Trigonometrical Survey. 507 
Of the Scilly Isles, Menawthen is the nearest to the Land’s 
End, being about 1-^ miles eastward of the Day-Mark ; and 
the cluster of rocks, called the Bishop and his Clerks, the most 
remote, being gi miles west of St. Agnes’ Light-house. Com- 
bining, therefore, the above particulars with those distances, 
we may conclude, that the nearest part of the Scilly Isles is 
about 24,7 miles from the Land’s End, and the farthest 
nearly 34. 
PART SECOND. 
SECTION I. 
Account of a Trigonometrical Survey carried on in Kent, in the 
Tears 1795, and 1796, with the small circular Instrument. 
article 1. Particulars respecting the Instrument. 
The instrument used in this survey was announced in the 
Philosophical Transactions for 1795, p. 590. It was made by 
Mr. Ramsden ; and is about half the size of his large theodo- 
lite, or circular instrument, with which we take the horizontal 
angles, but nearly similar to it in all its parts ; consequently a 
very brief description will be sufficient. 
The most material variations in the construction are, 
1. The levelling or feet screws. These are below that hori- 
zontal movement which serves to direct the lower telescope to 
any particular object. By this position of the screws, the hori- 
zontal circle being once made level, the whole instrument may 
be moved round without disturbing its horizontality ; the 
levelling screws remaining stationary during that operation, 
mdccxcvii. 3 U 
