8o CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



of two and one-half or three inches, lost the satellite much 

 sooner than we observed its disappearance in the 6.4-inch 

 Clark Equatorial, when we followed it into the factitious 

 limb ; and with a disturbed atmosphere this advantage should 

 always pertain to the larger objective and higher power. 



Numerous observers might be quoted who have seen 

 stars and satellites projected within the apparent limb of 

 Jupiter at occultation. Some of the details are rather 

 startling, and perhaps the most notable is that by Admiral 

 Smyth, in 1828, supported in part by two other observers 

 at stations a few miles distant. The satellite II remained 

 for some minutes projected upon the apparent edge of the 

 planet, and thirteen minutes afterwards it was outside of the 

 disc; then it remained visible four minutes and " suddenly 

 vanished." If the observers had been experts, observing 

 with instrumental means adequate to give sufficient light, 

 definition, and size to the images — noting the times with 

 accuracy, and fully recognizing the effect of the locally 

 disturbed atmosphere — we are satisfied that some satisfac- 

 tory explanation would have been reached. 



Such details as these, and others upon different occa- 

 sions, are rather astonishing. Such remarkable conditions 

 must be due to imperfect instrumentation, to inexperience, 

 to weariness or lack of quick and positive accommodation 

 of the eye, to erroneous estimates of small intervals of time, 

 to extraordinarily abnormal conditions of the atmosphere, to 

 intervals of unconscious cerebration, or to gross mistakes. 

 It was from the abnormal observations at Melbourne that 

 Proctor undertook to deduce the depth of Jupiter's atmo- 

 sphere, and concluded that the star 64 Aquarii was seen 

 through a range of 10,000 miles of atmosphere below a 

 depth of 300 miles. 



We may here mention incidentally that for many years we 

 have been on the outlook for Saturn and his ring system to 

 occult some star of moderate magnitude; but the phenome- 

 non has not occurred in our experience. We were anxious to 

 learn how the ring system would treat the star. 



