Q44, REPORT—1 05, 
Astron. Astron. 
Authority Longitude  Latitud minus. ‘Geod. 
Geod. Lat. me 
zimuth 
ie} , ° wr a“ 
SirT.Maclear: Cape Point . .| 18 29 34 21 — 0-04 _ 
‘s Zwartkop (C.C.) . 18 27 34 13 —1-27 — 
— Gill: Royal Observatory | 18 29 33 56 + 0:48 — 5:92 
Colonel Morris: Tygerberg . . 18 35 33 51 +1:98 —3-02 
“ Robben Island. 18 23 33 48 +0°75 —7 06 
Sir T. Maclear: Klipfontein (Sec- ‘ ; 
Cations | 18 29 3241 | 47-42 ~— 
5 Heerenlogements kK : 
’ Ten, b| 18 38 | 3158 | —0-67 zn 
3 Kamies SectorBerg) 18 8 30 21 +814 +1-09 
ji North End(Sector ‘ 
, Suny . 1833 | 2944 | +012 2 
Mr, Bosman: Upington ,. 4 21 14 28 26 — 0:50 — 
a Vet Rivier . .| 20 0 26 49 —0:96 —2:49 
; Reitfontein . . 20 2 | 26 44 +060 —289 
Cola rete Cteon ee ear ee) os 9 ony eee 
“aad “Arita Wathen .3| 18474] 922 BF —1:12 — 4-80 
; .__|Oliphants Kloof .| 20 5 22 11 +302 —4:02 
ee Ee ecko |). |. 20879 | S0'6b. |" 0M ae 
The astronomical amplitude of the extreme stations of the are is 
12° 25’ 18”:39. The geodetic amplitude (Clarke’s elements), 12° 25’ 18'°31. 
This arc, properly speaking, rests on two base lines, viz., the Zwart- 
land base, measured by Sir Thomas Maclear, and a base of which one of 
its terminals is the point Gill’s Wald, measured by the Anglo-German 
Boundary Commissioners. 
Métres. 
The length of the latter base, computed through the long chain of 
intervening triangles from one of the sides of the geodetic circuit, is= 9457-850 
The directly measured length was ‘. . 5 . ‘ . .= 9157:440 
Difference computed-measured is therefore . . . . . = 0410 
or =1: 23-000 
The geodetic amplitude of the arc has, however, been computed solely 
from the Zwartland base, and it would have been increased by about 
0:5 if the Commissioners’ base had been taken into account. There is 
unmistakable evidence of strong local deviation of the direction of gravity 
at Klipfontein and Kamies Sector Berg, but, apart from these stations, if 
we divide the arc into groups we have the following results :— 
No. of Mean Astron. minus 
Stations Latitude Geodetic 
at : t uw 
Southern End of Maclear’s Arc 5 Be’ | 22, +038 
Northern “ 7 cy, i 2 30 51 — 0°22 
Southern End of Boundary Survey 4 26 31 — 0-02 
Northern + 3 5 3 22 22 + 0°60 
The reason why the northern base was not taken rigorously into 
account in the computations is, that it is desirable in so long an are to 
measure at least one other base, say in the neighbourhood of Reitfontein, 
