1(^2 HISTORY OF 



mountain-spring comes rolling down to such a lodging-place, 

 where the ice has already seated itself, they all freeze, and add 

 their tribute to it. This, by degrees, waxes to a body of ice, 

 that can no more be overpowered by the sun ; and which, thougb 

 it may indeed, at certain seasons, diminish by a thaw, yet, upon 

 the whole, through annual acquisitions, it assumes an annual 

 growth. Such a body of ice is often prominent far over the 

 rocks. It does not melt on the upper surface, but underneath ; 

 and often cracks into many larger or smaller clefts, from whence 

 the thawed water trickles out. By this it becomes at last so 

 weak, that being overloaded with its own ponderous bulk, it 

 breaks loose, and tumbles down the rocks with a terrible crash. 

 Where it happens to overhang a precipice on the shore, it 

 plunges into the deep with a shock like thunder ; and with such 

 an agitation of the water, as will overset a boat at some distance, 

 as many a poor Greenlander has fatally experienced." Thus 

 are these amazing ice.mountains launched forth to sea, and 

 found floating in the waters round both the poles. It is these that 

 have hindered mariners from discovering the extensive countries 

 that lie round the South Pole ; and that probably block up the 

 j)assage to China by the North. 



I will conclude this chapter with one effect more, produced 

 by the saltness of the sea ; which is the luminous appearance of 

 its waves in the night. All who have been spectators of a sea 

 by night, a little ruffled with winds, seldom fail of observing its 

 fieiy brightness. In some places it shines as far as the eye can 

 reach ;' at other times, only when the waves boom against the 

 side of the vessel, or the oar dashes into the water. Some seas 

 shine often ; others more seldom ; some, ever when particular 

 winds blow ; and others, within a narrow compass ; a long tract 

 of light being seen along the surface, whilst all the rest is hid in 

 total darkness. It is not easy to account for these extraordinary 

 appearances : some have supposed that a number of luminous 

 insects produced the effect, and this is in reality sometimes the 

 case ; in general, however, they have every resemblance to that 

 light produced by electricity ; and, probably, arise from the agita- 

 tion and dashing of the saline particles of the fluid against each 

 other. But the marmer in which this is done, for we can pro- 



1 boyle, vol. J. p. 2M. 



