ctuations in width and position of this bow,
we will add a few of the minutes taken at the time with great care, in
hopes some other observer had been equally precise. When first seen,
there were three luminous patches, or elongated clouds of light; one in
Leo, one in Bootes, and another in Ophinchus, all in line. This was
about 9h. 15m. The times following are correct to 30 seconds:

9h. 42m. 30s. Bow complete; south edge 2d north of Arcturus.

9 45 30 Northern edge diffuse south; edge bright, and well
defined; 10d wide in zenith; north edge on Alphacca.

9 47 30 South edge 5d north of Arcturus; north edge close to
Cor. Caroli.

9 53 30 Eastern half composed of four detached bands
_shingling_ over each other.

58 30 Arcturus on south; bow narrower.

9 59 30 Arcturus in the middle of the band; very bright and
regular in outline, and widest at the zenith.

10 0 30 Arcturus on northern edge; north side better defined
than the southern.

10 2 0 Arcturus 1d north; very bright.

10 2 30 Gamma and Delta Leonis, northern edge.

10 3 Regulus on southern age; getting faint.

10 5 Fast fading away.

10 5 30 Scarcely visible; bank in north faint.

This aurora was due to the _inner vortex ascending_, whose period was at
this time 28 days.

There are several circumstances to be observed in this case. The bow
brightened and faded simultaneously with the aurora, and respected the
vertex of the auroral bank, being apparently concentric with it. The
bow, therefore, depends on the same cause, but differs from the aurora
in being limited to the _surface_ of the atmosphere in which the vortex
has produced a wave to the southward of its central path, as may be
understood by inspecting Fig. 2, Sec. 1,--the figure representing the
polar current of the central vortex. On the 29th of May, 1840,[32] the
author saw a similar phenomenon, at the same time of night, and passing
over the same stars southward until it reached within 5d of Jupiter and
Saturn, to which it was parallel. This atmospheric wave offers a greater
resistance to the passage of the ether: hence the light. On this account
it is, also, that when the passage of a vortex is attended by an auroral
display there will be no thunder-storm. There may be an increase of
wind; but t