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ftances, we fhall be immediately fatisfied by them. 
Each obferver had a fecond- watch in his hand ; the 
three obfervers were at the fame window of the fame 
room, one of them on the leads immediately with- 
out the window, and the other two within the win- 
dow 5 therefore each obferver was within hearing and 
feeing of each other j confequently the inftant one of 
the obfervers flopped his watch, may it not be pre- 
fumed that the noife of the nicking of it might be 
heard by the reft ? efpecially as there was a profound 
filence during the time of the obfervation. 
I have thought proper to take notice of thefe fads, 
becaufe feveral perfons both at home and abroad have 
exprefled their furprize at this coincidence, and that 
fuch an exadnefs may not be eftablifhed as a prece- 
dent in thefe fort of obfervations ; and becaufe I think 
it eftentially neceftary, in all forts of obfervations, 
efpecially in one of fo much importance in aftronomy 
as this, that every the minuteft circumftance fhould 
be particularly related. 
We are now to find the limits of the error arifing 
from the difference of longitude between Tobolfk 
and the Cape. I find that an error of i' 10" in time 
in the difference of longitude between thefe two 
places will caufe an error of 1" in the Sun’s parallax. 
But as we are certain that this error in longitude 
does not take place ; therefore we are certain that 
the error in the parallax is within one fecond of the 
truth. The difference of longitude between the 
Cape of Good Hope and Paris is determined, both 
by the obfervations of M. de la Caille and Mr. Ma- 
fon ; the difference of longitude between Paris and 
Upfal in Sweden is fettled by the obfervations of Ju- 
piter’s 
