could not tell where it was visible. You little thought that while
you were looking at the vibrations of those beautiful streamers of
red and white light, I was watching sympathetic oscillations of
little steel magnets, which we suspended by silk threads, in the
underground magnetic house that you see the top of in the
foreground of the picture. The magnets were sometimes moving about
so rapidly that I could scarcely read them; and although the aurora
was with you nearly at an end probably about ten o'clock, yet the
magnets did not resume their normal position for nearly twenty-four
hours after. You will see from this the advantage to be derived
from noting all particulars with regard to these phenomena,
whenever one has an opportunity of seeing them; for we must always
consider the possibility of their not being visible at places where
there are observatories, on account of clouds and other causes. One
great point that has yet to be satisfactorily determined is,
whether the effect on a magnet at one end of the world is
simultaneous with the auroral discharge at the other; or whether a
certain time is required for the effect to be communicated through
the earth. I had a letter from my father yesterday, enclosing the
one you sent him. By-the-by, this day week is Christmas-day; and,
if I am not mistaken, your birthday as well as Hannah's is near
about this time. She must be thirteen or fourteen; but, upon my
honour, I do not certainly know my own age. Was I born in January
1834 or 1835? I wish you all may have a merry Christmas and many
returns of the same. Please to give my love as usual, and

Believe me, my dear mother,

Your affectionate son,