Tht RURAL NEW-YORKER 
1499 
Trees and Lightning Stroke 
Is it true that some varieties of trees are more sus¬ 
ceptible to lightning than others? If that is so, why is 
it? Can you give me a list of such trees to show their 
liability to lightning stroke? T. c. b. 
Pennsylvania. 
LThe following statement was sent us by C. T. Mar¬ 
vin, Chief of the Weather Bureau of the Department 
of Agriculture. It is an article prepared by Roy N. 
Covert for publication in the Monthly Weather Re¬ 
view.] 
ACTORS DETERMINING LIABILITY.—It is 
desired to consider first what the factors are 
which determine the relative liability to lightning 
damage of trees as determined by their location, the 
character of the soil in which they grow, and its 
moisture condition, the electrical conductivity of the 
wood itself, etc. As a general statement the tree 
which is a relatively good electrical conductor, and 
has a root system which is widespread, or which 
reaches deep into the moist soil, is the one which is 
in most danger of being struck by lightning. No 
tree is immune, however. Following are the factors 
which govern, as determined by careful studies made 
in Western Europe of the effects of lightning on 
trees: 
(a) Among trees of the same kind, the one which 
stands well above its neighbors is in most danger, 
even in a dense forest. This dominant position may 
be due to the greater height of the tree, or be the 
result of the configuration of the ground. 
(b) Trees growing in the open, either singly or in 
small groups, are in more danger than 
those in the dense forest or other thick 
stand of timber. 
(c) Trees growing along avenues or 
in the border of a wood are also struck 
by lightning more often than those in 
thick woods. 
(d) A tree growing in moist soil, 
that is, along the banks of a stream or 
a lake, or close to some other source of 
moisture, is a better conductor for 
lightning than one growing in drier 
soil. 
(e) Trees growing in loam and 
sandy soils are struck much more fre¬ 
quently than those in clay, marl and 
calcareous soils. Oaks grow mostly in 
loam and sandy soils. 
(f) Sound trees in general are less 
likely to be seriously damaged than 
those with rotten wood. If the sound 
tree is also a relatively good conduc¬ 
tor. lightning will go to earth easily, 
but rotten wood is a poor conductor of 
electricity, so that the passage of the 
lightning current through this nearly non-conducting 
portion often results in a shattering of the tree, and 
when dry the tree may he set on fire. The picture 
on this page illustrates what sometimes happens. 
(g) Starchy trees, of which the oak is a good ex¬ 
ample, are better conductors of electricity than oily 
trees like the beech. The conifers are intermediate. 
Experiments made by Jonesco of the Wurttemburg 
Society of Natural Science gave the following re¬ 
sults : 
One turn of a Holz’s electric machine passed the 
spark through oak wood, five turns through poplars 
and willows, and 12 to 20 turns through beech. 
COMPARISON OF TREES.—From the foregoing 
we learn that an oak is decidedly a good conductor 
of electricity so far as trees go; that it grows in 
loam and sandy soils, where trees are most fre¬ 
quently struck by lightning; and, furthermore, it is 
an excellent example of a tap-rooted tree with its 
root system * extending deep into the soil; all of 
which qualities place the oak in great danger of 
lightning damage as compared with other trees. The 
following question is therefore pertinent: 
What do statistical studies of the damage of trees 
by lightning show with regard to the relative fre¬ 
quency with which oaks are struck as compared with 
other trees? 
The following figures were taken from Schlich’s 
Manual of Forestry, Yol. IV, entitled “Forest Pro¬ 
tection,” by W. R. Fisher: 
Trees struck in the Lippe-Detmold forest, Germany, 
from 1874 to 1890: 
Oak. Beech. Spruce. Pine. Others. 
Percentage of trees. .11 70 13 0 
Trees struck . 310 33 39 110 30 
^Relative frequency... 60 1 6 37 
Results of 15 years of observations published in the 
Revue des Faux et Forets: 
Oak. Beech. Spruce. Pine. Others. 
Percentage of trees.. 11 70 13 6 
Trees struck . 159 21 20 59 20 
'’Relative frequency.. 48 1 5 33 
Observations in the Bavarian State forests, 1887- 
1S90: 
Oak. Beech. Spruce. Pine. Others. 
