CURRENTS. 13 



rium the water must fall to a crest on the opposite side of the earth 

 equal to that of attraction beneath the moon. 



The same law will hold good with regard to the sun. Therefore 

 when the moon and sun are in a line with the earth and each other, 

 the greatest elevation will occur, as it does at new and full moon ; 

 and when the moon is farthest from the sun, the attraction of the 

 sun will be exerted on the line of depression 90° from the line of 

 greatest elevation, which is always beneath the moon, and attract 

 that portion to the corresponding depression of the other portion, 

 so that the moon exerts its least influence upon the water beneath 

 it and the tides are the lowest ; these occur at the ist and 3rd quar- 

 ter. The action of tides may be thus briefly described ; we then 

 come to local variations in height of tide. Thus if the sea beach 

 of any given surrounding is low, and the tide has free access to all 

 parts at once, one can easily see that the tides of that place will be 

 moderate in height and depth and least liable to change, while if 

 the surroundings are narrow and confined and the sea is obliged to 

 force itself against high cliffs and into narrow passages the accu- 

 mulated waters must form an abiding place by raising the level of the 

 water to that of the nearest open basin, which often causes the 

 tides to rise to the extraordinary height of forty, fifty, and even 

 sixty feet above ordinary level. In that narrow arm and clifted 

 channel of the sea, the Bay of Fundy, this remarkable phenomenon 

 actually occurs. At the head of the bay the tides are eighteen to 

 twenty feet high ; here the highest springtides occasionally reach 

 seventy feet. Marine currents are so influenced by local irritation 

 that it would be difficult to describe them, but let us notice a few 

 of the most important ones : — 



It is pretty generally conceded that a constant current sets out of 

 the Gulf between Newfoundland and Cape Breton, in a southeasterly 

 direction. This is changed more to the southward by a current en- 

 tering the Gulf from the Straits of Belle Isle. There are other minor 

 currents due to prevailing winds at the time that affect the waters, 

 but, unfortunately, they have not been studied with sufficient care 

 to define them. There is, however, no doubt about the northern 



