THE MIDDLE AGES AND DURING THE REVIVAL. 53 



older authors. Gunpowder was the result of gradual modifi- 

 cations of several explosive substances known from time 

 immemorial ; there was really no single inventor. 



1 220. Algebra, which powerfully developed mathematics. 

 The Hindus, as we now know from Sanskrit writings, 

 originated it. It was introduced into Europe by the Arabs, 

 who extended it. But it was greatly improved by our 

 mediaeval mathematicians. 



1300. Spectacles, which restored the sense of sight to 

 millions and millions, were invented in Italy, by either 

 Alessandra da Spina of Pisa, or Salvinus Armatus of 

 Florence. The Assyrians were already in possession of 

 the magnifying glass one (now in the British Museum) 

 having been found in Sennacherib's library. The CHINESE, 

 too, seem to have invented spectacles as early as the Vlth 

 century of our era. Alhazen had pointed out the mag- 

 nifying property of lenses ; but our spectacles appear to 

 have been invented independently of these sources. 



1310. Watches, a natural outgrowth of the clock, were 

 invented as early as the XlVth century (1310). 



1320. Cannon, known to the Arabs of Spain before 1200, 

 but much improved in Europe. 



1364. Muskets, a clever modification of the cannon. 



1500. Pistols, a most serviceable modification of the 

 musket. These three weapons prove the practical ingenuity 

 of mediaeval Europe. 



Xth to Xlllth c. Stained Glass, immensely improved ; 



1 300. Mirrors, made of glass ; Enamelling, and 



XVth c. Glazed Pottery, imitated from the Arabian and 

 Greek, but perfected ; 



XVth, XVIth c. Majolica, all of which demanded so 

 much practical knowledge, originated in Italy. DELLA 

 ROBBIA (1415) and PALISSY (1580) were the masters of the 

 ceramic art. 



1415. Oil Painting was invented about 1400 by Van 

 EYCK BROTHERS. This proves the progress made in practical 

 -chemistry. Great strides in art since then. 



1440. Engraving, the medium of illustration in art and 

 science. 



