Tidal Phenomena at Inland Boreholes near Cradock. 83 
The daily record sheets of Tarka Bridge were first exarained and the 
ourved ordinates of 9-inch radius inserted at the beginning and end of 
each record. Then the straight lengths of records were measured and the 
average clock rates for each day determined. The following list gives 
the time at which each record was put on and taken off, together with 
the length of record afterwards measured, and the deduced clock rate. 
List of June, 1905, Records at Tarka Bridge. 
Put on at— 
Taken off at— 
Length as 
Measured. 
Clock Rate Calculated. 
9.30 
i.m., June 4 
8.20 { 
i.m., June 5 
6 
33-81 cm. 
1.48 cm. per hour 
8.22 
8.0 
33-50 ,, 
1-42 
8.2 
8.0 
7 
35-18 ,, 
1-47 
8.2 
7 
8.0 
8 
35.28 ,, 
1-47 
8.2 
8 
8.0 
9 
35.18 „ 
1-47 
8.2 
9 
8.0 
10 
35-21 „ 
1-47 
8.2 
10 
9.29 
11 
35-10 ,, 
1-44 
9.30 
11 
8.0 
12 
34-41 ,, 
1-53 
8.0 
12 
8.0 
13 
34-53 ,, 
1-44 
8.0 
13 
8.15 
14 
35-05 
1-45 
8.15 
14 
8.15 
15 
34-98 ,, 
1-46 
8.15 
15 
8.15 
16 
35-28 ,, 
1-47 
8.15 
16 
8.15 
17 
34-90 „ 
1-45 
8.15 
17 
8.30 
18 
35-06 „ 
1-45 
The total length of record for the fortnight is 4*54 meters, and the 
average clock rate for the fortnight is 1-46 centimeters per hour. 
The high-water and low-water points on each day record were then 
determined as carefully as possible, and the times at which these points 
were attained estimated by means of the various time scales indicated by 
the above clock rates. 
At the same time the vertical heights of each of these maxima and 
minima were measured on the records, the upper edge of the record sheet 
being used as the datum line in these vertical measurements. The record 
sheets had been cut to fit accurately to the edges of the revolving drum. 
The accompanying Schedule I. contains a list of times and heights of 
all these maximum and minimum points for the fortnight. 
Tide gauges of the Lege type (see figure in G. H. Darwin's " Tides 
and Kindred Phenomena," page 11) have been established for a consider- 
able number of years at Cape Town, Port Elizabeth, East London, and 
Durban. By the courtesy of the respective Government engineers in 
charge of these gauges, I have been enabled to examine the automatic 
records of these instruments for the months of May and June, 1905, and 
I have measured on these records the times and heights of all the high 
