DIRECTIONS TO WORKMEN.

135

thinner the layers, and the higher the temperature,the greater will be the proportion of gas, the greaterthe bulk of coke, and the smaller the quantity oftar.

The coal before it is submitted to the distillatoryprocess, should be as dry as possible, and the moreit is comminuted the better. The very refuse of thecoal called slack , provided it is perfectly free fromforeign matter, answers best. It should also bespread in the trays, in even layers.

When the retort is in a good working state, thetemperature should be kept up by the applicationof small quantities of fuel at a time. A prodigioussaving of fuel may be effected by attending the fireproperly, and it is this which distinguishes a care-ful stoker from a bungler. For in the working ofthis retort particularly, it is a wasteful process toclog up the fire-place with a large quantity of fuelinjudiciously, applied. The difference in thisrespect, with regard to the economy of fuel is sogreat, that an expert stoker will work the retortwith one-third less of fuel and half the labourthat would be employed by a negligent workman.

The quantity of gas produced from a chaldron of