412 Capt. Kater/s experiments for determining the variation 
unfavourable to the measurement of a base. The signal post 
however was visible from the farm, and I selected the most 
level part of the hill I could find, on which, with the assistance 
of Mr. Franks, I measured a line of 1140 feet. The angles 
were taken with the greatest care, and are given with the 
other necessary data in the Appendix, from which the distance 
from Dunnose to the chimney of the summer house appears 
to be 3901 feet, and its bearing 6o° 58' 11" to the north east; 
whence the distance on the meridian is 1893 feet, or 18", 67. 
The distance from the signal post was also calculated, and 
found to differ only one foot from that of the station. 
Fearing from the nature of the ground on which the base 
was measured, that this determination might be erroneous, I 
was anxious to verify it by some other method. For this 
purpose I chose a spot on the side of the hill, which was very 
level, on which I measured with great care a distance of 100 
yards. The direction of this base was perpendicular to a line 
joining the summer house and the signal post, in which line 
was also its commencement. I then measured the distance from 
the signal post to the commencement of the base. By means 
of eight repetitions with the Repeating Circle, the angle sub- 
tended by this base, at a spot 22 feet from the chimney of the 
summer house towards the signal post, was determined with 
great precision ; and having also the angle of elevation, the 
horizontal distance from the commencement of the base was 
obtained, to which 22 feet being added, and also the measured 
distance from the base to the Signal Post, the result was 3896 
feet, for the distance from the Signal Post, to the chimney of 
the summer house, differing only four feet from the former 
determination. 
