IN BEAMS SUBJECTED TO TEANSVEESE STEAIN. 
479 
No. of fusion. 
Franklin iron. 
6-pounder gun, 
3rd fusion. 
Gun No. 61, 
2nd and Srd 
fusions. 
Mean. 
lbs. 
lbs. 
lbs. 
1st 
25,969 
15,861 
20,915 
2nd 
29,143 
20,420 
24,781 
3 id 
27,755 
24,383 
26,569 
4th 
30,039 
25,773 
27,906 
7th 
29,690 
Although not bearing directly on the subject of this paper, I cannot refrain from 
calling attention to the extraordinary development of strength in cast iron, obtained in 
the experiments made by the United States Government. It will be seen, on referring 
to the Reports from which the above Tables are taken, that by frequent recasting and 
keeping the metal under fusion durmg periods of from three to four hours, an increase 
of 60 per cent, is obtained; and that the strength of the American iron so treated is 
more than double that of English under the usual mode of manufacture. 
The general accordance presented between the value of the tensile resistance, obtained 
by direct experiment, and that computed by means of the foregoing formulae in so many 
varieties of form of section, is such as to confirm the view here taken of the laws which 
govern the action of the resistance of flexure. 
It remains only to refer to two points connected with it, first, as to the ratio it bears 
to the tensile resistance. If the metal were homogeneous and the elasticity perfect, it 
is probable that the resistance of flexure would be precisely equal to the tensile resist- 
ance, instead of beaiing the ratio of nine-tenths, as found by experiment. It is evident, 
however, that it varies in difierent quahties of metal, and that the tensile resistance does 
not bear a constant ratio to the transverse strength. 
The following Table, taken from Major Wade’s valuable Reports, shows, that with the 
same metal and difierent modes of casting, an increase of transverse strength is obtained, 
while a decrease takes place in the tensile resistance. 
Transverse strength. 
Tensile strength. 
Specific gravity. 
Guns. 
Bar cut 
Bar cast 
Bar cut 
Bar cast 
Bar cut 
Bar cast 
from gun. 
separate. 
from gun. 
separate. 
from gun. 
separate. 
6-pounder gun, No. 6 ... 
8415 
9,880 
30,234 
29,143 
7*196 
7*263 
6-pounder gun, No. 8 ... 
9233 
9,977 
31,087 
30,039 
7*278 
7*248 
8-inch gun. No. 64 
8575 
10,176 
26,367 
24,583 
7*276 
7*331 
Mean 
8741 
10,011 
29,229 
27,922 
7*250 
7*281 
Proportional 
1-000 
1-145 
1-000 
-955 
1-000 
1-004 
From the above, it appears that with a decrease of about one-twentieth in the tensile 
strength, there is an increase of nearly three-twentieths in the transverse strength. 
It is easy to conceive also, that though the resistance of flexure might be supposed to 
maintain nearly the same proportion to the tensile resistance in bodies similarly consti- 
