31.76 32.5

These figures prove the accuracy of the calculations that had been
made in an approximate way.

The experiments were performed upon the Elba, above Dresden. Other
experiments still had reference to the influence of immersion. In
order to diminish polarization, only instantaneous currents from the
measuring pile were employed. It was to be supposed that the current
of water through which the bubbles of gas were removed from the
electrodes would not have permitted of a notable resistance of
polarization. Later measurements, made upon a ribbon buried, like the
plates, in the earth, gave likewise most favorable results.

As a result of these experiments, the State railways of Saxony have,
in such cases as were practicable, introduced the annular network of
copper. There are some manufacturers, too, who seem desirous of
adopting this system, although it has hardly emerged from the period
of experiment. The pecuniary advantages that will result from an
application of it ought, it would seem, to dispel a large proportion
of the criticisms directed against the erection of lightning rods,
from the standpoint of expense, and contribute to extend an
arrangement which may be considered as a very happy one.

If we compare the square plate with the equivalent annular network,
constructed as above indicated, and which should possess, according to
the author an external diameter of 1.26 m. and of 3.45 m., we find
that:

The square plate, 1 mm. thick weighs 8.9 kilos.
" 2 " " " 17.8 "
The annular network " 1.64 "

The cost of reticulated ribbon per meter amounts to about 4.4 francs,
supposing it to be arranged as shown in the cut.

As term of comparison, we may admit that the following forms are
nearly the equivalent of a horizontal, unburied plate one meter
square.

Length. Diameter.
Vertical cylinder buried 1.40 m. 0.13 m.
" " " 1.80 m. 0.06 m.
Vertical bar " 2.60 m. 0.013 m.
Horizontal bar " 5.20 m. 0.013 m.

Horizontal flat ring 1.32 m. in external diameter, and 1.08 m.
internal.

Horizontal network 1.01 m. square, and having meshes of the same size
as those of the reticulated ribbon.

Horizontal reticulated ribbon 3 m. in length and of the structure
described.

Horizontal annular ring 1.26 m. in external diameter, 0.9