Mr Robertson on tho Mechanical Arts of Persia. 303 



As this substance, however, emits little flame, the brick-kiln 

 has to be supplied with withered plants and bushes, which 

 are collected in abundance on the hills, whose strong though 

 transient flames ascend through the interstices of the closely 

 packed bricks. 



The brick-kiln may be shortly described as a small vault, 

 dug out of the ground, and surrounded by a wall of sun-dried 

 brick, having a door- way at each end for receiving the fuel. 

 It is closely covered by a series of very narrow arches, the 

 top of which forms the floor on which the bricks are placed ; 

 and this again is surrounded by a brick wall, with door-ways 

 for putting in and removing the bricks. See fig. 18. 



The bricks are arranged on edge in the kiln, and the door- 

 ways are built up. A regular supply of fuel is kept up, by 

 the two lower doors, until the required quantity has been con- 

 sumed. During the first two or three hours, clouds of white 

 vapour ascend from the top of the kiln. When this appear- 

 ance has ceased, and thick volumes of dark smoke begin to 

 arise, two or three layers of unburnt bricks are laid flatways 

 over the top of the kiln. In about twelve hours the whole of 

 the fuel has been thrown into the vault, and the two feeding 

 door-ways are built up. The kiln is allowed to remain in this 

 state for tvp'o or three days, and, when perfectly cool, the 

 burnt bricks are removed for use. 



The bricks, when well prepared, are of a fine red colour, 

 and of considerable hardness ; but, from the mode of manu- 

 facture, one side is always exceedingly rough and uneven, but 

 this is no disadvantage, as the joints in buildings are seldom 

 less than one inch and a half thick. 



It may become a question whether the method above de- 

 scribed might not be successfully imitated in our own country, 

 particularly in those inland and secluded districts where coal 

 is dear, and yet where a demand exists for tiles and bricks for 

 agricultural and other purposes. 



It is difticult to compare the Persian process with our own, 

 but it may be noticed, that, in this country, a workman can 

 mould about 700 paving tiles in a day, of exactly the same 

 dimensions as the Persian bricks, but then the clay is prepared 

 by machinery, and the moist tiles are removed by otlier hands. 

 The price of these tiles, w hen made of common clay, is L.5 



