Year: 1872

THE apparent orbit OF Sirius, the 'dog
star" to whose sscendency the heat of the
summer months and the prevalence of
hydrophobia at this season have from
time immemorlal been attributed, is at
the present time so near to that of the
sun that the star Is Invisible to us. But
although absent from our nightly Geld OF
stellar observation, we are continually re.
minded by the thermometer and other.
wise, OF the supposed influence of this
body; and a few considerations Of Its
peouliariGieS will not, therefore, be out Of
place.


OF the enormous distance of Sirius and
the other stars, no adequate conception
can be formed; but here statistics come to
our aid. 1t has been demonstrated that,
If our sun were removed to the distance
of the nearest so. called fixed star, 1t would
assume the apparent size of star of the
second magnitude. But Sirius is many
times as far from our earth as the nearest
fixed star, and its immense separation
may be formulated by stating that it is
1875, 900 times the radius of the earth's
orbit away from our planet. This radius
equals 92, 400, 900 miles, and the result of
the calculation astounds us with its mag
nitude, and leads to still further astonish.
ment at the distance of the multitudinous
bodies of the nebule which, when con.
gregated millions together, scarcely suf-
hcc, in some instances, to render the
aggregation visible to the unaided eye.


Such is the enormous mass of the star
Sirius that 1t has frequently been sup
posed to be the center of the universe, as
far as our powers of research can reach.
1t is certainly possible that our whole
30 l.
bright particular star, but its obviously
increasing distance points out the deduc-
ton that the orbit of the system is an &c.
centric one, and that its center is still
travelling away from that part of the
heavens with which we are familiar. Of
the rate at which Sirius is leaving us be-
hind it is sufficient to give the results of
the best astronomical observation. Mr..
Huggins, whose discoveries with the spec
troscOpe have done much to make us ia.
miliar with the enormous powers Of that
invaluable instrument, has found by
watching the hydrogen line given by this
star that its displacement equals 1850 of
an inch toward the red end of the spec
trum, and he deduces from this fact that
the reirangibility of the light of Sirius is
much diminished, as the red are the least
relrangible of all the colored rays, and
this is complete proof that Sirius is re-
ceding from the earth. Then the ques-
tiOn arises: At what rate is this retrograde
motion taking place? Computation from
the spectrum gives it at about 4115 miles
per second; but at the time in question
the earth was, by its own revolution, re-
ceding from Sirius at the rate of 12 miles
per second, and the motion of our whole
solar system accounts for an additional .
miles per second. This reduces Sirius
retrograde speed to about 2415 miles per
second. Further modifying this figure by
the result of Sirius transverse motion, we
arrive at 20 miles per second, or 900, GOO,
600 miles per year.


What result does this enormous increase
of distance have upon this star, so well
known to US in the wintry heavens 7
Sirius is the fiery red SOthis of the Egyp
tians, and Seneca described it as being
redder than Mars. But in these days il
shines with perfectly white light, and il
was so even in the days Of the Danish
astronomer, Tycho Brahe Its rapid re
cession is thus causing a constantly vary
ing change in its color Whether any
further mutation in its aspec, will take
place during the lives of our now living
observers, it would perhaps be presump
tuous TO predict and as to what color il
will next assume, We have no guide. Al
its present rate of travel, it will take 20,
600 years to double its distance, and as il
is now a star of the first magnitude, al
most an inllnity of time must elapse be
| fore it is no longer accessible to the in
| strumcnts of modern astronomers.


However, we must believe the effect o
the ascendency of the dog star to be
mere superstition. The concurrence o
this event with the hot weather of sum
mer is a mere coincidence, the dogs arr
effected by rabies and men by sunstrok,
without regard to the position of Siriu
in the heavens. Indeed, the so-called doI
days, according to the almanac, are owe
before the star rises with the sun, anC
thus are twenty days too early to be iusti
fled by the theory that caused the an
clients to describe them as the caniculdreS
There is no doubt, therefore, that the ef
fecls of summer heat will continue lon


after the power of Sirius in our skies i
considerably diminished; and the do
days must certainly be considered as


curious tradition, only important so ia
as it throws light on the condition o
learning among the ancents.-Scienttf
American.