GARDENING AS A SCIENCE. 
are oxygen gas^ hydrogen gas^ and charcoal ; not that it would be correct to assert 
that wood, while it exists as such, is composed of tliose elements. Coal had doubt- 
less its origin in wood^ decomposed by the action of water under the surface of the 
earth. Coal varies much in its components ; the basis, however, being, in the main, 
charcoal, with bituminous and earthy matter, varying according to the locality of 
the mine. 
The common soldering or caking coal has been reduced by analysis to — 
Carbon „ 75 28 per cent. 
Hydrogen „ „ 4-18 „ 
Nitrogen 15-96 „ 
Oxygen „ „ 4-58 „ 
100-00 
When distilled in iron retorts, the products are the coal gas of illumination, tar, 
ammonia, water, and much foetid sulphurous gas. 
This coal cokes well, but if heated strongly, runs into clinker, and is liable 
to be suddenly extinguished. 
The Staffordshire coal does not generally coke ; it burns steadily without clinker, 
but abounds with much white-ash, which will effervesce with acids. 
The best and most available fuel appears to be the Leicestershire Moira coal ; 
it is very hard, and of difficult fracture, but burns steadily, never deceives the 
furnace man, and consumes entirely to a moderate quantity of grey ash. 
The economy of heat is a point of importance in horticultural science ; and 
so is that of time ; but the chief and paramount considerations are the health and 
comfort of the labourer. 
We do not discuss the merits of the various methods of producing and conveying 
heat, for a good and soundiy-constructed brick flue and hot-water apparatus may 
equally be rendered costly or economical, by a due regulation of the fuel. 
Experience has proved that by employing common cinders and ' breese,' with an 
occasional lump of Moira left undisturbed, a steady heat is maintained for hours. 
At night a lump of 7 or 81bs., pushed far toward the neck, another of less size laid 
on the ignited fuel, covering the whole with small screenings of sea-coal and 
cinders, and banking with wet ashes at the door, have prevented accident and 
entirely obviated night labour. The draught must of course be reduced by means 
of the ash-pit door, or chimney-damper ; but with this precaution, a fire has been 
kept up, without re-kindling, during six weeks. 
