rgo Gen. Roy’s Account of a 
the icale or ladder would be perfectly parallel, but the diagonal 
Reps, marking the progrefs from one extremity to the other, 
would be alternately fo throughout the whole length. The 
fir'd: fide is iuppofed to be found by the meafurement of a bafe 
II, of about half its length ; and the lafl fide to be verified by 
fuch another bafe R at the oppofite extremity. 
In any particular cafe, where only two angles of a triangle 
can be actually obferved, thefe fhould be as near as poffible each 
45 degrees. At any rate their fum fhould not differ much from 
90° ; for the lefs the computed angle differs from 90°, the lefs 
chance there will be of any confiderable error in the inter- 
fection. 
Romney-Marjh , from its levelnefs, as well as other advan- 
tageous circumidances attending its fituation, which the bare 
infpedtion of the map will render obvious, feeming to me to 
afford the bed bafe of verification for the laid triangle, I have 
given the feries the Ihortefd direction from Hounflow-Heath 
to that part of Kent. The right hand ftations occupy in 
general the heights which extend acrofs the Wealds. Thofe 
on the left are placed on the great range of chalk hills, which 
end, on our fide of the Channel, between Folkftone and Wal- 
mer-Caftle, and re- commence on the oppofite fide between 
Cape Blancnez and Calais. 
It will be perceived, that I do not mean to make St. Paul’s 
a ftation in the fuite ; becaufe in that cafe Harrow and Hamp- 
idead mnfd likewife have been made life of, all three extremely 
inconvenient for the reception of the great inflrument. Befides, 
Greenwich Obfervatory being hidden from the country to the 
fouth-wefd by the Norwood heights, and from that to the 
fouth-eaft by Shooter’s-Hill, after having made the detour of 
Harrow and Hampftead, and come acrofs the fmoke of the 
Capital, 
