Report of fhf Housf of Coiunimts on S/ram-Boats. 12.5 



np aiid down a liatcliway without pulling up oi* desti'oying the 

 decks." 



Mr. Donkiii and Mr. T. Bi'amah are of opinion that all 

 boilers are now made too large, and that the same quantity of 

 steaming power might be obtained with a smaller body of 

 water, it" the surface of tlie boiler exposed to the fire was suffi- 

 ciently large. 



All the witnesses agree in opinion as to the necessity of 

 keeping the machinery as low as possible m the vessel: Mr. Watt 

 says, " This will diminish the top weight, make the vessel more 

 steady at sea, improve the action of the machinery, and add to 

 the safety of the vessel." — Messrs. Maudslay and Field say, 

 *' The best arrangement of the machinery, and in which en- 

 gineers are most agreed, is to place the boiler or boilers a few 

 feet abaft the centre of buoyancy of the vessel ; the two engines 

 on each side, a few feet forward of this point ; and the coals 

 on the centre of buoyancy : this arrangement brings the fuel, 

 which is constantly variable, on a point that will not affect the 

 trim of the \'essel ; it also brings the wheelshaft, which is at 

 the foremost end of the engine, to its best position as regards 

 the length of the vessel, viz. at about one-third fi'om the head : 

 the weight of the boiler, engine and coal, is thus spread pretty 

 equally over the space allotted for them, and partial and intense 

 weight on any one part is thus avoideil." 



Several of the witnesses having mentioned tlie injurious ef- 

 fects of sea-water upon the boilers, your Committee examined 

 Mr. Michael Faraday, who acts as chemical assistant to 

 IVIr. Brande at the Royal Institution, concerning the chemical 

 properties of sea-water. Mr. Faraday's evidence explains the 

 temperature and degree of saturation of the water in the boilers 

 at which various salts are deposited, and by what })rocess the me- 

 tjds of which the boilers are made, are injui'ed. It appears tliat 

 the greatest care is recjuisite on the part of the engine-keepers 

 to prevent the water in the boilers irom being so much satu- 

 rated as to occasion the deposition of the salts. When this 

 takes place, these salts corrode the metal, and destroy a por- 

 tion of it, and form crusts over the internal surface of the 

 boilers, which having bad conducting jjowers as regards heat, 

 diminish the quantity of the steam, antl cause the fire to biu'ii 

 the boilers and the flues. 



Mr. Faraday ex}>lains, that the injury done to iron boilers 

 by the dejiosition of salts, is much greater than the injury which 

 is done to copper boilers; — an additional and a very strong 

 reason for using the latte)-. 



Messrs. Maudslay and Field state, that the fire-places and 

 Imilcrs are I'recjiicMlly burned and injured lit)in the incrusta- 

 tions 



