404 SEVENTH REPORT—1837. 
The greater degree of weakness here exhibited in the hot blast 
iron than the cold renders our comparative experiments in this 
Table defective ; several bars were tried in succession, but they 
separately gave way, some on laying on the load, 448 lbs., and 
others after supporting it for a few seconds. 
In experiment Ist, Table XIV., it will be noticed that a bar 
from the cold blast iron, after being charged with the full load, 
448 lbs., continued to support it for a period of 37 days; this 
was not however accomplished without signs of weakness, as 
will be seen from the progressive increase which took place in 
the deflections from the 6th to the 17th of March; and also 
from observed discrepancies sometime previous to its rupture. 
In making these statements it must be observed, that the bar 
in experiment 1st was thinner than any of the others, and had 
borne for thirty-seven days a weight greater than had broken 
bars of the same size in previous experiments upon the Coed- 
Talon iron, when the weights were laid on without loss of time. 
Abstract of comparative increase and ratio of deflections on the 
whole bars from March 6th, 1837, to June 23rd, 1838. 
Cold Blast Iron, | Hot Blast Iron, 
: A Ratio of 
increase of deflec-| increase of deflec- : 
tion in inches. | tion in inches. | Seflections. 
Increase of deflection, Table XI. 033 9043) be seeceeeenens 
Increase of deflection, Table XII. 046 077 witidhetamesnes 
Increase of deflection, Table XIII. 140 O88 it ieee ewes 
Increase of deflection, Table XIV. O47." SD Miteees Mr le erweeeaaeeens 
Mean... 066 “069 1000 :1045 
The mean increase of deflections on the whole bars is there- 
fore ‘066 for the cold blast, and ‘069 for the hot blast, being in 
the ratio of 1000 to 1045. 
The interest which experiments of this kind may be expected 
to excite, and the nature as well as the value of the material on 
_which they are here made, will, it is hoped, prove an induce- 
ment for extended investigation on this subject. 
There cannot be a doubt that the phenomenon of cohesive 
force is strongly developed in the preceding tables; the minute 
crystalline particles of the bars are acted upon by loads, which, 
in the heavier weights, are almost sufficient to produce fracture : 
yet fracture is not (except in one instance) produced, and to what 
extent the power of resistance may yet be carried is left for time 
to determine. It nevertheless appears from the present state of 
the bars (which indicate a slow but progressive increase in the 
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