70 CONSTRUCTION OF RETORTS. 



bricks moulded on purpose to suit the curve, the joint being kept as close as 

 possible. As this arch is permanent, much care should be taken in its for- 

 mation. 



A bench of retorts on this plan, if well and regularly used, ought to last 

 from 12 to 14 or even 15 months, and ought never to be suffered to become 

 cold. The first portion of oxide which forms upon the surface, when allowed 

 to cool, cracks and falls off, leaving a new surface to be acted upon the next 

 time it is heated. 



When it becomes necessary to reduce the number of working retorts on the 

 approach of summer, those that are nearly burned out should be selected ; or, 

 if there are none in this condition, " let them down" very gradually, by 

 keeping the damper closed after the fire is raked out : it will be a week be- 

 fore they become quite cold. The same precaution should be taken in " get- 

 ting up " the heat opening the damper gradually. 



When a bench of retorts is newly set, the green work must be suffered to 

 get quite dry before any fire is lighted. 



The following is a detailed estimate for taking down and resetting a bench 



of five D retorts, including the main arch. 



s. d. 



5 D retorts, each weighing 13 cwt. at 7 10s. per ton - 24 7 6 



1 Man, jointing mouth-pieces and pipes, 3^ days at 5s. 17 6 



300 Square Newcastle fire-bricks at 10s. 1 10 



150 Arch ditto. - 15 



25 Split ditto. 026 



12 Fire-tiles, at 4s. 6d. 2 14 



20 Fire-tiles, at Is. 6d. 1 10 



100 Pavior bricks for front, at 6s. 060 



500 Stocks for filling bed, at 5s. 150 



8 Bushels of lime and sand, at tyd. - 050 



I Ton of Newcastle clay, at 30s. 15 



1 Labourer, taking down old retorts, clearing away, and 



cleaning bricks, six days, at 3s. - 0180 

 1 Bricklayer and 1 labourer, resetting and finishing, six 



days, at 9s. 2 14 



^ Cwt. of cement for joints, at 7*- - 036 



38 3 



The results of a chaldron, or 36 bushels of Newcastle coal, weighing 27 



