Page:Report from the Select Committee on Steam Carriages.pdf/93



John Farey, Esq. 10 August, 1831. chimney to produce a draft. Mr. Gurney formerly used a singular fanner to blow the fire, and also a chimney of some height; but I understand he has lately laid it aside, and adopted the plan of carrying the waste steam which has passed through the engines into the bottom of the upright chimney, and there discharging that steam through a contracted orifice in a vertical jet, which, by rising upwards with great velocity in the centre of the chimney. tube, gives a vast increase to the draft of heated air and smoke in the chimney tube, without any great height being necessary; and this plan occasions a most active current of fresh air to pass up through the fire, and urge the combustion. This is a most important improvement in locomotive Engines, which has been introduced by Mr. Stephenson into his Engines on the Liverpool and Manchester Railway, and being there combined with an improved boiler, it has been one of the great causes of the brilliant success of that undertaking. I believe 'the same plan will be indispensable to the complete success of Steam Carriages; for chimneys cannot be used high enough to obtain a draft, and blowing the fire is a very troublesome affair. I fear Mr. Stephenson's plan would occasion more noise than is allowable on common roads; but that may perhaps be avoided or diminished by some new expedient.

Do you think any danger would arise from the waste steam being discharged over a large mass of fire on Mr. Hancock's plan?—Not the least danger; all the waste steam which blows off at the safety valve, and which the engines do not require, is got rid of in the same way; but I expect Mr. Hancock does not help the combustion of the fuel by thus mixing the waste steam with the flame before it acts against the boiler. Mr. Stephenson's improvement, which Mr. Gurney has adopted, is to discharge all the waste steam into the bottom of the upright chimney with a violent vertical jet, in order to accelerate the draft up the chimney. The waste steam; therefore, is mixed with the smoke and gas, after the smoke has ceased to act on the boiler. The waste steam was very commonly discharged into the bottom of the chimney, in