CIRCULATING PIPES, DAMPERS, &c. 13 



conducted there by tubes : the men avoid being scalded by this arrangement, at the risk of 

 the destruction of the ash-pits by the brine there deposited. Water in ash-pits has a cooling 

 and draught-exciting property on account of the evaporation ; but it ought on no account to 

 occupy the ash-place of an iron boiler, unless a cistern, constructed for that purpose, was 

 appropriated for its use. In copper boilers I have disregarded the water arising from 

 " weeps " in the ash-pits, no chemical action taking place here, when employed at sea, on 

 account of the frequent removal of their contents. The intrusion, however, of sea-water into 

 the ash-holes, no matter from what cause, ought by no means in any boiler to be encouraged. 

 My object having been to show by comparison the advantages of copper over iron boilers 

 for marine purposes, and to set in a proper point of view the deposition of salts, their effects, 

 and the means of avoiding the same in boilers, as now adapted and arranged, I think that for 

 the future, as regards these matters, all vague speculation, with practical men, may be laid 

 aside ; the evils complained of having been shown to arise, in all cases, both from want of 

 sufficient care in construction, and in the ultimate management. 



CIRCULATING PIPES, DAMPERS, &c. 



24. Circulating pipes, that is, pipes of communication between boilers when more than one 

 is used, are generally fitted with a small bonnet for the purpose of cleansing. The situation of 

 these pipes generally is such as to deprive the engineer of examining them at all times : the 

 pipes on the sides are concealed by the coal-boxes ; those abaft and forward being usually at 

 hand. 



Now, in many instances, the feed, or water for the supply of evaporation, is injected into 

 the front boiler or boilers, those abaft depending mainly on the condition of these pipes, 

 through which they are intended to be supplied. Instances occur where the flues have been 

 much burnt and injured from incrustation, while the fire-places situated in the front boilers 

 were in perfect order. The pipes have been choked, and of course a sufficient supply could 

 not be maintained in the after boilers; hence the deposit and permanent injury. The coal- 

 boxes, therefore, and other obstructions, should be so modified and cut, as to afford 

 convenience for examination ; which should take place at least on the return from every 

 voyage, the small bonnet being removed from each pipe, and its condition strictly looked into. 

 If duties be ever so pressing, commanders should always afford time for, and engineers strictly 

 fulfil, this most important one. 



Circulation of the water through all the boilers should never depend entirely upon the 

 pipes, but should be maintained moreover by free communication above the flues; and these 

 communications should be cut as near the surface of the flues as possible, in order that the 

 blowing off one boiler may to a certain extent affect the condition of the water in the rest. 

 The ' Flamer ' and some other of the government steam vessels have lately been fitted with 

 two tiers of connecting pipes, the upper ones three inches below the level of the flues, and 

 thereby favoring the circulation desired. Cutting the passages through the joining 

 boilers, for sea-going vessels, sixteen or eighteen inches above the flues, has been deemed 

 necessary to prevent the water from leaving the flues of the side boilers when rolling : 

 experience shows this precaution to be unnecessary, the temporary inclination of the 

 ship never exposing the flues to injury, when rolling simply ; and no extraordinary angle is to 



