THE GLASS INDUSTRY. 437 



But a locality which furnished silica, alkali, and lime would 

 still be badly off as regards the needs of glass-making if it were 

 out of reach of adequate supplies of substances refractory enough 

 when fashioned into crucibles to permit the fusion of the mixture. 

 For this purpose fire clay is the material par excellence, since it 

 withstands both the chemical action of the molten glass and the 

 disintegrating effect of the intense heat of the furnace. It is an 

 essential to glass-making. Bulk for bulk, however, much less 

 fire clay is needed than crude material for the batch, so that it is 

 less needful that the fire clay shall be a local product. It can be 

 brought to the batch more economically than the batch can be 

 taken to it. It does not happen, therefore, in the history of the 

 glass industry, that the mere presence of suitable clay ever deter- 

 mines the location of works. At the present time much of the 

 clay used in both England and America comes from Germany. 

 It is significant, in looking over the columns of our trade journals, 

 that the advertisements are for the most part of the imported 

 rather than the native article. There are, however, large deposits 

 of excellent clay in northeastern New Jersey, in western Penn- 

 sylvania, in Missouri, in Ohio, and in other parts of the country, 

 which must eventually be utilized. The American clay is, if any- 

 thing, purer than the foreign, but it is less dense, and will probably 

 require somewhat different treatment from the German. The 

 attempt to substitute it for the imported in the earlier days, before 

 the requirements of the pot clay were so well known and our own 

 deposits had been so well exploited, led to financial disaster, and 

 even to the suspension of a large works at Boston, where the ex- 

 periment proved absolutely fatal. Our knowledge of refractory 

 materials is less scientific than of any of the other materials used 

 in glass-making. In consequence we are the more dependent 

 upon rule-of -thumb methods in working them, and pay the more 

 dearly for the experience when we venture any innovation. 



The third element involved, fuel, is of all the most important, 

 both as regards quality and cost. In America it has been the 

 dominant element, and largely determined the location of our 

 glass-houses and the measure of their success. The choice lies 

 between four varieties — wood, coal, petroleum, and natural gas. 

 In the earlier days a fifth fuel is found on the list, North Carolina 

 rosin, but it can hardly be said to figure in the present production. 

 In England coal does not seem to have been used as a fuel to any 

 extent until the beginning of the seventeenth century. About 

 1623 Sir Robert Mansell obtained a patent for a " method of mak- 

 ing glass with sea coal, pit coal, or any other fuel not being timber 

 or wood." The patent was probably for some particular method, 

 as the simple use of coal was well known, even in the preceding 

 century, though by no means common. The early Virginia glass 



