202 MR W. GORDON AND MR G. H. GULLIVER ON 
13, and 15 inches for each series of bars. The extension on a 1-inch length is the 
measured extension of the inch within which fracture took place; that on a 3-inch 
length is the extension of the fractured inch plus the extension of the inch on each 
side; the extension on a 5-inch length is the extension on the 3-inch length plus 
the extension of the next inch at each end, and so on. In the case where, owing to 
4 inch thick, showing the gap left between the fractured 
surfaces. The variation of thicknessin the constricted region 
is indicated on the contour lines in hundredths of an inch. 
position of the fracture within this length has been neglected; this error is more 
important in the wider bars. In the extension of longer lengths the error diminishes 
rapidly, and is negligible for greater lengths than 5 inches, even in the widest bars 
used ; it is therefore of little consequence from the present standpoint. Another cause 
