THE DEVELOPMENT OF MECHANICS 243 



Moreover, and this was of the greatest importance, men were 

 developing the measuring habit, the habit of exact observation, 

 of comparing one force or power with another, generalising 

 these observations, and deducing from general laws other effects 

 up to then unforeseen or unknown. 



It is easy to understand that very soon there were practical- 

 minded men alert to take advantage of all this new knowledge, 

 and keen to apply it in a practical way. In the very early 

 years of the century, while Galileo was at work upon his ex- 

 periments with falling bodies, a rich compatriot, della Porta, was 

 throwing out some interesting guesses as to the way advantage 

 might be taken of the force of steam. Very soon Rivault had 

 imprisoned water within a cannon-ball, and blown the ball to 

 pieces simply by heating it. Before Galileo's death a number 

 of inventors were at work reviving the old contrivances of 

 Hero and Ctesibius for doing work with steam. Somewhere 

 about 1628, says Thurston, Lord Somerset, second Earl of 

 Worcester, had a> rude contrivance for raising water working 

 in Vauxhall. A little later he had a still more developed 

 machine at Raglan Castle. In 1666 he had taken out the first 

 patent for a steam-engine. 



It was about this time that a new mechanical device lent an 

 added perfection to astronomical observation, for that matter, 

 to the whole art of physical investigation a perfection which 

 neither could have otherwise attained. This was the invention 

 of an accurate measure of time in a word, of clocks. It is 

 almost beyond belief that they should have come so late. 

 Not, indeed, that clocks of one sort and another were not known 

 to the most ancient times. Sun-dials were in use, not perhaps 

 in the Garden of Eden, where a reminder of the flight of time 

 would have been an annoyance, but certainly in prediluvian 

 days. Even the Chaldeans knew how to " weigh " time in 

 a word, had clepsydras or water-clocks. Some very wonder- 

 ful examples of the latter were constructed by the Arabians. 

 The famous clock sent by Haroun-al-Raschid to Charlemagne 

 indicated the hours by the fall of little balls and by the coming 

 forth of small horsemen from as many open doors. 



It is to the Arabians, too, that we probably owe the first 

 application of the pendulum as a time measurer. This was 

 certainly made by the great astronomer Ibn-Junis along at the 

 end of the tenth century. He thus anticipated Galileo by some 



