NATURAL THEOLOGY. \) 



We see, therefore, that the elements bear not 

 only a strict relation to the constitution of organ- 

 ized bodies, but a relation to each other. Water 

 could not perform its office to the earth without 

 air ; nor exist, as water, without fire.^ 



IV. Of Light (whether we regard it as of the 

 same substance with fire, or as a different sub- 

 stance,) it is altogether superfluous to expatiate 

 upon the use. No man disputes it. The observa- 

 tions, therefore, which I shall offer, respect that 

 little which we seem to know^ of its constitution. 



Light travels from the sun at the rate of twelve 

 millions of miles in a minute. Urged by such a 

 velocity, with what fo7^ce must its particles drive 

 against (I will not say the eye, the tenderest of 

 animal substances, but) every substance, animate 

 or inanimate, which stands in its way ! It might: 



' The conducting powers of different substances are beautifully 

 adapted to the wants of the animal and vegetable kingdom. 

 Snow is so bad a conductor, that it protects the ground effectu- 

 ally in rigorous climates. It is said that in Siberia there have 

 been known to be as many as 38 degrees (Fahrenheit) of differ- 

 ence between the temperature of the air and that of the ground 

 under the snow ; the latter not being cooled much below the free- 

 zing point. So, too, the animal which, transported to warmer 

 climates, becomes covered with hair, has in its own cold country 

 a woolly covering, and this conducts heat so slowly as to accu- 

 mulate that M'hich respiration is continually producing. 



The peculiarity which distinguishes water from other fluids in 

 freezing, likewise merits attention. It expands, instead of contin- 

 uing to contract, when cooled to the freezing point ; and this has 

 the useful effect of crumbling earth and even rocks, so as to render 

 them fit for assisting the process of vegetation. 



