[ I2 5 ] 
tion. Nor would the inftruments for this purpofe, if 
well contrived, be either lefs portable, or more expen- 
five, than thofe for meafuring a degree on the 
meridian 3 the fame telefcope which would be ne- 
ceffary for finding the meridian, would ferve likewife 
for tracing the arc of a great circle 3 but it is befide 
my prefent purpofe to confider any farther what kind 
of inftruments would be moft proper upon this occa- 
fion,or what would be the beft manner of conftru&ing 
them. 
I mull not, however, difmifs the prefent fubjedl, 
without obferving, that, by means of the above-men- 
tioned method, a country not too near the asquator, 
nor attended with any other unfavourable circum- 
ftances, might be laid down with wonderful exa&nefs. 
By running a great circle nearly Eaft and Weft 
through the midft of it, we fhould get the longitude 
of all the places, the great circle palled over 3 and if, 
by means of the meridian telelcope, we fhould trace 
meridians through a few of thefe places, as far North 
and South, as the furvey was intended to be carried, 
we fhould then have a number of ftations, in feveral 
parts of the country, whole longitudes, with refpedt 
to one another, would be very accurately determined, 
and to which other places might eafily be referred, 
when the length of a degree of longitude In thofe 
fituations was known. 
XVII. Ob- 
