Page:Philosophical Transactions - Volume 095.djvu/282

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Dr. Herschel on the Direction of the

with its apparent motion, we may soon obtain a certain minimum of the other parallactic motions; but as Sirius is not the star which has the greatest proper motion, it occurred to me that another minimum, obtained from the line in which Arcturus appears to move would be more accurate; for, on account of its great proper motion, we have reason to suppose it more affected than other stars, by the parallax arising from the motion of the sun; and, with a view to this, I soon was led to a point not only in the line of the apparent motion of Arcturus, but equally favourable to Sirius and Procyon, the remaining two stars that have the greatest motions.

If the principle of determining the direction of the solar motion by the stars which have the greatest proper motion be admitted, the following apex must be extremely near the truth; for, an alteration of a few minutes in right ascension or polar distance either way, will immediately increase the required real motion of our stars. Its place is: right ascensicm 245° 52' 30", and north polar distance 40° 22'.

The calculated motions of the same stars by this apex will be as in the following Table, and are delineated in Fig. 4.

Table VII.


Angles of the parallactic Motion
with the Parallel.

Angles of the apparent with the
parallactic Motion

Least Quantities
of the
real Motion.

° ' " ° ' " "
Sirius 58 24 56 south-preceding 10 24 44 following - 0,20157
Arcturus 55 29 45 south-preceding 0 0 3 preceding - 0,00003
Capella 83 44 17 south-preceding 24 40 21 following - 0,19358
Lyra 36 28 33 south-following 92 49 30 following - 0,32396
Aldebaran 89 48 35 south preceding 13 18 58 following - 0,02842
Procyon 59 43 10 south-preceding 9 40 46 preceding - 0,20839
Sum 0",95595