304 Mr Robertson on the Mechanical Arts of Persia. 



per 1000. A Persian will prepare the clay and make about 

 2000 per day, and the selling price is only 9s. per 1000 ; but 

 it need scarcely be remarked that the bricks are of very infe- 

 rior workmanship. 



Lime-hurning. — The kiln is constructed in the following 

 manner. A circular excavation, of about ten feet diameter, 

 and six feet deep, is made in the ground in a dry situation, 

 and a sloping pathway cut down to the bottom on one side. 

 A circular wall of rubble stone, two feet in thickness, is then 

 built round the interior of the excavation. At five feet from 

 the foundation, a scarcement of six inches is left in the inside, 

 and the wall, thus diminished, is carried up six feet higher. 

 A small door-way is left opposite the path, and another small 

 opening immediately above it. A narrow door- way is also left 

 in the upper part of the wall, but on the opposite side. See 

 fig. 19. 



In charging a kiln of this description a layer of limestone 

 is first laid all round the scarcement, each piece projecting a 

 little inwards, and these are firmly packed and wedged to- 

 gether. A second layer, of larger pieces, is then laid over the 

 first, which also projects inward beyond the first course ; a 

 series of similar courses succeed, each being of less diameter 

 than the preceding, the whole forming a dome-shaped ceiling 

 of limestone, which is closed by a single stone at the top. 

 Great attention is rec^uired, during the filling up, that the 

 larger masses of limestone may be laid lowest and nearest the 

 centre, and the smaller pieces towards the wall and upper 

 part of the kiln. The door-way, in the upper part of the wall, 

 is now built up, and a conical hill of chips thrown on the top 

 of the broken limestone, in the kiln, and it is now ready for 

 being lighted. A sufiicient quantity of furze or withered 

 bushes having been collected, near the kiln, the workman 

 throws gradually, through the feeding aperture, so many loads 

 of fuel as he judges necessary, to calcine the limestone. When 

 the white vapour and smoke disappear, then a quantity of 

 lime-riddling, ashes, or other refuse, is spread over the top of 

 the kiln, and the feeding door-way built up. The kiln re- 

 mains in this state for two or three days, and is then emptied 

 by opening the upper door-way, and removing the burned 



