416 



THE CniL ENGINEER AND ARCHITECT'S JOURNAL. 



[Dkoembkr, 



My allcntion was first called to llie subject by observing great quantities 

 of pig iron on the wharfs at the iron foundries and other places in this neigh- 

 bourhood, very recently broken into pieces so short as to prevent the la- 

 bourer piling them in cubical tiers in the usual manner, and on inquiry, I 

 found that they were so broken by loading and reloading, and that they 

 were made by the new process of using hot air in the furnace, greatly mis- 

 called an improvement in the manufacture of cast iron. From these and 

 other circumstances I thought it a duty due to the iron trade to call the at- 

 tention of the public to it, and having mentioned the subject at the meeting 

 of the British Association in Dublin, its importance was at once recognised, 

 and a sum of money appropriated for making the needful experiments, whicli 

 were carried into execution by Mr. Fairbaim, the highly intelligent and in- 

 defatigable engineer of Manchester ; and I was very sorry to see in his re- 

 port read at the Liverpool meeting, as well as in several conversations with 

 me on the subject, to find that he had experienced great difficulty in ascer- 

 taining the composition of the irons experimented upon, in consequence of 

 many of the manufacturers being unwilling to give information ; added to 

 this, it is well known that in more recent experiments, one of the strongest 

 irons in Yorkshire has been placed in the scale of strength so much below 

 other iron, long since known to be no stronger, both irons being made from 

 the same coal and ironstone, a fence only parting the mineral fields of each 

 work, that I am driven to the conclusion that the object of the experiments 

 in question has in a great measure been defeated. There are, however, some 

 experiments in them, which may not have been affected in their results by 

 these circumstances, two of which I shall point out for your consideration. 

 The first will be that of iron from two works using the same materials. 

 Elsecar iron (cold blast) mean ratio of its strength .. 1000 



Milton iron (hot blast) mean ratio of its strength . , 809 



Elsecar iron mean ratio of power to resist impact . . 1000 



Milton ditto ditto ditto .. 858 



In this case, however, the difference is much greater than appears on the 

 face of these experiments, inasmuch as the specimens of pig iron from the 

 Milton Works were made with the addition of a portion of the red hematite 

 iron ore from Ulverstone, for the express purpose of giving greater strength 

 to that iron, as was invariably done many years for the purpose of making 

 tin plate, and during the war for the casting of cannon. 



The second circumstance is that where Mr. Fairbaim states that in a trial 

 of 50 sorts of iron, of which each bar " of hot and cold blast iron were made 

 of the same materials, and under the same circumstances. 



Cold blast iron, with a load of 392 lb. increased the deflection in 108 days 

 from 1"8G to 1-843 inches. 

 Hot blast iron ditto ditto 1-891 to 1-966 inches. 



Cold blast iron with a load for 448 lb. continued to increase in deflection, 

 and ultimately broke, after sustaining the weight 35 days. 



Alt the liol blast iron bars broke in the act of loading them with the above 

 weight of as lb. 



Notwithstanding these and many similar facts brought out by the experi- 

 ments in question, certain portions of them are constantly being quoted 

 through the press for the purpose of proving that iron made by hot air is 

 stronger than that produced by the use of cold air. 



Contemporary with these experiments on a small scale, others of far 

 greater importance have been going on j and we hear of hundreds of railwaj- 

 chairs, cast from iron made by the improved process, constantly breaking 

 where tens only broke before, » of steam engines and other valuable machinery 

 breaking in rapid succession, and in parts where, by regular work, they were 

 never known to give m ay before the introduction of the improved iron— of the 

 more respectable portion of mill-wrights Iwing obliged to make new calcu- 

 lations, and a new stock of patterns, in order to lessen, as far as is in their 

 po«-er, the enormous losses and the great disappointment of (heir friends by 

 such breakages. We hear of districts of coal masters and other prudent and 



" I take this to mean each pair of bars. 



° In a paper recently read before the Institution of Civil Engineers, Mr. 

