rrates, in this connexion, the
sacrificing of red dogs at the feast of Floralia, and Ovid of a dog on
the Robigalia. The experience of the ancient Greeks that Sirius rose
with the sun as the latter entered Leo, i.e. the hottest part of the
year, was accepted by the Romans with an entire disregard of the
intervening time and a different latitude. To quote Sir Edward Sherburne
(_Sphere of Manilius_, 1675), "The greater part of the Antients assign
the Dog Star rising to the time of the Sun's first entering into Leo,
or, as Pliny writes, 23 days after the summer solstice, as Varro 29, as
Columella 30.[2] ...At this day with us, according to Vulgar
computation, the rising and setting of the said Star is in a manner
coincident with the Feasts of St Margaret (which is about the 13th of
our July) and St Lawrence (which falls on the 10th of our August)."

Sirius is the most conspicuous star in the sky; it sends to the earth
eleven times as much light as Aldebaran, the unit standard adopted in
the revised Harvard Photometry; numerically its magnitude is -1.6. At
the present time its colour is white with a tinge of blue, but
historical records show that this colour has not always prevailed.
Aratus designated it [Greek: poikilos], many coloured; the Alexandrian
Ptolemy classified it with Aldebaran, Antares and Betelgeuse as [Greek:
upokirros], fiery red; Seneca describes it as "redder than Mars"; while,
in the 10th century, the Arabian Biruni termed it "shining red." On the
other hand Sufi, who also flourished in the 10th century, pointedly
omits it from his list of coloured stars. The question has been
thoroughly discussed by T.J.J. See, who shows that Sirius has shone
white for the last 1000 to 1200 years.[3] The parallax has been
determined by Sir David Gill and W.L. Elkin to be 0.37"; it is therefore
distant from the earth over 5 X 10^13 miles, and its light takes 8.6
years to traverse the intervening space. If the sun were at the same
distance Sirius would outshine it 30 times, the sun appearing as a star
of the second magnitude. It has a large proper motion, which shows
recurrent undulations having a 50-year period. From this Bessel surmised
the existence of a satellite or companion, for which C.A.F. Peters and
A. Auwers computed the elements. T.H. Safford determined its position
for September 1861; and on the 31st of January 1862, Alvan G. Clark, of
Cambridgeport, Mass., telescopically observed it as a barely visible,
dull y