396 
MINUTES OF PROCEEDINGS OF 
as just to toucti the beam when it was balanced bj any stationary weight 
upon the bridge; it was held in this position by a collar, but was free to 
move upwards on the rising of the beam consequent on any additional 
weight coming on the bridge, which upward motion was controlled by a 
spiral spring, the upper end of which pressed against the fixed bracket and 
the lower end against a mill-headed screw nut on the spindle; by turning 
this nut the spring was regulated to any degree of strength. The head 
of the spindle was so arranged as to lift, during its upward motion, a 
sliding indicator on an index, which was graduated by repeated trials so as 
to shew where the indicator would rest for every additional hundredweight 
placed on the bridge. 
By these means the stationary weight of any body being known and the 
beam weighted accordingly, the additional vertical pressure exerted on the 
bridge and due to the same body moving over it was accurately ascertained. 
The experiments were made with the following natures of guns, mounted 
on travelling carriages with their full equipment of stores, viz :— 
40-pr. Armstrong, 18-pr. smooth-bore, 10-inch mortar, 20-pr. Armstrong, 
and 12-pr. Armstrong. 
Pour pairs of horses with their military drivers were used to draw the two 
former, and three pairs for all the others; each pair with the driver weighing 
about 25 cwt. 
In all cases they were walked over at the usual walking pace, and the 
mean of three trials recorded as the result. 
The following is an account of the experiments :— 
No. 1. 40-pr. Armstrong. 
Weight of Carriage, Gun, &c., Stationary. 81*5 cwt. 
„ „ Moving. 106*3 „ 
Increase . 24*8=30 per cent. 
No. 2. 18-pr. Smooth Bore. 
Weight of Carriage, Gun, &c., Stationary. 79*3 cwt. 
„ ,, Moving. 100*5 „ 
Increase . 21*2=26 per cent. 
No. 3. 20-pr. Armstrong. 
Weight of Carriage, Gun, &c., Stationary. 46*75 cwt. 
„ „ Moving. 61*75 „ 
Increase 
15-00=30 per cent. 
