748 REPORT—1863. 
At 30 yards from the point of exit the dust contained - 9‘0 per cent. of Lime. 
At 60 do. do. do. 12°5 do. 
At 130 do. do. do. 140 do. 
In order to supply that deficiency in silica noticed as existing in the slags, 
and which might possibly affect the quality of the iron itself, there was added 
to the charge at the Clarence Works a siliceous mud, and subsequently, at 
Eston, freestone, by Messrs. Bolckow and Vaughan. A vitreous slag resultcd ; 
but no very marked improvement being noticed in the iron, the addition was 
discontinued, 
Temperature of Blast.—The uniform practice in the whole district is to blow 
the furnaces with heated air. Sufficient data are not possessed to enable us 
to speak with any degree of certainty respecting the application of cold blast ; 
but, as far as actual experience goes, it is in favour of the idea that the lias 
ironstone would prove very intractable under that mode of smelting. In the 
year 1841, from some reason or another, cold air was used during four months 
at Birtley. The furnaces only ran 42 tons per week of white iron, produced 
by a consumption of 33 tons of coke to the ton. At Clarence an attempt 
was made recently to operate on the Cleveland ore in the same way; twice 
the quantity of coke was used which is required when making foundry iron, 
and only white pig was obtained. 
A more elevated temperature being wished for than is easily commanded 
by means of heated iron pipes, various experiments were tried at the Clarence 
works, and ultimately Cowper’s stoves were introduced. In these, by an 
alternate system of heating a mass of brickwork in closed vessels of iron, and 
passing the air through the same, a temperature of 1000° F. and upwards in 
the blast was obtained. The condensation, however, of the furnace-fume, the 
apparatus being heated by the waste gases, so interfered with the efficiency of 
the apparatus that the system was modified. Previous experiments were then 
continued, in which an arrangement of clay pipes, iron pipes, and forge 
cinders was made to replace the bricks. This was a great improvement; the 
temperature of the air was increased up to 1200° F., and the tubular arrange- 
ment permitted the apparatus to be more easily cleaned. In time, however, 
the same inconyenience from the condensed fume interrupted the value of the 
results, and the plan was abandoned, At no time was the high temperature 
maintained with that regularity upon which success alone depends. Enough, 
however, was ascertained to give encouragement to the idea that a steady in- 
crease of 500° or 600° in the blast would have been serviceable. 
To ayoid the inconyenience of the flue-dust, Messrs. Cochrane erected large 
gas generators to obtain carburetted hydrogen and carbonic oxide from the 
imperfect combustion of coal. The writer is unable to say what have been 
the advantages attending this mode of operating. The loss of heat from such a 
plan of applying coal, and other sources of expense, will probably be a serious 
impediment to the full measure of usefulness of the system*, At the Wylam 
and Wear Ironworks the writer has introduced an arrangement by which the 
blast is heated by means of the waste heat from the coke ovens. 
Shape of the Blast Furnaces—In shape, our blast-furnaces present no 
novelty worthy of notice. The width of the boshes varies from 14 to 18 fect, 
and the height from 42 to 50 or 55 feet, in one case 75 feet having been 
reached with beneficial results. An average proportion will, probably, be 
* Since the foregoing was written, Messrs. Cochrane have informed the writer that they 
experience no difficulty in maintaining a temperature of 1150° in Cowper’s stoves, which 
they have had in operation for two years, and that they thereby effect an economy of 5 cwt. 
of coke in the blast-furnace on the ton of iron, as compared with the furnaces using air 
heated in the ordinary way. Messrs. Cochrane also state that in any future furnaces they 
. ropose using this form of apparatus. 
