ic8 Mr . Pictet’s Confi derations on the 
farther fouthwards, the central and inaccefiible chain of the Alps 
being in the way ; but if a greater arch ffiould be defired, it 
might be eafily protradted about 26 minutes north of Geneva. 
I lately made an excurfion to St. Jean de Maurienne, to exa- 
mine whether the portion of the town would be convenient in 
other refpe&s ; and if, in particular, the lateral attraction of 
foine neighbouring mountain was not to be feared. It appeared 
to me, that the place being furrounded by mountains of nearly 
equal maffes, and fituated at almoft equal diftances, their 
effe&s would be hardly perceptible ; and, fuppofing there fhould 
remain any doubt about their influence, this influence might 
be eafily afcertained by zenith diflances, obferved at the two 
extremities of a little plain in which the town is built, and 
compared with the real diftance of the ftations, determined by 
an actual meafurement. That town being the refidence of 
a bifhop, and containing near 3000 inhabitants, might furnifli 
the obfervers with a convenient building for the zenith fedtor, 
and the occafional help and neeeflaries which might be required. 
The great poft-road from hence into Italy, over Mount Cenis, 
paffing through it, is alfo an advantageous circumftance. 
The difpofition and bearing of the vallies from that town, 
which would be the fouthernmoft extremity of the arch, is 
advantageous for the feries of triangles : for I have feen 
from the top of a mountain near St. Jean, called Le Mont 
Sapey , two parallel chains extending to the north on both fides 
of the river Arc , and there appeared to be in their fummits a 
great choice for convenient ftations, as far as the confluence of 
the Arc and the river Ifere near Aiguehelle , from whence the 
mountains in the parallel of Chamber} are all vifible. From 
this laft parallel to Geneva, and farther, there are not only no 
difficulties, but the ftations are for the greateft part already deter- 
mined. 
