Green-Mountain freeman. [volume] (Montpelier, Vt.) 1844-1884, 1852-02-26

feet will be the discharge insensibly. To en-
sure this the point should be composed of plai-
mum, on which metal the atmosphere has no ef-
feet A cap of thin sheet platinum an inch or
two long, drawn to point, and soldered upon
the iron rod, is sufficient.
The old fashioned method of connecting sew
eral rods by kind of hook and eye connection
is all wrong. Rust may and certainly will inter-
fere to break the connection-for it must be
borne in mind that the oxyde (rust,) of any metal
IS non conductor of electricity. The whole
rod must be made of one continuous rod of iron.
This may be effected by perfectly welding the
several pieces together, till you have the length
required. In its connections for support TO the
house nothing but perfect non conducting ma.
terials should be used. Clamps of wood with a
section of horn or ring of glass for the rod TO
pass through, are good contrvances The high
er the point of the rod is elevated above the
highest part of the house, the more protection
will be afforded. From casual shafts Of light
ming II is calculated that an elevation of the
point four feet above the highest part OF the
house, will protect the house to the distance of
eight feet each way, and that an elevation Of
eight feet will protect it to the distance of six
teen feet each way. The rule should be how.
ever to elevate the point Of the rod as high as
it can be supported against the wind, for the
higher it is the more protection it will afford.
Let me once more caution against jointed rods
and placing the rod opposite nails or spikes or
any metallic substanc, as these may attrOct the
current from the rod. | would also caution
against branch rods; that is, several rods above
reading to single rod below; and also against
horizontal rods, running a distance along the
roof or top of house or tower, TO the perpen-
dicular stem Its nature is to descend to the
earth, and the horizontal rod affords an unnatu-
raj medium; they may pass over a nail or spike
which would be very likely to attract the cur
rent and discharge it in the house. The rod
may be painted black or left without paint, at
the option of the builder. 1t makes no differ
ence.
A word as TO the nature of electricity. Many
} if not most people suppose that lightning is fire,
of course that it is hot. This is not so; it is
cold, or of the temperature of the surrounding
atmosphere. But it is matter, commonly called
a fluid, and by its rapid passage through the all
produces the appearance of fire IN The atmosphere
: by its friction, and in passing over wood or met
$ al, ignites the one and melts or fuses the othe
by its friction merely. Franklin did not drn,
If fire from heaven, as he is generally credited wit
'r having done, but he drew down current
IN electricity, in cool state, and did it so cool
i that he did not even burn his fingers with it.,
'e How often do we see green tree that has bet
re struck by lightning, side of it exhibiting Il
of track Of the fluid shivered into splinters. d.
It, tree is often set on fire by the friction. A baI
/ is also set on fire by the friction; and nails an
1T o,her metallic euh7tences are fused hut still II
le fluid itself is cold. G. B. SMITH.
s. Baltimore, Dec, 1851.