THE FACE OF THE SKY FOR JULY. 



Bv A. C. D. CROMMELIN, B.A., D.Sc, F.R.A.S. 



Table 29. 



Table 30. 



P is the position angle of the North end of the body's axis 

 measured eastward from the North point of the disc. B, L 

 are the helio-(planeto-)graphical latitude and longitude of the 

 centre of the disc. T is the time of transit of the zero 

 meridian across the centre of the disc. In the case of Jupiter 

 System I refers to the rapidly rotating equatorial zone, System 

 II to the temperate zones, which rotate more slowly. To 

 find intermediate passages of the zero meridian of either 

 system across the centre of the disc, apply to Ti Tj multiples 

 of 9" 50"- 5, 9" SS""-? respectively. In the case of Mars applv 



multiples of 24'" 40"'. 

 The data for the Moon and Planets in the Second Table 

 are given for Greenwich Midnight, i.e., the Midnight at the 



end of the given day. 



The letters tn, e stand for morning, evening. The day is 



taken as beginning at midnight. 



The Sun has commenced to move Southward. Its 

 semi-diameter increases from 15' 45" to 15' 47". It is at its 

 greatest distance from the Earth at 10*'e on 5th. Sunrise 

 changes from 3" 48"" to 4" 23"" ; sunset from 8" 18" to 7" 49". 

 The Sun's surface is likely to repay careful scrutiny, owing 

 to the recrudescence of activity. 



Mercury is a morning star. West Elongation, 20° from 

 Sun, on 19th. Semi-diameter diminishes from 6" to 3". 

 Illumination increases from Zero to i". 



Venus is a morning star. Illumination almost Full. Semi- 

 diameter diminishes from 5i" to 5". Venus is 38' North of 

 Saturn on 17th at \^e. 



The Moon.— Last quarter 4'" 5" 54" in. New 12'' 9" 31" m. 

 First quarter 19" 9" 9" e. Full 26" O" 11" c. .•Apogee 

 S" 11" in. Perigee 24" 5" m, semi-diameter 14' 45", 16' 29" 

 respectively. Ma.ximum librations l" 7° W., 7" 7° S., 17" 6° E., 

 21" 7° N.,2y"6°\V. The letters indicate the rogion of the Moon's 

 limb brought into view by libration. IC, VV. are with 

 reference to our sky, not as they would appear to an 

 observer on the Moon (.see Table 32). .\t ihc Full Moon 



on 26th the Moon enters the Earth's penumbra, and a 

 smokiness will be visible on the Northern portion of the disc. 

 The phenomenon is invisible in Europe. 



Mars is still badly placed, but may be observed as a 

 morning star. Semi-diameter 2i". Width of unilluminated 

 lune I". 



Jupiter is a morning star, in Pisces; stationary on 20th 

 Equatorial diameter 45", Polar 42". Width of unilluminated 

 lune §". Rises at ll''-5 e on 1st, at g""- 5 e on 31st. 



Configurations of satellites at l"" 30™««. 

 Jupiter's Satellites. 



The following satellite phenomena are visible at 

 Greenwich:—!" O" 44" m. 111. Tr. E., l" 36" m. I. Sh. I. 

 2" 59" m, I. Tr. I.; 2" 2" 27" m, I. Oc. K., U" 44" e 

 I. Tr. I.: 7" U* 22" <r. III. Sh. E. ; 8" l' 3" 46" w. 11. Ec' 

 I)., 1" 41" m, III. Tr. I.. 3* 30" m, I. Sh. I. ; 9" O" 44" 29^ 

 m, I. Ec. D., 11" 11" c, I. Tr. I.; 10" O" 17" »«. I. Sh. E. 

 1" 2'" <ii. II. Ii. 1:., 1" 35"' III. I. Tr. F. ; IS'' O" 7" m. Ill' 



187 



