d 



In Dublin, my observation that the deteriorated value of 

 hot blast iron in the market was 1 7s. 6d. per ton was contra- 

 dicted ; but after seven more years of unceasing application, 

 practised in the manufacture on a very large scale, of nu- 

 merous experiments by indefatigable practical men of great 

 ability, of the attention of learned Professors of chemistry, 

 mineralogy, and geology, together with the aid of that no 

 inconsiderable engine, the public press, the price of pig iron 

 so made is 32s. 6d. per ton below that made by cold blast in 

 the smelting furnaces.* 



If you ask why iron so made is sold for 32s. 6d. less in the 

 market, the answer is — 1st, its great weakness under impact, 

 and therefore its total unfitness for most purposes in which 

 the greatest weight of iron is used ;t 2nd, its greater loss in 

 remelting in the cupola of 2 cwt. per ton ; 3rd, the great 

 irregularity in the contraction of castings when cooling, if 

 made from hot blast iron, on which account many castings of 

 different sizes are produced from the same pattern, causing 

 great expense in their after fitting, or, if this expense is not 



* March, 1842:— Per Ton. 



Price of Scotch hot blast iron at Hull, (No. 1.) £3 7 6 

 To which addfor its general inferiority to Yorkshire 



iron when both were made from cold blast 0 5 0 



£3 12 6 



Price of Yorkshire cold blast iron at Hull, ( No. 1 . ) 5 5 0 



Difference in favour of cold blast iron generally £1 12 6 



t In Mr. Fairbairn's recent experiments, published in the Manchester Memoirs, 

 the difference in this respect is very striking : — 



Each bar being 1 inch square and 4 feet 6 inches long between, supports — 



Breaking weight. Power to resist impact, 



Oldberry cold blast iron 453 lbs. 822 lbs. 



Oldberry hot ditto 543 549 



Using the same coal and ironstone — 



Elsecar cold ditto 446 992 



Milton hot ditto 353 538 



Working in the same mineral field in N. Wales — 



Ponkey cold ditto 567 992 



Plaskynaston hot ditto ............ 378 51 7 



