But in this case it is
evident that the E.M.F. produced would be much less, because the
magnetization of the core would only undergo a variation of intensity,
and would nowhere be reversed, except, perhaps, just in front of the
poles. In machines modeled on the Brush type it is evident that the
distributor need not be continuous.
Enough has, however, been said to indicate the extent of the field upon
which the principle may be applied.--_The Electrician._
* * * * *
OBSERVATIONS ON ATMOSPHERIC ELECTRICITY.[1]
[Footnote 1: Abstract of a paper read before the British
Association meeting at Manchester, September, 1887.]
BY PROF. L. WEBER.
I will try to give a short report of some experiments I have made during
the last year in regard to atmospheric electricity. It was formerly
uncertain whether the electrostatic potential would increase by rising
from the surface of the earth to more elevated region of the atmosphere
or not, and also whether the potential in a normal--that is,
cloudless--state of the atmosphere was always positive or sometimes
negative. Sir William Thomson found by exact methods of measuring that
the increase of the potential with elevation is very important, and
values about 100 volts per meter. That fact is proved by many other
observers, especially lately by Mr.
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