PHILOSOPHICAL TRANSACTIONS. 481 



that it came to about SS'"; but now the same diameter came out much less: for, 

 the whole duration of this occultation being known, viz. SS'" 10% and at the 

 same time the diameter of the moon being 32' 40''; it presently becomes known, 

 from that moment of time when the first limb of Jupiter touched that of the 

 moon, and when again his body was just all hid, which took place in the space 

 of 55', that the diameter of Jupiter comes out 30'^ 53"'. 



The principal observations were the following, the times of the pendulum 

 clock being corrected by observed altitudes : — The moon rose at 1*^ 54™ 25'; 

 the sun rose at 3*^ 28*" 25'; Jupiter touched the eastern limb of the moon at 4** 

 IS'" 5'; the planet was wholly covered at 4*^ ig*" o* ; a considerable part of Ju- 

 piter was emerged at 5^ 16"^ 25'j and the whole of the planet was emerged at 



The Observation of the Eclipse of Jupiter and his Satellites by the Moon, the 5th 

 ^ June 1679, ^' S' By M. Cassini. Philos. Collect. N° 1, p. 33. 



Having found by calculation, that the moon ought to eclipse the planet Ju- 

 piter the 5th of June this year 1679 ; I was ready with a 20-foot telescope to 

 observe after the rising of the moon, with which I discovered 3 satellites : the 

 1st was distant westward of the limb of Jupiter a little less than a diameter ; 

 the 2d was distant on the east side a little more than a diameter; the 3d was 

 more eastward than the 2d, by somewhat less than a diameter of Jupiter; and 

 the 4th being less than the other, which according to calculation, should have 

 been near its greatest digression eastward, appeared not by reason of the cre- 

 pusculum. 



At 3^ 0™ 11% the first satellite was hid by the east limb of the moon. At 

 3h 2^ o-i^^ the east side of the moon touched the west side of Jupiter: then I 

 took the height of Jupiter, which was 8° l', at 3*^ 2"^ 5 1 '. At 3^ 2"» 57' Jupiter 

 was entirely hid by the moon. He entered at equal distance from the two spots 

 Grimaldi and Aristarchus ; the last of which was in the section of the moon, 

 which distinguished the light from the dark part. At 3^ 5™ 1% the 2d satellite 

 was hid by the east side of the moon. At 3^ b^ 48' the 3d satellite was hid, &c. 



Then followed a multitude of small clouds of the colour of shining fire, 

 which were formed near the horizon. Whilst we were looking at these, without 

 losing sight of the moon, we perceived by the eye that Jupiter was parted from 

 the obscure side of the moon at 3^ 56'". 



M. De la Hire, who observed near the gate of Montmartre, 2 minutes after ^ 

 the parting, took the height of Jupiter, and found it 17° 17'« We afterwards 

 made divers observations for determining the parallax and the diameter of the 



VOL. II. 3 Q 



