318 DE. EAIEBAIEN ON THE EEEECT OE IMPACT, VIBEATOEY ACTION, 
The beam A, Plates VI. & VII., is composed of an iron plate riveted with angle- 
irons 22 feet long, of an inch thick, and 16 inches deep. 
It was supported on two brick piers 20 feet apart. Beneath the bottom flange is 
fixed the lever B, which, by means of the link and shackle C, grasps the lower web of 
the beam close to the fulcrum D. This fulcrum, on which the lever oscillates, is 
formed of a vertical bar E, which acts as a standard, and has screw-nuts to regulate the 
height from the cast-iron plate F to the fulcrum D. The machinery for lifting the 
lever and scale at H consists of the shaft and pulley I, driven by a water-wheel ; and 
from this shaft the apparatus for lifting the load is worked by a strap from the pulley 
on the pinion-shaft K, which drives the shaft and spur-wheel L, giving motion to the 
connecting rod M. This rod has an oblong slot at its lower end, in which the pin at 
the end of . the lever works. From this description it will be seen that, in turning the 
spur-wheel L, the weight is not raised until the bottom of the slot comes in contact with 
the pin of the lever, when the load is taken entirely off the beam. That being accom- 
plished, the connecting rod descends, when the load is again laid upon the beam and 
left suspended with a vibratory motion for some seconds, until the remainder of the 
stroke is completed, when the connecting rod again rises for the succeeding lift. In 
this way the weights are lifted off and replaced alternately upon the beam at the rate 
of seven to eight strokes per minute. The apparatus is worked night and day by a 
water-wheel, and the number of changes are registered by the counter attached to the 
vertical post at G. 
The girder subjected to vibration in these experiments is a wrought-iron plate beam 
of 20 feet clear span, and of the following dimensions : — 
inches. 
Area of top, 1 plate 4 inches xi inch 2-00 
„ 2 angle-irons 2x2Xf^ 2*30 
4-30 
Area of bottom, 1 plate 4 inches x^ inch TOO 
„ 2 angle-irons 2 X 2 X inch 1-40 
2-40 
Web, 1 plate 15|xi 1*90 
Total sectional area 8-60 
Depth 16 inches. 
Weight 7 cwt. 3 qrs. 
Breaking-weight (calculated) 12 tons. 
