C 4? ] 
lefs than 30 Werfts afunder : And this Diftance once 
known exadly, will fcrve as a Foundation for all the 
Triangles that are to be taken * of which each of the 
Sides may have not lefs than from 30 to 40 Werfts, 
according as we fhall find Objeds advantageoufly fituatc 
for that Purpofe. W e have, to begin with, the Moun- 
tain of T)ouderhof, which, with the Imperial Obfer- 
vatory, and the Steeple of Cronftad Church, forms 
one of the rnoft convenient Triangles imaginable for 
the Subjed we propofe. 
In taking Obfervations at thefe three Places, we 
fhall fee if we can difcover others of the fame advan- 
tageous Situation 5 but when .no remarkable Objeds 
are found of the Situaticm and Diftance fought for, 
theymuft be ereded on purpofe, in the fame manner 
as was of neceffity done in other Countries: And 
this may be done here with more Eafe, feeing, in- 
Places where the Woods intercept our Sight, fimall 
Towers may be raifed, at very little Expence, out of 
thefe fame Woods, with Signals placed on them, 
which may be feen as far as may be required. In open 
Places, where confequently Wood is not fo common. 
Signals alone, without Towers, willfuffice. 
The moft necefiary Inftruments for executing this 
Undertaking, are, befides the ordinary Aftronomical 
Inftruments, a common Quadrant of between two 
and three Feet Radius , for obferving the Angles of 
the Triangles that fhall be taken ; and a Portion of a 
Circle of the greateft Radius that can be convenient- 
ly had, for obferving the Arches of the Heavens cor- 
refponding with the Diftances meafured on the Earth, 
I fay, the Quadrant ought not to have a Radius of 
more than between two and three Feet : For if it be 
F z bigger* 
/ 
