156 GENERAL EVOLUTION. 



could advance a little in knowledge through the accumulation of 

 the experiences of their predecessors, they possessed no means of 

 accumulating the power of labor, no control over the activity of 

 numbers — in other words, no wealth. 



But the accumulation of knowledge finally brought this ad- 

 vance about. The extraction and utilization of the metals, espe- 

 cially iron, formed the most important step, since labor was thus 

 facilitated and its productiveness increased in an incalculable de- 

 gree. We have little evidence of the existence of a medium of ex- 

 change during the first or stone period, and no doubt barter was 

 the only form of trade. Before the use of metals, shells and other 

 objects were used ; remains of money of baked clay have been 

 found in Mexico. Finally, though in still ancient times, the pos- 

 session of wealth in money gradually became possible and more 

 common, and from that day to this avenues for reaching this stage 

 in social progress have ever been opening. 



But wealth merely indicates a stage of progress, since it is but 

 a comparative term. All men could not become rich, for in that 

 case all would be equally poor. But labor has a still higher goal ; 

 for, thirdly, as capital, it constructs and employs machinery, 

 which does the work of many hands, and thus cheapens products, 

 which is equivalent in effect to an accumulation of wealth to the 

 consumer. And this increase of power may be used for the intel- 

 lectual and spiritual advance of men, or, otherwise, at the will of 

 the men thus favored. Machinery places man in the position of a 

 creator, operating on Mature through an increased number of 

 *' secondary causes." 



Development of intelligence is seen, then, in the following 

 directions : First, in the knowledge of facts, including science ; 

 second, in language ; and, as consequences of these, the accumula- 

 tion of power by development — first, of means of subsistence ; and, 

 second, of mechanical invention ; and, third, in the apprehension 

 of beauty. 



Thus, we have two terms to start with in estimating the be- 

 ginning of human development in knowledge and power : first, 

 the primary capacities of the human mind itself ; second, a mate- 

 rial world, whose infinitely varied components are so arranged as 

 to yield results to the energies of that mind. For example, the 

 transition-points of vaporization and liquefaction are so placed as 

 to be within the reach of man's agents ; their weights are so fixed 

 as to accord with the muscular or other forces which he is able to 



