1867.] Astronomy. 521 



Astronomers are of opinion that we may look this year for a 

 recurrence of the November shooting-star shower. Assuming the 

 position of the meteor-stream to have remained unchanged, the 

 maximum display should take place at about seven o'clock on the 

 morning of November 14. But if we assume the shifting of the 

 node (investigated by Adams) to take place uniformly, the epoch of 

 maximum intensity must be placed at about twenty minutes past 

 seven or five minutes after sunrise. This determination, however, 

 does not take into account temporary disturbances in the figure of 

 the ring. The progression of the nodes is not uniform, but subject 

 to variation ; neither is the ring always in one plane ; and occasionally 

 one of the nodes may regrede for a time. From the position of 

 Jupiter it would appear that the node we traverse in November is 

 at present regreding. This would make the passage occur somewhat 

 earlier, and it seems not unlikely that the maximum display will 

 occur some time before sunrise on the morning of November 14th. 

 The beginning of the display may be looked for several hours 

 earlier. 



Jupiter was seen without satellites by several observers on the 

 evening of August 21. The only noteworthy fact we hear of in 

 connection with this phenomenon, is the observation that the shadow 

 of the fourth satellite appeared larger than that of the third, though 

 the third is the larger satellite. This observation, if confirmed, 

 would show that the apparent dimensions of the shadow depend 

 rather on the extent of the penumbra than of the true shadow. 



Mr. Proctor has obtained a new determination of Mars's rotation- 

 period. Madler's determination, founded on seven years' observations, 

 makes the period 24h. 37m. 23 ■ 8s. Kaiser extending his calcula- 

 tions over a longer interval obtained 24h. 37m. 22 ■ 6s. Mr. Proctor's 

 determination combines observations by Hooke in 1665, by Sir W. 

 Herschel in 1783, and by Dawes in 1864. The result is a period 

 of 24h. 37m. 22 ' 75s., with a probable error of one-fiftieth part of a 

 second. 



Mr. Stone has formed a table exhibiting the probable dimensions 

 of seventy-one asteroids. On the assumption that their surfaces 

 have equal reflective powers, the apparent brilliancy of these objects 

 enables us to determine their relative dimensions. Mr. Stone then 

 converts these results into miles by adopting the diameters of Ceres 

 and Pallas resulting from the observations of Sir W. Herschel and 

 Lamont. We append the diameters of the five largest and of the 

 five smallest asteroids : — 



Vesta . 



. . . 214 Miles. 



Themis 



. . 24 Miles. 



Ceres 



... 196 „ 



Asia 



• • 22 „ 



Pallas 



... 171 „ 



Maia . 



. . 18 „ 



Juno 



. ... 124 „ 



Atalanta 



. . 18 „ 



Hygeia 



. ... 103 „ 



Echo . 



• • 17 „ 



2 m2 



