682 
MR. FAIRBAIRN’S EXPERIMENTAL INQUIRY 
Table JV. Strength of Plates. — Shropshire Iron. 
No. 
of 
exp. 
Description of plate 
and dimensions in the 
middle. 
Weight 
laid on in 
lbs. 
Reduced dimensions in 
middle of plate through 
weights laid on. 
Breaking 
weight 
in lbs. 
Mean breaking weight 
in lbs. 
Remarks. 
13. 
Drawn in the di- 
rection of the fibre. 
Area of section 
2-00 X -265 = -53 in. 
28,275 
25,923 
Form of specimen the same as shown 
in Table I. fig. 2. 
In the first experiment the fracture 
showed an ii'on very uniform, except a 
few bright spots like steel. 
Experiment 2. Appearance of fracture 
as before, but a crack up the middle 
showed that the plate was formed of two 
plates of equal thickness, not well united. 
14. 
27,099, or 22-826 tons 
per square inch. 
15. 
Plates of the same 
iron drawn across 
the fibre. 
200 X -265 = -53 in. 
26,315 
25,923 
26,119, or 22 tons per 
square inch. 
Fracture as before, with a laminated 
diversion, as in last experiment. 
16. 
The Shropshire iron gives better indications of strength than those obtained from 
the Derbyshire plates ; the mean breaking weights in the last Table being 22‘41 tons. 
From the Yorkshire plates we have a mean breaking weight of 24‘85 tons, exhibiting 
a difference of 2^ tons in favour of the Yorkshire iron, and 2 tons or about ^th 
greater than the Derbyshire. 
Table V. Strength of Plates. — Staffordshire Iron. 
No. 
of 
exp. 
Description of plate 
and dimensions in the 
middle. 
Weight 
laid on in 
lbs. 
Reduced dimensions in 
middle of plate through 
weights laid on. 
Breaking 
weight 
in lbs. 
Mean breaking weight 
in lbs. 
Remarks. 
17. 
18. 
Drawn in the di- 
rection of the fibre. 
2-00 X -26 = -52 in. 
23,571 
22,003 
22,787, or 19-563 tons 
per square inch. 
Form of specimen the same as before, 
fig. 2. 
Fracture dark gi-ey colour, very similar 
to that from the four preceding plates. 
It had however a few specks of bright 
matter in it, and was without any lami- 
nated appearance. 
19. 
Plates of the same 
iron drawn across 
the fibre. 
Area of section 
2-00 X -265 =-53 in. 
24,335 
25,531 
24,943, or 21-01 tons 
per square inch. 
Irregular in texture, air-bubbles in frac- 
tured surface, with bright crystallized 
matter like steel. 
This iron has much of the same irregu- 
larity as the Derbyshire iron. 
Surface of fi-acture showed the iron to 
be very irregular, one-half being bright 
matter like steel. 
20. 
23,571 
The thickness "26 
On comparing the strengths of the different irons, it appears that the Derbyshire 
and Staffordshire plates are nearly equal, the former indicating 20‘] 65 tons as the 
mean of the breaking weight per square inch, and the latter, as in the preceding 
Table, 20‘28 tons per square inch. The same comparison further applies to the above 
and those made on the Derbyshire plates in Table III. 
Taking therefore the results as derived from these experiments, it will be observed, 
that in every instance little or no difference appears to exist in the resisting powers 
of plates, whether drawn in the direction of the fibre or across it. This fact is clearly 
established by the following comparison, which evidently shows, that in whatever 
direction the plates are torn asunder, their strength is nearly the same. 
