NOTES ON CHAIN CABLES. 165 



uniform operation, greater ease in handling work around it, and less care and at- 

 tendance. 



An interesting point was brought out in connection with such oil welding 

 fires in the course of the experiments conducted at Boston. The first fire was of 

 the form shown in Fig. i8, Plate 96, the link being suspended through the opening in 

 the top and hanging down into the chamber of the furnace. It was found that in 

 spite of careful attendance the link would burn away and be badly scored or other- 

 wise damaged. A heating chamber was constructed on top of the forge, as shown 

 in Fig. 18A, Plate 96, and the link raised to the height of this chamber. No further 

 trouble was experienced, and heats were readily obtained. 



The explanation seems to be that in the first design the link was hanging 

 into the combustion chamber, where there was present free oxygen in excess of 

 that required for the combustion of the oil with the result that this oxygen com- 

 bined with the incandescent iron and served for its combustion, the chemical con- 

 dition being much the same as found in the oxy-acetylene cutting flame. When 

 the upper chamber was constructed it became a heating chamber, and the lower 

 one was devoted to the combustion of the oil. The combustion being complete 

 when the flame struck the link, no oxidation of the iron took place. It is only 

 necessary to see that the fire is kept "fat" by giving it enough oil. 



The following table compares the breaking stress of five doublets heated in 

 oil fire and five doublets heated in coke fire, all formed and welded by hand, and 

 of 3-inch iron : 



Oil Fire. Location of Break. 



532,940 lbs. W^ — Across weld. 



544,240 

 532,100 

 530,220 

 504,448 



2,643,940 

 528,796 



Qw — Welded quarter, 

 gw — Welded quarter. 

 Qw — Welded quarter. 

 Wo — With and across weld. 



Average. 



Coke Fire. Location of Break. 



572,560 lbs. Qw — Welded quarter. 



538,640 " Qw — Welded quarter. 



507,320 " Wc — With and across weld. 



568,940 " WsL — Across weld. 



519,320 " Cw — Pulled out welded crown. 



2,706,780 " 

 541,356 " Average. 



The advantage in favor of the coke fire is slight and easily offset by the fact 

 that the work was all done by chainmakers accustomed to a coke fire, who had 



