AND THE MEAN SPECIFIC GRAVITY OF THE EARTH. 
595 
7'he amplitudes derived from the latitudes in the first table, when compared with 
those we have considered as most probable, show the following differences : — 
A-S ....H-0"-26 
N— A....+0"*02 
N— S.... + 0"-28. 
Geodetical Amiplitudes. 
By means of a small network of triangulation connected with the secondary trian- 
gulation of the Ordnance Survey in the county of Edinburgh, the following results 
were obtained : — 
From 
To 
Distance. 
Bearing. 
Arthur’s Seat, Trigonometrical Station | 
S. 
N. 
ft. 
1426-7 
2490-0 
179 42 7 
6 0 17 
The bearings being reckoned from North round by East. The corresponding ampli- 
tudes are 14"‘06 and 24"‘40 : in order, however, to the comparison of these with the 
amplitudes before considered, the quantity 0"'13 must be added to the first of the 
geodetical amplitudes and deducted from the second for the difference of the two 
stations on the summit of the hill. The geodetical amplitudes are therefore 
A— S=14"-19 
N — A = 24"-27 
N — S =38"-46. 
By comparing these amplitudes with the actual astronomical amplitudes we find 
the following results : — 
(1) Between the vertex of the hill and the South Station, the astronomical ampli- 
tude exceeds the geodetical by 2"'81. 
(2) Between the vertex of the hill and the North Station, the astronomical ampli- 
tude exceeds the geodetical by l"'26. 
(3) Between the North Station and the South Station, the astronomical amplitude 
exceeds the geodetical by 4"'07. 
Geodetical Latitudes, 
The latitude of the Trigonometrical Station on the summit of Arthur’s Seat, is, 
when referred to, or projected on that spheroidal surface which best represents all 
the astronomically determined points in Great Britain, 
55° 56' 38"-31, 
from which, by the application of the geodetical amplitudes, we obtain the latitudes 
