PRINCE RUPERT. 157 



into perspective, and for which they deputed a select committee 

 ot their members to return him their thanks. 



He was the inventor of a gun for discharging several bullets 

 with the utmost speed, facility, and safety; and the Royal 

 Society received from His Highness the intimation of a certain 

 method of blowing up rocks in mines and other subterraneous 

 places. Dr. Hooke has preserved another invention of his for 

 making hail shot of all sizes. He devised a particular kind of 

 screw, by means of which observations taken by a quadrant at 

 sea were secured from receiving any alteration by the unsteadi 

 ness of the observer's hand or through the motion of the ship. 

 It is said that he had also, among other secrets, that of melting 

 or running black lead like a metal into a mould, and reducing 

 it again into its original form. 



But there is one invention of which he has the credit, which 

 requires more particular notice. Besides being mentioned by 

 foreign authors, with applause for his skill in painting, he was 

 considered as the inventor of mezzotinto, owing, as it is said, 

 to the following casual occurrence. Going out early one morn- 

 ing during his retirement at Brussels, he observed the sentinal 

 at some distance from his post very busy doing something to 

 his piece. 



The Prince asked the soldier what he was about ? 

 He replied that the dew had fallen in the night and made 

 his fusil rusty, and that he was scraping and cleaning it. 



The Prince, looking at it, was struck with something like a 

 figure eaten into the barrel, with innumerable little holes 

 closed together like friezed work on gold or silver, part of 

 which the fellow had scraped away. The Prince immediately 

 conceived that some contrivance might be found to cover a 

 brass plate with sudi a grained ground of fine Dressed holes, 



