SCIE.XTIFIC SUMMARY. 
81 
tliB line r (a Lyclrogen line) of tlie solar spectrum. We must confess^ how- 
ever, that we are rather perplexed by this result. We may he ready to 
reject the view that the orange line is due to the existence of sodium in the 
flames which surround the sun,* but the exact coincidence of the red line 
with the solar line c compels us to believe that these flames consist in 
part of burning hydrogen : this being so, how is it that the green line of 
hydrogen is not seen, though one very near to it makes its appearance ? In 
the spectra of the nebulse the green line r of hydrogen is seen, while the 
red line c is not seen. This phenomenon, though perplexing, is not so per- 
plexing as that presented by the prominence-spectra. Is it possible that the 
two phenomena may be in a sense correlative ; that hydrogen is in reality a 
compound substance, and that the line c belongs to the spectrum of one of 
its elements, the line F to that of another? 
The Transit of Mercury . — This phenomenon was well observed by many 
of our leading astronomers j amongst others, by Messrs. Stone, Dunkin, 
Lassell, Huggins, Professor Smyth, Captain Noble, and Mr. P>rowning. We 
have little to add to what is already known respecting Mercury. Some 
observers (amongst others Mr. Huggins with his fine 8-inch refractor) saw 
one spot ; others (including Mr. Browning, with his great 12^-inch reflector) 
saw two ; and Mr. Stone (with the great Greenwich equatorial of I2|-inch 
aperture) saw none. It appears to us that this diversity proves beyond 
dispute that the phenemonon is purely optical. On the other hand, Mr. 
Huggins noticed that a ring of light could be seen round the planet even 
when a very strong darkening glass was made use of. This would seem to 
show that the ring has a real existence ; though it is still possible that the 
appearance may be due to irradiation. One observation of the transit strikes 
us as important. All the observers we have named noticed an apparent 
change of figure in Mercury as the planet approached the edge of the sun's 
disc ; but Mr. Henry Pratt, who observed the phenomenon by projecting the 
solar image on a screen of finest white cardboard placed in a darkened room, 
noticed that the last internal contact took place without the slightest ap- 
pearance of elongation or distortion in the shape of the planet’s disc. This 
circumstance seems to suggest important considerations with respect to the 
observation of the transits of Venus in 1874 and 1882. 
The Kovemher Shooting-Stars . — Contrary to the general expectation of 
astronomers, the November star-shower was well seen in England. The 
display lasted until five in the morning of November 14, having commenced 
shortly before midnight. The display was also well seen in America, at 
about 11 o’clock, local time, corresponding (for the eastern parts of the 
United States) to the hour at which the display ceased in England. The 
visibility of the display, after all that had been predicted by astronomers, 
suffices to show that we are not nearly so well acquainted with the habitudes 
of the meteoric system as we had imagined ourselves to be. Probably many 
years will elapse before we shall be able to predict the character and extent 
of an approaching shower, and the places at which it will be visible. 
The niajority of the meteors seen this year were orange, but a few pre- 
sented a blueish light. 
The Sun's Distance . — Astronomers have long been discontented with the 
explanations which have been put forward from time to time, to account for 
VOL. YIII.— NO. XXX. G 
