234 REPORT—1905. 
directly, ares of meridian, and they are therefore given in the order of 
these arcs, reckoning from west to east :— 
Along Name of Base Latitude Denes hi Measured with 
Zwartland Base Hesse 42819:065 | Colby compen- 
sating bars 
19° E. Long, rim | S. Damaraland Base — Not yet 
measured 
N. Damaraland Base 23 31029°97 | Steel and brass 
Jiiderin wires 
{ Port Elizabeth Base 34 6000-000 | Troughton & 
Simms steel bars 
er ieee es [| Himberley Base .] 283 | 59004185] Do. do. 
Ottoshoop Base , 25% | 57212:39 | Nickel steel Jide- 
rin wires 
Wepener Base ; 30 7104814 | Do. do. 
| 28° E. Long. Kroonstad Base. 28 64919°67 | Do. do. 
Ottoshoop and Bel- 26 See foot- | 
| fast Base note _ 
Natal Base, : 293 10800°457 | Troughton & 
| Simmssteelbars 
! Belfast Base . .| 253 | 6231692 | Nickel steel Jiide- 
rin wires 
ig bw ate Houts River Base 232 -- Do. do. 
along 30° K. Inseza Base . F 20 62019°673 | Steel and _ brass 
Long. Jiiderin wires 
Gwibi Base . : 174 71165°270 | Nickel steel and 
steel Jiiderin 
wires 
Loangwa Base : 15 57087°61 | Nickel steel Jiide- 
rin wires. 
The northern side of this are is checked both by Ottos-hoop and Belfast base. 
With exception of the first bases, measured by parties who used thie 
Jiderin apparatus for the first time — ive., on the Inseza and North 
eens bases—the probable error of ‘pase measurement is about 
: 1,000,000. I estimate the uncertainty of the length of the Inseza and 
North Damar aland bases at 1 : 100,000. 
The chief errors do not lie in the discordances of the repeated measure- 
ments of the base, but in the standardisation of the wires. But when 
the most complete methods are taken for standardising the wires, the 
chief source of error is the error of the absolute length of the standard 
bar, which cannot be relied upon, even after the most rigorous comparison, 
within less than 1 3°15000; 000. Full details of the basis of these conclu. 
sions are published in Vol. i. of the ‘ Geodetic Survey of South Africa,’ 
with reference to the bases measured with the Troughton & Simms 
apparatus, and show the accidental probable error of measurement to be 
from | in 8 to 5 millions. 
In regard to the Gwibi base, which enters into the great arc along the 
30th meridian, having regard to the fact that the standardisation of the 
wires employed was carried out not on the field, but at the Cape Obser- 
vatory, before and after the base measurement, the following particulars 
may be given :— 
In the centre of the base-line site a ground standard of 400 yards 
