330 Letter to Mr. Arthur Aikin 



brightness of the twilight made it disappear. Venus wa^ 

 then horned, and this phsenonienon, the diameter whereof 

 was nearly a fourth part of the diameter of Venus, was of 

 the same shape. It was distant from the southern horn of 

 Venus, a diameter of the planet, on the western side. In 

 these two observations I was in doubt w hether it was not a 

 satellite of Venus of such a consistence as not to be very well 

 fitted to reflect the light of the sun, and which, in magni- 

 tude, bore nearly the same proportion to Venus as the moon 

 does to the earth, being at the same distance from the sun 

 and the earth as Venus was, the phases whereof it resembled. 

 Notwithstanding all the pains 1 took in looking for it after 

 these two observations, and at divers other tunes, in order 

 to complete so considerable a discovery, I was never able to 

 see it. I thereixire suspend my judgment of this phseno- 

 menon. If it should return often, there will be these two 

 epochas, which, compared with other observations, may 

 be of use to find out the periodical time of its return, if it 

 can be reduced to any rule." 



' A similar observation was made by Mr. Short on the 

 23d of October 1740, about sunrise. He used at this time 

 a reflecting telescope of about 16" 5 inches, which magnified 

 between 50 and 60 times, witli which he perceived a small 

 star at about lo' distance from Venus, as measured by the 

 micrometer J and, putting on a magnifying power of 240 

 times, he found the star put on the same appearance with 

 the planet herself. Its diameter was somewhat less than a 

 third of that of the primary ; but its light was less vivid, 

 though exceedinglv sharp and well defined. The same ap- 

 pearance continued with a magnifying power of 140 times. 

 A line, passing through the centre of Venus and it, made 

 an angle of IS" or 20° with the equator : he saw it several 

 times that morning for about the space of an hour, after 

 which he lost sight of it, and could never find it again. 



' From this time the satellite of Venus, though very fre- 

 quently looked for by astronomers, could never be perceived ; 

 which made it generaUij believed that Cassini and Mr. Short 

 had been mistaken : but as the transits of the planet over 

 the sun in 1761 and 1769 seemed to promise a greater cer- 

 tainty of finding it, the satellite was very carefully looked 

 for by almost every one who had an opportunity of seeing 

 the transit, but generally without success. Mr. Baudouin, 

 at Paris, had provided a telescope of 25 feet, in order to 

 observe the passage of the planet over the sun, and to look 

 for its satellite : but he did not succeed either at that time, 

 or in the months of April and May following. Mr. Mon- 

 taigne, 



