( 209 ) 
between Tarts, and Collioure , with the abovemention d 
Inftrument of ten Foot Radius ^ but they made Ufe 
of a Quadrant, wliofe Radius was only thirty nine 
Inches, and fometimes an Odant of three Foot Ra- 
dius. Nay, they fay themfelves, in their Account, 
that it is not the Obfervations made at the Ends of 
the Meridian, that we are to deduce the Difference of 
the Length of a Degree from, but the Altitudes taken 
at feveral Places between the Extreams j and, if we 
grant, that they can take an Angle very well, to four 
or five Seconds, with the great Inftrument, they can- 
not come nearer than twelve or fifteen Seconds, with the 
Quadrant or Odant, which we muff depend upon for 
■the Difference of the Meafure of Degrees : So that upon 
the whole, we are to determine a Length of thirty one 
Toifes, by an Inftrument which is liable to err above 
two hundred. 
If any Confequences of this Kind cou’d be drawn 
from adual meafuring, a Degree of Latitude fhou d be 
meafur’d at the ./Equator, and a Degree of Longitude 
likewife meafur’d there ; and a Degree very northerly, 
as for Example, a whole Degree might be actually 
meafur’d upon the Baltick Sea, when frozen, in the 
Latitude of fixty Degrees. There, according to 
Monf. Caffini's laft Suppofition, a Degree wou’d be of 
56653 Toifes, whereas, at the .Equator, it wou’d be 
of 58019 Toifes, the Difference being 1364 Toifes, 
about the two and fortieth Part of a Degree, which 
muft be fenfible ; and likewife the Degree of Longi- 
tude wou’d, according to him, be of 56817 Toifes, lefs 
by 1201, or the forty eighth Part, than a Degree of 
Latitude at the fame Place. 
But here it may be objeded, that tho’ the Latitude 
was not taken with the ten Foot Se&or, in the inter- 
mediate Places between Tarts and Collioure , yet the 
Vol. XXXIII. Hh Lati- 
