INTO THE STRENGTH OF WROUGHT-IRON PLATES. 
723 
Here it appears that the rate of elongation of bars of wrought iron increases with 
the decrease of their length; thus while a bar of 120 inches has an elongation of 
•216 inch per unit of its length, a bar of 10 inches has an elongation of *42 inch per 
unit of its length, or nearly double what it is in the former case. The relation be- 
tween the length of and its maximum elongation per unit, may be approximately ex- 
pressed by the following formula, viz. — 
/=- 18 +^, 
where L represents the length of the bar, and I the elongation per unit of length of 
the bar. 
These results are of some value, as they exhibit the ductility of wrought iron at a 
low temperature, and also the greatly increased strength which it exhibits with a re- 
duced section under severe strain. 
On some future occasion we may refer to this subject in order to show the bearing 
powers of wrought iron when compared with its elongated transverse section when 
reduced by forces sufficient to ensure fracture. 
The following experiments were made to determine the transverse strength of beams, 
recommended by Mr. Kennedy of Liverpool, for supporting the decks of iron ships. 
Experiment 8. — October 10, 1845. 
On a malleable iron beam, of the annexed sectional form, 1 1 feet 7 inches long, 
and 1 1 feet between the supports. 
Dimensions at a= 1-000 in.X2 
Dimensions at 6= '325 in. X 7 
Dimensions at c= ’380 in. X 4 
Weight of beam=227 lbs. 
Weight of shackle=885 lbs. 
Weight 
in lbs. 
Deflection 
in inches. 
Deflection 
load 
removed. 
Remarks. 
885 
•04 
2,581 
•12 
4,317 
•20 
6,050 
•26 
7,743 
•35 
9,493 
•46 
11,253 
12,955 
•60 
•09 
With this weight the beam became distorted, and continuing the weight for 
some time, the deflection kept increasing until it bent laterally so as to be no 
longer able to sustain the load. 
Ultimate deflection =*69. 
4 z 2 
