The Hydrosphere 



It now remains to consider the origin and effects of 

 the tides, phenomena so general in their distribution 

 and so well known as to need little in the nature of 

 description. 



Sir Isaac Newton, after prolonged study of natural 

 phenomena, enunciated certain laws which govern not 

 only the motions of the planets, but apply also to the 

 most minute particles of matter, and one of these laws, 

 known as Newton's first law, runs as follows : Every 

 particle of matter in the Universe attracts every other 

 particle with a force proportional to its mass, and 

 inversely proportional to the square of the distance 

 between the particles. This is usually expressed in 

 the form of an equation thus 



_ M, x M 2 

 ~^~' 



where F is the force, M x and M 2 the masses of the 

 particles, and d the distance between them. 



Now, suppose we have two particles each having a 

 mass of i and separated from each other by a distance 

 of i, we shall then have 



i x i i x i 



If, however, we make the distance between the particles 

 2, then 



i x i i x i i 

 p __ - _ - __ _. 



2 2 2X2 4 



Similarly, if the distance be increased to three units, 



F = -, and so on. 

 9 



Now we know that it is the attraction of the Sun 



53 



