CHARCOAL. 545 



riment it can be shown that the cells constitute -f-ths of the 

 whole cuhic contents of the charcoal; and allowing for the 

 space occupied by the charcoal, the actual surface of the cells 

 would be about 73 square feet. When charcoal is plunged into 

 carbonic acid gas, it absorbs into its cells no less than 56 

 times their cubic contents at the ordinary temperature and 

 pressure, and consequently the gas is condensed to 56 atmo- 

 spheres. But according to the experiments of Adami, car- 

 bonic acid liquefies under a pressure of 36'7 atmospheres, and 

 we are hence compelled to conclude that above one-third of the 

 carbonic acid which is condensed on the walls of the cells is in 

 the hquid state." 



Of late years a great deal lias been said of the value of charcoal in 

 soil. Experiments have shown that in powdered charcoal alone plants 

 flourish with an extraordinary degree of vigour ; charcoal has been 

 recommended as the best of substances in which to strike cuttings, and 

 by degrees it has gained a reputation which nothing now can shake. 

 It is true that some experiments with it have failed, owing, probably, 

 to its having been used in too fine a state, or to other accidental causes ; 

 nevertheless, the opinion of practical men is setting steadily in its 

 favour. Messrs. Loddiges employed it advantageously in the cultivation 

 of Orchidaceous plants, charring the wooden blocks on which they are 

 attached : that practice was introduced beneficially at Chatsworth, and 

 nothing can be more striking than its good effects in other gardens, 

 where a few weeks sufH.ce to give a dark green healthy colour to the 

 plants attached to charcoal blocks. By mixing it with the soil of 

 Orange-trees their health is increased in a remarkable degree ; and it 

 is used largely as an ingredient in the soil employed by Mr. Barnes for 

 the production of the fine Pine-apples of Bictoni This may be in part 

 ascribed to the mechanical action of charcoal, and to its freedom from 

 insects ; or, as chemists maintain, it may be owing to the power 

 possessed by charcoal of condensing within its pores carbonic acid and 

 other gaseous substances which are slowly yielded up to plants as they 

 are required ; or it may arise from a slow formation of carbonic acid, 

 as Mr. Eigg ascertained to occur ; for in six weeks he obtained more 

 than half a cubic inch (.64) of carbonic acid from 50 grains of soft Elm 

 charcoal ; and we know from experience the softer the charcoal the 

 better it is suited to cultivation ; as indeed is shown by Peat charcoal, 

 a most valuable substance for gardeners. 



Fortunately it matters little in practice whether charcoal acts bene- 

 ficially on plants by forming gaseous compounds from its own substance, 

 or by seizing them from the atmosphere, locking them in its pores, and 

 then releasing them as plants require them for their food. That it does 



