GENERAL PRACTICE. SOILS AND SUBSOILS. 33 



Sandy soil over sand and gravel, loam over rock, calcareous soil on chalk, silt on 

 coarser washings, may or may not require draining, for it depends entirely on the inter- 

 vening strata. Beneath a sandy or gravelly subsoil an impervious bed of clay may hold 

 up the water so that it may stand within 3 feet of the surface, and although the land 

 may appear dry enough, fruit trees do not thrive. Horsetail (Equisetum) and thistles, 

 however, grow freely a clear indication that water does lodge at a distance from the 

 surface that is prejudicial to the trees (see Fig. 6). Nothing short of actual testing 

 can determine the necessity or otherwise of draining. Experienced cultivators tell very 

 accurately by the indications of plants growing naturally which soils require draining, 

 but a far greater number of persons need definite evidence. Holes dug 4 feet deep and 

 about 22 yards apart will indicate the condition of the subsoil in respect of water. If 

 between October and March inclusive water accumulates and remains longer than a 

 fortnight in excavations covered to exclude rain, ample proof is afforded that water 

 lodges longer than is good for vegetation, and those parts for it may not be the whoK 

 of the ground require under-draining. A means of ascertaining the condition of the 

 subsoil as regards the need or otherwise of draining is shown in the figure ; a is a pit 

 4 feet deep ; #, 1 foot depth of worked soil ; c, hard pan or sole soil ; d, undisturbed 

 sandy loam ; e, sand saturated with water ; /, aluminous hard soil impregnated with iron; 

 g, clay ; A, level of stagnant water ; ?, proposed drain as represented by the dotted line. 



Strong loam resting on clay passes much surplus water off its surface. When it runs 

 off to lower impervious ground it forms sheets of water, causing a rank growth of sub- 

 aquatic grasses or sedges. Such land is liable to bake and crack in summer. Fissures 

 formed in that way admit air and rain, and earthworms perforate the clay, the water that 

 would otherwise stand and form a morass gradually passing down to the underlying 

 strata levels. A section showing the formation of soil of this description is represented in 

 the illustration (Fig. 7). Eeferences \j, chalk ; k, calcareous matter and loam in- 

 terspersed with flints ; J, conglomerate 'loam with shingle and mother stones ; m, stiff 

 clay mingled with pebbles and stones ; n, strong loam inclining to clay ; 0, ameliorated 

 soil, the result of plough husbandry ; p, test hole, showing water standing in it ; q, 

 proposed depth of drains indicated by the dotted line, r. The more or less vertical lines 

 represent the channels of earthworms. 



Soils in the conditions indicated require drainage, as well as others that may be 

 readily ascertained by the test holes. Having settled the point that under-draining is 

 required to render soil suitable for an orchard or fruit garden, we have next to consider 



VOL. I. V 



