Page:Report from the Select Committee on Steam Carriages.pdf/92



John Farey, Esq. 10 August, 1831. chambers will burn through in time, the same as that of Mr. Gurney's tubes will do, but not so soon; I think, taking the thickness of metal to be the same in both cases, no injury will be done by such burning through. The flat chambers in Mr. Hancock's boiler are very judiciously combined, and are secured against bursting by causing the pressure which tends to burst each one open, to be counteracted by the corresponding pressure of the neighbouring chamber; and the outside chambers are secured by six bolts of prodigious strength, which pass through all the chambers, and unite them altogether so firmly that I see no probability of an explosion. Mr. Gurney's vessels, called Separators, are secured by hoops round them, and being of a small size, may be made very safe. Hence I think the two boilers may be put on a par as to their security; but there is a decided preference in my opinion of Mr. Hancock’s form of subdividing the water and steam compartments, which I believe is carried too far in Mr. Gurney's tubes, whereby the water included within the several tubes, cannot make way to allow the bubbles of steam to pass by it. This is owing to the great length and the small bore of the tubes; and they are so isolated one from another, that the water within them is not able to act as a common stock of water, or to keep all the interior surfaces of the metal tubes thoroughly supplied with water: thence there is a deficient production of steam and an unnecessary destruction of metal.

Are you aware that, in Mr. Hancock's Carriage, the waste steam which is discharged from the engines after having performed its office, is thrown into the fire-place, and makes its escape upwards along with the fame, smoke and heated air, and gas, which ascend from the fire to act on the boiler?—That is the way in which he gets rid of the waste steam which the engines discharge, and I understand that he there by avoids the puffing noise and appearance of steam which is common with high-pressure engines. Mr. Hancock blows the fire with a current of air, produced by a revolving fanner, which is turned rapidly round by the engines, and therefore he requires no tall