Notes on Steam Boilers. 329 
trifle, if any thing, in excess of those built in iron. For 
the furnace it has the advantage over iron, of not being 
so liable to laminate, and blister; when adopted for the 
shell it is essential that it should be of mild duftile quality. 
It is of more importance that boiler plates should be 
duftile, than that they should possess a high tensile 
strength. The thinner steel plates admissible in con- 
struftion for the same strength of boiler, materially 
increases its efficiency by very considerably facilitating 
the conveyance of heat to the water. This opportunity 
may be taken of pointing out that, owing to the very 
special treatment required for the manipulation of steel 
plates, they are totally unfit for repair jobs in the hands 
of the inexperienced boiler-makers not conne6led with 
steel boiler shops. 
Wrought-iron plates, somewhat thinner than the old 
original plates, are the best for repairs. However much 
depends on the sele6lion of a boiler, more depends on 
the seating ; the old fashioned plain cylindrical boiler, is 
simply a plain round pot placed over a fire, and if this is 
seated efficiently, it will be found capable of making 
steam as cheaply as the more recent types ; and consi- 
dering that it is the seatings that are mainly responsible 
for a boiler being considered old after 13 years work in 
this colony, whilst in England the same stage of decay 
is not reached before 26 years of work has been done, I 
hope you will tolerate some remarks from me in a future 
paper on this subje6l. 
