ON MARINE BOILERS. 7 



times with safety. Independently of these difficulties, the pipes through the ship's bottom 

 were frequently of cast iron, and were often severely attacked by bilge water between the 

 cocks and the sea ; and thus the safety of the vessel depended on the slightest tenure. 

 These remarks still apply to existing arrangements on board many vessels. 



15. The safety valve and pipe lately invented by Mr. John Kingston is so constructed 

 that a conical valve, fitted in the pipe which is introduced through the bottom of the vessel, 

 opens outwards to the sea, and is attached to a copper rod under the control of the engineer : 

 thus, in case of any difficulty arising with the blow-out cocks, the valve can be immediately 

 closed ; and being entirely within the thickness of the ship's bottom, is always protected 

 from accident ; while in case the pipe within the vessel were broken, the pressure of the 

 sea would maintain the valve firmly in its place. 



It is not generally known, except to those practically acquainted with engineering, that 

 a steam vessel's bottom is perforated with many large holes, each equal to sink a ship in a 

 very short space of time, particularly when it is understood that they are for the most part 

 pierced close to the keel, where the pressure of water is greatest. It would give additional 

 confidence to every one crossing the seas by steam, if all these holes were rendered as secure 

 as the blow-out pipes now are by Kingston's safety valve : and from the necessity of 

 frequently examining and grinding the sea cocks, the adoption of valves would obviate the 

 necessity of docking for these purposes alone, and is a strong inducement to their general 

 employment in every steam vessel not confined to the limits of river navigation. 



16. Instances are not rare of boilers being permanently injured, and sometimes totally 

 ruined, in a first voyage, whether iron or copper ; occasioned alone by neglect of proper 

 precautions. Incrustation, which is certain, strongly opposes the efforts of the men to 

 generate steam, the combustible portion of the fuel being consumed in heating the plates of 

 the boiler ; and the heat must necessarily pass through strata of stone, (if I may be allowed the 

 comparison,) a very bad conductor of heat, before it is given out to the water; which being 

 highly saturated, requires an additional, instead of a diminished, supply of caloric, to sepa- 

 rate its aqueous and volatile portions from those that are fixed, which are constantly subsiding 

 on the tubes. It requires no argument to show that the fire places and flues thus subjected 

 to intense heat, become nearly red hot, and consequently expand much beyond their usual 

 limits ; while the stay bolts and other ties, holding them with immense force, either break or 

 cause the plates to crack in the weakest place, which is generally in the wake of the stays, 

 joints, or bends, parts, of course, the most heated from the increase of mass; sometimes 

 even the tubes collapse, the powers of expansion resisting all opposition. 



Serious delays and many inconveniences arise from the evils here described, since in 

 most cases immediate repair is absolutely necessary, and can only be effected at the expense 

 of great physical exertion. In fact, from observations on sea water, and its effects on marine 

 boilers, for many years, I am convinced that it is absurd to expect to make a voyage with 

 success if blow-out pipes are choked or otherwise disordered ; or even that at the end of 

 three days, without a change of water, the boilers will not be incrusted to a considerable 

 extent. 



17. The injury sustained by some boilers, either from the above cause or from the 

 neglect of blowing-off uniformly at sea, has by some been erroneously attributed to the 



