MR ROBERTSON ON THE IRON MINES OF CARADOGH. 



705 



The operator having carefully selected charcoal of a small size and light 

 weight, proceeds to clear it from dust and sand with a small meshed riddle, re- 

 moving all the heavy pieces of charcoal or stones that may be accidentally mixed 

 with it. The raw ore being next selected and mixed, and being broken into small 

 pieces about the size of a hazel-nut, is thoroughly moistened with water. A dam 

 is then made between the iron and slag hearths, composed of charcoal and char- 

 coal dust Avell rammed down, and the top is coped with iron-slag from a former 

 smelting. The following sketch will shew this arrangement : 



The Twyere pipe (Fig. 7), which is made of white clay, and bears a violent 

 heat for a long time without melting, is then inserted through the small hole in 

 the side wall of the first iron hearth. The point of the pipe is made to reach 

 half-way across the iron hearth, and within six inches of the bottom, as shewn in 

 Fig. 6. A layer of charcoal, of three inches thick, is then spread over the bottom 

 of the iron hearth, and upon this two other layers laid across, one directly under 

 the Twyere pipe of about six inches in breadth and three inches deep, and the 

 other at the front of the hearth of the same thickness, to correspond with the 

 overlying part of the dam. Tlie two trenches which are thus formed are filled 

 up with the moistened ore, well rammed down. A second layer of charcoal, in a 

 state of ignition, is thereafter laid over the former under the twyere pipe, and 

 other successive layers of charcoal and ore are filled in, corresponding with those 

 in the bottom. When the hearth has been nearly filled up in this way, a covering 

 of charcoal is spread over the surface of the whole on a level with the top of 

 the dam. The bellows are then blown, and a workman, who stands at the side 

 of the hearth, keeps constantly pushing doA^'n the charcoal in the middle with an 

 iron rod (Fig. 8), and from time to time throAvs small quantities into the centre 

 of the fire as it gradually subsides. At the commencement, one man at a time is 

 sufficient to blow the bellows, but, towards the close, two are required, the one 

 standing behind the other. The bellows, of the form shewn in the figure marked 

 9, are in general use all over Persia. After blowing for an hour or an hour and 

 a half, part of the twyere pipe having melted from the violence of the heat, the 

 blast is stopped for a moment, for the purpose of pushing the t\yyere pipe farther 

 in towards the centre of the hearth. It is then again continued, and in about 



