[410] 
be the difference of Meridians httwixt the place of the 
obfervation and London which lies f'o near the Meri^ 
dian of the Objervatory that the diftance need not be 
accounted for. And this determination may be relied 
on, if the firft or third Satellit were obferved; but I 
dare not be fo confident of the fecond and fourth 
for the reafons formerly given. However Ifhallmake 
it my bufinefs to obferve all fuch Eclipfes of as many 
of them asfliall be vifible with us, that by comparmg 
my obfervations with fuch as fliall be made abroad, 
the error, if any, may bedifcovered and Corrected. 
When ^ is in §luartile of the Sun : the diftance of 
the firft Sattellit from his next limb when it falls into 
his fhadow, and is Eclipfed, is one Semidtameter of 
Of the fecond, two or a whole Diameter nearly. Of 
the third, three. Of the fourth, five of hx^Semidiame- 
ters^ or fomething better when th^ parallax of t'^e 
Orbe is greateft. But thefe quantities diminifh gradu- 
ally as he approaches the a" or cP of the Sun fome- 
what nearly but not exacStly in the proportion of Sines. 
As the Sun removes from the cr of the Ingreffes 
of the Satellits into his fhadow become obfervable. 
When he is about thirty degreees from ir, the Emerfions 
of the fourth, and at fixty degrees of the third begin 
to be feen betwixt the fhadow and body continuing fo 
till the Sun be arrived within fixty degrees of the 3^ of 
^% when the Emerfions of the third fall behind his body, 
but the Emerfions of the fourth continue vifible till he 
be lefs then thirty degrees diftant from thec^^ at which 
time they alfo are hid behind him, all the appearances 
being made really to the right hand or in antecedence 
of tho with inverting Telefcopes, they appear to the 
contrary, the left. 
^ After the oppofition of the ©and ^ we begin to fee 
the Emerfons of all the Satellits from the fhadow, now 
on the left hand or in confequince of but t^irough 
in- 
