lxx Votes. 
calculations, which are necessary in the application of the formulas.” — WN. 4. 
Review, Vol. xx. p. 364. See also Eloge de M. Lagrange, in Mém. de 1’In- 
stitut, Tom. xiii, p. lx. 1° Série. 
NOTE G. p. xviii. 
Ir will be perceived, that the observations of Dr. Bowditch upon the 
Variation of the Magnetic Needle were made thirty years ago; since which 
time far more extensive researches, than were then practicable, have been 
made in different parts of the United States, as well as in Europe, on this 
important subject. A highly valuable Table of Observations, made on the 
Variation and Dip of the Magnetic Needle in different parts of the United 
States, for more than a century past, has been lately published by Professor 
Loomis (of the Western Reserve College, State of Ohio), in the American 
Journal of Science. Professor Loomis urges upon men of science the great 
importance of observations of this kind ‘‘to a much greater extent than has 
2 
been hitherto done ;”’ and he states his conclusions, from the present data, 
as follows : — 
“From an attentive examination of the preceding Table it will be seen, 
that, from the time of the earliest observations down to the commencement 
of the present century, the westerly variation was decreasing, and the easterly 
increasing in every part of the United States ; that more recently, the reverse 
has taken place, that is, that a retrograde movement of the needle has 
commenced. The precise year when this change took place cannot be 
certainly known. To determine this, we need more numerous and more 
accurate observations. All the observations, however, agree in this, that the 
change began as early as 1819, while the Philadelphia observations would 
make it as early as 1793, and those at Newbern (North Carolina) not far 
from the same year. The annual motion is much greater in the eastern 
states than in the south and west. I have carefully compared all the observa- 
tions contained in the preceding table, and, without giving the particulars of 
this discussion, will state at once the conclusion at which I have arrived, viz. 
that the westerly variation is at present increasing and the easterly diminishing 
in every part of the United States; that this change commenced between the 
years 1793 and 1819, probably not everywhere simultaneously ; and that the 
