2 4 3 THE POPULAR SCIENCE MONTHLY. 



manufacture for fluxing being consumed while the sand is transformed 

 to a greater or less degree of transparency. The sand used in glass- 

 making is almost pure silica, so nearly pure that there is less than one 

 per cent of iron, magnesia, and aluminum, to ninety-nine + per cent of 

 the other. And of this sand, which is quarried out of the hills and 

 ground down to varying degrees of fineness, and washed to varying 

 degrees of whiteness, eight hundred tons are manufactured daily, 

 four hundred tons being consumed in and about Pittsburg, and four 

 hundred tons going into Eastern Ohio and West Virginia to Wheeling, 

 Bellaire, Columbus, and all points within a circuit of one hundred and 

 fifty miles from Pittsburg. 



In selecting, a darkish sand is found, containing more foreign sub- 

 stances than the ninety-nine per cent silica, which inferior grade goes 

 into green or "black" bottles, and a still darker and baser earth, 

 which is used for sanding fire-brick molds ; another and finer dark 

 grade, which is used by crucible-steel manufacturers ; and still another 

 quality, the whitest and grittiest, which becomes " flint," or what 

 might be called absolutely transparent glass. An inferior quality of 

 white sand is used for prescription-bottles, but the very best is for 

 the higher grade of flint-ware. 



Looking through the flat surface of window-glass, whether plate 

 or blown, it appears colorless ; but, if the sight is directed through the 

 edge, it will disclose a sea-green tinge. Flint-glass proper is not so. 

 It is absolutely colorless, except when cut into faces or prisms, when 

 it reveals the colors of the spectrum. 



The cost of a ton of sand to glass-manufacturers of Western Penn- 

 sylvania, Eastern Ohio, or West Virginia, is, of course, dependent on 

 the distance it is hauled from the quarry ; but, taking the eight hun- 

 dred tons daily manufactured and consumed, it will not average above 

 $2.25 per ton, damp. Dried sand will average $2.50 joer ton. Of 

 course, it costs a little less than those figures in Pittsburg, and a 

 little more in Bellaire, Ohio ; but even at this last-named place, the 

 cost of the sand which goes into the manufacture of a box of common 

 window-glass, containing the regulation fifty square feet of surface, is 

 about five cents ; that is, the box of glass consists merely of five 

 cents' worth of silica, transmuted to a state of transparency. 



The sand used in the glass industry in Western Pennsylvania, 

 Eastern Ohio, and West Virginia, comes from three quarries : one on 

 the Pennsylvania Railroad, overlooking the Juniata ; one on the Balti- 

 more and Ohio Railroad, near Connellsville ; and one on the Pittsburg, 

 McKeesport, and Youghiogheny Railway, twenty-five miles south of 

 Pittsburg. It is quarried out like building-stone, passed through a 

 quartz-crusher, further reduced under immense iron wheels, and finally 

 ground and washed in an endless screw. The washing releases some 

 of tbe foreign substances, but streaks of iron which are sometimes 

 found running through the stone are knocked off to undergo the 



