10 APPENDIX. 



t 



there, and of course are easily cleaned. By the above operation it will be readily seen that 

 the surfaces of the flues would be constantly approaching their original state; that is, each 

 scale of five or six years' formation leaves the copper bare; and the more frequently the 

 boilers are scaled, the greater opportunity is afforded the parts to detach themselves. 



I should recommend that boilers employed beyond a limited period, regulated by the 

 incrustations, should be scaled once a month while actively employed ; the operation would 

 then be simple, and would not occupy above two or three days to do it effectually : no violent 

 measures need be adopted, for reasons already given ; and, the matter removed always 

 exceeding that deposited, the condition of the flues, as before observed, would be constantly 

 improving, as regards the parts which are exposed to the water. 



ON THE CONSTRUCTION OF COPPER BOILERS. 



21. Copper boilers, to a certain extent, have fallen into disrepute, three or four sets having 

 been cut up after employment in the government steam vessels. The fire-places were ex- 

 ceedingly good, as well as the top and side plates of the flues, except in some instances where 

 permanent injury was sustained by incrustation, the result of negligence. 



Now, in every instance the destruction of the bottom plates of the flues was the prominent 

 cause of their disuse. Hence, after much inquiry and observation, I suggest that more care 

 and attention, than that usually paid in the construction of iron boilers, should be observed in 

 fitting the bottom of the flues and shell of copper boilers ; in fact, too much pains cannot be 

 taken in the first place, as it is amply repaid in the sequel. The rivet holes through the 

 lower " angle irons" and plates should exactly coincide, and the rivets properly fit them. One 

 of the greatest present nuisances is the defects of rivets ; many of them actually bend in the 

 disfigured holes in the act of clenching ; they certainly cannot fill a hole of a different figure. 

 The riveting merely swells the point, and not the body to any extent, as I have witnessed in 

 many instances : the result is, that water arrives at the clench of the rivet immediately, which, 

 if not well worked, seldom prevents the water from oozing through. The rivets should, in 

 these places, be well worked in the style observed by coppersmiths. The junctions of the 

 " angle irons" should be carefully fitted ; for neglect of this is almost irremediable : and the 

 caulking or chincing should be eventually executed with the greatest nicety, as no opportunity 

 is afforded, after construction, of properly making good any defects consequent on neglect, or 

 want of sufficient care in this stage of the manufacture. 



22. In IRON BOILERS, when water is first admitted after construction, hundreds of "weeps" 

 or channels in the plates and rivets, whence water oozes, are totally disregarded ; the most 

 important only being stopped mechanically; the rest are stanched merely by the rust the water 

 has formed in its passage, and the bulk of the oxide being greater than that of the original metal, 

 lingers where it is formed, and thus becomes a perfect iron cement, and the boilers are tight : 

 not so the COPPER BOILERS ; for the water, attacking the metal in its passage through, forms 

 the carbonate of copper, a clear transparent solution, which is not crystallised till deposited on 

 and spread over the bottom of the flues, where it continues its work of destruction. The 

 track of the water, as exhibited in defective rivets, precisely resembles the tortuous operation 

 of the worm in fruits or wood ; being partly in the plates and partly in the rivets, so as in 

 almost every case to require the hole to be much enlarged, in order to remove the defect prior 



