188 THE BOOK OF THE LANDED ESTATE. 



of the trees would disturb the pipes and make the drains of no avail, so 

 that a system of open drainage must be applied. I have found drainage 

 of land for the growth of trees of great benefit in opening out subsoils 

 where there was no apparent presence of water, but where there was a 

 hard band of soil through which the roots could not penetrate, and water 

 could not get through it from above. By having this kind of subsoil 

 opened out by means of open cuts made of sufficient depth, I have found 

 that the action of the air upon the subsoil, and water flowing over the 

 hard band into the drains, was the means of gradually loosening it, and 

 carrying away ingredients in it which were hurtful to vegetable life. I 

 am of opinion that, if drainage had been applied to arboriculture fifty 

 years ago, we should not now find so many of our old plantations in an 

 unhealthy state. 



The following is the mode in which I have usually drained plantation- 

 ground. Fig. 69 will give an idea of the form of drain referred to. 



The main drains I have made thirty-six inches wide at top, as from g 

 to g, sloping them on each side to a depth of thirty-six inches, as from 

 g on each side to the corners of the drain opposite e, leaving the bottom 

 twelve inches broad. The letters c d indicate the line of the small 

 drains running into the main drain &. The regular depth of the small 

 drains being thirty inches at a c, they should receive a greater descent 

 into the main drain, as shown from c to d, making the depth from g to 

 d fully six inches deeper than at a c. 



The small drains I have made thirty inches broad at top, thirty inches 

 deep, and nine inches broad at bottom. This has been done where the 

 subsoil was stiff and inclined to clay ; on lighter soil less dimensions 

 would answer the purpose. 



The distance apart of drains, of course, depends upon the nature of 

 the soil. On stiff soils I have kept them at seven to nine yards apart, 

 and on light soils as far as fourteen yards apart. 



The soil thrown from the drains should be spread back over the sur- 

 face of the ground to prevent it falling in again: 



The cost of such drains varies according to the character of the soil 



