388 On the luminous Arch.— Patents. 
arch is not formed by reflection, the sky being clear of va- 
pours at the time, but by streng emanations from the densest 
part of the aurora. 
The difference in the intensity of light of the awrora and 
the luminous arch, may arise from a difference in the density 
of the atmosphere through which these electrical emanations 
have to pass: and as the height of the electrical streams has 
often been found by trigonometrical measurement considerably 
above the allowed height of the earth’s atmosphere, when 
formed into a luminous arch; it may therefore appear to di- 
stant observers to be bent from its rectilinear course, by 
passing through media of different densities. 
By way of illustrating the arched form of the luminous 
arch, it is necessary to mention an atmospherical phenomenon 
of parallel bands of cirrostratus (like the meridians on an arti- 
ficial globe), that sometimes emanate from a dense cloud by 
the impulse of a freshening wind: these apparently equidistant 
bands of vapour, which overspread the whole hemisphere, from 
half to three-quarters of a mile in height, are blown in tolera- 
bly straight lines from a dark circular cloud in the wind’s eye, 
or in that part of the horizon from whence the wind proceeds ; 
yet from their height in the concavity of the northern hemi- 
. sphere, they all appear as regular arcs of a great circle. 
As it is probable the aurora borealis is produced by the 
agency of electricity, we may suppose that it is thus formed. 
In the cold northern regions, when the upper stratum of the 
atmosphere has become highly electrified by the union of 
winds of a different temperature and moisture, or by the as- 
cending heat from the earth, and the consequent mixture of 
atmospherical gases at certain seasons of the year, the quan- 
tity of electric fluid collected by these means may be sufficient 
to expand itself several degrees in extent, and be conducted 
by humid.vapours into the lower medium of the atmosphere, 
till it meets with a stratum of comparatively dry air that re- 
sists its descent: in this state of resistance it may be so vio- 
lently agitated as to appear to distant observers in very varied 
forms and colours; and in the case of a redundant quantity, 
strong emanations from this subtil fluid may produce a lu- 
minous arch. 
LIST OF NEW PATENTS. 
To William Wood, of Summer Hill Grove, Northumber- 
land, for his apparatus for destroying the inflammable air or 
fire-damp in mines.—Dated the 22d of April 1826.—6 months 
allowed to enrol specification. 
To John Petty Gillespie, of Grosvenor-street, Newington, 
Surrey, for his new spring or combination of springs for the 
purpose 
