The tonnage of Pittsburgh, owing to the character of the commodities in which it deals, is very large and exceeds that of any other city in the world. Coal, ores, iron, steel and other heavy articles constitute much of what the city receives and sends out. At the present time the tonnage handled by rail and water exceeds 175,000,000 tons annually, twice that of New York, London, Liverpool and Marseilles com bined, the aggregate of these in 1917 having been 84,376,000 tons. The rail traffic is repre sented by nearly 1,000 passenger and freight trains daily arriving or departing.
Manufactures and Mining.— Pittsburgh is located at the heart of the largest and most productive coal-field on the continent. Until the recent discoveries in the Southwest and Mexico, Pittsburgh was the centre of the most productive oil-fields in North America, which still have a great production. She has at hand one of the most extensive and richest fields of natural gas in the world. Pittsburgh annually uses in her grates and furnaces over 100 billions of cubic feet of natural gas, piped in the city through nearly 6,000 miles of gas-pipes, which reach out in every direction through western Pennsylvania and into West Virginia. The abundance of cheap fuel at her command has made the city the natural centre of all those in dustries which depend upon fire for their suc cessful prosecution. She is the hearth of the nation, at which the spirit of Tubal Cain min isters to the wants of man. She used to be called "The Iron City," to-day she is called "The City of Steel." The Pittsburgh district annually produces more than one-half of all the coke manufactured in the United States and 10 per cent of all the bituminous coal mined in the world. Three-tenths of all the pig iron produced in the western hemisphere is made in Pittsburgh and four-tenths of all the steel; and the combined production of these commodi ties considerably exceeds in the Pittsburgh dis trict alone the entire output of iron and steel annually produced in Great Britain and her colonies. Pittsburgh makes more steel rails, more plates for the hulls, boilers, and armament of ships, more pressed steel cars and coaches than any other city in the world. During the World War the capacity of her mills and fur naces was taxed to supply the needs of the Allies and later of the government of the United States, and it is said upon excellent authority that 60 per cent of the metal supplies used by the United States came originally in the rough and largely in the finished shape from the Pittsburgh district. Before the output of the great steel-making establishments of Pittsburgh, that of the Krupp works at Essen in its palmi est days sinks into relative insignificance.
Pittsburgh is the seat of the manufacture of aluminum in America and the industry was originally developed here, the process being the result of experimental work by Pittsburgh men, followed by the application of their efforts and capital. Bronze, brassware, copper in various
shapes, tin-plate and white lead are extensively manufactured. In short all the industries in which the metals play a part are developed in this great metallurgical centre, more especially so far as the production of raw materials is concerned, although finished product is pro duced in vast quantities. Recent statistics show that Pittsburgh supplies with their raw material certain great industries in the United States in the following proportions: manufacture of automobiles, 46 per cent; hardware, 45 per cent; agricultural implements, 44 per cent; machinery, 37 per cent.
The making' of structural steel shapes em ployed in the building of edifices had its be ginning here and it is said that the plans and specifications for a majority of the "sky-scrap ers" built in the great cities of America are to be found in the archives of the steel-mills of Pittsburgh.
Pittsburgh leads the world to-day in the production of plate glass, window-glass, pressed table-ware, bottle-ware and lamp chimneys. The finer manufactures in glass are also well represented by establishments which make dif fracting prisms used in lighthouses, lenses for opera-glasses, telescopes, range-finders and mi croscopes. The optical establishment of Dr. J. A. Brashear has a world-wide reputation for the excellence of the lenses turned out. The output of the Pittsburgh Plate Glass Company in 1918 was 31,600,000 square feet and the total production of plate glass in the district in 1918 was nearly 60,000,000 square feet, which if made into one sheet would cover an area of 1,377 acres, or make a pane of plate glass three miles high by one mile wide and the ordinary win dow-glass made here would, if in one piece, be a pane nearly three times as large. The largest manufactory of corks in the world (corks are the corollary of bottles) is located here and not only makes stoppers for phials and bottles, but everything which can be made from cork, including life-preservers and linoleum. En ameled ware is extensively manufactured and the Standard Sanitary Manufacturing Company is famous for its beautifully perfect wares. Its trade with South America has attained very large proportions and it exports its products to every quarter of the globe. In recent years a great development has taken place in the chemical industries, especially those which are connected with the by-products of the coke in dustry. The manufacture of coal-tar, ammonia and various derivatives of coal-tar has assumed large proportions. During the European War, Pittsburgh produced an immense quantity of high explosives, which her position fitted her to supply at low rates of cost, and train-loads of trinitrotoluol were continuously shipped from the district.