Physics and Chemistry. 415 
_ The search for intra-Mercurial planets will be facilitated by 
the use of similar screens of a larger size. The following pro- 
position is laid down as one hardly admitting of doubt. If the 
great motion of the perihelion of Mercury deduced by Le 
Verrier from the observations of transits of that planet is 
caused by the attraction of matter in the solid or liquid state, 
that matter can be seen during a total eclipse if the direct 
licht of the corona and protuberances is shut off from the eye. 
This is founded on the following propositions : 
The masses of matter in question cannot be more than half 
of Mercury’s distance from the sun. 
Hence, taking equal surfaces of them and of Mercury, they 
Ae ae with more than four times the brilliancy of that 
planet. 
If they are not smaller than the second magnitude they will 
be visible to the naked eye, properly prepared by being kept in 
previous darkness and shaded by the screen. 
If they are smaller than the second magnitude, they must 
be a hundred or more in number. Some of them will then be 
easily detected with a telescope of large field of view unless 
they are below the fifth magnitude. 
If they are below the fifth magnitude, they must number 
thousands, and they will then be visible to the naked eye as a 
continuous diffused light. 
The screen for this search should be large enough to pro- 
tect_the telescope from the sun during the entire period of the 
total phase, 
It is hoped that these arrangements and observations will 
be found to merit the attention of a share of the observers 
during the total eclipse of August next. 
SCIENTIFIC INTELLIGENCE. 
I. PHYSICS AND CHEMISTRY. 
1. On the refrangibility of the brilliant yellow ray of the sun’s 
aimosphere.—The fact that the yellow ray seen in the spectrum 
of the protuberances from the sun’s photosphere does not corres- 
ond with the lines D of the solar spee observed by 
eut. Herschel, then by Mr. Lockyer, by Secchi, and finally 
Janssen, er has now determined the tion of this line wi 
accuracy, using a troscope of high dispersive er and 2 
plain at bane te Pakin she distaaane aig ai se te lines D 
as unity the author found for the distance of the yellow line from 
the more refrangible ray D the number 2°49, with a probable error 
of less than 0:03. Taking the wave lengths of the two lines D 
