30 APPENDIX. 



low soil with a stiff retentive subsoil. Whatever 

 pains may be taken with the tillage of the former, 

 however expensive the dressing which may be used 

 in its cultivation, the nature of the subsoil will 

 always counteract its beneficial effects. Many per- 

 sons have endeavored, by trenching, to obviate this 

 difficulty, but where the subsoil is of that sterile 

 nature, and requires exposure to the atmosphere for 

 so long a period to make it produce, few farmers 

 have been found bold enough to repeat the experi- 

 ment. Mr. Smith's ingenious invention by breaking 

 the subsoil without bringing it to the surface, renders 

 it pervious both to air and water. The same chem- 

 ical changes, which take place in a fallow, owing to 

 its exposure to the action of wind and rain, are thus 

 brought into operation in the subsoil ; whilst the 

 upper is in the ordinary course of cropping, and 

 when, after a few years by a greater depth of plough- 

 ing, the subsoil is mixed with the upper, it is found 

 to be so completely changed in its nature as to be 

 capable of producing every species of grain. The 

 experiment has been tried for twelve years, and with 

 uniform success." 



THE RACK HEATH PLOUGH. 



"The plate introduces to public "notice, what in 

 my humble estimation, promises to be one of the 

 most useful inventions ever exhibited to the farmer, 

 whether of sharp clays, or stiff gravels; and when I 

 say this, I do not mean in the slightest degree to 

 disparage the subsoil plough of Mr. Smith. I would 

 rather include his implement in my encomium; be- 

 cause the objects of each being the same, viz: loos- 

 ening not turning up the subsoil, I do not see why 

 each invention should not have occured simultane- 

 ously, without either of the authors being chargeable 



