Physics and Chemistry. 115 
the autumnal equinox: the mean range being under 1’ 2’. From the 
-observations for 1843, Mr. Broun has concluded that there is a maxi- 
mum of westerly declination when the sun and moon are in opposition, 
and a minimum when they are in conjunction ; that there is a maximum 
of westerly declination when the moon has its greatest north, and also 
when it has its greatest south declination, minima occurring when it 
Crosses the equator. In the diurnal period, the double maximum and 
minimum have been found to exist in each month of the year. In the 
‘Transactions of the Royal Society of Edinburgh,’ Mr. Broun has giv- 
€n certain results relating to the horizontal and vertical components of 
the earth’s magnetic force ; but these results were obtained in scale di- 
visions corrected for temperature by his method. In order to reduce 
obtained by the new method, the following results have been deduced. 
2d. Magnetic Dip.—The dip is a minimum when the sun and moon 
are in conjunction, and a maximum when they are in opposition. In 
mean diurnal period for the year, me 
y= Phe principal maximum occurs at 10> 10™ a, m. 
_ minimum = * S 40 rae 
A secondary maximum “ 2 O 4. mM 
3 iT mi 24 
: intmu + 5 40 a.™M. 
Makerstoun mean time being always used. These periods vary to 
Some extent throughout the year, the principal minimum occurring at 
6 4. mu. in winter; the two minima being nearly equal to the equinoxes, 
* 
