1 8 Pioneer Labourers 



converted into soil before they can turn it to account ; 

 and how is this to be accomplished ? 



If man had to make his soil from the rocks before 

 he could grow his crops, he would have to begin with 

 crowbars and pickaxes, if he did not first resort to 

 blasting with gunpowder or dynamite, and even then 

 his progress would be slow and laborious. 



Nature usually works in a much more quiet and un- 

 obtrusive fashion, but there are times when she, too, 

 has recourse to blasting as a preliminary measure. She 

 mines the rocks and shatters them by means of the 

 earthquake, compared with which the power even of 

 dynamite is insignificant ; and if these rough measures 

 do but little towards preparing the soil, they unques- 

 tionably make things easier for the army of labourers 

 who follow. 



But it is the noiseless and often invisible workers 

 who accomplish most, for they are at work, some or 

 other of them, incessantly during every moment of 

 every hour, day and night, summer and winter, through- 

 out the whole year. 



Usually the first of the silent labourers to begin work 

 upon the rocks are also the invisible ones the gases of 

 air and water, which wear away the very hardest rocks 

 by degrees. They are not able to work equally fast 

 upon all rocks, but where they can be employed, there 

 the work goes on most rapidly. Those rocks which are 

 best able to resist them decay more slowly, even though 

 they be actually softer and yield more readily to such 

 labourers as wind and rain. In other words, the un- 

 seen chemical workers produce more effect on the rocks 

 than do the seen, mechanical workers. 



The two gases which do the chief part of the chemical 



