
TRANSACTIONS OF THE SECTIONS. 123 
increasing the after-resistance. The different forms of ploughs, many of which vio- 
late this principle, illustrate a remark previously made, that too little attention has 
been bestowed on the reasons for agricultural practice. The peculiarity of running 
the share of the plough several inches beyond the coulter evidently occasions a loss 
of power, because that projecting portion is pressed on every side by the undivided 
soil. It is true that an advantage is claimed on the ground of the plough working 
more steadily and not tilting up; but that advantage might be secured without so 
unnecessary a waste of power. Again, the varying degree of polish on different 
forms of ploughshares shows a variation in the resistance accompanying those 
forms, but which has by no means been subjected to careful investigation. In the 
case of mould-boards something has been done; but I am not aware that even this 
subject has been treated in a scientific manner, although eminently suggestive of 
such treatment. 
The Upton draining tool, it will be perceived, is trough-shaped, or consisting of 
two sides united at an angle of 60°, so that its section would be like the letter V. 
The spit of earth taken out by such a tool is evidently an equilateral prism, and such 
a prism is one of those regular solids which will fill up space, so that the length of 
a drain may be marked out into successive prismatic spits of earth fitting against 
one another. This consideration suggested the peculiar use of the tool, which I will 
presently describe. : 
Previous draining implements have consisted of two kinds, according as the blade 
is plain or curved, and with all of them it has been considered necessary to excavate 
the upper part of the drain 10 or 12 inches wide, when a narrower tool is substi- 
tuted for the requisite depth beneath. The width actually necessary at the bottom 
of a drain for the insertion of draining pipes does not exceed 3 inches, so that the 
greater width at the top, if it can be avoided, is only a waste of time and labour. 
It will be found that in the practical use of both the flat and curved tools three 
thrusts are made by the workman for every spit of earth withdrawn. In a clay soil, 
the adhesion of the spit of earth to the sides of the drain is too strong to allow of 
its being forced out without the assistance of lateral thrusts to detach it from the 
sides. The workman therefore uses his tool as is represented in plan in fig. 1, where 
the black lines show the marks on the surface which are made by the insertion of 
the tool, and the Nos. 1, 2, 3 indicate the spits of earth thus successively removed. 
What is here done by ¢hree thrusts the instrument now described effects by one. 
Fig. 1. 

The manner in which the instrument is used is represented in plan by fig. 2. Here, 
as in the preceding figure, the black lines represent the marks made by the insertion 
_ of the tool; and it will be seen that the right and left sides of the tool are placed 
