METHOD OF MAKING CHARCOAL. 39 



and equable coal is used ; such as that of alder, willow and dogwood, or 

 buckthorn. The wood is charred in iron cylinders. Gunpowder is 

 composed of 75 parts of nitre, 15 charcoal and 10 sulphur. The char- 

 coal of the oak or beech is preferred for the assay of metals, or alloys, 

 and that of the vine or willow for draughtsmen. The use of charcoal 

 as fuel is often dangerous, as it renders the air, when burned openly, 

 unfit to support life, by reason of the carbonic acid gas it evolves and 

 which, it is thought, covers the lungs when inhaled so as to prevent 

 the access of oxygen. Charcoal is used for making printers' ink, 

 Indian ink, black chalk, etc. Charred turf is a preparation of the re- 

 mains of vegetables imbedded in soils. To preserve wood from the 

 attacks of insects and from decomposition, the surface is often charred. 

 Charred fruits, wheat and pulse intended for use by the people of Her- 

 culaneum and Pompeii are now found in their houses. The discovery 

 of innumerable strata of ferns, palms and grasses in the coal measures 

 and other carboniferous deposits, prove that the temperate zones 

 of the earth, and even the polar regions, were at one period of the 

 world within a tropical climate. 



The method of making charcoal is by the arrangement of billets or 

 sticks of wood so as to ensure the dissipation of all the parts except 

 the carbon, and the escape of as little of this as possible. The tree 

 is generally cut the previous season and the wood subsequently pre- 

 pared and piled in a regular conical form and then covered by a coat- 

 ing of turf with the grass inwards. Over this is spread a dressing of 

 earth mixed with charcoal ashes. A course of billets is first laid 

 horizontally a foot apart radiating from a central space to a circle, say 

 100 feet in diamater. The central space is filled with under brush 

 and 4 large billets set up endwise converging and secured together 

 at their tops. The inclination of these forms a guide for the conical 

 pile of billets placed endwise around them to the extent of the circle. 

 Above these another horizontal layer is made, and on this is placed a 

 central stick reaching above the top of the pile, and around this is again 

 arranged another erect pile of billets inclining to the centre like the 

 first. The interstices are filled with smaller sticks. The dressing of 

 turf and earth is then laid on and the inside brush fired by drawing 

 out the central billet and introducing brands of fire from the top. 

 Another method is by piling the whole of the wood horizontally around 

 the upright billets and withdrawing the upper and one of the lower 

 ones of these to fire the brush. Another is to set up the first range 

 of billets perpendicularly in a pit, then to place three billets conically 

 as before, and lay the other courses horizontally to the top, the cone 

 formed by the three sticks being filled with inflammable materials. 

 Another mode is to form a triangle horizontally in the centre with bil- 

 lets, notched into each other and three feet high, with an upright 

 timber running from the top to the bottom of the pile. The wood is 



