548 The Account of a 



The stations chosen and observed this year, but not visited 

 with the instrument, were Monymoor, near Penhow ; the moun- 

 tain Twymbawlin, near Newport ; and Scilly Point, in Glamor- 

 ganshire. These stations in South Wales will connect with three 

 in Somersetshire, also selected this season ; one on Bleak Down, 

 which is situated on the western extremity of the Mendip range ; 

 a second on Brent Beacon ; and a third on the Quantock Hills. 



Subsequent to the operations on Salisbury Plain, enquiries 

 had been often made after a spot on which a third base might 

 be measured. Experience had almost convinced us that, if Sedge- 

 moor were excepted, the southern part of England did not con- 

 tain one of sufficient extent for a base of three miles. Aware, 

 therefore, of the imperfect state in which our work must rest, 

 without a fresh base, Mr. Dalby and myself passed over into 

 South Wales, and examined the extensive level between the new 

 Passage House and Cardigan. After, however, a very diligent 

 search, we could not find any spot, four miles in length, suffici- 

 ently unobstructed. The advantages which the situation itself 

 holds out, are so great, that we should not have scrupled to dis- 

 pense with a desideratum, heretofore required, of the base being 

 one continued line. So much, however, is this flat cut up with 

 rhynes and ditches, that we were not able to find any point 

 from which two right lines might be measured, and so inclined 

 to each other as to afford, by means of an including angle, a third 

 side of five miles in length : necessity, therefore, compelled us 

 to think of measuring a base on Sedgemoor, which we immedi- 

 ately examined. That which relates to this situation, will be found 

 in an ensuing article : it is now only necessary to observe, that 

 we concluded the operations of 1797, after the practicability of 

 measuring a base upon it had been decided in the affirmative. 



