1866. | Astronomy. 398 
of November are, therefore, dates deserving special attention, 
partly with a view of determining for the future the directions of 
the detonating meteors, and partly as showing, by their frequent 
return within very narrow limits of time about these dates, that 
aérolitic meteors, like the acknowledged star-showers of August and 
November, revolved in fixed orbits round the Sun. 
In a note on the spectrum of the variable star « Orionis, 
W. Huggins, F.R.S., and W. A. Miller, M.D., LL.D., F.R.S., men- 
tioned an important change which has been recently observed in the 
spectrum of this star. « Orionis is a variable star of great irregularity, 
both of period and of extent of change of brightness. These ob- 
servers have recently found that the group of lines, and “shading 
as if of fine lines,” terminated at its more refrangible end by the 
strong line No. 1069°5 in their diagram, is not at present visible 
in the spectrum of the star. The absence of this group is of great 
interest in connection with the variability of the star’s light, 
especially as the time of disappearance of this group coincides with 
the epoch of the maximum brilliancy of the star. 
Mr. Baxendell, whose successful prosecution of this branch of 
astronomy is so well known, mentioning this star, says:—“ The 
yariable « Orionis is irregular both in the extent of its variation 
and the duration of its period. I have often thought its light was 
at times variable in colour as well as intensity, being sometimes 
perceptibly more ruddy than at others.” 
The variation in colour, so well described by Mr. Baxendell, 
corresponds exactly to the change in colour of the star which would 
be produced by the absence or presence of the group of lines 
referred to above, since the position of this group in the spectrum 
is about the boundary of the “ orange” towards the “ yellow.” 
The Astronomer Royal read an important and interesting paper 
“On the supposed possible Effect of Friction in the Tides in 
influencing the Apparent Acceleration of the Moon’s Mean Motion 
in Longitude,” in reference to a communication to the Institute of 
France by M. Delaunay, in which he explains a portion of the 
apparent acceleration of the Moon as possibly due to a real retarda- 
tion of the rotation of the earth, and conceives that such retardation 
may possibly arise from friction in the tidal movement of the waters. 
In suggesting this explanation, he lays down as fundamental 
theorems the two following :—First, that if the solid globe of the 
earth were covered with water, there would be high water under the 
Moon (considered as the only tide-producing body); secondly, that 
the effect of friction would be to make the semi-diurnal tides later 
than they would be if there were no friction. 
Any treatment of the tides is, necessarily, very imperfectly 
applicable to the real motion of the waters, under all taeis com- 
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