THE GLASS INDUSTRY. 581 



$2,600,000. It will be noticed that while the number of establish- 

 ments only doubled during this interval of twenty years, the value 

 of the product was nearly quadrupled. At the time of the tenth 

 census — that is, in 1880 — there were fifty-one factories, yielding an 

 annual output of about $0,000,000. The importance of Pittsburg 

 as a glass center can best be appreciated by considering these 

 figures relatively to the whole American output. The one district 

 of Allegheny County produced a little over a quarter of the entire 

 glass manufactured in this country, while the State, as a whole, 

 made a trifle over two fifths of the total. The product was win- 

 dow glass, hollow ware, and green glass, no plate glass appearing 

 in the State returns up to that time. 



While the other conditions were also favorable, the chief cause 

 of this marked development in Pennsylvania has undoubtedly 

 been her fuel. During the first ten years of the century her for- 

 ests alone were used to any extent, but the substitution of coal for 

 wood went on continuously for the succeeding seventy years, until 

 in 1880 it was everywhere the chief fuel, wood being employed 

 only in heating the annealing ovens and for other minor purposes. 

 Up to 1880, however, the development of the industry consisted 

 for the most part in the improvement of already existing devices. 

 The furnaces were made larger, the chemicals were purer, the 

 melting pots more capacious. The coal was burned to better ad- 

 vantage, and consequently the batch was more thoroughly fused. 

 Greater differentiation of the processes was being slowly brought 

 about. In window-glass factories separate furnaces were provided 

 for melting and blowing. In the handling of the glass there were 

 similar improvements. The continuous rod leer was coming into 

 use, while bottles and other hollow ware were annealed in iron 

 trucks and no longer needed separate handling. All these were 

 substantial gains ; yet up to 1880 the fact remained that no very 

 radical changes had been introduced into general glass-making 

 practices — we do not here refer to the subsequent working of the 

 material — and it was undeniable that the American product was 

 in many respects inferior to the imported. We could not at that 

 time successfully compete with Belgium even in the matter of 

 window glass. 



But during the past decade there has come a change so rad- 

 ical and so far-reaching in its results that more glass history has 

 been condensed into these busy ten years than is to be found 

 in the previous eighty years. The natural-gas well has been a 

 veritable Aladdin's lamp to the glass industry. The fuel itself 

 has been known for many years. As early as 1775 Washington 

 had a "burning spring" on the tract of land deeded to him in 

 the Kanawha Valley for military service, which he desired to 

 make public property ; but through some technicality the grant 



