84 TERRESTRIAL ADAPTATIONS. 



displace water warmer than itself. Hence we can 

 never have ice formed at the bottom of deep water. 

 In appoaching the freezing point, the coldest 

 water will rise to the surface, and the congelation 

 will take place there ; and the ice so formed will 

 remain at the surface, exposed to the warmth of 

 the sun-beams and the air, and will not survive 

 any long continuance of such action. 



Another peculiarity in the laws which regulate 

 the action of cold on water is, that in the very 

 act of freezing a further sudden and considerable 

 expansion takes place. Many persons will have 

 known instances of vessels burst by the freezing 

 of water in them. The consequence of this ex- 

 pansion is, that the specific gravity of ice is less 

 than that of water of any temperature ; and it 

 therefore always floats in the unfrozen fluid. If 

 this expansion of crystallization did not exist, 

 ice would float in water which was below 40 

 degrees, but would sink when the fluid was 

 above that temperature : as the case is, it floats 

 under all circumstances. The icy remnants of 

 the effects of winter, which the river carries down 

 its stream, are visible on its surface till they melt 

 away ; and the icebergs which are detached from 

 the shores of the polar seas, drift along, exposed 

 to the sun and air, as well as to the water in 

 which they are immersed. 



These laws of the effect of temperature on 

 water are truly remarkable in their adaptation to 



