92 TERRESTRIAL ADAPTATIONS. 



warmth, all the snow which lies on the roofs of 

 our houses would descend like a waterspout into 

 the streets : all that which rests on the ground 

 would rush like an inundation into the water 

 courses. The hut of the Esquimaux would 

 vanish like a house in a pantomime: the icy 

 floor of the river would be gone without giving 

 any warning to the skaiter or the traveller : and 

 when, in heating our water, we reached the 

 boiling point, the whole fluid would " flash into 

 steam," (to use the expression of engineers,) and 

 dissipate itself in the atmosphere, or settle in dew 

 on the neighbouring objects. 



It is obviously necessary for the purposes of 

 human life, that these changes should be of a 

 more gradual and manageable kind than such as 

 we have now described. Yet this gradual pro- 

 gress of freezing and thawing, of evaporation and 

 condensation, is produced, so far as we can dis- 

 cover, by a particular contrivance. Like the 

 freezing of water from the top, or the floating of 

 ice, the moderation of the rate of these changes 

 seems to be the result of a violation of a law : that 

 is, the simple rule regarding the effects of change 

 of temperature, which at first sight appears to be 

 the law, and which, from its simplicity, would 

 seem to us the most obvious law for these as well 

 as other cases, is modified at certain critical points, 

 so as to produce these advantageous effects : why 

 may we not say in order to produce such effects ? 



