76 
Transactions of the Boyal Society of South Africa, 
increase the yield of No. V. enormously by the insertion of a siphon. 
After the removal of the siphon the potential level recovered its normal 
position only after the lapse of days. 
During the next two years I contented myself with occasional visits to 
the farm, during which I obtained a few short records of a day or two, 
which, with general observations, were sufficient to show that the fluctua- 
tions were apparently going on as before. I verified most of my earlier 
observations and examined the surface geology of the farm. The 
geological examination of the farm brought to light various facts which, 
r V 
Arrangement of N'v in 1908 P 
Fig. 5. 
though interesting in other connections, did not seem to have any imme- 
diate bearing on the behaviour of the wells. The only observation that 
seemed to be worth mentioning in this connection was that the course of 
a dolerite dyke, prominently exposed on the mountains on the north 
boundary of the farm but hidden under the thick soil in the low ground, 
ran in a direction from a little east of north to a little west of south, in 
such a position as to indicate that its hidden portion probably passes 
between the two groups of boreholes. 
