Tidal Phenomena at Inland Boreholes near Cradock. 95 
I have made various rough analyses of the gases escaping from the 
wells, showing that methane is the principal constituent in each case, and 
that oxygen and carbon dioxide are absent. A gas sample which I 
collected in January, 1912, from No. III. was analysed by Mr. James 
Moir, M.A., D.Sc, F.C.S., at Johannesburg, and yielded him the following 
results : — 
Methane 94-0 per cent. 
Hydrogen 2*7 ,, 
Nitrogen and other unabsorbables 3-2 „ 
Oxygen and carbon dioxide — traces, together less 
than 0-1 
I have observed various loose stones (some of them apparently showing 
signs of Bushman work) which seem to have been lying for a long time 
in the water escaping from the natural springs beside No. V. These 
stones are covered with a smooth siliceous enamel, and some of them with 
a smooth coating of iron pyrites. During the progress of a little excava- 
tion around the spring I also observed that the shales exposed were highly 
impregnated with small crystals of iron pyrites. The inference seems 
unavoidable that the sulphurous water deposits the iron pyrites from 
solution or by reaction of the sulphuretted hydrogen on the ferruginous 
constituents in the shales. 
The bacterium already alluded to is present in all the five boreholes 
and in the natural springs associated with them. It appears as white or 
pink feathery loose tufts, which from time to time are emitted in the 
escaping water. On exposure to the air and sunlight these tufts soon 
become dark in colour. I submitted specimens to my colleague Professor 
Pearson, South African College, and he informs me that it is a sulphur 
bacterium which flourishes in water impregnated with sulphuretted 
hydrogen. I have observed similar tufts issuing with the water of the 
sulphurous springs of Cradock and Aliwal North. 
As the quantity of gas delivered by the boreholes I have no very 
definite data. Nos. III. and VI. seem to be the holes which are most 
prohfic in gas, but the rate of gas discharge obviously varies much in all 
the wells. On several occasions I inserted a 6-inch funnel in inverted 
position into the borehole, and so collected most of the escaping gas as it 
issued from the thin end of the funnel. The gas was led through a pipe 
into a 3 -litre bottle, from which it easily displaced the contained water. I 
noted the time taken to fill the bottle with gas. The results indicated that 
No. III. and No. VI. each delivered from 3 to 4 litres of gas per minute. 
Messrs. Eayner and Eoberts state that the rate of gas delivery as 
estimated roughly by the apparent trouble of the water surface is con- 
siderably affected by changes of weather, and that they obtain predictions 
