84 Transactions of tJie Boyal Society of South Africa. 
Stations. 
Johannesburg, South African School of Mines and Technology 
(formerly Transvaal Technical Institute). 
Latitude 26° 11' 47" S. 
Longitude 28° 2' 32" E. 
Altitude 1,749 metres. 
The measurements were carried out in the basement of the old Telephone 
Tower, the pendulum (on the "pfeiler-stativ ") resting on a massive concrete 
block : temperature was satisfactorily steady. The times were observed 
sometimes by means of signals transmitted from the sidereal clock of the 
Observatory over the telephone lines to a relay and thence by a separate 
battery to the coincidence apparatus, and sometimes by the Carroll 
chronometer."- Although in the centre of the town, the building was free 
from shaking. The land slopes very slightly upwards to the north, near 
the building, but it may be taken as practically flat for half a kilometre in 
every direction. Further away the land slopes downward both northwards 
and southwards, Johannesburg being placed on the ridge of the Witwaters- 
rand hills. The underlying strata are shales and quartzites, to a depth of 
at least 1,500 metres below the surface : density probably about 2'7. 
Johannesburg Observatory . 
Latitude 26° 10' 55" S. 
Longitude 28° 4' 30" E. 
Altitude 1,805 metres. 
The pendulum was placed on the ledge of the east window of the 
basement, being screened from the sun by a wooden shutter, the pfeiler- 
stativ " used, with the usual glass cover. The times were observed by 
signals from the mean-time (Eiefler) clock of the Observatory ; this was 
compared chronographically with the sidereal. Temperature steady, and 
support solid. The Observatory is situated at the highest point of the 
town, on a ridge of quartzite, the land falling away sharply both to north 
and south. 
Vereeniging {Post Office). 
Latitude 26° 401' S. 
Longitude 27° 551' E. 
Altitude 1,436 metres. 
The pendulum was placed on the " pfeiler-stativ " on the ledge of a 
window, which was too narrow to allow the usual cover to be used : it 
* The best set out of several is alone quoted below. More weight is to be given to the 
measurements at Johannesburg Observatory. 
