§ 48-51. TPIE SEA AND THE ATMOSPHERE. 17 



Monuments of their i^lea may be formed from the coral islands, the marl 

 industry. |^g(jg^ tj^g gl^gl^ baiilvS, the challv clifis, and other 



marine deposits which deck the sea or strew the land. 



48. Fresh water is composed of oxygen and hydrogen gas in 

 Analysis of sea-wa- thc proportlon by Weight of 1 to 8 ; and the prin- 

 *'''■• cipal ingredients which chemists, by treating small 

 samples of sea-water in the laboratory, have found in a thousand 

 grains are, 



Water 9G2.0 grains 



Chloride of Sodium 27.1 " 



Chloride of Magnesium 5.4 " 



Chloride of Potassium 0.4 " 



Bromide of Magnesia 0.1 " 



Sulphate of Magnesia 1.2 " 



Sulphate of Lime 0.8 '« 



Carbonate of Lime 0.1 " 



Leaving a residuum of. 2.9 " =1000, 



consisting of sulphureted hydrogen gas, hydrochlorate of ammo- 

 nia, etc., etc., in various quantities and proportions, according to 

 the locality of the specimen. 



49. If we imagine the whole mass of the earth to be divided 

 Proportion of water into 1786 CQual parts by weight, then the weight 



to the mass of the n ^^ i • i it t 



earth. 01 all the watcr m the sea would, according to an 



estimate by Sir John Herschel, be eqxiivalent to one of such parts. 

 Such is the quantity, and such some of the qualities of that de- 

 lightful fluid to which, in the laboratories and workshops of na- 

 ture, such mighty tasks, such important offices, such manifgld 

 and multitudinous powers have been assigned. 



50. This volume of water, that outweighs the atmosphere about 

 The three great ^^^ timcs, is divided iuto thrcc great oceans, the 

 oceans. Atkutic, the Pacific, and the Arctic; for in the 

 rapid survey which in this chapter we are taking of the field be- 

 fore us, the Indian and Pacific oceans may be regarded as one. 



51. The Atlantic Ocean, with its arms, is supposed to extend 

 The Atlantic, from the Arctic to the Antarctic — perhaps from 



pole to pole ; but, measuring from the icy barrier of the north to 

 that of the south, it is about 9000 miles in length, with a mean 

 breadth of 2700 miles. It covers an area of about 25,000,000 

 square miles. It lies between the Old World and the New ; pass- 

 ing beyond the "stormy capes," there is no longer any barrier, but 



B 



