Trigonometrical Survey. 565 
this distance, used as a base in the above triangle, gives the dis- 
tance between the Observatory and the Church 3 6% feet; 
now the angle at the Church, comprehended by the Academy 
and the Observatory, being 2° 44' 30", we shall find the angle 
at Dunnose, between Portsmouth Church and the Observa- 
tory, to be i° 3' 30", and the distance of the Observatory from 
Dunnose 6996 2 feet. 
Remarks. 
In an operation of this kind, it naturally follows, when the 
objects intersected are at considerable distances from the sta- 
tions, there must be great difficulty in ascertaining their pre- 
cise situations from the appearance of the country. Under 
such circumstances their names sometimes cannot be disco- 
vered ; and it has been found, that the best maps of which we 
are in possession, were by no means sufficiently correct to be of 
much service in that particular. It is obvious also, without a 
very intimate knowledge of the interior parts of the country, 
(of which it is impossible, in the present state of the survey, we 
can be altogether possessed), there must be some difficulty to 
identify them, when their distances exceed twelve or fourteen 
miles. We have, therefore, when such an uncertainty existed, 
had recourse to some intelligent person well acquainted with 
the country, by whom we have been informed of their names. 
In this respect we have to acknowledge the services of Mr. 
<tardner, chief Draftsman at the Tower, by whose assistance, 
from his intimate knowledge of the county of Sussex, we have 
been able to determine, with certainty, the names of many 
places, which we might otherwise have considered as doubtful. 
Of the triangles here given, there is not much reason to believe 
mdccxcv. 4 D 
