PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 397 



the greatest efficiency for vigorous work. These boilers are 

 applicable in many cases where they are not used because people 

 are afraid of them. But for gun-boats, there is no reason why 

 they should not be adopted ; for they w^ill be safer as well as more 

 efficient than marine boilers. 



Mr. Montgomery expressed his views in relation to the proper 

 boilers for gun-boats, adverse to the use of the locomotive boiler 

 as being inferior to a boiler proposed by himself. 



Mr. Garbanati said that the gun-boats of the olden time were 

 merely flat-bottomed boats, or rafts, carrying a large gun, and 

 found to be very effective in taking a vessel at anchor. The 

 English government introduced the steam gun-boat in the Cri- 

 mean war. We need gun-boats of a small draught of water, to 

 run up rivers; and if we can use the locomotive boiler so as to 

 obtain also great speed, it will be an advantage. 



Mr. Fisher. — In speaking of the space required by the 

 locomotive boiler, he had not referred to the shape of the loco- 

 motive boilers in common use, but with certain changes which 

 would diminish the height materially, and which had been found 

 successful in practice. Allan's boiler, for instance, Avhich has 

 been used upon a Scottish railway, can be put up within the 

 height of four feet. The receptacle for steam, instead of being a 

 dome above, may be placed on the same level with the boiler, 

 there being no lack of room in this direction; and, it could be 

 furnished with a pump to remove the water as it accumulates 

 from condensation. He would not deny that other boilers might 

 be used, or that they might be better than locomotive boilers; 

 but the locomotive boiler has been so generally used that its effi- 

 ciency is known and cannot be questioned. He had not felt at 

 liberty at this time to undertake the discussion of plans which 

 had been proposed but had not been brought into general use. 

 There may be others which may be more economical of fuel ; but 

 what a gun-boat Avants is not economy of fuel but to catch the 

 enemy. When running easily the locomotive boiler will evapo- 

 rate 10 J lbs. of Vvater to the foot of heating surface ; when driven, 

 it may not evaporate more than seven pounds. 



Dr. Vanderweyde stated that gun-boats were very common 

 before the introduction of steamboats. As early as 1825, before 

 steamers were generally introduced, England, Prance, and Hol- 

 land, had gun-boats, and they were in the Baltic also. They 

 were sailing vessels having a large gun in front, and usually four 



