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When the engine had been at work a shorttime, it was soon found that sufficient adhesionexisted upon the edge-rail to perforin the re-quisite traction to the load; at first, groovedsheeves were fixed upon the hinder travellingwheels of the engine, and similar groovedsheeves upon the fore-wheels of the convoy-carriage containing the coals and water, withan endless chain working over each, to procurethe adhesion of the wheels of the convoy-car-riage, in addition to the adhesion of the engine-wheels ; but, on trial, it was not found necessaryto resort to the aid of this contrivance, as theadhesion of the engine-wheels alone was foundsufficiently adequate to produce the desiredeffect.
The communication of the pressure uponthe piston, through the means of the crank tothe cog-wheels, produced great noise, and, insome parts of the stroke considerable jerks ;each cylinder alternately propelling or becom-ing propelled by the other, as the pressure ofthe one upon the wheels became greater orless than the pressure of the other, and this,when the teeth became at all worn, caused arattling noise; for, when the leverage of theone crank became greater than the other, thelatter was propelled by the other through theintervening wheels; but when the former