rn
hemisphere. Its precedence over its rivals Vega and Capella, long in
dispute, has been settled by the Harvard photometry. You notice that the
color of Arcturus, when it has not risen far above the horizon, is a
yellowish red, but when the star is near mid-heaven the color fades to
light yellow. The hue is possibly variable, for it is recorded that in
1852 Arcturus appeared to have nearly lost its color. If it should
eventually turn white, the fact would have an important bearing upon the
question whether Sirius was, as alleged, once a red or flame-colored
star.

But let us sit here in the starlight, for the night is balmy, and talk
about Arcturus, which is perhaps actually the greatest sun within the
range of terrestrial vision. Its parallax is so minute that the
consideration of the tremendous size of this star is a thing that the
imagination can not placidly approach. Calculations, based on its
assumed distance, which show that it _outshines the sun several thousand
times_, may be no exaggeration of the truth! It is easy to make such a
calculation. One of Dr. Elkin's parallaxes for Arcturus is 0.018". That
is to say, the displacement of Arcturus due to the change in the
observer's point of view when he looks at the star first from one side
and then from the other side of the earth's orbit, 186,000,000 miles
across, amounts to only eighteen one-thousandths of a second of arc. We
can appreciate how small that is when we reflect that it is about equal
to the apparent distance between the heads of two pins placed an inch
apart and viewed from a distance of a hundred and eighty miles!

Assuming this estimate of the parallax of Arcturus, let us see how it
will enable us to calculate the probable size or light-giving power of
the star as compared with the sun. The first thing to do is to multiply
the earth's distance from the sun, which may be taken at 93,000,000
miles, by 206,265, the number of seconds of arc in a radian, the base of
circular measure, and then divide the product by the parallax of the
star. Performing the multiplication and division, we get the following:

19,182,645,000,000 / .018 = 1,065,702,500,000,000.

The quotient represents miles! Call it, in round numbers, a thousand
millions of millions of miles. This is about 11,400,000 times the
distance from the earth to the sun.

Now for the second part of the calculation: The amount of light received
on the earth from some of the brighter stars has bee