Tidal Phenomena at Inland Boreholes near Cradock. 67 
bluish like that of a Bunsen burner, but by night the flame appears rather 
yellow (sodium flame), presenting a very weird appearance. The flame, 
after burning thus for a minute or two, is easily extinguished by the 
slightest puff of wind. 
My personal observations of these boreholes began in January, 1905. 
About the end of 1904 I heard that Messrs. Eayner and Eoberts had 
noticed a serious periodic variation in the apparent yield of borehole 
No. V. They said the variation was like a " tide," and although I was 
very sceptical about the propriety of this term as applied to the fluctuation, 
I thought this report was worthy of some inquiry. 
In January, 1905, I spent a fortnight on the farm and made the 
following series of measurements. 
1. Temperature of the Water issuing from the Boreholes. — The tempera- 
tures were observed on a maximum mercurial thermometer graduated in 
Fahrenheit degrees. Tenths of a degree were estimated by eye. 
The National Physical Laboratory Certificate dated April, 1903, gives 
the correction at 72° and 82° as -0-1°. 
In each case the mercury column was fully immersed in the water at 
the mouth of the borehole. 
Keadings. Corrected Keadings. 
Borehole No. II 78-5° F. 784° F. 
III 81-0° F. 80-9° F. 
IV 77-6° F. 77-5° F. 
V 80-5° F. 80-4° F. 
During the fortnight I frequently took readings of the temperatures at 
various hours of the day and night, but was unable to find any variations 
of temperature during that period. The various readings at any one bore- 
hole always agreed within jL- of a degree, and a few discrepancies were 
clearly within the limits of observation error. 
II. Yield of the Boreholes. — The yields of the four flowing wells were 
measured from time to time by allowing the water to flow into an iron 
vessel of llj galls, capacity and determining by means of a stop watch the 
time occupied in filling the vessel. 
The following were the readings obtained : — 
Borehole No. III. on Jan. 27 at 6.50 p.m. gave 11^ galls, in 13 sec. 
28 10.0 a.m. „ 13 „ 
11.35 a.m. „ 13 „ 
2-55 p.m. „ 13 „ 
7-0 p.m. „ 13 „ 
