1 10 THE WORLD'S LUMBER ROOM. 



found in the palace of Nimroud, among the relics of Baby- 

 lon, and the tombs of Egypt, amply testify. 



The discovery may well have been made by accident, 

 since lumps of impure glass are sometimes found among the 

 ashes when a rick of straw has been burnt down. For straw 

 contains, as has been said, a good deal of silica, and as it 

 also contains potash, the melting of the two together pro- 

 duces glass. 



Many minute particles of glass are tound in granite, 

 formed in a similar way, by the union of silica with the 

 potash or soda contained in the felspar.* 



Most silicious sands for it is of these only that we are 

 now speaking are more or less yellow from the iron they 

 contain, and it is this which gives the green tinge to 

 common glass. The finest and whitest sand ever seen was 

 some brought from America and exhibited in the Crystal 

 Palace, in 1851, which was perfectly pure quartz and as 

 white as snow ; but sand such as this is not easily obtained, 

 and, though millions of tons are scattered throughout the 

 British Isles, it is rarely found free from colouring matter 

 and other impurities, and needs washing and burning before 

 it can be used. 



The chief places from which glass-making sand is ob- 

 tained in England are Alum Bay, Lynn, Aylesbury, Ware- 

 ham, Reigate, and the New Forest ; and large quantities are 

 also brought from Fontainebleau, in France, as well as from 



* Though the variety of felspar called orthoclase contains so much potash 

 as to be known as potash-felspar, no cheap and easy way has been found of 

 extracting the potash, which is therefore prepared from the ashes of plants. 

 Soda-felspar is called albite. 



