244 WALKS AND TALKS. 



as possible with water-breathing populations. The highest 

 type of animals had been reached and its aquatic class had 

 lived a Striking career. Nature had now paused for the puri- 

 fication of the air for the next class. The plan of nature was 

 blocked till this could be done. 



The Power which had called matter and force into exist- 

 ence, could have made other disposition of this difficulty. 

 The carbonic acid could have been combined with lime and 

 fixed in limestones. It could have been banished from the 

 planet. But carbon is precious. It is the basis of all our 

 combustion. It warms and blazes in coal and petroleum, 

 peat and gas. The carbon must be preserved for future use. 

 Man would discover its utilities, though the age then passing 

 had no use for it. Man was yet far off; but man was antici- 

 pated ; man was involved in the plans of the world ; man 

 was prophesied in these preparations. 



So vegetation was appointed to do the work and conserve 

 the material. This explains the presence of coal-making trees 

 upon the shores of the preceding epoch. They came by ap- 

 pointment, they were to fulfill a plan ; they stood waiting by 

 the border of a domain which had been promised them for a 

 possession. All the conditions favored. This was not fortui- 

 tous ; it was a preparation. Unlimited supplies of aliment 

 pervaded the atmosphere. The marshy situation exhaled the 

 abundant vapor in which vegetation delights. The earth in 

 its comparative newness, retained the warmth to stimulate at 

 the root. So tree-fern and herbaceous fern, calamite and 

 sigillaria, begin work. Atom by atom, they selected the poi- 

 son from the atmosphere, and, returning the oxygen, fixed 

 the carbon in their tissues. Frond, stem, and root treasured 

 up the fuel, impelled by the force of sunlight ; every pound of 

 vegetable answered to a given amount of solar force. 



The work was begun. Generations of plants succeeding 

 each other, fell prostrate at last, and added their substance 

 to the growing bed of peat. Standing water protected the 

 peat from decomposition. Now the skies again were lowering 

 and forebodings of change trembled through the continent. 



