4 PROGRESS OF SCIENCE. 



evidence which proves the fact to have been a universal one. 

 " The properties of the scales and of the lever, involving the 

 first principles in mechanics, were only generalised under the 

 stimulus of commercial and architectural needs. To fix the 

 times of religious festivals and agricultural operations were 

 the motives which led to the establishment of the simpler 

 astronomical periods, so that at first science was merely an 

 appliance of religion and industry." 



A later, but not less conspicuous instance of the same fact, 

 we may add, is found in the reform of the Calendar (1581-2), 

 the main object of which was the fixing afresh of the Roman 

 Catholic feasts. " Such small knowledge of chemical relations 

 as was involved in ancient metallurgy, was manifestly ob- 

 tained in seeking how to improve tools and weapons. In the 

 Alchemy of the later times, the intense hope of private benefit 

 contributed to the disclosure of a certain class of uniformities." 

 " How to fix religious festivals, when to sow, how to weigh 

 commodities, how to measure ground, were purely practical 

 questions out of which arose astronomy, mechanics, geometry." 

 We need not do more than indicate these facts; for 

 further evidence we refer the reader to the works we have 

 mentioned ; but it is not unnecessary to remind the student 

 that throughout the Middle Ages also, utility was the main- 

 spring of activity among inventors and searchers. The wind- 

 mill, spectacles, stained glass, glazed pottery, mirrors, oil- 

 colours, clocks, fire-arms, the organ, paper, the compass, the 

 violin, printing, the suction-pump, the cross-staff, mathematical 

 symbols, the Rudolphine Tables, etc., were one and all 

 devised to serve a useful purpose, and " the useful and the 

 practical were the incentives " which led to them. The same 

 fact is observable in our times. And considering the inter- 

 action of the sciences upon one another, of the arts upon one 

 another and upon science ; considering also the natural 

 filiation of discoveries, their evolvement, that is, from one 

 another, we plainly see that science, after springing from 

 common knowledge and being promoted by utility, flows 

 from science itself, and can be promoted by nothing but 

 science, however much genius and chance may at times 

 assist it. It is then easy to perceive that books are 



