Major-General Roy’s Account of the 
of the ftem of the deal rods indifferently, but always at the fixed ^ 
br hindermoft end of the glafs rods, the brafs ruler was advanced 
fo near as almofi: to touch the wire, and there made fail. This 
being done, the mahogany half-crofs was laftly moved back- 
wards or forwards, in the direction of the line of meafurement, 
until the interfedfion, as feen by a perfon lying down on the 
ground for the purpoie, accurately coincided with the gilt wire, 
where it was likewife fattened by its proper fcrews. A tent 
was then pitched very near the apparatus, for the foldiers who 
furniihed the centinel for its fecurity, till the meafurement 
was refumed ; and particularly to guard it from being 
diflurbed by cattle during the night. 
Wheels for terminatings in a permanent manner , the extremities of 
the Safe. Tab. XVIII. ; 
Before any accurate meafurement could ultimately be made 
of the bafe by means of rods, in order that we might with 
certainty refer to the fame point, on any occafion that might 
arife of corredfion or repetition of the work, it had all along 
been forefeen, that it would be abfolutely neceffary to fink deep 
into the ground wooden pipes, or fuch like things, at the ex- 
tremities of the bafe, which could not be removed, or even 
diflurbed, by idle or ignorant people, without very confiderable 
labour. Mr. Mylne, F.R.S. was accordingly requeued to 
* That this might be conveniently done, a moveable ftand was placed, under 
the glafs rod, about four feet from the fixed end, and its table elevated till, by 
bearing againft the lower part of the cafe, it received its weight. This permitted 
the ftand under the fixed end to be lowered and removed, to make room for the 
apparatus, 
order 
