president's address — SECTION B. 93 



iii HOI of any consequence. The critical points, ?".e., the flame pheno' 

 mena for slag and for copper, are said to be less easily observed, but 

 this may, without fear, be put down as an almost triHing dra^\back, 

 if correct, which experience will very soon remedy. 



With regard to the important subject of the correct position of 

 the tuyeres an interesting solution may be added, which was devised 

 by Auerbach, in 1886, for the small Bogoslowsk converters of that 

 time. It consisted in placing the tuyeres, pointed upward at an angle 

 of '15° from a bottom wind-box, in a circular line around the circum- 

 ference of the dish-like bowl of the converter cavity. By this means 

 the metallic copper collecting in the bowl was not disturbed by the 

 blast. The arrangement, though clever, no doubt suffers from tlie 

 usual difficulties so far inseparable fiom the proper maintenance of 

 bottom tuyeres, the wear being inade specially objei^tionable by their 

 position. 



Conditions for Successful Converting. — The considerations which 

 govern the efficiency of the converting operation are simple, but must 

 not be neglected if the best achievable results are desired. They are, 

 first, a sufficient biilk or mass of substance to act upon ; second, the 

 production of sufficient heat by the chemical reactions to keep all solid 

 products well molten ; and third, an enercetic and rapid oxidation of 

 the oxidisable constituents by means of an adequate column of air or 

 blast. In small converters the mass treated easily suffers a cooling, 

 particularly with an excess of blast towards the end, and this cooling 

 grows in proportion to the diminution in size of bath, i.e., capacity of 

 vessel. The production of heat by internal reactions, fortunately, is 

 accompanied by the creation of a solid product — slag — which, remaining 

 within the vessel, conserves the greater part of the heat evolved, the 

 escaping gases not carrying off enough to affect the maintenance of 

 the slag and enriched matte in a state of liquidity. This fact is still 

 more marked in the after-blow, or second period, when the sulphur of 

 the cuprous sulphide is the only fuel consumed, the thermal work being 

 materially supported by the superheating which the cuprous sulphide 

 derives from the preceding combustion of the iron sulphide and from 

 the formation of the slag. Finally, the rapidity of combustion is directly 

 determined by the proportions of the column of blast absorbed in the 

 unit of time. Velocity of reaction tends to counteract the robbing 

 influence of radiation, of the convection of heat by the escaping gases, 

 and of the absorption of heat by che metallic product which it does 

 not yield up for any chemical purpose, and these abstractions of heat 

 grow with the temporal extension of their influence. Quickness of 

 reaction is an essential, therefore, and piesupposes an adequate blast 

 supply ; and, for the best thermodynamic results, magnitude of mass 

 treated is scarcely less important. These principles point the way to 

 future progress in the work, 



The Lininri".- The question of the linings has been made one of 

 the metallurgical spectres of the method, and much lament has been 

 wasted on it from the inception. Their constant replacement is one of 

 the main elements of cost, it is true ; but, however serious this may be, 



