62 THE OCEAN— A LECTURE. 



Mr. B. here went into a definite statement relative to the 

 area covered by Lakes Superior, Michigan, Huron and 

 Erie, from which it appeared that those named covered an 

 area of more than 87,000 square miles. That the hand of 

 nature had, in this extent of country, afforded the means 

 of measuring, with a good degree of accuracy, the amount 

 of evaporation as compared with the annual fall of rain. 



He stated that from numerous observations, continued 

 through a series of years, in various parts of this district, 

 the annual fall of rain had been carefully noted, and was 

 shown to amount to about forty vertical inches. The 

 position of the Falls of Niagara, the uniformity of the depth 

 and velocity of the stream, afibrded very reliable means 

 for determining the quantity of water annually discharged, 

 and which, from careful calculation, has been shown to be 

 equal to fifteen vertical inches, spread over the whole area 

 of 335,500 square miles of country drained, from which it 

 would appear that nearly one half of the annual fall of rain 

 is carried off by evaporation. 



Mr. B- next took up the subject of the currents of the 

 Ocean, and after briefly stating the causes as laid down in 

 our popular works, took the position that the main cause 

 is due to the law of inertia of matter. He illustrated his 

 position by supposing the solid portions of the earth to 

 present the perfect figure of a sphere, with no elevations 

 or depressions, and covered with an equal depth of water 

 upon all parts of its surface. In obedience to the law of 

 inertia, this fluid covering would incline to remain in a 

 state of rest, while the solid nucleus would turn within it, 

 thus causing an apparent flow of water to the westward 

 upon the equator. If land should occupy both the polar 

 regions, this current would become more apparent, flowing 

 westward with unobstructed and equal velocity along the 

 shores of both continents. Should the land occupy the 

 equatorial regions, we should then have two currents, one . 

 at the North and one at the South. 



