(42.)
Besides rendering the machine independent of manual [Pg072] superintendence, this process conferred upon it much greater regularity of performance than any manual superintendence could ensure.
This contrivance of Potter was very soon improved by the substitution of a bar, called a plug frame, which was suspended from the arm of the beam, and which carried upon it pins, by which the arms of the levers governing the cocks were struck as the plug-frame ascended and descended, so as to be opened and closed at the proper times.
The engine thus improved required no other attendance except to feed the boiler occasionally by the cock T, and to attend the furnace.