



LESSONS IN ARITHMETIC.- XLII. 



THE CHAIN ETJLE (continued). 

 EXAMPLE 5. 2COOO copies of a perfny paper weigh a quarter of 

 a ton, and a reduction in the price of paper increases the profit 

 by 4i per cent. What is the reduction per pound on paper ? 



1 lb. paper. 



112 



100 



1 cwt. 



20000 copies. 



1J- profit. 



112 x 5 x 100 20000 x 4J. 



Answer. l.^d. per pound. 



N.B. Notice that evidently factors which are common to 

 both columns may be cancelled. 



EXAMPLE 6. A Bavarian gulden is equivalent to 60 kreutzers. 

 When the exchange in London is 25 francs 20 cents, what shall 

 I gain or lose per cent, by talcing French gold instead of English. 

 to Bavaria, the exchange there being 11 gulden 40 kreutzers for 

 an English sovereign, and 9 gulden 20 kreutzers for a French. 

 napoleon ? 



100. 



25'20 francs. 



9J gulden. 



Anaixer. 108, which is 8 per cent. gain. 

 EXAMPLE 7. 1 kilogramme (15432 grains) of French standard 

 gold, fine, is coined into 155 napoleons. Find the par of 

 exchange between London and Paris, by comparing the gold 

 coinage of the two countries. 



1 English sovereign. 



1869 



40 Ibs. Troy. 



lilts, fine gold. 



10 Ibs. French standard gold. 

 / 

 1 <- ; 5760 grains. 



15432 



:, 1 kilogramme. 



3100 francs. 



Answer. 25 fr. 22 o. for 1. 



