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, 0.94 m.
internal.

In conclusion, let us meet an objection that might be made to the
accuracy of the hypotheses that serve as a base to the preceding
calculations, in cases where ground plates for lightning rods and not
for telegraphs are concerned. Between the two ground plates of a