THE STEAM-ENGINE. 135 



having cups projecting downwards to add to the surface, 

 and between the two bottoms, and surrounding the cups 

 there was an amalgam of quicksilver and lead that was kept 

 at a temperature of, I think, about 450. There was no 

 water whatever in the boiler, and when it was desired to 

 start the engine, the attendant, by means of a, hand-pump, 

 injected as much water on to the cup surface as would 

 generate sufficient steam for a half revolution of the engine. 

 The feed-pumps of the engine were forced inwards not by 

 eccentrics, but by springs, and the amount of their inward 

 stroke could thereby be regulated to a nicety by a set screw, 

 and in that way the engine ran without there being at any 

 time an appreciable quantity of water in the boiler, the 

 stored up heat between each injection of water accumulating 

 in the amalgam. This steamboat ran for very many mon-ths, 

 and the factory engine, I believe, for very many years. The 

 government tried it in one of their boats, but eventually it 

 was abandoned, and I merely mention it to you as an interest- 

 ing link in the history of the steam-engine. 



With respect to the staying of boilers, there is one other 

 boiler I must mention, and that is the boiler of Hancock's 

 common-road locomotive to which I alluded yesterday. This 

 was composed of a succession of flat chambers ranged side "by 

 side like books on a shelf, the spaces between the chambers 

 being about one inch, and the chambers themselves being 

 about 1^ inches wide, and, according to the size of the boiler, 

 from. 20 inches to 30 inches square or broad and high.. These 

 chambers thus arranged side by side, were put over the fire 

 which played between them in the spaces. The water was 

 contained in the lower part of the chambers, and the steam at 

 the top, and I think we shall all agree that a more impossible 

 form for withstanding high-pressure steam, it would be diffi- 

 cult to imagine that is, at first sight. But each of these 

 chambers had raised upon it hemispheres, and the hemisphere 

 on the side of one chamber abutted against the corresponding 

 ones on the side of the next chamber, and thus the chambers, 

 say to the number of fourteen, stood side by side, each chamber 

 supporting its neighbour, and there remained only to be stayed 

 the two outside plates of the outside chambers. This was 

 done by means of thick boiler plat3s which pressed on the 

 hemispheres of those outer chambers, and those outer chambers 

 and plates were held together by outer tie-rods and cross 



