96 



CASSELL'S POPULAR GAEDENING. 



To use this table, look for the lowest temperature 

 in the left-hand column, and at the top for the 

 highest temperature at which the house is required 

 to he kept, and where the two columns intersect wiU 

 be found the number of feet of 4-inch piping required 

 to heat 1,000 cubic feet of air per minute. Ex- 

 ample : — A house containing 10,000 cubic feet of air, 

 which it is required to keep at 70°, taking the ex- 

 ternal air at 32°, will require 1,640 feet of 4-inch 

 piping to heat it. 



GEOUND OPERATIONS. 



TBENCHING. 



THIS is one of the most important preliminary 

 operations within the whole range of horti- 

 cultural practice. If the maxim " Dig deep to find 

 the gold " be true, and it is, how much more gold may 

 be — is, in fact — found by trenching for it ? No one 

 can say how much, though without doubt it may be 

 leckoned by millions and tens of millions sterling. 

 For the statement that " mass is might " is as true 

 of the earth as of mechanical force. The productive 

 force of the earth may, in fact,' be measured by its 

 mass plus its quality. Now the very germ and 

 substance of all good trenching is to add to the bulk 

 of the cultivated earth, and improve its quality, by 

 converting a certain amount of hard subsoil into 

 porous surface soil. 



Mere Inversion of the Soil not Good 

 Trenching. — Mistakes about trenching have pre- 

 vailed to such an extent as almost to upset its true 

 theory, ■ and arrest its practice. The simple turn- 

 ing of the earth upside down may be good or bad 

 according to circumstances, although it has been 

 mostly and almost everywhere had. For it must be 

 a very wretched surface soil, indeed, that would not 

 prove something better than that found a yard lower 

 down. Effeteness or sterility alone is not likely to 

 contribute much productive force to surface tilths, 

 and the lower-l}'ing layers are mostly the worst 

 soils or subsoils. Even the worms, the last dis- 

 covered, though doubtless the first great creators, 

 transposers, and transformers of surface mould, 

 can make little or nothing of the harsh, sterile sub- 

 soil, but confine their operations chiefly to the sur- 

 face, and the strata in semi-transition in direct 

 proximity to it. 



, Nature, the great teacher of the cultivator, never 

 attempts to improve her surface tUths by inversion. 

 Under the economy of nature, surface soils are 

 grown slowly but surely from the surface down- 

 wards, rather than from their base upwards. The 

 gradual decomposition of the roots and tops of 



plants, the disintegrating and enriching forces of the- 

 atmosphere, the deposits left by water and the heat of ' 

 the sun, all work from the surface downwards ; even ', 

 the worms always spread their rich excretions on 

 the surface, thus being the fii-st to teach the great, 

 modem art of top-dressing land. Subsoils are 

 gradually transformed into soils in a similar order ; 

 the soluble substances held in suspense by the 

 surface mould — and these are ever the most valu- 

 able — are carried down by the rains into the subsoil, 

 and gradually though surely convert these into'sur- 

 face mould. 



It is most important to bear all this in mind in, 

 order to gain all the solid advantages, and run as few- 

 risks as possible of iajury to the surface by trenching. • 

 The first example of trenching ever observed by 

 the author, proved such.a failure that the boU ha,d to- 

 be un'trfm7i'id,' io' coin a word, before it could be of 

 any use. It was simply inverted and turned over to- 

 a depth of four feet, the last two being sheer clay. 

 During the winter and early spring the clay was^ 

 as plastic as bird-hme. As the drought and heat 

 of summer came it hardened into something akin 

 to brickbats. Planted with broccoli, by means of a 

 crow-bar, these simply refused to grow, or made- 

 such little progress as to be useless. The trenching, 

 in a word, had ruined the soil. So the following 

 winter it was retm-ned, and carefully mixed during 

 the process ; and the whole mass, by the addition of 

 enormous masses of stable manm-e, in a rough state, 

 was converted into fairly productive growing soil. 

 However, the -vital mistake of mixing an excess of 

 clay with the surface staple made the whole difficult 

 to work, and unsuitable for garden purposes for 

 years. 



Tentative Deepening of Soils the only 

 Safe and Profitable Trenching. — ^As we have 

 already seen, trenching proceeds in an opposite cora-se 

 to nature in the deepening of soils. That suggests 

 the necessity of the utmost caution, and hence the 

 importance of proceeding a little at a time. The 

 fundamental error in most trenchings may be said to 

 lie in looking upon them as something done once for 

 all, and not to be repeated for many years; and 

 hence the temptation to trench too deeply. Of 

 course it is often useful to practise trenching in this 

 sense ; in the planting of fruit-trees and bushes, 

 for instance ; as fortunately for such purposes it is 

 not needful to trench so deeply as for the cultivation 

 of less durable crops of vegetables and flowers. As 

 little as eighteen inches or two feet is sufficiently 

 deep for most of the former, and thus a fair soil or 

 subsoil may usually he seciu-ed without serious dan- 

 ger of converting fruitful fields into barren gardens 

 or orchards thi-ough heavy deposits of barren earths 



