EFFECTS OF DEPRIVATION OF SOLAR HEAT. 69 



admission of so many premises of which we have no 

 proof; its postulates are, indeed, in many cases so 

 gratuitous, that notwithstanding the array of talent 

 which stands forward in its support, we must not allow 

 ourselves to be deceived by the deductions of its advo- 

 cates, or dazzled by the brilliancy of their displays of 

 learning. 



Radiant heat appears to move in waves ; but that 

 calorific effects in material bodies are established by any 

 system of undulation, is a deduction without a proof; 

 and the thermic phenomena of matter are as easily ex- 

 plained by the hypothesis of a diffusive subtile fluid. 



AVe have not, however, to prove the correctness of 

 either of the opposing views ; indeed, it is acknowledged 

 that many phenomena require for their explanation 

 conditions which arc not indicated by either theory. 



The earth receives its heat from the sun ; a portion of 

 it is conducted from particle to particle into the interior 

 of the rocky crust. Another portion produces warmth 

 in the atmosphere around us, by convection, or the 

 circulation of particles ; those warmed by contact with 

 the surface becoming lighter, and ascending to give 

 place to the colder and heavier ones. A third portion is 

 radiated off into space, according to laws which have 

 not been sufficiently investigated, but which are depen- 

 dent upon the colour, chemical composition, and mecha- 

 nical structure of the surface. 



It caaaot but be instructive to contemplate the 

 indications which we have of the dependence of all that 

 is beautiful on earth, on the heat and light radiations 

 which we receive from the sun. Let us endeavour to 

 realise some of the effects which arise from even the 

 temporary deprivation of solar heat. 



It is winter, the vegetable world appears chilled to its 

 centre. The trees, except a few of the hardy evergreens, 

 are bare of leaves, and stretching forth their branches 

 into the cold air, they realise the condition of vegetable 



