744 



PRACTICE OF AGRICULTURE. 



Part III. 



of gunpowder, as is done with a cannon ball, only, instead of a spherical ball, to employ one of a conical 

 form [tig. 707.). by which the full effect of the wedge is given in every direction at the lower part of the 

 charge, but particularly downwards 3. And, in the last place, to add to the effect of the whole, to 

 insure a fourth part of the depth of the bore at the bottom {b) to be free from the gunpowder ; so that, 

 when inflamation ensues, a red heat may be communicated to the air in the lower chamber,' whereby 

 it will be expanded to such a degree as to have the power of at least one hundred times the atmospheric 

 pressure, and thereby give this additional momentum to the explosive power of the gunpowder. {Dr. 

 Brewster's Edin. Journ. Oct. 1826. p. 343., and Gard. Mag. vol. ii. p. 467.) 



4527. The Assamese close the mouth of the hole by driving in with a mallet a stout wooden plug some 

 inches in length, through which a touch-hole is bored. Between the powder and the lower part of the 

 plug, an interval of several inches is left. The communication is perfected by means of a tin tube filled 

 with powder, and passing through the centre of the plug. {Monthly Magaxine.) 



Sect. III. Improving Woody Wastes or Wealds. 



4:62B. With surfaces partially covered with bushes and stumps of trees, ferns, &c., the 

 obvious improvement is to grub them up, and subject the land to cultivation according 

 to its nature. 



4529. The growth of large trees is a sign that the soil is naturally fertile. It must also 

 have been enriched by the quantity of leaves which in the course of ages have fallen and 

 rotted upon the surface. Such are the beneficial effects of this process, that after the 

 trees have been cut down, the soil has often been kept under crops of grain, for a number 

 of years without interruption or any addition of manure : but land thus treated ulti- 

 mately becomes so much reduced by great exhaustion, that it will not bear a crop worth 

 the expense of seed and labour. [Comm. to the Board of Agr., vol. ii. p. 257.) It is 

 evident, however, that this deterioration entirely proceeds from the improvident manage- 

 ment previously adopted. In reclaiming such wastes, the branches of the felled trees, 

 are generally collected and burnt ; and the ashes, either in whole or in part, are spread 

 on the ground, by which the fertility of the soil is excited. Indeed, where there is no 

 demand for timber on the spot, nor the means of conveyance to any advantageous 

 market, the whole wood is burnt, and the ashes applied as manure. 



4530. Much coppice land has been grubbed up in various parts of England, and brought into tillage. 

 Sometimes woods are grubbed for pasture merely. In that case the ground should be as little broken as 

 possible, because the surface of the land, owing to the dead wood and leaves rotting time out of mind upon 

 it, is much better than the mould below. It soon gets into good pasture as grass land, without the sowing 

 of any seed. {Comrn. to the Board of Agr. vol. iv. p. 42.) But by far the most eligible mode of converting 

 woodland into arable is merely to cut down the trees, and to leave the land in a state of grass until the 

 roots have decayed, cutting down with the scythe from time to time any young shoots that may arise. 

 The roots in this way, instead of being a cause of anxiety and expense, as they generally are, become a 

 source of improvement; and a grassy surface is prepared for the operation of sod burning. {Marshal's 

 Yorkshire, vol i. p. 316.) 



4531. Natural woods and plantations have been successfully grubbed up in Scotland. In the lower 

 Torwood in Stirlingshire, many acres of natural coppice were cleared ; and the land is now become as 

 valuable as any in the neighbourhood. {Stirlingshire i port, p. 213.) On the banks of the Clyde and the 

 Avon, coppices have been cut down, and the land, after being drained, cultivated, and manured, has been 

 converted into productive orchards. In Perthshire, also, several thousand acres of plantations have been 

 rooted out, the soil, subjected to the plough, converted into good arable land, and profitably employed in 

 tillage. {Perthshire Report, p. 329.) 



4532. For pulling up or rending asunder the roots of large trees, various machines and contrivances have 

 been invented. Clearing away the earth and splitting with wedges constitute the usual mode ; but blasting 

 is also, as in the case of rocks and stones, occasionally resorted to. For this purpose a new instrument, 



called the blasting.screw {fig. 708.), has been 

 O lately applied with considerable success to the 



rending or splitting of large trees and logs of 

 timber. It consists of a screw (a), an auger 

 {b, c), and charging-piece (d). The screw is 

 wrought into an auger-hole, bored in the 

 centre of the timber : here the charge of 

 powder is inserted, and the orifice of tlie hole 

 in the log is then shut up or closed with the 

 screw, when a match or piece of cord, pre- 

 pared with saltpetre, is introduced into a small 

 hole {a), left in the screw for this purpose, by 

 which the powder is ignited. The application 

 of this screw to the purposes of blasting is not 

 very obviously necessary ; because, from what 

 we have seen (4525.), it would appear that the 

 auger-hole, being charged with powder and 

 sand, would answer every purpose. One great 

 objection to the process of blasting applied to 

 the rending of timber is, the irregular and 

 uncertain direction of the fracture, by which great waste is sometimes occasioned. It may, however, be 

 necessary to resort to this raode of breaking up large trees, when cut down and left in inaccessible situa- 

 tions, where a great force of mentind implements cannot easily be procured or applied; and certainly it 

 is one of the most effectual modes of tearing their stools or roots in pieces. {Sup. Encyc. Brit. art. 

 Blasting.) 



4533. Land covered ivith furze, broom, ayid other shrubs, is generally well adapted for 

 cultivation. The furze, or whin (C7lex europaea), will grow in a dense clay soil; and 

 where found in a thriving state, every species of grain, roots, and grasses, may be cul- 

 tivated with advantage. The broom, on the other hand, prefers a dry, gravelly, or sandy 

 soil, such as is adapted for the culture of turnips. A large proportion of the arable land, 

 in the richest districts of England and Scotland, was originally covered by these two 

 plants ; and vast tracts still remain in that state, which might be profitably brought 



