Models of Blast Furnaces 9 



general use in Europe during the eighteenth century 

 and in this country at the time of the Revolution and 

 for some years after. Forges of the same general 

 type have been used among peoples of the more primi- 

 tive cultures in relatively recent times and they may 

 have persisted in places to the present day. The forge 

 is small, not much larger than an ordinary blacksmith's 

 forge. The model is on a scale of one inch to the foot. 

 At the left is the large hammer which finishes the iron. 

 In the center is the hearth in which the ore is reduced 

 and at the right is the trompe in which air is com- 

 pressed to provide the air blast which urges the fire 

 on the hearth. 



THE TROMPE which provides the air blast for 

 the hearth is a simple device by which falling water 

 is made to trap air and deliver it under pressure. It 

 consists of an upright hollow log fed with water from 

 a flume above and connected below with an air tight 

 tank. A valve at the top controlled through a lever 

 and hanging cord admits and shuts off the water. 

 Near the top of the log are a number of perforations. 

 Water falling freely draws air in through these per- 

 forations and delivers it to the tank below under a 

 pressure dependent on the height of the log. The 

 water escapes through a gate near the bottom of the 

 tank and the air passes through a pipe at the top to 

 a conduit which conducts it to the hearth. 



THE HEARTH which appears in the center of 

 the model is much like a blacksmith's hearth with a 

 blast from the tromp instead of from bellows. On 

 this hearth a charcoal fire is built and urged to in- 

 tensity by the air blast which enters through a nozzle 

 called the TUYERE which passes through the rear 

 wall. This fire is fed by a mixture of iron ore and 

 charcoal. Under the influence of heat the ore, which 

 is a combination of iron and oxygen, gives up its oxygen 



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