of XFO %p~S Ht%E> .*# 



nary (lone prove foadvantagious, what would one of them do, if 

 the Joijls and Laths at leaft were made of the Cornifi warming-flone, 

 that will hold heat well eight or ten hours ? or of Spanijh Ruggi- 

 ola's, which are brozdplates like tiles, cut out of a Mountain of 

 red fait near Cardcna, which being well heated on both fides, will 

 keep warm 24 hours ? 



92. To which may be added the Invention of making Glaffes 

 of Hones, and fome other materials, at Henly upon Thames, lately 

 brought into England by Seignior de Cofta a Montferratees, and car- 

 ryed on by one Mr. Raven/croft, who has a Patent for the fole 

 making them ; and lately by one Mr. Bifiop. The materials they 

 u(ed formerly were the blacked Flints calcined, and a white Chri- 

 ftalline fand, adding to each pound of thefe, as it was found by 

 folution of their whole mixture, by the ingenious Dr. Ludwell 

 Fellow of Wadham College, about two ounces of Niter, Tar tar -, and 

 Borax. 



93. But the Glaffes made of thefe being fubjeft to that unpar- 

 donable fault called Crizelling, caufed by the two great quanti- 

 ties of the Salts in the mixture, which either by the adventitious 

 Niter of the Air from without, or warm liquors put in them, 

 would be either increafed or diffblved ; and thereby indnre a Sca- 

 hrities or dull roughnefs, irrecoverably clouding the tranfparency 

 of the glafs they have chofen rather fince to make their glaffes 

 of a great fort of white Pebbles, which as I am informed they 

 have from the River Po in Italy ; to which adding the aforemen- 

 tioned falts, but abating in the -proportions, they now make a fort 

 of Pebbleglafs, which are hard, cjurable, and whiter than any 

 from Venice, and will not Crizel ,' but endure the fevereft trials 

 whatever, to be known from the former by a Seal fet purpofelv 

 on them. 



94. And yet I guefs that the difference, in refpefr ofCrizeling. 

 between the prefent Glafs and the former, lies not fo much in the 

 Calx, the Pebbles being Pyrites (none but fflch I prefume being fit 

 for vitrification) as well as the Flints; but rather wholly in the a~ 

 batement of the falts, for there are fome of the Flint glaffes frricl- 

 ly fo called (whereof I have one by me) that has endured all try - 

 als as well as thefe lafi. But if it be found otherwife, that white 

 Pebbles are really fitter for their turns than black Flints, I think 



See Mr. WiUu&hbfs Voyage through Spain, p. 471 . 



they 



