2 
revolves round a certain point, at tlie intersection of tlie plan of tire wheel 
with the line joining the centres of the collars, Z, Z'. This centre of rota¬ 
tion being other than that of the wheel, we readily see that in turning the rod 
B one way or the other we make the battens either approach or recede from the 
wheels. The construction is such, that if we turn the bar like the hands of a 
watch for an observer placed on the left side of the gun limbered up, and look¬ 
ing across the gun-wheels the battens recede. We shall call that a turn to the 
right , and the reverse movement a turn to the left . 
( a ) Suppose we turn the bar to the left , or in other words apply the brake. 
When the gun recoils, as the brake is not yet strongly applied, the wheels can turn. 
But as the battens adhere to the wheels they are carried with them, so that the 
bar B turns to the left , and the battens are thereby more and more strongly applied 
to the wheels, so long as these continue to move. When the friction between the 
battens and the wheels is in excess of the friction between the wheels and the 
ground, then of course the wheels slip, but do not roll. The bar B has a curve 
such, that the line, which joins the centre of the wheel to the point round which 
the batten turns, makes an angle of about 135° with the line joining this point to 
the centre of the batten when in contact with the wheel. Experience has shewn 
this to be the most favourable construction for ensuring the combined action of 
the wheel and the batten. The battens are attached to the bar B by joints revolv¬ 
ing round a horizontal axis to secure their perfect adjustment throughout to the 
tires of the wheels. 
( b ) We now turn the bar to the right : the battens at once recede and the 
wheels are free to turn. 
Let us then see how these two movements are effected automatically. 
The arrangement is as follows : The trace hooks r, r' are fixed, not to the 
splinter-bar, but to the swingle-trees M, M'. At the middle of each swingle-tree 
is fixed a double hook P, of which one end is attached to the splinter-bar by 
means of an iron loop Q and a ring 0, while the other end is hinged by means of 
the bolt U to the end of the traction rod L. The rear extremeties of the 
two traction rods are connected by the beam K. The beam K, by means of the 
chain V, the connecting rods h, If and the levers C, C', actuates the bar B of the 
brake. (The two slides S, S', are provided on each side of the limber for the 
beam K to move on). When the beam moves forward by the advance of the team 
the bar B is made to turn to the right, i.e., as we remember, to remove the battens 
from contact with the wheels. 
The spiral springs G, G', acting by means of the pistons E, E', actuate the 
levers C, C', so as to apply the brake. The springs are not designed to serve in 
themselves as brake springs, but simply to give strength and cohesion to the 
general design. The spring boxes E, E', are attached to the carriage by means of 
bolts and screws X, X', which can be tightened or released at will, within a 
margin of 6 inches. On the other hand, a force of 80 lbs. will only move the 
springs T 6 ^ of an inch. The alteration of the position of the spring boxes, ren¬ 
dered necessary by the wearing away of the soles of the two brakes or by what¬ 
ever cause, renders necessary a special adjustment of the traction machinery of 
the system. That adjustment is effected by means of the screw coupling-boxes 
2 , z\ which are turned in either sense until the beam K is at the marks 7r, 7 r', of 
the slides S, S', the team being at the halt. On coming into action, while one 
number unkeys the limber hook, the other number disconnects the chain Y at the 
point I where there is a carbine hook attachment. When in action, as already 
mentioned, the brake is automatically applied. However, the lever b, when 
released, allows the curved bar B to drop and turn to the right, unshipping the 
brake and allowing the carriage to be run up by hand. The lever h is controlled 
by the rod a running in a groove, and with a swelling at one end. The rod a is 
