As many distressing accidents happen from carts over-powering the shaft-horse, when proceeding down declivities, Mr. Thomas Col-ley laid before the Society for the Encouragement of Arts, etc. a contrivance for preventing such casualties ; in consequence of which, he was rewarded with their silver me-dal. The following cut represents this useful invention:
A, The hollow, which lies on the nave of the wheel.
B C, The chains, that clip the felly of the wheel.
In order to apply this locking-pole, the chain C is put round the felly of the wheel; the pin B is passed through the last link of C, and turned back through the movable ring e: thus the wheel is secured, and any waggon, however laden, may descend the steepest hill with safety.
To prevent the locking-pole from breaking, Mr. Colley directs it to be made of the stem of an ash-tree, the spurns, that is, the beginning of the roots of which, have not been cut off in felling. He farthe remarks, that if a horse, which has been accustomed to such situation and to descents, be put in the shafts, the animal will be so much inclined to hold back, that it will be extremely difficult to make him draw. This exertion, however, is absolutely necessary ; as otherwise the chain-horse, which should always be linked to the locked side, will be obliged to pull an unnecessary weight, occasioned by his being considerably lower than the points of the shafts.
Lastly, in conveying the locking-pole from one declivity to another, it is to be placed between the lower part of the cart and the axle-tree, while the smaller end is to be buckled with a strap fixed under the body of the cart, on the driving side.