from Dr. Thornfo/i. 331 



taignc, however, one of the members of the society of 

 LiiDoges, had better success. On the 3tl of Mav 1761, he 

 perceived, aljout half an hour after iiine at night, at the 

 distance of 20' from Venus, a small crescent^ with the 

 horns pointing the same way as those of the planet; the 

 diameter of the former being about one-fourlh of that of 

 the latter; and a line drawn from Venus to the satellite 

 making an angle with the vertical of about 20" inwards the 

 south. But though he repeated this oijsen^alion several 

 times, some doubt remained whether it was not a small 

 star. N<.>xt day he saw the same star at the same hour, 

 distant from Venus about half a minute, or a minuie more 

 than before, and making with the vertical an angle of 10* 

 below on the north side ; so that the satellite seemed to 

 have described an arc of about 30", whereof Venus was the 

 centre, and the radius 20'. The two following nights were 

 hazy, so that Venus could only be seen; but on the 7 th of 

 Way, at the same hour as before, he saw tlie satellite agaia 

 above Venus, and on the north side, at the distance of 25 

 or 26' vipon a line which made an angle of about 45", with 

 the vertical tov.ards the right hand. The light of the satel- 

 lite was ahvavs very weak, but it had the same phasis with 

 its primary, whether viewed together with it in tlie lield of 

 his telescope or by itself. The telescope Vv'as nine feet long> 

 and magnified an object between forty and iifty times, but 

 had no micrometer ; so that the distances above mentioned 

 are only from estimation. 



' In four days it went through 155°. Then, as 155° is to 

 four days or 96 hours, so is 360 to a fourth number, which 

 gives 9 days 7 hours for the whole length of th.e svnodical 

 revolution. Hence Mr. Baudouin concluded that the di- 

 stance of this satellite was about sixtv of the semidiameters 

 of Venus from its surface ; that its orbit cut the ecliptic 

 nearly at right angles ; had its ascending node in 22" of 

 Virgo ; and was in its greatest northern digression on the 

 7th, at nine at night ; and he supposed that at the transit of 

 the primarv the satellite v>ould be seen accompanying it. By 

 a subsccpient observation, however, on the 1 1th of May, he 

 corrected his calculation of the periodical time of the satel- 

 lite, which he now enlarged to twelve days : in consequence 

 of which he found that it would not pass over the disk of 

 the sun along with its primary, but go at the distance of 

 above 20' from his soutlicrn limb ; though, if tiie time of its 

 revolution should be IJftcen hours Ioniser tlian twelve days, 

 it might then paPS over the sun after Venus was gone oil. 

 He imagined the reason wliv this satellite wai so difficult to 



be 



