172 
PROTECTION OF BUILDINGS FROM LIGHTNING. 
few accidents by lightning; second, the very recent 
adoption of lightning protectors ; third, the want of 
confidence in the efficacy of the latter ; and fourth, 
their cost. 
Although the extreme magnitude of accidents by 
lightning cannot be otherwise than recognized by 
all, and the almost certainty of some one or more 
buildings being the marked victims at every season; 
yet each man builds with the chance of his edifice 
not being the fatal one. Amongst so many, the 
chances are so much in his favor, that he will run 
the risk ; or else he comes to the still more unphi- 
losophical conclusion, that, as storm after storm 
has left him unscathed, so will he for ever be safe. 
With regard to the very recent discovery of 
means of averting the effects of lightning, it will 
be remembered that it was not until the month of 
June, 1752, that mankind knew what lightning 
really was. Then it was that Dr. Franklin first 
drew down lightning from the clouds, by means of 
a kite, and proved its entire identity with electri¬ 
city, which discovery led him to the construction 
of lightning conductors. But before treating of 
these, perhaps it may be interesting to give some 
of the precautions adopted by the ancients, in order 
to protect themselves against this “ethereal fire.” 
According to Heroditus, the Thracians, in times of 
lightning, were in the habit of shooting arrows 
against the sky, to repel it from the earth. Au¬ 
gustus used to retire into a cave during thunder 
storms, on the strength of an opinion then preva¬ 
lent, that lightning never penetrated into the 
ground more than five feet deep. The emperors of 
Japan, it is said, possessed a refinement on this 
mode, by building reservoirs above the caves, into 
which they retired, and kept them constantly filled 
with water, in order, as they thought, to put out 
the fire of the lightning. Augustus, who appears 
to have been terribly alarmed at this element, used, 
also, to wear a seal-skin cloak during storms, on 
account of its assumed protecting efficacy.' The 
Romans used to build seal-skin tents into which 
the timid retired ; and the shepherds of Cevennes, 
even at the present day, wear hat bands of serpent 
skins for the same purpose. Tiberius wore a 
chaplet of laurel, whenever he dreaded danger from 
a storm, with a belief that lightning never touched 
the foliage of the laurel. And it is a notorious 
fact, that the American Indians, whenever the sky 
wears the appearance of a thunder storm, quit their 
pursuits and take refuge under the nearest beech, 
with the full assurance that the electric bolts never 
scathe that tree. 
If the ancients were thus industrious to use what, 
in -their ignorance, they thought to be the means of 
safety against an agent, the nature of which they 
knew little or nothing, and the action of which 
they knew still less, how much more does it aeem 
to be the duty of the present generations, who 
both understand this agent and the means of avert¬ 
ing its effects, to avail themselves of the advantages 
of their knowledge, and employ the remedies they 
have at their command. Not a year passes with¬ 
out numerous cases of buildings being struck by 
lightning, for want of proper protection, particu¬ 
larly barns, which, in consequence of the humid 
gases ascending from the newly-gathered crops, are 
peculiarly liable to this injury. The necessity .and 
value of lightning rods are obvious and need nc 
further comment. 
As scientific knowledge has now obtained its 
proper rank in our schools, but few of our readers 
can be ignorant of the fact, that all matter is di¬ 
vided into two general classes, conductors and non - 
conductors of electricity. These names, however, 
are only comparative; for the two classes gradu¬ 
ally merge into each other, leaving the distinctive 
term merely an expression of degree. For instance, 
copper ranks very high in the scale of conductors ; 
and air occupies a very’low rank among insolators ; 
yet, an electric shock will sooner pass through a 
short interval of air than along a long copper wire. 
This fact is dependent on a law, the due observance 
of which, can alone ensure the efficacy of any pro¬ 
tecting apparatus. Another modification in a con¬ 
ducting body of a comparatively high rank, is its 
capacity , which exercises an important influence 
over its, conducting power. Thus an electric 
charge, which will pass safely and quietly along an 
ordinary copper wire, will deflagrate and burn up, 
entirely, an extremely fine wire of the same kind of 
metal. 
The most important things to be considered in the 
choice of lightning rods, are, that they should con¬ 
sist of good conducting materials ; good capacity ; 
and should have a good connexion with moisture 
in the earth. In addition to these, the area of 
their protecting influence should be regarded; the 
number of rods required for each building; their 
position in special cases ; and the modes of arrang¬ 
ing them. 
With regard to the conducting materials employ¬ 
ed in their construction, metal is undoubtedly the 
best, and the choice would seem to lie between cop¬ 
per and iron. M. Pouillet makes the conducting 
power of copper from 5 k to 6 k times that of iron; 
Dr. Priestly makes it 5 times as much ; and Pro¬ 
fessor Faraday 6f times as much; so that, after 
having determined the sectional area of an efficient 
copper rod, an iron one of about 6 times that area, 
will possess the same conducting power. Iron, 
however, will not make durable and efficient con¬ 
ductors, unless they are entirely coated with silver, 
gold, copper, or tin, in consequence of their liabil¬ 
ity to rust, or oxidate, by the action of the weather. 
As to the capacity to be given to a rod, it has 
been decided by common consent, that, the sec - 
tional area of one composed of copper, should vary 
from a circle one half of an inch to three fourths of 
an inch in diameter, the larger area being for very 
tall conductors, and the smaller, for shorter ones. 
And now, in respect to the form of the rods, it is 
quite immaterial whether they be square, round, or 
flat; but let it be remembered, that, in all cases, 
each conductor should be as entire and as straight 
as possible, presenting a single point to the clouds, 
with the apex tipped with palladium, or gold. 
Of all considerations, the most important is a good 
connexion with the earth , which is so very essential, 
that without this, all other precautions will be in 
vain. It is not enough that the conductor enter the 
earth; for it must penetrate it to some depth, in 
fact, till it reaches the subsoil, where it is well im¬ 
pregnated with water. In order to reduce the de¬ 
structive action of this moisture (the oxydation of 
the metal), and at the same time to give the buried 
