Its
current strength is about one volt, but can be made up into any
required voltage in series. A battery of a dozen cells should cost
not to exceed 50 cts. for the material, which will give a strong,
steady current, amply sufficient for all ordinary experimental
work.
A strong solution of common salt may be used in place of the oil
of vitriol in the porous cup, but is not so good.
--Contributed by C. H. Denniston, Pulteney. N. Y.
** A Home-Made Equatorial [253]
By Harry Clark
The ordinary equatorial is designed and built for the latitude of
the observatory where it is to be used. This is necessary since
the hour axis must point to the north pole of the heavens whose
elevation above the horizon is equal to the latitude of the
observer's station. The final adjustment of an ordinary equatorial
is very tedious so that when once set up it is not to be moved.
This calls for a suitable house to protect the instrument. It has
been the aim of the writer to build a very simple instrument for
amateur work which would be adjustable to any latitude, so easily
set up ready for work and so portable that it need not be left out
of doors from one evening until the next.
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