THK II \\l>\ \l\s OS THE FARM. Sf>*. 



. Where coal is not obtainable, charcoal is a good substitute. In the pion 

 ing days of the State, when transportation was difficult, charcoal was much 

 used, but during recent years coal has almost altogether taken its place. 



The place for the fire is immediately in front of tin- tue pipe, or, in those 

 forges where the tue opening is in the centre, immediately above it. The 

 tue pipe is the pipe which leads the blast to the fire. 



The cinders, ashes. &c., of the last fire should be scraped away to leave a 

 depression exposing the mouth of the tue pipe. All the coal, cinders, &c, 

 -on the top of the forge must not be removed, as these are required to keep 

 the heat in the fire. The actual space on the hearth occupied by the fire is 

 comparatively small, and the remainder of the surface, with its coal. &c, 

 lets, so to speak, as an insulator. 



Shavings, small chips, &c, are placed in the bed of the depression and 

 Lighted. When they are well ablaze, coke from the previous fire is put on, 

 and the fire forced with the blast. Green coal, i.e., fresh coal moistened 

 with water, is finally added. 



The actual heating material in the fire is coke, which is produced on the 

 hearth by the action of the fire. In its formation from coal the volatile com- 

 ponents, such as gases, &c, are driven off, and practically little left but carbon 

 and ash. The special value of coke lies in its difficulty of combustion, which 

 enables it to be brought to a high temperature under blast, and its freedom 

 from flame and smoke. 



In practice, green coal is backed up behind the fire. The heat converts it 

 into coke gradually, and when the fire begins to get low, some of this coke 

 is drawn down. At the same time the coal forces the fire forward and prevents 

 it coming in contact with the tue pipe. 



The coke, in addition to acting as fuel, serves as a coat to keep the heat in 

 the centre of the fire. If the fire breaks through this coat, the heat passes out 

 into the air, and it is difficult to secure a good welding heat. 



The fire is not ready for use until a good supply of coke has formed. It 

 must be cleaned regularly, as the coke burns away, by throwing out the 

 clinkers, and fresh coke drawn in from the back or sides. The character 

 of the fire has a most important influence upon the nature of the work turned 

 out. It is, in fact, practically impossible to produce good work with a bad 

 fire. This applies particularly to welds. 



Effect of Heat upon Iron. 



To appreciate the importance of the fire, its effect upon iron and steel 

 must be understood. These metals, when cold, are hard, and cannot be 

 changed in form without in some way injuring their strength. When, how- 

 ever, they are properly heated they can be worked at will without in any 

 way impairing the strength. Heat causes marked changes in the metal. 

 It becomes easily flexible, and if heated still further, plastic, and finally 

 passes into a molten condition. A homely illustration of the behaviour of 

 iron is seen in the change which takes place in wax when heated. It gradually 

 passes from a hard state into a pliable, then into a plastic, and finally into 

 a molten condition. The changes in iron are not quite the same, but 

 uear enough for illustration. 



