Tidal Phenomena at Inland Boreholes near Cradoch. 
85 
From Schedule I. — 
From first L.W. at 11.55 a.m., June 4, 
to last H.W. at 8.0 a.m., June 18 
is a period of 332 hrs, 5 min., and comprises 26| wave-lengths. Average 
wave period at Tarka Bridge : 12 hrs. 32 min. 
From Schedule II. — 
From L.W. at 11 a.m., June 4, 
to H.W. at 5.5 a.m., June 18 
is a period of 330 hrs. 5 min., comprising 26^ wave-lengths on the tide 
curve. Average wave period at East London : 12 hrs. 28 min. 
From Schedule IV. — 
From L.W. at 10.31 a.m., June 4, 
to H.W. at 4.25 a.m., June 18 
is a period of 329 hrs. 54 min., comprising 26f wave-lengths on the tide 
curve. Average wave period at Durban: 12 hrs. 25 min. 
From Schedule V. — 
From L.W. at 11.15 a.m., June 4, 
to H.W. at 5.5 a.m., June 18 
is a period of 329 hrs. 50 min., comprising 26|- wave-lengths on the tide 
curve. Average wave period at Cape Town : 12 hrs. 25 min. 
The nearest point of the South African coast to Tarka Bridge is on 
the northern shore of Algoa Bay, and the distance is about 100 miles 
measured on a straight line. Port Elizabeth is about 114 miles from Tarka 
Bridge, and the distance between East London and Tarka Bridge is about 
136 miles. 
The East London tide gauge is the nearest one which was giving 
reliable records during the early half of June, 1905. 
If we tentatively correlate the East London record with the Tarka 
Bridge record in such a way as to regard the East London high water of 
4.55 a.m., June 4, as corresponding to the Tarka Bridge high water of 
5.45 p.m. on the same day, and correlate all the remaining high waters 
consistently with this first assumption, we find that for the period June 4 
to June 18 the average lag of Tarka Bridge high waters behind East 
London high waters is 14 hrs. 27 min., while a similar treatment of the 
low waters of the same period gives an average lag of Tarka Bridge low 
water behind East London low water amounting to 14 hrs. 51 min. 
