y 



78 VA-LIFORNIA ACADEMY OF SCIENCES [Proc. 3D Ser. 



planet, but saw nothing of the kind. Professor Holden 

 informs me, however, that with the thirty-six-inch Equa- 

 torial the whole disc of a satellite has been visible within 

 the planet's atmosphere at every occultation he has ob- 

 served." In the "Astronomical Journal," volume VIII, 

 page 64, there is a record by these observers of the occul- 

 tation of 47 Libras (6.4 magn.) by Jupiter, on June 9, 1888. 

 With the thirty-six-inch objective and power 672, the images 

 were below the average of good seeing. Director Holden 

 reports that "the star entered the limb and was seen 

 bisected" at i™ 30^ after it had touched the outer edge. 

 " The entire image of the star was seen, inside as well as 

 outside the limb, being easily distinguishable from the 

 planet's surface by its brilliancy and peculiar color." In 

 2™ 35" "the star was entirely inside the limb, but still vis- 

 ible. For the next ten seconds the star was alternately 

 visible and invisible, and the planet's limb was quite un- 

 steady." In 1^ 51* from the star's first touching the limb it 

 was certainly gone. Professor Barnard observed the same 

 occultation with the twelve-inch objective, reduced to eight 

 inches because " the images were too unsteady with the 

 full aperture" (magn. power 240). He noted the time of 

 " contact of the following edge of the star with the preced- 

 ing limb " of Jupiter. At i™ 12^ after,^he star was partly on 

 the limb; at i"" 51* the star was seen by glimpses to that 

 epoch, and three seconds later it had certainly disappeared 

 when it had advanced about three-quarters of its disc within 

 the limb. On the usual scale of seeing, the conditions were 

 below the average; but even when the star had encroached 

 on the limb the disc was small, round and bright, and as 

 clearly defined as that of a satellite entering transit. No 

 certain diminution of its light was observed. 



Professor Barnard makes no allusion to the color of the 

 star, and as its spectrum is recorded as that of the first type, 

 there seems no reason why the first mentioned observer 

 should attribute a " peculiar color " to it. 



Under date of April, 1894, Professor Barnard thinks 

 " astronomers should reject the idea that the satellites of 

 Jupiter can be seen through his limb"; since, under good 



