18 On the Caloptrical and Dioptrical 



gated. But I would by no means insinuate that all adder- 

 stones whatever are opake ; and much less that the anticnt 

 Britons did not possess the art of making transparent glass. 

 Soeh a conclusion would scarcely appear more rational than 

 it would be in our present antiquaries, it" no anticnt vessels 

 of transparent glass had been found, to deny that the artists 

 of those davs could niakc such glass; or that they could 

 make window-glass, if the curious specimen, described by 

 Mr. Nixon, had not been disinterred at llerculaneum. 



15. Hence, on reflection, 1 cannot help wondering that 

 some antiquaries, as observed in my last letter (§ Qfi), should 

 believe that the autient Egyptians made opake glass, but not 

 transparent glass. For, waving the well known logical prin- 

 ciple, I'hat negative propositions, such as this is, admit not 

 of prool', it is allowed that those autients were acquainted 

 with the reduction of metallic ores, and consequently with 

 fluxes or vitriliable substances, which, though opake when 

 in thick masses, would transmit more or less light when, 

 as woukl often take place, they happened to be sufficiently 

 thin. A rude kind of transparent glass, thus obtained from 

 crucibles or smelting furnaces, (not to mention potteries 

 and brick-kilns,) would furnish a hint, which, it is natural 

 to suppose, would not pass unimproved among so ingenious 

 a people. Besides, it is very improbable that the manufac- 

 ture of glass could flourish, as we liave seen it did among 

 the Sidonians, v/ithout becoming known to their enlight- 

 ened neighliouvs the Egyptians ; some of whose monarchs 

 have immortalized themselves by their encouragement of 

 the arts and sciences, 



IC. Accordin;2; to the venerable Bcdc, glass windows were 

 lirst introduced uito this country about the year 674, when 

 Bencdid Biscop, the cotemporary of the famous IViifr'idy 

 bishop of York, founded the monastery of Weremouth. 

 *' After the work was far advanced, he sent agents into 

 Eranee to procure, if possible, some glass-makers, a kind 

 of artilicers quite" unknown in England, and to bring them^ 

 over to glaze the windows of his church and monastery. 

 These agents were successful, and brought several glass- 

 makers with them ; who not onl\' performed the work re- 

 quired by Benedict, but instructed the English in the art 

 of makiiig glass for windows, lamps, drinking vessels, and 

 other uses *." 



17. I have introduced these passages, to save the reader 



* Biihr IJisl. Ab'':U. Wi-rrnniibcn. a-s qvuncd in Jleiirf i Hist, of Great 

 liiitain, vo!. iv. p. 116. cd. 3. 



