the Trigonometrical Operation. i 65 
were (applied with this crane, we made (Lift, by the help of 
a long beam, and a moveable treble by way of fulcrum for it 
to reft upon, to get the inftrument up to the top of its own 
proper fcaffold, and one that was ftill higher, e.re&ed over the 
tranfit room of the Royal Obfervatory at Greenwich. 
Art. VI. Reajons for changing certain Stations , 
In the courfe of the trigonometrical operation, the center 
of the inftrument has conftantly been brought, even aim oft 
to mathematical exa&nefs, over the precife point marking 
the ftation, whereby feduSions to the center on account of 
excentricity have been avoided ; and the ftation s have been 
diftinguifhed, as far as poflible, by permanent marks in fuch a 
manner, that, w 7 hile thefe remain, the center of this or any 
other inftrument may be again brought into the fame vertical 
line. By thefe means our recent obfervatlons may be repeated 
on any future occafion, and conne&ed with others, which it is 
to be hoped will be made hereafter : for this operation, the firft of 
its kind in Britain, (hould only be coniidered as the foundation 
or commencement of a feries of others, which by degrees will 
be carried to the remoteft parts of the ifland. 
By comparifon of the annexed plan of the triangles with 
that communicated to the Royal Society in 1787, as only a 
(ketch of the fcheme then propofed to be carried into execu- 
tion, it will be perceived, that fome few ftations are omitted 
entirely, and others fubftituted in lieu of fome that were then 
intended to be occupied. Of this laft number Hanger-hill 
Tower has been made ufe of inftead of Kew Pagoda. This 
laft had been propofed on a fuppofition, that without a fcaffold 
of an enormous height, it would have been impoffible to fee 
Hanger-hill Tower from King's Arbour* Neverthelefs, after 
1 a good 
