'CONSTITUENTS OF SEA-WATER. 99 



One of the constituent parts of sea-water is a 

 solution of lime. The river or brook to which 

 the visitant of the sea-shore approaches as he 

 wanders along the beach is perpetually engaged, 

 especially if it flows through a country in which 

 limestone abounds, in carrying away to the sea 

 solutions of that substance, which themselves are 

 poured into the channel of the rivers by the rain 

 which percolates through the soil, and dissolves 

 part of the lime it meets with in its course. The 

 solutions which the river thus carries along in its 

 waters are too delicate to be discovered by the 

 sense of taste ; nevertheless the aggregate quantity 

 of lime thus poured into the ocean from all the 

 rivers of the earth must be vast. 



Now it is from this lime so dissolved and 

 mingled with the sea-water, that in some parts of 

 the ocean, as for instance the Pacific, the prodi- 

 gious coral reefs are constructed. These reefs 

 form under the waters a solid mountain of 

 stone, often of immense extent. On the coast of 

 New Holland there is one coral reef a thousand 

 miles in extent, and unbroken for a distance of 

 three hundred and fifty miles. In the Pacific 

 there are groups of twelve hundred miles in extent 

 by more than three hundred in breadth. All these 

 vast structures are the work of countless myriads 

 of coral-building polypes (Madrephyllicea), and 

 afford one of the many proofs how vast a work 

 may, in the complicated processes of divine pro- 

 vidence, be executed by a feeble instrumentality. 

 A little worm which could in a moment be crushed 



H 2 



