224 AGRICULTURAL HEPOKT. [1H 20, 421, 422, 423 



soil. The hills wash very freely, and this circumstance is now complained of 

 by the planters; whereas it might be a real blessing, if, instead of allowing the 

 sand to accumulate, and cover over altogether some of the best lands, ihey would 

 take the trouble of diverting the water a little from its usual channel, slanting to 

 the right and left, which would spreadjt evenl) over a laige suiface. In truth, 

 in locations as favorable as these for" such a purpose, it might lie remunerative for 

 planters to aid nature with a cart or two, during the time when their held hands 

 are almost unoccupied. 



2. CHEMICAL MANURES. 



420. Vegetable Matteu, and "Humus." — Thus far, in speaking of the 

 nourishment ot plants, 1 have alluded only to the fixed mineral ingredients;, 

 wh ch U ey derive from the soil, and to those which, being derived horn the 

 atmosphere, return to it ma gaseous condition when vegetables are burnt; 

 while the vegetable matter, contained in most soils, and usually considered nofc 

 only as a sign, but even as the cause, of fertility, has only been casually men- 

 tioned. As it is indispensable, that we should undeistand the true value and 

 mode <>f action of this portion ol the soil, if we would use manures correctly, 

 1 shall premise what nnty be necessary in this respect, belore speaking ol manures 

 specially. 



4Jl. Experiments have shown conclusively, that the carbon which plants 

 contain, and which forms the basis. a> it weie, if their vegetable substance, is 

 derived lioni the air, and not from the soil. It has been si own, that plants 

 pan grow in soils absolutely void of vegeiable matter, provided only that these 

 toils contain the mineral ii gradients required by the plant, in a salable stale, or 

 at least, m such a condition,, that they shall be accessible to the vegetable or- 

 ganism , i| o57/* 



4Z'.2. The h$er condition, however, we do not often find fulfilled in soils m 

 their natural condition. It has b. en stated above, that only a part of the sum 

 total of nutritive ingredients present in the soil, is usually in an available 

 cond tion, the greater part being "locked up" in the uiK.etouipcsed or partially 

 .decomposed minerals, and but very gradually set at hbeity by the action of the 

 atmosphere. 



'i his very action is due chiefly to the cat Ionic acid contained in air, and will 

 -of course be the more powerful and lapid, the moie cai I onic acid is piesent, 

 How, carbonic acid is continually toinied in the process ol decay of vegetable 

 matter, such as is constantly in progress in soils containing the same ; in such 

 soils, therelore, the nutritive mineral ingiedients ate being made available mora 

 rapidly than would be the case, were no vegetable matter present in them, and 

 weie the decomposing process lelt to be perioiru d by the < ai borne acid of th» 

 air alone. In this respect, vegetable matter must, therelore, be classed among 

 the stimulant manures, as above defined (If 41(5). 



4'Zo. l J i qper 1 1 es cf " liuv.u s." — 'Iheie are, however, other highly important 

 offices in vegetal le economy, performed by this class ot constituents, and more 

 particularly by the (so mew hat indefinite; substance, now familiar]} known aa 

 iiuuius, or vegetable mold. One ol these — its reientiveness oi moisture — has 

 already been mentioned; it serves as a corrective, in ths respect, or light, sandy 

 8oi.s ; while on the other hand, it renders heavy claj soils le.-s compact anU stitt". 

 "Yet there is still another \irtue posse-sed by humus, more lmiortant than 

 either ol the twojust reeiied to; r. is its power oi absoib ng (,n.moma Hem 

 the atmosphere, thus fixing in the soil this important stimulant as vveh as nutritive 



* I have generally, iu ihe text, used the word 'available" in prefeienceto 

 "soluble," bjcau.>e tne former involves no unproved t cory concerning ihe pecu- 

 liar condition ot iho poiLion oi the sod in question ; winch is certainly wot 

 soluble m tlie ordinary acceptation el the lo.in (^|o7bj. 



