of Jupiter, by which he demonstrates, that for the distance of about 3000 Leagues, such as is very near the bigness of the Diameter of the Earth, Light needs not one Second of Time.
Let (in Fig. 3. Plate 3.) A be the Sun, B Jupiter, C the first Satellit of Jupiter, which enters into the shadow of Jupiter, to come out at D, and let EFGHKL be the Earth, placed at divers distances from Jupiter.
Now suppose the Earth , being in L , towards the second Quadrature of Jupiter , hath seen the first Satellit, at the time of its emersion, or issuing out of the shadow at D , and that about 42½ Hours after ( viz. after one Revolution of this Satellit ) the Earth being in K , do see it return'd in D : It is manifest, that if the Light require time to traverse the Interval LK , the Satellit will be seen