Since 1870 the output of the company from its various manufactories has more than doubled. It now amounts, in round numbers, to 800,000 square mètres a year of polished plate glass; to 500,000 square mètres a year of rough glass; to a million kilogrammes a year of blocks and castings for floors and roofings, and to eighty thousand kilogrammes a year of optical glasses of all sorts.
In the time of Louis XIV. and before Lucas de Nehou had made his invention of plate glass, there was absolutely no public demand for what in those days were called 'large mirrors' made in the Venetian fashion, mirrors which to-day would not find a market in the most remote frontier towns of America or Australia. Colbert then wrote to the Comte d'Avaux apropos of the works of Lucas de Nehou in Normandy, that 'there was absolutely no market for large mirrors in the kingdom, the king being the only person who could possibly need them!'
In 1702, ten years after the invention of the process by which plate glass is made, a mirror with a surface area of one mètre cost 165 francs. In 1889 such a mirror costs 30 f. 25 c. A mirror with four mètres of surface area cost, in 1702, 2,750 francs. In 1889 it costs 136 francs.
When we come down to modern times and to the much larger mirrors produced of late years, the fall in prices is extraordinary. In 1873 a mirror with ten square mètres of surface cost 1,200 francs. To-day such a mirror can be bought at St.-Gobain for 467 francs, showing a fall of nearly two-thirds in price within sixteen years!
To-day the total production of polished plate glass in the world is estimated as follows:--
square mètres England (4 companies) 900,000 Belgium (6 companies) 600,000 Germany (4 companies) 150,000 United States (7 companies) 500,000 France (not including St.-Gobain) 130,000 St.-Gobain 800,000 --------- Total 3,080,000