136 THE BORDERLAND OF SCIENCE. 



subserve its purpose or if the vocabulary of teleology 

 must be eschewed, this great machinery would no longer 

 do what it is actually doing, would no longer maintain 

 active life upon the earth. If life still continued it 

 would be sluggish, little more, in fact, than living death. 

 And if the failure of the solar supply at this present 

 time would lead to such a result, how much more com- 

 pletely fatal to the existence of all such life as we now 

 see upon the earth, would have been a defalcation of 

 solar light and heat during the long-past ages when so 

 many forms of force were stored up. To take one such 

 form alone, and. to consider it only as it affects the 

 requirements of our own country c the " deposits of 

 dynamical efficiency " laid up in our coal strata are 

 simply,' as Tyndall tells us, ' the sun's rays in a poten- 

 tial form. We dig from our pits annually a hundred 

 million tons of coal, the mechanical equivalent of which 

 is of almost fabulous vastness. The combustion of a 

 single pound of coal in one minute is equal to the work 

 of three hundred horses for the same time. It would 

 require one hundred and eight millions of horses work- 

 ing day and night with unimpaired strength for a year 

 to perform an amount of work equivalent to the energy 

 which the Sun of the Carboniferous Epoch invested in 

 one year's produce of our coal-pits. The further we 

 pursue this subject, the more its interest and wonder 

 grow upon us. Here we find the physical powers 

 derived from the sun introducing themselves at the 

 very root of the question of vitality. We find in solar 

 light and heat the very mainspring of vegetable life.' 



