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fieurs Daubentdn and Adanfon , a great number of 
experiments, of which the duke has favoured the 
public with a particular account. 
In the year 1757, there were two accounts pub- 
lifhed upon this fubjedt: the one is a memoir of M. 
iEpinus, read to the Royal Academy at Berlin, in- 
tituled, De quibufdam experimentis eleffricis notabi- 
lioribus. The other is a treatife in quarto, printed 
at Roflock, intituled, Difputatio de eleflricitatibus 
contrarih. Auclore Joa?ine Carolo Wilke. Since 
which time, Dr. Heberden, who is ever delirous of' 
extending the bounds of icience, having procured 
fome of thefe Hones from Holland, a great number 
and variety of experiments with them have been made 
here, particularly by the ingenious Mr. Wilfon ; an 
account of which he has very lately communicated 
to the Royal Society. 
XXXVIII. An Attempt to account for the re- 
gular diurnal V ariation of the horizontal 
magnetic Needle ; and alfo for its irregular 
Variation at the Finie of an Aurora Borea- 
lis : By John Canton, M. A. and F. R. S. 
Read Dec. 1 3, f | ^HE late celebrated Mr. George 
1759 Jl Graham made a great number of 
obfervations on the diurnal variation of the magne- 
tic needle, in the years 1722 and 1723 j but declared 
himfelf ignorant of the caufe of that variation, in 
N° 3 S3 of the Philofophical Tranfadtions, where 
many of thofe obfervations are to be found. About 
2 the 
