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Sheet of Glass
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ribbon which passes over a roller bed into a roller lehr or annealing chamber.
    There is something rather grand and a little terrifying if one can visualise the inexorable march of this ribbon which, if it was not cut, would in six months time stretch from St. Helens to London.
    GRINDING AND POLISHING. Having made a rough glass we have now got to grind and polish it. The first stage is the grinding of the surface by means of a cast-iron runner, fed with coarse sea-sand until the whole of the rough cast surface has been removed, and then with graded sands, which become progressive finer, until a frosted surface of the finest possible texture is obtained. Then comes the very delicate process of polishing, which consists of rubbing the glass with felt discs fed with rouge. The rouge, obtained by carefully calcining ferrous sulphate to a definite colour, acts as an abrasive in the earlier stages, but to what extent molecular flow contributes to the final polish is a rather contentious subject which I have not time to discuss to-night.
    There are two main methods of grinding and polishing plate glass--
  1. The round table method.
  2. The continuous method.
    ROUND TABLE METHOD. In the round table method the glass is laid and ground and polished on a circular table 36 ft. in diameter and weighing 60 tons. There is not time to describe the details, but by comparison with the Continuous Grinder, which will be described in detail, the process has the following marked disadvantages--
1. The glass has to be cut to cover the whole table,