MifieUanea Curio fa. 119 



ded by fo much time, as the Light (hall have 

 taken in pafling from Ito K.? an< ^ tnat on H* 5 

 contrary, in the other Quadrature. F G, where 

 the Earth by approaching goes to meet the Light, 

 the Revolutions of the Emerfions will appear to 

 be fhortned, by fo much as thofe of the Emer- 

 fions had appear'd to be lengthned. And be- 

 caufe 41 J Hours, which this Satcllit very near 

 takes to make one Revolution, the diftance be- 

 tween the Earth and Jupiter, in both the Qua- 

 dratures, varies at lea if zio Diameters of the 

 Earth : It follows, that if for the Account of 

 every Diameter cf the Earth \ here were requi- 

 red a Second of Time, the Light wou'd take 

 3! Minutes for each of the Intervals G F, K L j 

 which would caufe near half a quarter of an 

 Hour between two Revolutions of the firft Sa- 

 tellite one obferv ci in F G, and the other in 

 J£ L, whereas there is not obkrvtA any fenfible 

 difference. 



Yet doth it not follow hence, that Light de- 

 mands no time. For after M fymer had exa- 

 min'd the thing more nearly, he found that what 

 was not fenfibJe in two Revolutions, became very 

 confiderable in many being taken together ; and 

 that, for Example, forty Revolutions obferved on 

 the fide F, might be fenfibly fhorter, than forty 

 others obferv'd in any place of the fydiacf^ where 

 Jupiter may be met with ; and that in propor- 

 tion of Twenty two for the whole Interval of 

 H E, which is the double of the Interval that is 

 from hence to the Sun. 



The neceifity of this new Equation of the Re- 

 tardment of Light, is eftabliflid by all the Gb- 

 fervations that have been made in the J{pyal 

 Academy, and in the Obferv at ory % for the fpace 

 of eight Years ; and it hath been lately confir- 

 I 4 med 



