460 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



condition of our Bessemer Steel establishments. The prod- 

 uct of American Bessemer Works has been steadily increas- 

 ing from various causes better organization, better refracto- 

 ry materials, and chiefly numerous large and small improve- 

 ments in mechanical details. In 1868 an output of 500 tons 

 of ingots per month was barely reached in the best works ; 

 in 1870 the production at Troy and Harrisburg had risen to 

 about 1700 tons per month, maximum. Early in 1872 the 

 Harrisburg Works turned out above 2000 tons per month, and 

 for a year or more these and the Cambria Works took the 

 lead in this direction, the latter plant having run as high as 

 640 tons in one week. During 1873 the Cambria, Harrisburg, 

 North Chicago, and Joliet Works averaged 25 to 30 heats of 

 five tons each per 24 hours. During the week ending July 

 12, 1873, the Harrisburg Works made 180 heats, yielding 890 

 tons of ingots. The product of the Cambria Works for the 

 w r eek ending January 17, 1874, was 189 heats, giving 956 tons 

 of ingots. During 24 hours (Friday, January 16) 46 blows 

 were made. On Friday, February 13, 1874, the Troy Works 

 made 50 heats in 24 hours, yielding 267 tons of ingots. This 

 is the most remarkable run on record. During the week end- 

 ing April 4 the Troy Works made 195 heats, yielding 972 

 tons of ingots, which is the largest week's work. In Janua- 

 ry, 1874, the Troy Works made 2899 tons of ingots; and in 

 April the North Chicago Works made 3526 tons, which is the 

 largest month's work. These are all five-ton plants, consist- 

 ing of two five-ton vessels and accessories, and they work 

 only eleven turns, or five and a half days per week. 



FIRE-PROOF JOISTS. 



A practically fire -proof joist, invented by Mr. Walker, 

 promises to be an important addition to the means of erect- 

 ing approximately fire-proof edifices. This consists of a slip 

 of wood five inches wide by five eighths of an inch thick, 

 bolted between two flanged strips of quarter-inch iron, mak- 

 ing a beam quite as strong as those of wood ordinarily em- 

 ployed. The iron sides, in addition to affording strength, it 

 is claimed, render the joist substantially fire-proof, while the 

 centre of wood affords the means of putting down floors and 

 nailing on laths in the usual manner. The impediment to 

 the manufacture of these joists heretofore has been the diffi- 



