ON STRENGTH AND PROPERTIES OF CAST IRON. 397 
of the weights becoming permanent upon the bars. From the 
methods thus adopted it will be seen that the value of the 
set has been given with the deflections at regular intervals of 
weights, from the commencement of the experiment to the time 
of fracture, andthe connection between the weights, deflections, 
and set, will therefore in all probability be better observed. 
The early period at which the elasticity became injured caused 
in addition to the above an extended series of experiments, to 
determine whether such injury to the elasticity would not (with 
the weight continued) ultimately break the bar. This became 
a debatable and very important question between Mr. Hodgkin- 
son and myself, the one contending for time, and the other for 
a permanent state of elasticity in the ratio of the loads and the 
forces respectively. 
The inquiry therefore was, to what extent can cast iron be 
loaded, or how much would it permanently bear without en- 
dangering its security? This was in reality a question of great 
interest, one which involved important considerations, such as 
the stability of bridges, warehouses, factories, and many other 
erections to which cast iron is applied, and which depends al- 
most entirely upon our knowledge of its ductility and strength. 
It assuredly must be of importance to know that a material 
of such value, and so extensively used in almost every branch 
of art, can be trusted, and that we may with safety depend upon 
its security throughout the endless variety of forms and strains 
to which it is subjected. 
Cast iron has hitherto been considered a brittle, and by many 
persons an insecure material; yet, notwithstanding the distrust 
and suspicion with which it was viewed, it still continues to 
increase in demand, and that toa great extent, in most countries 
where the arts are cultivated. Every inquiry therefore which 
tends to exhibit its peculiar properties as respects strength, 
ductility, &c., must be regarded as an additional step towards 
a greater degree of security in its application. Under these 
impressions the following experiments were instituted. 
Five bars of cold, and five of hot blast, Coed-Talon No. 2 
iron, cast to be one inch square, were selected, and having loaded 
them with different weights, with their ends supported on props 
4 feet 6 inches asunder, they were left in this position, to de- 
termine how long they would sustain the loads without breaking. 
It is now upwards of 15 months since the bars were charged, 
and if we are to judge from the hardihood displayed in their re- 
sistance to the load, there is every chance of a long and pro- 
tracted experiment. In fact, there is every probability of the 
experiments outliving the experimenter. 
