344 CALIFORNIA ACADEMY OF SCIENCES. 



" The satellite entered on the planet's disk at the upper 

 edge of the dark equatorial belt of the northern hemisphere. 

 At about 9h. 25m. the second or inner contact of the two 

 limbs occurred, and I carefully and anxiously watched for 

 the possible dark appearance of the satellite. 



"In five minutes after the second contact, I caught 

 glimpses of the satellite as a ivhite spot, after which it was 

 invisible, but at 9h. 35m. it was recovered as a dusky spot, 

 but not at all dark. Making allowance for the brightness of 

 Jupiter, the satellite might be called dark gray in color, but 

 it was quite easily followed, although the definition was 

 much blurred from increasing unsteadiness of the atmos- 

 phere. 



"Leaving the telescope at 9h. 40m. the observer returned 

 at lOh. and found the satellite as & black spot, but apparently 

 two-thirds smaller than before the transit." 



From recollection the observer thinks that it was not so 

 black as the transit observed in February, 1884, but as it 

 was in the present case within the dark belt at the equator, 

 this may have detracted from its apparent blackness. 



The President said: This observation suggests the possi- 

 bility that the satellite has an area of white surface (say at 

 one or both of the poles) and a remaining larger area of 

 dark surface. When the satellite approached the planet 

 the white area was the visible part; but when it was well in, 

 on the body of the planet, this white part was lost in the 

 superior brightness of the planet, but the dark area became 

 visible; and the intermediate phases are accounted for on 

 this supposition. It is a very great pity the satellite was 

 was not watched throughout the whole transit to detect its 

 phases to the end. It might even lead to the determination 

 of the rotation period of the satellite. 



