132 Horticultural Chemistry. 



coated with fibres : digging two spades deep produced no mate- 

 rial advantage, the gardener applying as usual manure to the 

 surface ; but, by trenching as before, and turning in a small 

 quantity of manure at the bottom, the roots always spindle 

 well, grow clean, and have few lateral fibres. For late crops 

 of peas, which mildew chiefly from a deficiency of moisture to 

 the root, it is an object to keep their radiculae near the surface 

 for the sake of the light depositions of moisture incident 

 to their season of growth ; hence it will always be found of 

 benefit to cover the earth over the rows with a little well 

 rotted dung, and to point it lightly in. Plants are very much 

 benefited by having oxygen applied to their roots, being 

 found to consume more than their own volume of that gas in 

 twenty-four hours ; and, when applied by Mr. Hill to the roots 

 of melons, hyacinths, &c, the first were found to be improved 

 in flavour, the second in beauty, and all in vigour. [Hort. Trans. 

 vol. i. p. 233. and Gard.Mag. vol.i. p. 232.) Everything, there- 

 fore, that promotes the presentation of oxygen to the roots of 

 plants must be beneficial : hence we find that frequently stirring 

 the ground about them promotes their growth ; for, in propor- 

 tion as the soil is loose, can the atmosphere easily penetrate it. 

 Moist earth rapidly absorbs oxygen from the atmosphere, as 

 Humboldt has demonstrated, but dry soil does not : this affords 

 another reason for frequently stirring the earth about plants 

 during the droughts of summer ; for well pulverised soils ad- 

 mit the evening dews, &c, more freely than consolidated ones, 

 and consequently dews will be deposited more within their 

 texture, and moisture is more firmly retained in such pul- 

 verised soils, inasmuch as that they are not so much heated by 

 the sun's rays, being more pervaded by the air, which, like all 

 gases, is one of the worst conductors of heat. The decom- 

 posing parts of animals and vegetables contained in a soil are 

 also highly absorbent of moisture ; hence, the more freely the 

 air is exposed to them, the more effectually will they be 

 enabled to exert this power. By being freely exposed to the 

 influence of the air, such substances are more rapidly de- 

 composed, which leads to a consideration of the practice of 

 exposing soils as much as possible to the action of the at- 

 mosphere by ridging, &c. When a soil is tenacious, or 

 abounding in stubborn vegetable matters, as in heath lands, it 

 cannot be too completely exposed to the action of the air ; but, 

 to light soils, which are in general deficient in organic decom- 

 posing matters, Chemistry would say that ridging is accom- 

 panied by evils more injurious than can be compensated by 

 the benefits obtained: for such light soils are easily pulverised 



