ON THE STEENGTH OE PILLAES OE CAST lEON. 
867 
per square inch to crush them, and small rectangles cut out of masses 1 inch square 
required 103692 lbs. only. 
In some experiments made by Captain (now Colonel) James, as a Member of the 
Koyal Commission for inquiring into the application of Iron to Railway Structures*, it 
was found that the central part of bars of iron planed was much weaker to bear a trans- 
verse strain than bars cast of the same size. He states that “ it was found by planing 
out f-inch bars from the centre of 2-inch square and 3-inch square bars, that the central 
portion was httle more than half the strength of that from an inch bar, the relation being 
as 7 to 12 ” (there may be some doubt whether the iron was sound at the centre). In 
page 111 of the same Report, I showed that rectangular bars of cast iron, cast 1, 2, and 
3 inches square, laid upon supports 4^ feet, 9 feet, and 13^ feet asunder, were broken 
by weights of 447 lbs., 1394 lbs., and 3043 lbs. respectively. These weights, divided by 
the squares of the lengths, should give equal results ; the quotients, however, were as 
447, 349, and 338 respectively. I attributed this falling otf and deviation from theory 
partly to the defect of elasticity, which I had always found in cast iron, but principally 
to the superior hardness of the smaller castings. 
From the experiments on the resistance to a crushing force of the various kinds of 
iron used in this research, it was found that short cylinders, f inch in diameter and 
1-| inch high, cut out of pieces cast 2 } inches diameter, resisted with more force when 
cut out of the part near to the surface than when cut out of that near to the centre. To 
try this, many small cylinders, from four or five kinds of iron, were cut from the centre, 
and from the part intermediate between the centre and the circumference (Table VIII.), 
and it was found that the cylinders from the latter part were always stronger than those 
from the centre; thus, in cylinders from pillars of Old Park iron. No. I, cast as above 
mentioned 2^ inches diameter, the mean crushing force of the iron near to the circum- 
ference was 39‘32 tons per square inch, and that from the centre 33-33 tons per square 
5-99 
inch, the diflerence being 5-99 tons. Whence ^ ^^ =' 1523 , the ratio of the falling oft' 
of the resistance of the central part to the resistance of the external part. 
Cylinders from other irons used gave the results below (see Table VIII.). 
Low Moor Iron, No. 2. — Crushing force per square inch. 
Centre, 29-65 tons. Intermediate part, 34-59 tons. 
External ring of a hollow pillar, 4 inches diameter, of which the outer crust had been 
removed, 39-06 tons. 
External ring of a hollow pillar, about 3^ inch, diameter, 51-78 tons. From another 
pillar, of about the same diameter, 49-20 tons; the iron of both of these being very thin, 
Blaenavon Iron, No. 3. 
Centre, 34-22 tons. Intermediate part, 37-28 tons. 
* See Eeport, 1849, p. 250. 
