14 On the Theory of Manures. 



capable of suiDplying these wants, a proper allowance being 

 given for the portion washed away from soils ; but there is 

 still more to be done before correct data can be furnished. 

 It is evident that saline substances are wanted for other pur- 

 poses besides forming constituents. The quantity found in 

 the young branches and leaves of trees is great, in comparison 

 with what is found in the trunks ; the quantity found in trees is 

 comparatively much less than that found in annual crops ; and 

 the quantity in these is also much greater in the young suc- 

 culent growing portions, than in the ripened tissue. These 

 facts all show that a liberal comparative supply is needed for the 

 young growth, teaching the necessity of applying these and 

 ammonia early to young seedling plants ; and also teaching 

 that these substances are necessary to assist in the transform- 

 ations going on where life is most active, to fit the circulating 

 juice for the purposes of the organs of assimilation, and that, 

 where extra vigour is wished, a liberal supply of these sub- 

 stances must be furnished. The effects of this supply may be 

 observed, wherever the burnt ashes of young unsaleable trees, 

 or the clippings of hedges, have been applied to vegetable crops ; 

 I have seen the effect often such as to defeat the end in- 

 tended, by an over-luxuriance of stem and leaves to root crops. 

 I have seen very powerful effects, this season, follow the 

 mixing of composts for pots with ashes of small branches burned 

 and bruised to small pieces. At Roselle, the geranium leaves 

 were like those of tussilago for size, of a deep green, and the 

 vigour of growth so great as to injure the flowering. The ex- 

 cellent preparation of branches, straw, cabbage leaves, and 

 other haulm, set fire to and kept at a smothered heat till charred, 

 as pointed out in the November Number of the Magazine by 

 Mr. Barnes of Bicton Gardens, will be very powerful. The 

 greater the variety in the small branches, leaves, roots, &c., 

 charred, the more likely are the ashes to answer general pur- 

 poses. They contain the great variety of saline substances 

 found in the most vital portions of the plants burned, which 

 accounts for much of their action. Leaves will not grow, nor 

 vital activity become active, till all the essentials of vital che- 

 mistry are provided ; though the compost they are furnished 

 with contains sufficient of carbon and ammonia. The ashes, 

 also, act mechanically, as keeping the soil open by their elasti- 

 city, which is one of the principal benefits of farm-yard ma- 

 nure. They also absorb oxygen and ammonia from the soil 

 and air; or, if the oxygen is from water, perhaps form am- 

 monia from the nascent hydrogen, and absorb it, as most 

 oxidising substances likely do. These absorbed gases will be 

 given off to the roots. Roots are always exceedingly fond of 

 running round such porous substances, and are found to increase 



