C. U. Shepard on Meteoric Iron from Sonora. 369 
Recapitulation.—1. All observations agree in demonstrating 
that the aurora borealis is a phenomenon taking place in our at- 
mosphere, and that it consists in the production of a luminous 
ring whose center is the magnetic pole, and having a diameter 
more or less large. 
2. Experiment demonstrates that in causing in highly rarified 
air the reunion of the two electricities near the pole of an artifi- 
cial magnet, a small ring of light is produced similar to that 
which constitutes the aurora, and having a like movement of ro- 
tation. 
principally in the equatorial regions. 
As these electric discharges take place constantly, though 
with varying intensity, depending on the state of the atmosphere, 
the aurora should be a daily phenomenon, more or less intense, 
and consequently visible at greater or less distances, and only 
when the night is clear—which accords precisely with observ- 
ation. 
5. The phenomena that attend the aurora, such as the pres- 
ence and form of the cirro-stratus clouds, and especially the dis- 
turbances of the magnetic needle, are of a kind to demonstrate 
the truth of the electric origin attributed by the author to the au- 
tora—an hypothesis with which these phenomena correspond 
even in their minutest details. 
_ 6. The aurora australis, according to the few observations on 
it which have been made, presents exactly the same phenomena 
as the aurora borealis, and is explained in the same manner. 

Arr. XX XVIII.—Notice of three ponderous masses of Meteoric 
Tron at Tuczon, Sonora ; by CHartes Urnam Sueparp, M.D. 
the Gila, in the month of February previous, he observed two 
large pieces of meteoric iron, which were used by the blacksmiths 
Seconp Series, VoL XVIII, No. 54.—Nov., 1854. 47 
