and the Absolute Size of the Fixed Stars. 3ll 
fact, about } brighter than the Sun. Sir J. Herschel makes 
the disproportion greater, but that is on the estimate that 
the Moon is only s5¢g50 of the Sun, which I cannot but 
think too low, also. If I had the correct comparison of Venus 
with Sirius, our results might agree better ; but, considering 
the rudeness of the method, it is a satisfaction to have come 
sonear. Probably the zenith correction ought not to have 
been applied, as-we seldom see Venus in the zenith ; in which 
case the light of a Centauri would come out= 1-67 of the Sun. 
Thus much, therefore, we may assume as already known 
regarding this interesting star, and, on full consideration of 
_ the whole of the facts, it certainly seems that all observers 
who have @ Centauri above their horizon should lose no time 
in beginning their observations to determine the nature of the 
perihelion passage of the star; and we may then hope in a 
very short space of time to have much more exact results 
than any we at present possess on the various results which 
may be deduced from the observations; the importance of 
which will be still further increased by micrometrical mea- 
surements with extra meridian telescopes being carried on at 
the same time, to perfect the determination of the parallax. 
Notice respecting a Deposit of Shells near Borrowstounness. 
By CHARLES MACLAREN, Esq., F.R.S.E., &e.* 
This deposit of shells is situated about a mile and a half 
west from Borrowstounness, where the Carse of Falkirk ter- 
minates in a strip of flat land a furlong in breadth. The 
shells are exposed in two openings, made in the soil to pro- 
cure limestone for Mr Wilson’s iron-works, and which have 
been subsequently converted into pools by unfiltered water. 
They are each about 300 feet in length, and from 20 to 30 in 
breadth. The bed can be traced in these openings along 
lines having an aggregate length of 1000 feet. Over all that 
space the shells form an unbroken stratum of very uniform 
depth (nearly three inches), and almost perfectly horizontal, 
as shewn by their parallelism with the surface of the water 
* Read befure the Royal Society of Edinburgh, on 7th January 1850. 
