TRANSACTIONS OF THE SECTIONS. 199 
centre. Having enumerated the facts respecting the trials to which he 
had subjected this curious material, Captain Johnson stated the con- 
clusion that he had come to, namely, that it is sufficiently tough not to 
break, and hard enough not to bend, under the trials to which it would 
be fairly exposed ; and that being alike free from magnetic properties 
and liability to oxidation from exposure to the atmosphere, it possesses 
the requisite qualities for the pivot of the mariner’s compass ; and he 
could not but anticipate that, when fitted with a ruby cap to corre- 
spond, it would be found greatly to improve the working. Besides the 
application of this substance for compass pivots, Captain Johnson stated 
that it might probably be found advantageous for other instruments, 
and especially for the points of the axes of the dipping needles fitted, 
on Mr. Fox’s plan, for use on board ship. 
On the Fan-Blast as applied to Furnaces. By Mr. FAirBAIrNn. 
In explaining the methods to be pursued in adapting furnaces to the 
fan-blast, Mr. Fairbairn observed, that it was well known that its ap- 
plication to the cupola for melting pig-iron was attended with the most 
complete success; and the object of the present.inquiry was to deter- 
mine how far the same mode of blowing was applicable to furnaces on 
a large scale, for the purpose of smelting ores. Objections had been 
made to Mr. Fairbairn’s plan, on account of the very low pressure at 
which the air is introduced into the furnace, and its insufficiency to 
force it through a mass of material such as is contained in the furnaces 
of this country, and which is from thirty to forty feet in depth. To 
these objections Mr. Fairbairn replied, that the same had been urged 
against the introduction of the fan-blast to the cupola; that, in his 
opinion, its efficiency was as the quantity discharged, and not the press- 
ure, which regulated the passage of the air from the “ twyres” to the 
top of the furnace. The fan-blast, when supplied with large apertures 
into the furnace, would, in his opinion, increase the process of calcina- 
tion, effect a more equable temperature, and produce a superior quality 
of metal. It appeared, therefore, of importance that the experiment 
should be made; and Mr. Fairbairn offered to superintend its intro- 
duction, provided the proprietors of the numerous works in this coun- 
try agreed with him in opinion, that the process would be advantage- 
ous both as regards expense, and the improved quality of the metal 
produced. 
On the Combustion of Coal, and the Prevention of the Generation of 
Smoke in Furnaces. By Mr. Wit.iams. 
Mr. Williams observed, that in treating on steam and the steam- 
engine, the subject divides itself into the following heads :—I1st, the 
management of fuel in the generation of heat; 2nd, the management 
of heat in the generation of steam ; 3rd, the management of steam in 
the generation of fuel. The first belongs to the furnace, the second 
