Book III. ALTERATION OF THE PARTS OF THE SOIL. 321 



benefited by aeration, this benefit alone the effectual eradication of weeds is suf> 

 ficicnt to justify the use of fallows on such soils. 



2127. Many of the objections to fallows have arisen in consequence of the parties not 

 previously agreeing as to what a summer fallow is. In England generally, or at least 

 formerly, a fallow was a portion of land, left a year without culture or cropping, unless 

 being once or twice ploughed can be denominated the former, and an abundant growth 

 of coarse grasses and weeds can constitute the latter. The jacheres of the French are 

 the same thing. In Scotland and the best cultivated districts a summer fallow is a por- 

 tion of land which is begun to be cultivated after the crop is removed in autumn, and is 

 frequently, as need requires, ploughed, harrowed, and otherwise comminuted, and freed 

 from stones, weeds, inequalities, &c., till the autumnal seed-time of the following year: it is 

 thus for twelve months in a state of constant tillage and movement. The result is that the 

 land is thoroughly freed from roots of weeds ; from many seeds of weeds, which are thus 

 made to germinate, and are then destroyed; and from many eggs of insects which are 

 thus hatched, but being without plants to nourish them in their larva state, speedily die. 

 The land is also thoroughly pulverised, and the top, bottom, and middle, mixed together ; 

 stones are picked out, inequalities unfavorable to surface drainage removed or lessened, 

 and various other useful objects attained. Such a fallow can no more be compared with 

 what usually passes under that name, than the plough of Virgil (112.) with that of 

 Small. 



2128. That fallows of the common kind are much more universal than is necessary, 

 there can be little doubt ; but there can be as little doubt that fallows such as we have 

 described, are much less frequent than they should be ; and that wherever they are 

 practised, the agriculturist's produce and profits will be found far superior to where they 

 are omitted ; turnip soils are of course to be excepted, because the preparation for that 

 crop on light soils effects the same purpose in eight months, that the other does in twelve. 



2129. T/ie otigin of fallows is commonly traced to the idea, that land naturally requires rest as well as 

 animals : but a want of hands first, and afterwards a want of manure, is a much more likely cause. Men 

 must very early have observed, from what took place in the spots they cultivated as gardens, that pul- 

 verisation and manure would ensure perpetual crops on the same soil ; but they must at the same time 

 have felt, that they had neither the requisite laborers to bestow the cultivation, nor cattle to produce the 

 manure. Hence they would find it easier to break up one piece of fresh ground after another, and after 

 they had gone a round in this way, as extensive as their limits or other circumstances permitted, they would 

 return to where they began. As their limits became circumscribed by the increase of population, or 

 other causes, they would return the oftener, till at last, when property became more rigidly defined, and 

 more valuable, they would return at short intervals regularly. Then it was that the necessity and ad- 

 vantage of working fallows would be felt, and the practice become systematised as at the present day, 

 and from the earliest records in civilized countries. The practice of fallowing in Italy, during the time 

 of the Romans (128.) differed in nothing from that of the same country, and throughout the rest of 

 Europe at the present day : and if we trace field culture among savage and semibarbarous nations, and 

 gradually through such as are more wealthy and refined, we shall find the fallow in all its gradations, 

 from breaking up at random, to the septennial operations of the best British farmers. 



SuBSECT. 4. Alteration of the constituent Parts of Soils. 



2130. Tlie constituent parts of soils may be altered by the addition or subtraction of in- 

 gredients in which they are deficient, or superabound, and by the chemical changes of 

 some constituent part or parts by the action of fire. 



2131. In ascertaining the composition of faulty soils with a view to their improvement 

 by adding to their constituent parts, any particular ingredient which is the cause of their 

 unproductiveness should be particularly attended to ; if possible, they should be com- 

 pared with fertile soils in the same neighborhood, and in similar situations, as the dif- 

 ference of the composition may, in many cases, indicate the most proper methods of im- 

 provement. If, on washing a sterile soil, it is found to contain the salts of iron, or any 

 acid matter, it may be ameliorated by the application of quick lime. A soil of good ap- 

 parent texture, containing sulphate of iron, will be sterile ; but the obvious remedy is a 

 top-dressing with lime, which converts the sulphate into manure. If there be an excess 

 of calcareous matter in the soil, it may be improved by the application of sand or clay. 

 Soils too abundant in sand are benefited by tlie use of clay, or marl, or vegetable matter. 

 Light sands are often benefited by a dressing of peat, and peats by a dressing of sand ; 

 though the former is in its nature but a temporary improvement. When peats are acid, 

 or contain ferruginous salts, calcareous matter is absolutely necessary in bringing them 

 into cultivation. The best natural soils are those of which the materials have been de- 

 rived from different strata, which have been minutely divided by air and water, and are 

 intimately blended together ; and in improving soils artificially, the cultivator cannot do 

 better than imitate the processes of nature. The materials necessary for the purpose are 

 seldom far distant ; coarse sand is often found immediately on chalk, and beds of sand 

 and gravel are common below clay. The labor of improving the texture or constitution 

 of the soil is repaid by a great permanent advantage, less manure is required, and its 

 fertility insured ; and capital laid out in this way secures for ever the productiveness, and 

 consequently the value of the land. 



2132. The removal of superabundant ingredients in soils may sometimes be one of the 



