294 British Association for the Advancement of Science. 
Modulus of elasticity in lbs. for a bar of one inch square. 
Cold blast ; Sac gen ; 14,313,500 Ibs. 
13,947,000 
Hot blast ae : 14,322,500 Ibs. : 
Elslear Cold Blast, No. 1, against Melton Hot Blast, No. 1, (York- 
shire Iron.) 
Mean ratio of strength = - - - - - 1000 : 809 
Mean ratio of power to resist impact - - - 1000 : 858 
The modulus of elasticity in all the irons are computed ;_but only 
given in a few cases in the results. 
Relative strength of hot and cold blast iron to resist a transverse 
strain at different degrees of temperature. 
Cold blast 949.6 at 32°. Hot ditto 919.7, Mean. 
Ratio of strength, 1,000 : 977.6. 
Power to resist impact, 1,000 : 1,039. 
Cold blast 748.1 at 191°. Hot ditto $23.6. 
In these experiments, it appeared, that the cold blast lost in 
strength from 32° up toa blood red, perceptible in the dark as 
949.6 to 723.1; whereas, in the hot blast the strength is not so 
much impaired, being as 917.7 at the freezing point, and 829.7 
when perceptibly red in the dark. 
In all former experiments on the transverse strain of cast iron, it 
has been assumed, that the elasticity remained perfect up to one 
third the breaking weight. In pursuing these experiments, discrep- 
ancies were noticed, and results widely different to those generally 
received were observed. It was found that one seventh, and, in 
some cases one eighth the breaking weight was sufficient to produce 
a permanent set. ‘These facts induced an extended series of expe- 
riments, principally to determine what load was necessary to effect 
a permanent set; and, if such weight continued for an indefinite 
time, would break the bar. It became a question of great impor- 
tance to know, if a weight, having once impaired the elasticity, 
would or would not, if continued, increase the deflection. ‘The in- 
quiry, therefore, was—T'o what extent can cast iron be loaded with- 
out endangering its security? ‘T'’o solve this question ten bars of hot 
and cold blast, differently loaded, were placed upon a frame, to as- 
certain the amount of deflection at stated periods, and to determine 
what was necessary to break the bars with their respective loads. 
In the cold blast, with a load of 280 Ibs., the slate mene 
tion increased in 103 days from - = ,025 to 1,033 
so ad 