 Macneill states that on the Dublin and Drogheda Railway, where chairs were 

 used made of hot blast iron from Scotland, tlie breakage was very great as 

 compared with those on the .South Eastern Railway, which were made of 

 cold blast iron, and that in his opinion the latter would be cheaper than the 

 former at an increased price of il. per ton. 



humane proprietors of large establishments introducing clauses in their con- 

 tracts for castings, stipulating that no hot blast iron shall be used therein : 

 and at length the same has become common in contracts for gas and other 

 pipes, «hich it has liitherto been usual to make of the most inferior quality 

 of irons, it having been found that the sockets of some miles of piping have 

 been broken off in one or two years after being laid down, in consequence of 

 their having been made of hot blast iron. 



There has, however, still more recently, been a series of experiments made, 

 upon which a far greater dependence may be placed, inasmuch as the irons 

 were all supplied in tlie regular way of business, without the makers knowing 

 any such experiments were intended ; and they were undertaken for the pur- 

 pose of information only, to guide the founder and engineer who conducted 

 the operations at his own establishment. The detail of these valuable trials 

 by Mr. Todd, of Leeds, formed a paper read before this Society when last it 

 met at Leeds ; I need not therefore occupy your time with repeating them, 

 and here, will only call your attention to a few of the results, for the purpose 

 of more clearly explaining what I wish particularly to impress on your 

 notice. ° 



With respect to the strength of bar iron made from hot blast pig iron, very 

 few experiments have been made public that I am aware of; they are, how- 

 ever, of very great importance, because they were made with the greatest 

 possible care, and regardless of expense, by manufacturers of the first emi- 

 nence and ability for their private information. The irons were eight in 

 number ; the first set of bars were 2i inches in diameter, made with cold 

 blast scraps and hot blast respectively, all by Yorkshire manufacturers. The 

 weight required to draw- them asunder by a steady direct tension was not 

 very variable, but when all were cut round to the same depth, for the pur- 

 pose of being broken with the hammer, they required about the following 

 blows to do so : — 



Blows 

 Cold blast iron . . > . • • • • • • 6 



Scrap . . . . . . . . . . • . 3 



Hot blast . . . . . . . . . . 1 



The second and third set of bars you have now before you, ths result of ex- 

 periments on which stand thus : 



Blows required 

 to break them 

 Diam. of bar. Area of see. with a 171b. 

 in. where cut. hammer. 



Low Moor cold blast .. 2-66 ., 3-976 .. 18 

 Bierley cold blast .. 275 .. 4430 .. 18 



Milton hot blast .. 275 .. 4-430 .. 3 



Blows required 

 to break them 

 with a 201b. 

 hammer. 

 Elsecar cold blast . . 2-58 . . 3-976 . . 21 •> 



Milton hot blast .. 2-58 .. 4203 .. U J- 



Made from the same materials. ) 



So that the proportionate resistance of hot blast wrought iron to impact is 

 still less than that of cast iron. I need scarcely say, cold blast iron was 

 ordered at probably Gt. per ton more than the hot blast iron might have been 

 bought for. 



1 may here take leave to mention the circumstance of scrap iron being any 

 thing now but what it was formerly, when its name and excellent quality 

 were synonymous. In former times the importation of scraps from the con- 



« They took place from August, 1840, to February, 1841. 



Breaking weight 

 cwt. qr. 

 average 25 2 

 do. 24 

 do. 23 2 

 do. 17 2 

 do. 16 



Bierley jiig iron, No. 3, made with cold blast 



Elsecar do. 3, do. 



Low Moor do. 3, do. 



Summerlee (Scotch) 3, hot blast 



Level Staffordshire 3, do. 



Mixed pig iron 3, 5 parts Low Moor, 1 part Elsecar do. 30 



Mixed pig iron 3, 5 parts Bierley, 1 part Elsecar do. 33 



Mixed pig iron 3, equal parts Bierley, Elsecar, Low Moor, 



Staflbrdshire, (Cylinder iron in the market,) and Level iron, 

 also, Summerlee ^o- ^0 2 



