( 455 ) 
With respect to the triangulation of the West coast, I have remar- 
ked above that the steel tape, with which a base line near Padang 
of 4860 M. was measured in 1883, did not admit of a high degree 
of accuracy. The length of the steel tape was determined before 
and after the operation by measuring with it under the necessary 
precautions a line of 200 M., of which the true length was accurately 
known from measurements with the base apparatus of RePsoLD. 
Determinations of latitude and azimuth for the orientation of the 
chain were made at the West end of the base in 1885 *). 
The geographical longitudes were reckoned from the meridian of 
Padang, which passes through the West end of the base, for which 
meridian 6° 26’ 42’ West of Batavia has been preliminarily accepted, 
a difference in longitude formerly determined by chronometers. 
As zero mark for the altitudes was taken the Padang-zero, the 
mean sea level at Padang, formerly determined by observations 
during some months of 1874 *). 
For the astronomical determinations, the measurements of the 
horizontal angles and those of the altitudes, the 10-inch Universal 
instruments of Piston and Martins and of WeGENER were used in 
both triangulations. 
The telescopes of these instruments are placed excentrically ; each 
circle is read with two micrometer microscopes. 
With the exception of the Padang base-net, where directions 
were measured, the triangulation was made according to SCHREIBER’s 
method; the measurements of all combinations of angles were repeated 
so often that the weight of a direction adjusted at the station was 
about 24, the weight of one observation of a direction being adopted 
as unit. 
For the trigonometrical determinations of altitude, reciprocal but 
not simultaneous measurements were made; at each station, whenever 
possible, 6 zenith distances were measured for each point, under 
conditions as favourable as possible. With the exception of the first 
measurements on the West Coast, where signals were employed, 
all observations were taken on heliotropes. 
As to the adjustments and computations I remark that, for the 
South-Sumatra chain, exclusive of the connecting pentagon with Java, 
which was adjusted according to the method of least squares, the 
1) In 1896 determinations of azimuth and latitude were also made at the station 
Tor Batoe na Goelang, P 62. 
2) In 1889 the mean sea level at Siboga, about 350 kilometers off Padang, 
was determined by tidal observations; the connection of the two marks showed a 
difference of 0,85 M. 
