284 FIRST YEAR SCIENCE 



but they determine the area in which certain animals ma;y 

 live. 



The Bermudas, 32 north of the equator, are coral reef 

 formations, while the Galapagos, almost on the equator, 

 are surrounded by too cold water to have any such reefs. 

 At 68 north, near the Lofoten Islands, are the great cod 

 fisheries of Europe. On the western side of the Atlantic 

 these fisheries are on the Grand Banks, latitude 45 

 north. Many other similar illustrations of the effects of 

 these currents on the distribution of animal life might be 

 cited. 



The temperature of winds blowing from the sea is 

 modified by these currents and greatly affects the habita- 

 bility of the earth for man. Hammerfest at 71 north is 

 a flourishing seaport, but there are no important settle- 

 ments above 50 on the western side of the Atlantic. 

 Alaska, the prevailing winds of which are warmed by 

 blowing over the warm ocean, is a region which promises 

 much for human habitation, while the region on the op- 

 posite side of the Pacific must remain almost destitute of 

 human inhabitants. It should be noted that the effect of 

 the 'warm ocean waters would be slight, except along the 

 coast, were it not for the air movements. 



135. Tides. Probably the first thing that impresses us 

 on visiting the seashore is the regular rising and falling 

 of the water each day. These movements of the water 

 are called tides. If we observe the tides for a few days, 

 we find that there are two high and two low tides each 

 day. As the tidal current comes in from the open ocean 

 and the water rises, it is called flood tide, and as it runs out 

 or falls, ebb tide. When the tides change from flood to 

 ebb or ebb to flood, there is a brief period of " slack water." 



If we observe closely, we shall see that the correspond- 

 ing tides are nearly an hour later each day than they were 



