ABSTRACT
The power obtainable from the wheels was reduced by some 35 per cent when, in 1759, one of the piers at the middle of the bridge was removed, a single arch of 58 feet span replacing two of the former narrow channels. This plant was described by Henry Beighton in Vol. II of J. T. Desaguliers’ Course of Experimental Philosophy from which Illustr. 275 is reproduced. A group of units was assembled, and driven by cranks and levers from one water-wheel, or from several wheels coupled together. Such was the arrangement of the machinery at London Bridge. “Power,” according to Smeaton, was “the exercise of Strength, Gravitation, Impulse or Pressure, so as to produce motion.” Numerically it was the product of the weight applied by the height through which that weight descended in a given time. Power is taken from a large cogged “brake-wheel” built around a timber “wind-shaft,” which projects outside the mill building to carry the sails.
