440 USE CF CHARCOAL-DUSTj AND OF COAL-TAR. 



vation — but it is an important one — made by Mr. Morton, when des- 

 cribing the management of a well conducted farm in Gloucestershire, 

 (that of Mr. Dimmery, described in the Journal of the Royal Agri- 

 cultural Society^ I., p. 400.) " The quantity of soot used upon this 

 farm amounts to 3000 bushels a-year, one-half of which is applied to the 

 potatoe, the other half to the wheat crop." All the straw grown upon 

 this farm is sold for thatch, and for the last 30 years the only manure 

 that has been purchased to replace this straw is the soot, which is 

 brought from Gloucester, Bristol,* and Cheltenham. Soot no doubt 

 contains many things useful to vegetation, yet where all the produce is 

 carried off, and soot only added in its stead — even the rich soils of tlie 

 vale of Gloucester cannot be expected to retain a perpetual fertility. 

 The slow changes which theory indicates may altogether escape the 

 observation of the practical man, who makes no record of the history 

 of his land, and yet may be ever slowly proceeding. 



2^. Charcoal. — Wood-charcoal, from its porous nature, and its tend- 

 ency to absorb animal odors and other unpleasant effluvia (Lee. I., § 2), 

 has beeu found, when reduced to fine powder, to be an excellent admix- 

 ture for night soil, for hquid manure, and for other substances which 

 undergo putrescent decay. It is therefore employed to a considerable 

 extent by the manufacturers of artificial manures. It is also applied 

 with advantage in some cases as a top-dressing to various cropsf — its 

 eflicacy being probably due in part to its power of absorbing from the 

 air, or of retaining in the soil, those gaseous substances which plants re- 

 quire, and in part to the slow decay which it is itself capable of under- 

 going. In moist charcoal powder seeds are said to germinate with 

 great ease and certainty. 



3°. Coal-tor. — Another product of coal, the tar of the gas-works, has 

 recently been recommended as an admixture for peat and similiar com- 

 posts, and it is one of the substances with which Mr. Daniel impreg- 

 nates his saw-dust in the manufacture of his patent manure. It is im- 

 possible to say how much of the good effect derived from the use of 

 such mixtures as that described in the Appendix, No. VIII., is due to 

 the coal-tar they contain, — and as no experiments have hitherto been 

 made from which the true action of coal-tar can be inferred, it may 

 still be considered as a matter of doubt whether it can at all add direct- 

 ly to the fertility of the soil. 



^ 14. Of the theoretical value of different vegetable substances 

 as manures. 



Vegetable manures are known to differ in fertihzing virtue. Thus, 

 1 ton of rape-dust is said to be equal to 16 of sea-weed or to 20 of farm- 

 yard manure.* On what principles do these unlike fertilizing virtues 

 depend ? 



1°. According to Boussingault and other French authorities, the re- 

 lative efficacy of all manures depends upon the proportions of nitrogen 



* At Bristol the price of soot Is 9(i. a bushel, at Gloucester only 6d., yet the former is pre- 

 ferred even at the higher price. It is of better quality, owing, it is said, to the greater length 

 of the chimnies — it may be also to ihe quality of the coal and to the way it is burned. 



t See Mr. Fleming's experiment ipon Swedes (Appendix No. VIII.), in which 50 bunh- 

 e'8 of charcoal powder increased the crop by three cms an acre; 



