94- IMPROVEMENTS IN STEAM ENGINES. 



minute, for 16 hours in 24, during which time it consumes 

 from 25 to 33 bushels of Virginia coals of the best sort. Of 

 the amount of the saving, I cannot venture to make an esti- 

 mate ; on account of the great variety of coal with which 

 we are supplied, much of which is of a very indifferent 

 quality. That there is a great saving is certain; and while the 

 wooden boilers continue stream-tight, (for that part which 

 contains the water gives no trouble) they are certainly equal, 

 if not superior, to every other. The wood, however, which is 

 above the water, and is acted upon by the steam, seems to 

 loose its solidity in the course of time; and steam-leaks arise 

 in the joints, and wherever a bolt passes through. The joint- 

 leaks may for a considerable time, be easily stopped, by screw- 

 ing up the bolts that hold the planks together; but it is not. so 

 easy to cure the bolt-leaks; for the bolt, when screwed up, 

 bends the top or the sides inwards, and forces new leaks, 

 cither along the corners, or at some other bolt-hole. I do not, 

 however, believe, that every tiling has as yet been done, which 

 could be done, to obviate these defects. A conical wooden 

 boiler hooped would not be subject to some of them: such a 

 one has been applied by Mr. Oliver Evans to his small steam- 

 engine. During two years, which have elapsed since the 

 boilers of the public engines have been erected, much has 

 been done to improve them. Whether the last boiler will prove 

 as perfect in its wood-work, as it is in its furnaces and Hues, 

 is still to be ascertained by experience. At present nothing 

 can work better. 



I will only mention one other circumstance, the knowledge 

 of which may prevent similar mischief. — In the first boiler 

 erected in Philadelphia, oak timber was used to support the 

 sides, bottom, and top of the boilers, the plank of which was 

 white pine, 4 inches thick. In less than a year it was discov- 

 ered, that the substance of the pine plank, to the depth of an 

 inch, was entirely destroyed by the acid of the oak. Means 

 were then used to prevent its further action, by the interven- 

 tion of putty and pasteboard; and in most cases by substitut- 

 ing pine timbers in the room of those of oak. 



