CLOUDS A>~D RIVERS, ICE AND GLACIERS. 133 



elements from the edifices which they build, is enforced 

 to a surprising degree. Sulphuric acid has so strong 

 an affinity for water that it is one of the most powerful 

 agents known to the chemist for the removal of humiditv 

 from air. Still, as shown by Faraday, when a mixture 

 of sulphuric acid and water is frozen, the crystal formed 

 is perfectly sweet and free from acidity. The water 

 alone has lent itself to the crystallising force. 



341. Every winter in the Arctic regions the sea 

 freezes, roofing itself with ice of enormous thickness 

 and vast extent. By the summer heat, and the tossing 

 of the waves, this is broken up ; the fragments are 

 drifted by winds and borne by currents. They clash, 

 they crush each other, they pile themselves into heaps, 

 thus constituting the chief danger encountered by 

 mariners in the polar seas. 



34-2. But among the drifting masses of flat sea-ice, 

 vaster masses sail, which spring from a totally different 

 source. These are the Icebergs of the Arctic seas. They 

 rise sometimes to an elevation of hundreds of feet above 

 the water, while the weight of ice submerged is about 

 seven times that seen above. 



343. The first observers of striking natural pheno- 

 mena generally allow wonder and imagination more 

 than their due place. But to exclude all error arising 

 from this cause, I will refer to the journal of a cool and 

 intrepid Arctic navigator, Sir Leopold McClintock. He 

 describes an iceberg 250 feet high, which was aground 



