82 Mole-draining and the Renovation of Old Pipe Drains. 
that the mole has hit a stone, and these places should be dug 
out and a few 2 in. pipes put in to make the drain good. In 
some clays there are no stones and in others there are a good 
many. At the top end of the field the man on the plough 
winds it up so that it is gradually drawn out of the ground in 
the course of 5 to 6 yards. 
The other engine meanwhile having changed its position to 
the next eye pulls back the mole plough over the surface of the 
ground. The plough is dropped into the next eye, and so the 
work proceeds. The drainers follow behind to put the 2 in. 
pipes into the eyeholes to connect the mole drains to the mains 
and then to fill in. 
If (as in Fig. 4) an extra main has to be put into a hollow 
place this main should be put in after the mole-draining has 
been finished, the mole drains on either side being connected 
to it with pipes. Gores can be made by using a mole drain 
as a main (Fig. 4). 
The distance the mole drains are to be apart is governed 
as a rule by the furrows if these are not too far apart, but 
where there are no furrows, then the drains should be from 
5 yards to 9 yards apart, 7 yards being about the average. The 
depths of the drains are to a great extent governed by the soil. 
On very retentive soil 18 in. to 21 in. is deep enough. On 
rather lighter clay 24 in. to 27 in. deep will be found not 
too much. 18 in. deep is as a rule too near the surface to 
withstand the weight of ploughing engines, timber carriages, 
&c., but often it is advisable to drain at 18 in. so as not to 
disturb the old pipe drains. 
