412 SEVENTH REPORT—1837. 
In pursuing the experiments, it unfortunately occurred that 
the stock of No. 2 Coed-Talon metal became exhausted, a 
circumstance which interrupts the comparisons from below the 
freezing point to that of melted lead. ‘The No. 3 should have 
been broken at all the points of temperature, in order to have 
ascertained the loss of strength sustained upon this iron by the 
increase of heat. This was however not accomplished, and we 
can now only compare the two qualities No. 2 and No. 3 at the 
boiling point of water, and then proceed to the temperature of 
melted lead. Ihave already noticed that a considerable fail- 
ure of the strength took place after heating the No. 2 iron 
from 26° to 190°. At 212° we have in the No. 3 a much 
greater weight sustained than what is indicated by the No. 2 
at 190°; and at 600° there appears in both hot and cold blast 
the anomaly of increased strength as the temperature is ad- 
vanced from boiling water to melted lead, arising from the 
greater strength of the No. 3 iron. 
A number of the experiments made on No. 3 iron of different 
sorts have given extraordinary and not unfrequently unex- 
pected results. Generally speaking it is an iron of an irregular 
character, and presents less uniformity in its texture than 
either the first or second qualities ; in other respects it is more 
retentive, and is often used for giving strength and tenacity to 
the finer metals. 
Recurring to the No. 2 iron, it will be observed that the 
strength continued to diminish as the temperature was in- 
creased. Heating the cold blast iron in Experiments 11 and 
12 to a perceptibly red colour, we have the breaking weights 
663 and 723; whereas, in the hot blast, at nearly the same 
temperature, the breaking weight is 829°7, being as 693 (the 
mean) to 829, or in the ratio of 1000: 1289. 
From the experiments in Table 1, it appears that a bar of 
cold blast iron | inch square and 2 feet 3 inches between the 
supports, broke at the ordinary temperature of the atmo- 
sphere with 836°9, and in No. 3 cold blast from Table 3, the 
breaking weight is 1137°3. This gives an excess of strength 
for the No. 3 iron of at least one-fourth. 
When the bars were heated to a blood red the utmost care 
was taken to break them without loss of time. In every in- 
stance the deflection was considerable; rather more than 1} 
inches was observed on the 2 feet 3 inches bars before they 
gave way. 
» AS etwas 
