Tidal Phenomena at Inland Boreholes near Cradock. 
79 
frame of the lid. The hole was so placed and of such a size as to ensure 
that the movements of the cord could never allow of any friction of the 
wood on the cord. 
Mr. Oottell constructed the instrument, and as he was now stationed 
at Cradock he easily found opportunities of visiting the farm, setting up 
the instrument, and observing its behaviour. 
As was to be expected, this second instrument did not work so 
smoothly as the simpler one of 1905. The increased friction due to 
the introduction of the pulleys partly accounted for this, and the weights 
on the lever and float required careful adjustment and balancing. The 
most advantageous balance of weights to use was found only after several 
unsuccessful trials. Mr. Cottell set up the instrument in the beginning of 
February, 1908, when I was also able to visit the farm for a day or two. 
The month of February was spent in attempts to reduce the friction and 
improve the working of the instrument. Mr. Cottell meanwhile sent me 
one by one such records as he obtained, together with his remarks on the 
action of the machine and his suggestions for mechanical improvement. 
By the beginning of March he reported to me that fairly satisfactory work 
could be expected. 
From the beginning of March to the middle of June weekly record 
sheets were regularly obtained from the level recorder and from a baro- 
graph which I left on the farm. During all this period No. V. borehole 
was flowing uninterruptedly through the large tank into the dam, while 
the other boreholes on the farm were kept closed. Messrs. Eayner and 
Eoberts assured me that during the four months they took the greatest 
care to ensure absolute uniformity of conditions as far as the human 
control of the boreholes was concerned. In the superior intelligence and 
trustworthiness of these gentlemen I have every reason to feel confidence. 
The records obtained, moreover, yield no evidence of any disturbance 
caused by other than natural causes. 
Mr. Cottell undertook for me the general supervision of the instru- 
ment during the months February to June, paying frequent visits to 
the farm, and in his absence Mr. Eex Eoberts undertook the weekly 
winding of the clocks and the weekly renewal of the record sheets. 
Mr. Cottell meanwhile posted weekly reports to me of the progress 
of the machine. 
Mr. Eoberts kept a careful record of the exact times at which each 
weekly record started and ended, and this, together with the lengths of 
the records afterwards measured by me, gave a means of estimating the 
average clock rates for each week. 
The time as measured on Mr. Eoberts's watch was compared with 
official railway time whenever any one on the farm made the journey 
to Mortimer Station or to Cradock. This communication with the railway 
