508 



SCIENCE OF AGRICULTURE. 



Part II. 



every case. For all these purposes a deep open trench is requisite ; and, that this may 

 not be diminished in width and depth in the course of the operation, it must never 

 be increased in length. If allowed to become crooked by irregular advances in the 

 digging, it is thus increased in length, and necessarily diminished in capacity, unless, 

 indeed, the dug ground is allowed to assume an uneven surface, which is an equally 

 great fault. Digging for pulverisation, and mixing in manures, is best performed in dry 

 weather ; but for the purposes of aeration, a degree of moisture and tenacity in the soil is 

 more favourable for laying it up in lumps or entire pieces. The usual length of the 

 blade of the spade is from ten inches to a foot ; but as it is always inserted somewhat 

 obliquely, the depth of pulverisation attained by simple digging seldom exceeds nine 

 inches, and in breaking up firm grounds it is seldom so much. 



3124. Shovelling is merely the lifting part of digging, and the shovel, being broader 

 than the spade, is used to lift up fragments separated by that implement or the pick. 



3125. Marking with the line is an operation preparatory to some others^ and consists in 

 stretching and fixing the line or cord along the surface, by means of its attached pins or 

 stakes, in the direction or position desired, and cutting a slight continuous notch, mark, 

 or ^it,, in the ground, along its edge, with the spade. 



3126. Trenching h a mode of pulverising and mixing the soil, Or'of pulverising and 

 changing its surface,. to any greater depth. than can be done by the spade alone. For 

 trjQ^ching with a view to^ pulverising and clianging the surftice, a tifench is formed like 

 the furrow in digging, but twice or tlu"ee times as wide and deep ; the pl6t'6r 'piece to be 

 trenched is ^ext marked off with the line into parallel strips of this width ; and, begin- 

 ning at one of tliese, the operator digs or picks the surface stratum, and throws it irt the 

 bottom of the trench. Having completed with the shovel the removal of ^e surface 

 stratum, a seccMid, and a fcliird, or fourth, according to the depth of the soil and other 

 cifpuQfistanceB, ^re remotedin the same way ; and thus, when the operation is completed, 

 the position of the different strata is exactly the feverte of what it was before. In 

 treixphing with a view to mixture and pulverisation ( fig. 512.)^ all that is necessary is 

 to>open, at one corner of the plot, a trench or excavation of the desired depth, three or 

 fcjur feet laroad, and six or eight feet long. Then proceed to fill this excavation from 

 one end by working out a similar one. In this way proceed across the piece to be 

 trenched, and then return, and so on in parallel courses to the end of the'plot, observing 

 thpi,t,^xh^ f^^ or position pf the moy^d soil ini.tlte,;trinch must always bli that of" a slope, 

 inr.order that- whatever is thrown thefe thaybe rtflxed, ani^not deposited in regular4!iyers 

 aS^hn the other'case. To effect this most completely, the operator should always stand 

 in the bottom of the trench, and first picking down and mixing the materials, from the 

 solid side (aj, should next take them up with a, ghoyei, or thro>y ^hep[i q;^ th^e slope or 

 ^f'l?^M&'^^o^A& keeping a distinct spac^ of W^^gr^tl^^^^ Jf^<|>^t^?pn 



/lofi? 9oH M ' 



For want of Attention to this, in trenching new soils for plantations, or other '^^OsesV 

 it intay be truly said tiiat half the benefit derivable from the operation is lost. In general 

 in trenching, those points which were mentioned under digging, such as turning, breiak- 

 ing, dunging, &c. required tO be attended to, and sometimes an additional object ^thatoi 

 producing a level from an irregular surface is desired. In this case double care if 

 rei^uisite, to avoid forming subterraneous basins or hollows, which might retain water ir 

 the substratum, at the bottom of the moved soil, and also to mix inferior with better soil, 

 &c. where it becomes requisite to penetrate into depositions of inferior earthy matters. 

 The removal of large stones, rocks, or roots, from ground trenched for the first time, will 

 be treated of under Improvement of Lands lying waste. (Book III. Chap. IV.) 

 q;3127. Ridging is a mode of finishing the surface, applicable either to dug or trenched 

 gigounds, which, when so finished, are called ridge-dug or ridge-trenched.^ Instead of 

 being formed with anieven surface, ridged grounds iai finished in ridges or close ranges 

 of parallel elevations, whose sections are nearly equilateral triangles. Hence, supposing 

 the triangles to touch at their bases, two thirds more surface will be exposed to the 

 influence of the atmosphere gmd the weather, than in even 'surfaces. 



3128. Forking. The fork is composed of two or three separate, parallel, and uniform 

 wedges, joined so SiS to fprm one general blade, which is acted on like the spade, by means 

 of a shoulder or hilt for *^hrusting it into the matters to be forked, and a lever or handle 



