P. E. Chase on Terrestrial Magnetism, 377 
Suppose that electricity consists simply of vibrations, it will 
seem perfectly natural that the magnet should obey the strong- 
est vibrations, 
arlow’s and Lecount’s laws for the distribution of the in- 
duced magnetism in masses of iron, are precise y the same as 
if motions of different 
portions of the earth, provided the magnetic axis coincided with 
which the magnetism depends, and to hope that a careful stud 
mospheric polarity, precisely analogous to that which was indi- 
cated by our experiments upon the control of the magnetic 
needle by mechanical vibrations. 
In consequence of the earth’s rotation, this condition exists 
only at the instant of noon. At all other times, the flow of the 
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“Until it is so rarefied as to rise again. is process of alternate 
rise and fall, is continued until the air reaches the pole, and then 
Teturns by the same law, and in a similar manner, to the equa- 
Ss 
‘ David Brewster, to coincide with the magnetic poles. 
Now, if we consider that in addition to these permanent cur- 
Tents, there is a continual motion of silent convection, the warm 
ar rising, and the cold air descending in parallel columns, like 
the particles in a vessel of boiling water,” and if we remember 
4 Halley, in 1686 (Phil. Trans., No. 183), explained the trade wind, and the ne- 
cessity of a reverse upper current, but he found it “very hard to conceive why the 
limits of the trade i pra be fixt about the 30th degree of latitude all around 
. the gl problem has been solved by Prof. Ferrel. I am not aware that 
poi vut the combined effects ef convection, absorption of heat 
d the daily superposition of the rotation- and temperature-cu . 
‘i 1 i i i im t agency 
than has generally been sup If we close the lower drafts of a common air- 
stove, and open a register immediately over the fire, the cold air does not rush 
i velocity to the surface of the fuel, 
Serres, Vor. XXXVIII, No. 114—Nov., 1864. 
