112 
FIFTH REPORT— 1835. 
The sixth and seventh beams having borne the deflections 
1*05 and *92 as above, and the former being considered (from 
the result of the fifth beam) very near to fracture, they were no 
longer struck upon the middle, but upon a point half way be¬ 
tween the middle and one support; the pendulous ball being 
so ordered as just to touch that point of the beam when hanging 
vertical. The intention was to ascertain the deflection of each 
beam in this new point of impact, and the blow necessary to 
break it there. 
Impacts at half the distance between middle and one support . 
Chords of 
arcs fallen 
through, in 
feet. 
Deflection of the 
6th beam in point 
struck, in parts of 
an inch. 
Deflection of 
the 7th beam 
in point struck, 
in parts of an 
inch. 
Mean between 
deflections of 
the 6th and 7th 
beam at one 
fourth distance 
from one end. 
Ratio of deflections 
from equal impacts at 
one fourth span and 
middle of beam. 
2 
3 
4 
c 
o 
5'5 
6 
•22 
•40 
•50 
•60 
•70 
Broke the beam. 
*25 
■« 
•54 
•68 
Broke it. 
•24 
•42 
•52 
•64 
‘70 
M = -691 
**=•76 j | 
S 2 _ mo yrnean 
7 / — Db r moA 1 
**=■67 ! 
pr = -67J j 
Both beams were broken exactly in the point of impact, and 
with the same intensity of blow, an impact through an arc of 
6 feet. Now an impact, through an arc of 6 feet, against the 
middle of the 5th beam, had broken it; and as impacts in the 
middle through 3, 4, and 5 feet, had nearly bent each of the 
three beams through equal quantities, we may be convinced that 
an impact through about 6 feet against the middle of the 6th 
and 7th beams would have broken them. Hence we may con¬ 
clude that an uniform beam will bear the same blow whether 
struck in the middle or half way between that and one end. 
Previous to the preceding experiments upon the 7th beam, 
it was laid horizontal on two props, 4 feet asunder, and weights 
gently laid on the middle bent it as below 7 : 
168 lbs. bent it *26 inch; unloaded, no set. 
224 lbs. — '40 — ; unloaded, set inch. 
Remark.—From all the preceding experiments it appears that 
the deflection is nearly as the chord of the arc fallen through, 
or as the velocity of impact. 
Vertical Impacts . 
In the following experiments the impacts were given by a 
short leaden cylinder C falling from different small heights upon 
