Oj ) 
IY. An Account of/ome QhferVations of the Eclipfes 
of the Firft Satellite of Jupiter, compared 
with the Tables , by the fame * 
B Y comparing 244 Eclipfes of the firft Satellite 
of Jupitefy obferved between the Years 1677 
and 1731, with the Flamfteedian Tables, correfted 
by tny felf, from which Tables the preceding Ca- 
talogue of Eclipfes is deduced, I find there are 74, 
which make up near one Third of the whole Num- 
ber,. that do not differ one Minute from the Tables j. 
1 27, which are above one Half, that do not differ 
two Minutes j 181, which are two Thirds of the 
whole Number, that do not differ three Minutes ; 
and 214, which are feven Eighths, that do not dif- 
fer four Minutes, the reft not differing above five 
Minutes and one half, which is a Degree of Ex aft-- 
nefs fufficient in my Opinion to recommend the Ufe 
of thefe Eclipfes to our Navigators, to determine the 
Difference of Longitude, efpecially fince they may 
be feen with a Telefcope of three Feet, as is affect- 
ed in Page 169 of the Connoijfance Des tfemps for 
the prefent Year ; and if this be true, X will venture 
to affirm. That an Immerfton or Emerfion, obferved 
with this Telefcope, will not differ one half Mi* 
nute from the Time obferved with the largeft Tele- 
fcope : However that be, it is but comparing an 
Obfervation of the fame Eclipfe, made with thefe 
two different Tdefcopes together, .and the Difference 
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