TRENCHING, ANOTHER MODE. 516 TRENCHING, LOUDON ON- 



is oxygen ; about a third of alumina, or 

 pure clay, by measure, and a fifth of the 

 atmosphere by weight, are oxygen ; and no 

 plant or animal can exist without oxygen 

 entering largely into its constitution. 



Trenching, Another Mode of. 



In the description of trenching given 

 above, the width of the trenches has been 

 stated at I foot. In practice it will be 

 found convenient to make the width 18 

 inches or 2 feet, and in some cases, accord- 

 ing to the nature of the soil and subsoil, it 

 will be necessary to extend the width con- 

 siderably, putting it at from 3 to 5 or even 

 6 feet, especially when the ground is uneven, 

 and depressions and hollows have to be 

 rilled up. When the space to be trenched 

 is very long, in order to save the time and 

 trouble involved in wheeling the soil taken 

 ut of the trenches A and. B to the rear of 

 the ground, it is better to divide the ground 

 longitudinally into two equal parts, as 

 shown in the accompanying diagram. The 

 topmost spit from the trench A can then be 

 placed at D, the topmost spit from B at E, 

 and the second spit from A at F, as shown 

 by the dotted lines and arrow heads. On 

 arriving at the other end of the first portion 

 of the ground, the topmost spit from L will 

 go to G, the second spit from L to H, and 

 the topmost spit from K to H. The second 

 portion will then be trenched backwards ; 

 and, to complete the operation, the second 

 spit of soil from A deposited temporarily at 

 F will form the second layer in M, and the 

 topmost spits from A and B, at D and E, 

 will be transferred to M and N, and form 

 the topmost spits of these trenches. 



It must not be supposed from what has 

 been said about trenching that it is abso- 

 lutely necessary at all times to trench 

 ground to the depth of 2 feet, or, in other 

 words, three spits deep. In ordinary cases 

 it is sufficient to carry the trenching to two 

 spks in depth, or 16 inches ; but in this 



the modus 'operandi is precisely the same, 

 although the removal of the soil in the top- 

 most spit of the first trench, either to the 

 rear of the ground, or, as just described, to 

 the topmost end of the second portion to 

 be trenched, is all that is required. Nor 

 is it an invariable rule that the original 

 position of the three spits or strata is to be 

 retained, for sometimes it is found necessary 

 to reverse it, and to deposit the surface soil 



DIAGRAM SHOWING MODE OF TRENCHING WITH- 

 OUT WHEELING SOIL TO REAR OF GROUND TO 

 BE TRENCHED. 



at the bottom of the trench, while that 

 which is below it is brought to the top. 



Trenching, London on. 



" Trenching," says Loudon, " is a mode 

 of pulverising and mixing the soil, or of 

 pulverising and changing its surface, to a 

 greater depth than can be done by the 

 spade alone " that is to say, by thrusting 

 the spade as far as possible into the ground 

 and turning over the earth that can be 

 lifted at one time by it, for, after all, 

 trenching to any depth is performed by 



