r ?77 ] 
CaJJim examined the Inftrument feveral ways, at 
*\PariSy after his Return thither : but that a Cor- 
redion, owing to the Change of Centre, might be 
fafely applied to the Obfervations at "Dunkirk, the 
Examen of the Centre fhould alfo have been taken 
at Dunkirk', it being uncertain, whether this Altera- 
tion or Aberration of the Centre was caufcd by the 
Journey to or from Dunkirk. 
The Difference of 41 Seconds between the Obfer- 
vations taken to fettle the true Meafure of the Arc of 
the Heavens, feems to be enormous. Perhaps the 
Stars were not lucid enough to be well obferved by 
the Three Foot Tubes but might they not, for a due 
Degree of Accuracy, have been viewed through the 
Nine or Ten Foot Telefcope ? 
Our Author prefers the Obfervations of 1719, 
made after the Return to Daris, to thofe made be- 
fore s becaufe made at the fame time of the Year 
with thofe of Dunkirk, and fo not {landing in need 
of Mr. Bradleys Corredion : Though this Caution, 
perhaps, may be thought not necelTary here, where 
the Errors of the Obfervations are greater than the 
Corredion itfelf. Mr. Celfius remarks farther, if 
the Difference of Latitude between Dunkirk and 
Daris be fuppofed to be Two Degrees 12 Minutes 
12 Seconds and an half, which is a Mean between 
Four others he mentions, the Length of a Degree 
will amount to but 56,395 Toifes. And if the Ob- 
fervations at Malvoijlne and Amiens, be counted ac- 
cording to Mr. Bradleys Theory, for the Interval of 
a Month between the Obfervations, the Length of a 
Degree will come out to be 56,926 Toifes 5 which 
is 1 3 5 Toifes iefs than the Length of a Degree, found 
by 
