254 REPORT—1905. 
The density of the system is only 0-05, that is, the stars, like those 
that form V Puppis, are gaseous masses. There is no definite evidence of 
great tidal movements. 
RR Centauri (ch. 5099). 
This variable is in some respects the most remarkable star of the 
apioidal binary type. The two stars forming the system are not merely 
in contact, they slightly coalesce, thus forming one dumbbell body. As 
might be expected, the prolateness of figure of both components is much 
greater than we find in the case of any other star of the same class. 
The light-curve, which is very regular, indicates a slightly elliptical 
orbit. 
The density of the system is 0°25, and there is evidence of tidal con- 
traction and expansion. 
The variation of RA Centawri was discovered at Lovedale in 1894, and 
during the past four years it has been under constant observation. The 
Oxford wedge photometer has also been used by the writer in estimating 
the amplitude of its variation. 
8B Lyre (ch. 6758). 
This is the typical star of the apioidal type. For over a hundred 
years it has been more or less under constant photometric observation, and 
of late years the spectroscope has ‘added its tale of information regarding 
the size and motion of this distant, giant system. All observers— 
Argelander (1840-1859), Schur (1878-1885), Markwick (1898-1901), 
Belopolsky (1897)—agree in their testimony that the orbit of 3 Lyre is 
slightly eccentric. There is also distinct evidence of a secular change in 
the position of the orbit in space, but this cannot definitely be attested to 
before a rigorous inquiry into the character and extent of tidal perturba- 
tions has been carried out. One secular drift is, however, beyond doubt, 
viz., the slow but steady secession of the component stars from one 
another. This change is so important a matter in the problem of stellar 
evolution that I may be pardoned stating the facts more fully in the 
form of a table. 
The value of the various periods is obtained from an examination of 
all available data. 
Period from Obser- Computed Distance 
Date atione Computed Distance en mmtae 
i a as M. S&. 
1780 127 21 — 9 15:0 1:0000 40,000,000 
1800 26 11-9 “0006 40,024,000 
1820 36 37-2 “0010 40,039,000 
1840 43 29-7 0012 40,050,000 
1860 48 54:2 “0014 40,058,000 
1880 54 1:8 “0016 40,065,000 
1900 59 9°6 1:0018 40,072,000 
During the past hundred years the component stars of 6 Lyre 
have receded from one another at least 50,000 miles, a small distance 
truly in stellar measurement ; but then a century is in astronomical 
reckoning a paltry fraction of time. What would such a recession amount 
to in 1,000,000 years ? 
