If that much maligned potentate the Emperor Nero had any real notion of the capabilities of glass when he established the first glassworks at Rome, the lamentation with which he took farewell of the world, '_qualis artifex pereo_,' may have been inspired by regret at his not being allowed time enough to develop them. Certainly such gigantic mirrors as those which St.-Gobain has this year sent to the Exposition would have shown to better advantage in his colossal 'Golden House' than in any of our petty modern palaces. In what palace in England or in France to-day could a mirror measuring 7 metres x 63 centimetres in height by 4 metres x 12 centimetres in width, and thus displaying a surface of more than 30 square metres, be placed, without dwarfing everything about it? These immense and magnificent mirrors must go hereafter to decorate palaces of public resort--'palaces of the people,' not palaces of princes. What was a royal luxury when Colbert wrote to D'Avaux in 1673 has become a popular attraction. The smallest restaurant in Paris would think itself discredited to-day were it decorated with one of the _grandes glaces_ for which Colbert in 1693 thought St.-Gobain would find no purchaser save the king; but the Grand Cafe and the Hotel Terminus of the Gare St.-Lazare order mirrors in 1889 which no king of our times would very well know what to do with. Yet, once more, how the cost of these mirrors has fallen! In 1702 a plate-glass mirror showing two square metres only by surface, cost, at St.-Gobain, 540 francs. In 1889 such a mirror, showing four square metres of surface, costs, at St.-Gobain, 136 francs. A mirror showing ten square metres of surface, which could not have been made in 1702 at any price, can now be had for 467 francs!