Gravity in South Africa. 
85 
was screened from draughts by paper. The temperature was moderately 
constant. The coincidence apparatus was worked by the Carroll chrono- 
meter (with electric contacts), and the latter was checked by means of 
telephonic signals from the Johannesburg Observatory. There was, how- 
ever, some difficulty in getting these signals, which had to traverse about 
50 miles, owing to imperfections in the line. Only pendulum 62 was 
used. 
The surface and the underlying strata are very flat ; surface rocks, clay 
and shales. 
The measurements were made in the space under the floor of the 
Maclean telescope, the pendulum resting (on the " pfeiler-stativ ") on a 
massive buttress of the wall. Stability and temperature conditions very 
good. The coincidence apparatus could not be worked by the clock (a 
Eiefler) direct, so the Carroll chronometer was used, and compared by 
ear with a sounder worked by the Eiefler. The single coincidences could 
not be obtained in this way nearer than second. The rate of the 
chronometer varied a good deal during the day of observation, and an 
attempt was made to draw a curve of the variation and correct the 
observed periods by that (Fig. p. 125); but the results were uncertain. 
The Observatory is situated on a slight eminence in an otherwise flat, 
sandy country. The mass of Table Mountain (about 1,000 metres high) 
lies from 1 to 2 kilometres away to the SW., and stretches to a 
considerable distance, embracing about a quarter of the horizon. 
A large brick pillar was built in the basement of the clock-house, and 
the pendulum erected on it, and provided with the usual glass cover. 
The oscillations were in the EW. direction, the telescope being to the 
south. The temperature was very constant ; the pillar was tested for 
stability and appeared quite satisfactory. The coincidence apparatus was 
worked direct by the sidereal clock (Strasser and Eohde). 
The Observatory is placed on a small, sandy plateau, extending for 
300 or 400 metres to the east (towards the sea), and more than a 
kilometre in all other directions. A map of the coast was examined 
Gape of Good Hope [Boyal Observatory). 
Latitude 
Longitude 
Altitude .. 
33° 56' 3" S. 
16° 8' 26" E. 
16 metres. 
Lonrenqo Marques Observatory . 
Latitude 
Longitude 
Altitude .. 
26° 2' 31" S. 
32° 19' 48" E. 
55 metres. 
