The Ordnance Survey. 37 
ments in reducing the places of the stars, are extremely small, 
the greatest, that between Dunnose and Burleigh Moor, 
amounting only to 0-65, while that between Dunnose and 
Clifton amounts only to 0-04. 
In the present volume the amplitudes of the several arcs 
are first deduced from the observations of each star separately, 
and the most probable mean found by assigning to each 
partial result the weight due to the number of observations. 
The final results are contained in the following table: and it 
is only necessary to remark that the latitudes are obtained by 
adding consecutively the amplitudes deduced from the sector 
observations to the latitude of Greenwich (51° 28! 38"3) as 
determined by the Astronomer Royal. The former results 
are added for the sake of comparison. 
As published in the volumes of 
the Trigonometrical Survey. 
Station. Latitude. Aynplitude, 
Latitude. Amplitude. 
455 Mt ° a fe} iE!) Coy ODN) 
Dunnose ........ AUG Y/ VAL 50 37 8°60 
TAUBIEK. «csv 0secn 51 1 57:93| 0 24 50:90 
Greenwich (1) | 51 28 38°30] 0 51 31°27 | 51 28 40:00 | 0 51 31:39 
Greenwich (2) | 51 28 38:79. 0 51 31°76 
Arbury Hill ...) 52 13 27:14] 1 36 20°11 | 52 13 28:58) 1 36 19:98 
Delamere ...... 53 13 1877| 2 36 11:74] 53 13 20:80} 2 36 12:20 
Clifton Beacon} 53 27 30°45| 2 50 23°42] 53 27 31:59| 2 50 23:38 
Burleigh Moor | 54 34 19:48] 3 57 12°45 | 54 34 21-70| 3 57 13°10 
Kellie Law...... 56 14 50°51] 5 37 48°48 
Cowhythe...... 57 Al , 9°7 Tick, 27a 
Bi Aga cs asaensxs 60 45 2°31)10 7 55°28 
The difference, 0'"49, between the latitudes of Greenwich 
(1) and Greenwich (2), is owing to the circumstance that the 
position of the instrument in 1802 was fifty feet south of its 
position in 1836. 
It will be observed that the amplitude of the whole arc 
from Dunnose to Balta is 10° 7! 55-28. In point of extent 
this is the second arc which has been measured in Europe; 
but when we compare the instrument with which the astrono- 
mical amplitude was determined with that which was used for 
the French arc, we can have no hesitation in regarding it as 
undoubtedly the first in respect of probable accuracy. The 
amplitude of the French are of meridian, between the parallels 
of Formentera and Dunkirk, is 12° 22! 12"-74.; and that of the 
Russian arc measured by Struve and Von Tenner, 8° 2/ 28"-91, 
Balta, we believe, is situated about 52! west of the meridian 
of Greenwich, and consequently only about 20’ east of the me- 
ridian of Dunnose. 
