20 VARIOUS INVENTIONS. 



found by experience that size to be sufficient, and (especially in 

 an engine that works quickly) make the cistern high enough to 

 cover the condensing work well with water. 



" Query 6th. My reason for making the forcing pump witli 

 duck- valves is, because they do not bum like the others, and 

 we find them seldom out of repair ; but make it whichever way 

 you think best, and work it in any way you like. 



" Query 7th. I mean by f expansive, that the steam is to be 

 shut off from the cylinder when the piston has moved up from 

 the bottom one quarter of its stroke. Make the cam to your 

 own mind. 



" Query 8th. I do not think the engine will require a 

 heavier fly-wheel, as the stones will act as a fly, and the power, 

 though so very irregular, will be so sudden in its changes, that 

 the speed of the machinery will not let it be felt. If you make 

 a crank, you may make the fly-wheel 3 or 4 feet more in 

 diameter. But if with a pin in the fly-wheel, the beam would 

 come down on the top of it ; therefore, I think it will be better 

 to put a crank, and put the fly-wheel in the middle of the 

 shaft. 



" Query 9th. The steam will be raised to 25 Ibs. to the inch 

 above the atmosphere, or 40 Ibs. to the inch on a vacuum ; but 

 I think you need not calculate for much more strength on that 

 account. It is not the power that breaks the machinery, but 

 bangs, and not the uniform weight that this will give. 



" Query 10th. Twenty strokes per minute I propose, which 

 I think a fair speed. 



" Query llth. The fire-bars must be of wrought iron ; we find 

 them answer much better than cast iron. Let them be fths of 

 an inch from bar to bar, 1 inch thick at the top, fths of an inch 

 at the bottom, 2 inches deep, 4 feet long, with bits on them at 

 the ends, to prevent their getting too close together. I find 

 the . nearer the fire is to the door, the better and handier it 

 is to work. All the large engines are in this way, and we do 

 not find the door or front plate get hot, as they are lined with 

 brick. Cast the door with a rib to hold a brick on its edge. 

 Tube, 2 feet 9 inches by 1 foot 11 inches; manhole, 15 by 10 

 inches. 



