British Association for the Advancement of Science. 293 
comparing two irons, the greatest care was taken to subject them as 
nearly as possible to the same treatment. 
. A series of experiments was also made to determine the strength 
of hot and cold blast iron at various temperatures, from 82° (the 
freezing point) to the boiling point; for this purpose, a cast-iron 
trough was employed, in which the bars to be broken were placed, 
and covered with snow or water, (which was kept at the proper 
temperature by a jet of steam,) as the case required; the weights 
were then gradually laid on until fracture took place. 
The strength of bars made red hot was also tried, and, contrary 
to expectation, they retained their tenacity and power to resist the 
load to a considerable extent: the reduction of strength in a bar 
one inch square, in a range of temperature from 32° to that of red- 
ness, was rather more than one-sixth, the deflection being upwards 
of 14 inch in a bar 2 feet 3 inches long. 
RESULTS. 
Carron Iron, No. 2. (Scotch.) 
Mean ratic of transverse strength, assuming the cold 
blast iron ats - - - - - - 1,000 : 9,799 
Mean ratio of power to resist impact - - 1,000 : 1,038.9 
Whence, in the transverse strength of Carron iron, No. 2, using 
a variety of forms of section, the strength of the cold blast is to that 
of the hot blast, as 100 to 98, nearly. 
Deven Iron, No. 3. 
Mean ratio of strength in sections of various forms 
(thirteen experiments) —- - - - 1000 : 1409 
Power to sustain impact - 4- - - 1000 : 2742 
This is an exceedingly hard iron, with a singular appearance, the 
centre or more granulated parts of the fracture being surrounded 
with a circle having the appearance of hardened steel. 
Buffery, No. 1, Staffordshire Iron, cold and hot blast. 
Mean ratio of breaking weight - - - 1000 : 925 
Mean ratio of power to resist impact - - 1000 : 965 
In the buffery iron, the hot blast manufacture is weaker, whether 
Wwe view it in its transverse strength, or its power to resist impact. 
Coed Talon, No. 2, North Welsh Iron. 
Mean ratio of strength in a number of experiments 1000 : 1014 
Mean ratio of power to resist impact wir 1000 : 1219 
Vou. XXXITI.—No. 2. 38 
