i8 PROGRESS OF SCIENCE. 



which man requires to feed, to clothe, and to house himself, 

 and which TRADE, or Exchange in its broadest sense and 

 working, can alone distribute evenly. 



EXCHANGE rests on foundations absolutely needful, such 

 as 



I. MEANS OF TRANSPORT from the canoe and cart to 

 the steamship and railway. 



II. DURATION or perpetuation OF IDEAS and their 

 spread which had, and still has, to be secured by writing, 

 the plastic arts, printing, the telegraph, and so forth. 



III. The TRANSFORMATION OF THE EARTH to the 



requirements of man such as the draining and drying 

 of marshy land, the clearing of a forest, the digging of 

 canals for irrigation, the cutting of roads, and so on which 

 can only be achieved by the labour, inventions, trades, 

 industries, and arts of generations. 



IV. The PHYSICAL AND MORAL HEALTH of humanity 

 to be ensured by hygiene, medical science, education, and 

 practical morality. 



V. The FREE AND ORDERLY INTERCOURSE of all classes 



with one another in their own country, and of all nations 

 with one another throughout the globe an end obtained 

 by political development, international law, and social science. 



It is clear that all these elements demanded ages upon 

 ages for their birth and growth, and, to make the ancients 

 responsible for their non-appearance in the Greek or Roman 

 world, is equivalent to making them responsible, and re- 

 proaching them, for having been our juniors by two thousand 

 years, or for having failed to find out what required two 

 thousand years to discover. 



The ancients, far as they were from the point we have 

 now reached, have nevertheless achieved wonderful work, 

 even if we limit our estimate of it by the partial and frag- 

 mentary records of their knowledge in our possession. No 

 doubt but they knew vastly more than we give them credit 

 for ; but restricted to these limits, the advance they made 

 was so astonishing that we can never be tired of praising 

 them. To their ability, originality, and genius we can but 

 yield the amplest tribute of admiration. 



