the 'Trigonometrical Operation . 1 29 
Heath, to be firft verified by the meafurement of this new 
bafe. Every field is furrounded with a ditch, in cleaning of 
which the earth and mud are continually thrown out on each 
fide, whereby flat dykes are gradually formed 011 either fide. 
That the meafurement might be carried on as nearly as poffible 
in the fame plane, that is to fay, about fifteen or eighteen 
inches above the common furface, therefore, narrow grooves 
were cut in thefe flat dykes, which the different farmers rea- 
dily confented to without murmuring. Here it is to be ob- 
ferved, that there was no occafion for levelling the line, Rom- 
ney Marlh having been formerly covered by the fea, and a 
confiderable part of it, particularly towards the bottom of the 
range of hills that feparate it from the Wealds of Kent, being 
ftill lower than the fea at high water, would again be over- 
flowed by it, if much care and expence were not annually be- 
llowed in fecuring and repairing the dykes, whereby it is pro- 
te &ed. Thus the line of the bafe may be confidered as an 
inclined plane, defcendmg gradually about five feet from the 
mouth of High Nook pipe to within 246 yards of the Ruckinge 
end, where the ground 111 that direaion feems to be the lowefl. 
Thence it rifes comparatively fuddenly, about fifteen feet, to 
the mouth of the pipe fituated in a fmall field immediately 
adjoining to Ruckinge Church-yard. 
Art. VII. Refult of the meafurement. < 
Lieut. Fiddes, in the courfe of his trigonometrical fur- 
vey, and of the different meafurements he had aaually 
made of the line with a common iron chain, which from 
time to time was compared with ftandard rods of deal, had 
determined the total length of the bafe within a few feet 
of the truth, before the ultimate operation began. He 
.had likewife driven into the ground, at the end of every 
Voe. LXXX, S thoufand 
