CIRCULATING PIPES, DAMPERS, &c. 23 



from this inefficiency of the valves, points out the necessity of observing the above precautions 

 strictly, and not ofjijci>ig them to their places, which has been done occasionally, to avoid the 

 nuisance of leakage, by those not duly estimating their probable utility. 



31. Ultimately, the fixing of boilers in their places requires particular attention, the 

 bottoms often giving out before any other part of the shell. All copper bolts, securing 

 the sleepers to the ship's bottom, should be clenched beneath the surface of the 

 sleepers, and then covered with wood let in flush with the same : or plank may be brought 

 on each of the sleepers, when fixed, of the entire length of boilers, and secured with iron 

 nails ; for, if a copper bolt-head comes in contact with any part of the bottom of an iron 

 boiler, a hole will inevitably be eaten through in a short time in that spot, the most difficult 

 of any to be repaired in place. 



When the angle iron projects beyond the bottom of the boiler, in the manner of Messrs. 

 Boulton and Watt, it is customary to fill the space inclosed, with wood nicely fitted and coated 

 with white lead ; so that, when in place, the bottom is well supported and protected from 

 corrosion : but this method does not so well apply to other constructions of boiler ; in 

 bedding which, platforms laid across the sleepers should cautiously be employed. If a leak 

 should exist in any part of the bottom, which is almost certain, the water, not being able to 

 make its escape, flows beneath the bottom of the boilers, covering the surface of the platform, 

 which supports them at the seams or stays only : this water is imbibed by the wood, which is 

 thereby speedily rotted, the salt remaining in contact with the boilers, to effect their 

 destruction. Boilers then, when not too near the bottom, may rest on the sleepers only, which 

 should be thickly covered with some anti-corrosive, such as white and red lead ; and when 

 fixed in their proper places, some one should be sent beneath, to fill up spaces in such parts as 

 the irregularity of the bottom has prevented from coming in contact. The vapour arising from 

 the bilge-water does not at all affect the parts of the bottom exposed to its influence. Boilers 

 that have been in use for some years, placed as above, (the application of red lead excepted,) 

 have, when taken out, been found decayed in such parts of the bottom only as rested on the 

 sleepers, with the exception of a few defects arising from bad workmanship or straining; the 

 common lead-coloured paint remaining on the plates exposed, as when first applied by the manu- 

 facturer. But when the boilers by necessity are placed too near the wash of the bilge-water, 

 their bottoms, which are soon covered entirely with salt, are rapidly and completely decayed : 

 here platforms well covered with white and red lead must be resorted to. 



32. The most important parts of marine boilers, and those on which opinions have not gene- 

 rally agreed, having been considered, from the facts, apparent on a strict examination of their 

 details, when employed, and when totally dismembered after service, I have to observe, that if 

 the boilers be constructed distinctly from each other, or so as to permit each series of flues to 

 act on distinct bulks of water, the steam of each being under control, they will not only have 

 all the advantages before described, but, as the efficiency of our steam marine is of paramount 

 importance, and steam vessels are essentially ships, and liable to encounter the thousand 

 casualties to which all ships are exposed, a shot through one boiler would then by no means, 

 after the escape of steam or water, prevent a vessel from continuing her way from an enemy, 

 in the case of a merchant-ship ; and if a steam-frigate, there would still be an opportunity 

 afforded to manreuvre, while a single shot meeting boilers which are not distinct, would leave 

 the ship a certain prize to the enemy. These considerations are not trifling, when it is 

 recollected that steam vessels have already been extensively engaged for warfaring purposes in 



