VII. MISCELLANEOUS. 551 



On this air vessel (G) is built a retort H, partly of fire-brick, partly of cast 

 iron. The top of the cast-iron part of the retort is fitted with a hopper, T, in 

 the throat of Avhich is a damper, J, worked by a rocking shaft and lever, K, 

 from the ground. 



The lower portion of the retort made of fire-brick has two necks, L L, the 

 one leading to the combustion chamber for the passage of fuel, the other to 

 the outside of the furnace for the insertion of stoking tools, to force the fuel 

 forward into the combustion chamber. The entrance of the outer neck is 

 closed by an air-tight door M. The upcast or retort chamber (E) extends to 

 near the top of the retort, where it is closed by brickwork, but is opened at 

 the side by the flue N, leading to the stack O. 



Near the bottom of the chamber E, and in a line with the centre of the 

 circular air vessel G, are pipes P P, inserted in the walls of the chamber (E), 

 passing all round the chamber as shown in Fig. 5. In front of the inner side 

 of the circuit of pipes, and opening into the chamber E, are a number of port- 

 holes Q Q Q (see Fig. 5), leading to the space around the pipes (P P), which 

 space affords scope for expansion and a free circulation of heat. These pipes 

 (P P) are connected with the blast as shown at E, Fig. 4, and pass into the 

 central chamber G, as shown at F, Fig. 5, the outlet, R, from the air vessel 

 leads into the ash-pit S. 



The practice in working is to light a fire on the grate-bars, and generate 

 heat in the usual manner, until the furnace is well heated. The retort is then 

 filled with fuel, and the firing commences from the retort, and by the time the 

 fuel at the top descends to the bottom of the retort, it is well lieated, and a 

 continuous supply of heated fuel is then kept up. All raw fuel is from this 

 time supplied to the hopper (I) only, and let into the " retort " by the damper 

 without the access of air. 



The gases so generated in the combustion chamber (A) pass over the bridge 

 into heating chamber (B), down the neck (C), into the underground flue (D), 

 into the upcast or " retort " chamber (E), filling the spaces around, and giving 

 up their heat to the circular air chamber (G), the retort (H), and the air 

 pipes (P P), and their residue passing off by way of the flue (N) into the 

 stack (O), the heat so stored being carried back into the furnace by the 

 heated fuel. Combustion is supported by air under pressure from a fan. The 

 air entering in as shown at (E), Fig. 4, traverses the entire circuit of pipes, 

 passing into the 'central air-vessel (G), out through the outlet (B), into the 

 ash-pit (S), and so up through the grate-bars. 



256Gb, Patent Platinum Apparatus. 



Johnson, Matthey, and Co. 



Newest form for the concentration of sulphuric acid, securing great 

 strength, productive power, safety and economy in working, and highest 

 degree of purity of acid, with a minimum of platinum : 



Boiler. IJy the corrugated form of bottom (Prentice's patent) the greatest 

 possible amount of strength, surface, and consequent evaporating power is 

 obtained, and a considerable saving in fuel is effected. 



Pans. By means of these vessels the large and costly leaden tanks for the 

 previous concentration of the chamber acid, which require constant repair and 

 renewal and more or less contaminate the acid, are entirely done away 

 with. 



The setting of these boilers and open pans is of the simplest kind ; they are 

 placed upon an iron frame over a straight flue, and they may be multiplied or 

 enlarged to any desired capacity of production. without sacrifice of existing 

 plant. 



Cooler. An improved economical arid convenient form, securing great 

 cooling power with a minimum of water and space. 



