66 



CONSTRUCTION OF RETORTS. 



In the general arrangement of the hydraulic main two things must be ob- 

 served. First, the diameter must be sufficient to supply at least 20 inches per- 

 pendicular head of tar to each dip-pipe, without causing the general level to fall 

 below their immersed ends ; and secondly, the lower part of the circumference 

 of the pipe, which conveys the gas to the condensers, must be so placed that 

 the tar may always be kept from rising too high, and either choking the free 

 exit of the gas or increasing the working pressure of the retorts unnecessarily. 

 The diameter of the main in the engraving is 18 inches amply sufficient for 

 the fifteen benches of retorts as there arranged. 



F is a light, hollow, cast-iron pillar, supporting the hydraulic main in the 

 centre of each length ; it is based upon the cast-iron girder which supports 

 the firing floor. 



G is the pipe through which the gas makes its exit from the hydraulic 

 main to the condensers, furnished with a slide-valve to disconnect the mains 

 at each side of the house, when at any time it may be found requisite to re- 

 pair or clear them. (The detail of the slide-valve is given in Plate XIX.) 



H is a small pipe for conveying the surplus tar formed in the hydraulic 

 main to the tar-well situated beneath the firing-floor ; its lowest extremity is 

 sealed, by being immersed in the tar contained in the well, or in a small 

 vessel by the side and connected with it ; the latter is the most convenient. 

 This surplus pipe is not absolutely necessary, because the siphon at the bot- 

 tom bend of the first stand-pipe would perform its duty, but it is advisable 

 to draw off" the tar as soon as possible. 



In the construction of retort-houses (although it is not thought necessary 

 by many) I should always advise a coke vault to be built, provided the funds 

 are sufficient, both for convenience and for the comparative comfort of the 

 stokers ; I have given a drawing in Plate IX. which will explain the arrange- 

 ment of all the brickwork. The firing-floor is raised upon flat 9-inch brick 

 arches over the coke vault, high enough to give head-room, a space about 24 

 inches wide being left in front of the benches for the coke to fall through 

 when drawn from the retorts : it should be of such a material as will not be 

 injured by frequent blows. In Plate I. it is shown as constructed of York- 

 shire landings ; some prefer cast-iron, but either will do equally well. The 

 flat arches supporting the floor spring from cast-iron girders fixed at one end 

 in the brickwork of the benches, at the other in the wall of the retort-house. 



