REPLY TO CRITICS. i:» 



temperature of these places far below the freezing- 

 point, were it not for a compensating cause to which 

 I shall now refer, viz. the heat "trapped" by the fog. 

 The fog, although it prevents a large portion of the 

 sun's heat from ever reaching a place, at the same time 

 prevents to a great extent that place from losing the 

 little heat which it does receive. In other words, it 

 acts as a screen preventing the loss of heat by radia- 

 tion into space. But the heat thus " trapped " never 

 fully compensates for that not received, and a lowering 

 of temperature is always the result. 



Had all those considerations been taken into account 

 by Professor Newcomb, Mr. Hill, Mr. Searles Wood, 

 and others, they would have seen that I had by no 

 means over-estimated the powerful influence of fogs 

 in lowering the summer temperature. 



The influence of fogs on the summer temperature is 

 a fact so well established by observation that it seems 

 strange that anyone should be found arguing against it. 



Heat Evolved by Freezing. — There is one objection 

 to which I may here refer, and which has been urged 

 by nearly all my critics. It is said, correctly enough, 

 that as water in freezing evolves just as much heat as 

 is required to melt it, there is on the whole no actual 

 loss of heat ; that whatever heat may be absorbed in 

 the mechanical work of melting the snow, just as much 

 was evolved in the formation of the snow. Conse- 

 quently it is inferred, in so far as climate is concerned, 

 the one effect completely counterbalances the other. 

 This inference, sound as it may at first sight appear, 

 has been so well proved to be incorrect by Mr. Wallace 

 that I cannot do better than quote his words : — 



" In the act of freezing, no doubt water gives up 

 some of its heat to the surrounding air, but that 'in- 

 still remains helow the freezing -point, or freezing 



