328 TlMEHRI. 
praftice of turning out only the best work ; yet they as a 
rule prefer to be supplied with complete specifications, 
as otherwise it is not difficult for makers less capable, or 
less scrupulous, when competing, to underquote them by 
using plates of lower quality, or by adopting a cheaper 
form of constru6lion generally. And it is only after the 
boiler has been set to work that the insignificance of first 
cost cheapness is felt, as compared with good material 
and sound work. 
Material. — The quality of the material to be used in 
the constru6tion of a boiler is a matter of great impor- 
tance, depending on various conditions ; for instance 
some twelve months since I put two strips of metal, one 
iron, and the other steel, into two boilers, identical in 
every respe£t except the kind of feed water, one using 
exclusively fresh bush water, and the other feeding with 
old bush water sometimes mixed with river water. On 
taking the strips out a short time since, I found the fresh 
bush water had corroded, or eaten the iron strip about 
25 0/0 more than the steel ; and that in the other case 
the iron and steel decay was virtually equal; I have seen 
cases in England where the freeness from corrosion was 
in favour of iron. Of corrosion I shall have more to say 
in a future paper. When iron is decided upon, care 
should be taken to specify it of those brands only which 
are known to be of thoroughly good repute. Doubtless 
steel is the material of the future ; the special experience 
of boiler-makers in the working of steel, is now very 
considerable, and the appliances for its manipulation are 
well calculated to minimise straining during constru6tion. 
By the use of steel the weight of a boiler is reduced from 
10 to 15 per cent., and the price of steel boilers is a mere 
