But these mirrors disappeared with the bottles and other glass articles; and metal mirrors again became the fashion.  For fourteen hundred years we hear nothing of looking-glasses, and then we find them in Venice, at the time that city had the monopoly of the glass trade.  Metal mirrors were soon thrown aside, for the images in them were very imperfect compared with the others.

These Venetian glasses were all small, because at that time sheet glass was blown by the mouth of man, like bottles, vases, etc., and therefore it was impossible to make them large.  Two hundred years afterward, a Frenchman discovered a method of making sheet glass by machinery, which is called founding, and by this process it can be made of any size.

But even after the comparatively cheap process of founding came into use, looking-glasses were very expensive, and happy was the rich family that possessed one.  A French countess sold a farm to buy a mirror!  Queens had theirs ornamented in the most costly manner.  Here is a picture of one that belonged to a queen of France, the frame of which is entirely composed of precious stones.

[Illustration]

I have told you how the Venetians kept glass-making a secret, and how, at last, the Germans learned it, and then the French, and their work came to be better liked than that of the Venetians.  But these last still managed to keep the process of making mirrors a profound secret, and the French were determined to get at the mystery.  Several young glass-makers went from France to Venice, and applied to all the looking-glass makers of Venice for situations as workmen, that they might learn the art.  But all positively refused to receive them, and kept their doors and windows tightly closed while they were at work, that no one might see what they did.  The young Frenchmen took advantage of this, and climbed up on the roofs, and cautiously made holes through which they could look; and thus they learned the carefully-kept secret, and went back to France and commenced the manufacture of glass mirrors.  Twenty years after, a Frenchman invented founding glass, which gave France such a great advantage that the trade of Venice in looking-glasses was ruined.

You would be very much interested in watching this process of founding glass.  This is the way it is done.  As soon as the glass is melted to the proper consistency, the furnaces are opened, and the pots are lifted into the air by machinery, and passed along a beam to an immense table of cast iron.  A signal is given, and the brilliant, transparent liquid glass falls out and spreads over the table.  At a second signal a roller is passed by machinery over the red-hot glass, and twenty men stand ready with long shovels to push the sheet of glass into an oven, not very hot, where it can slowly cool.  When taken out of the oven the glass is thick, and not perfectly smooth, and it has to be rubbed with sand, imbedded in plaster of Paris, smoothed with emery, and polished by rubbing it with a woollen cloth covered with red oxide of iron, all of which is done by machinery.