seen on the dark Part of the Moon in May 1821. 291 
much the appearance of a small comet, on the meon’s surface*, 
It was then half-past nine: the moon 15° high, and 40° 16 west 
of the sun, I could perceive the shape to be extended towards 
Grimaldus, appearing in diameter equal to one of Jupiter’s 
moons. I continued observing it till the moon was about 11° 
~ only high; when it extended itself to right and left horizontally, 
and became so very faint for the last degree as to be scarcely 
distinguishable: and having observed the occultation of a fixed 
star very near to it, at three minutes before ten I discontinued 
all further attention to it. The star at the instant before its oc- 
cultation, from the then state of the atmosphere, appeared of 
about equal magnitude to, but far better defined than .dristar- 
chus did at its most perfect appearance. My telescope mag- 
nifies about 80 times. The star which was occulted was 136 
Tauri: and came in contact with the limb of the moon, as 
nearly as [ could ascertain, at the advancing pole of libration ; 
and the instant of occultation was at 10" 5’ 55’,9 P.M., Green- 
wich time, estimating Tamworth 6’ 40,8 in time west of Green- 
wich. 
I had written thus far, when I recollected that, as the fol- 
Jowing day was not a post-day, I could not call your attention 
to it, and that I should lose nothing in point of time by observ- 
ing the moon on the Saturday night; but it proved cloudy. 
Sunday night, a quarter before ten.—I have again examined 
* Would it not be possible for the makers of telescopic eye-pieces to in- 
troduce a half-inch mother-of pearl micrometer (such as are usually divided 
into 100 equal parts) across the focus and field of the eye-glass, when the 
planets are the objects under examination? This would answer two valua- 
ble purposes. An observer might arrange that the planet should traverse 
the field entirely within the mother-of-pearl, and thus be enabled to prepare 
his eye by keeping it in darkness: perhaps he might thus observe a satellite 
of Saturn which he had never before seen; or by using this method with 
Venus (whose light is far too brilliant-to allow a satellite to be seen), a 
more certain opinion would be obtained on the subject of her having or not 
having one. It may be applied even to the light which Mars diffuses over 
the field. But this method of viewing the planets is, I am aware, in direct 
contradiction to an assertion I have lately heard, that a very faint light is 
rendered visible by being near to, and perhaps within the diffusion of a su- 
perior one. I have not seen the arguments by which this opinion is sup- 
ported, or I should not perhaps have suggested this mode of searching for 
satellites. The other use of the micrometer alluded to is that, as Saturn 
moves five seconds in an hour, the micrometer would measure any separa- 
tion of a planet, from every star supposed to be a satellite; and thus, after 
afew hours’ motion of Saturn, put the inquiry beyond doubt.—M. W. 
+ Note by one of the Secretaries.--On the night here alluded to, when 
this phenomenon was invisisible at Tamworth, on account of the clouds, it 
was distinctly seen by me in the neighbourhood of London, through a 3} feet 
refracting telescope. Its appearance was nearly similar to that described 
by Mr. Ward.—F. Baily. : 
002 the 