Percentage of trees.. 1.8 10.S 41.5 30.8 15.1 
Trees stuck .61 7 155 131 
^Relative frequency.. 52 1 6 7 
* Relative frequencies are based on one for the beech, 
so that during the period covered by the observations 
one beech tree was struck to 60 oaks, six spruce and 37 
pine, each kind of tree being assumed to be present in 
equal numbers. 
NO TREE IS IMMUNE.—Other more recent 
studies confirm in general the above results, which 
show that the oak is struck much more frequently 
than other kinds of trees, with the possible excep¬ 
tion of the poplar, which does not appear to have 
been present in the Lippe-Detmold forest. The list 
of trees also subject to lightning damage includes 
the elm, ash and gum, while those least attractive 
to lightning are the chestnut, maple, alder and moun¬ 
tain ash. Those intermediate are the apple, cherry, 
linden and walnut, but no tree, as before stated, is 
immune. 
RODDING TREES.—An unsound tree containing 
rotted portions is likely to be damaged to a greater 
extent than a sound tree, or one which has received 
surgical treatment, which introduces highly-conduct¬ 
ing metal into the tree in place of the rotted wood 
with its low conductivity. The metal cables and 
rods quite often used according to the methods of 
modern surgery to protect the trees against wind 
damage and decay, while serving in a minor way as 
conductors, and furnishing some protection against 
lightning, can by no means be considered as a sub¬ 
stitute for the thorough protection possible to obtain 
by rodding, a more recent development than tree 
surgery. The rodding of trees, especially valuable 
ones, or those which involve the safety of a building 
or of animals, is now advocated by the Bureau of 
Standards, the Weather Bureau, the National Board 
of Fire Underwriters, the Ontario Department of 
Agriculture and others. 
FURTHER SUGGESTIONS—In this connection 
the follosving is quoted from a new bulletin in pro¬ 
cess of preparation, entitled “Protection Against 
Lightning of Buildings and Farm Property”: 
Protection of Trees.—If a building is more or less 
surrounded by high trees, these trees protect the build¬ 
ing to'quite an extent from lightning. This is especial¬ 
ly true of deep-rooted trees which are more liable to 
damage than others. Poplars, oaks, pines, elms; ash, 
etc., are of this kind. But the trees should be consid¬ 
ered only as an additional protection to the building, 
and the customary equipment should be provided for the 
latter. Large, full-grown trees near a dwelling are 
valuable, as a rule, and if it is desired to protect them 
against lightning, a few of the higher ones should be 
rodded, as follows: 
Place an air terminal in the top of the tree, but not 
so high as to 'be insecure, and ground it through one or 
two down conductors, the number depending upon the 
size of the tree. Screw fasteners with a long shank 
are desirable for holding the down conductors in place 
along the tree trunk in preference to a rigid fastening. 
One of the grounds provided for the conductors on the 
building may be used if convenient, or separate ones 
constructed at the foot of the trees. In order that a 
lightning discharge shall not damage the root system of 
the tree protected, it is generally advisable to construct 
shallow grounds, essentially as described under “strand¬ 
ed-cable grounds.” It is realized that the growth of 
trees will make it difficult at times to maintain the rod¬ 
ding, and its extension, partial renewal or repair will 
occasionally be needed, especially on the younger trees, 
but less so on the older trees which change but little 
from year to year, and are probably the most valuable 
and largest of a group and to be rodded in preference 
to the others. It is our conviction, however, that the 
additional protection of both trees and adjacent build¬ 
ing often makes the trouble and expense worth while. 
Description of a Chicken House 
Regarding damp chicken houses, and your advocating 
of open front, when one of our driving rains comes, 
what is to prevent the chickens from getting soaked, and 
the house, with a cement floor, flooded, .making the litter 
mud, and a terrible mess? Would the glass cloth give 
enough ventilation, and where is is best to put it; at top 
or bottom? We now have windows at the bottom. Ii 
was very damp last Wiuter with one window open most 
of the time, but when the rains came we had to close 
that. MRS. J. B. M. 
Connecticut. 
M ETHOD OF CONSTRUCTION.—Replying to 
the above question, I can answer only from 
personal experience. The last 19 years that I kept 
poultry they were kept in open-front houses, and I 
had no trouble with wet floors or litter. My houses 
were the “monitor” or sawtooth type, the openiug in 
the front being only 4 ft. high by 20 ft. long. I 
boarded up 2 ft. of this at each end of the front. 
The ends of the roof boards projected about 6 in., 
for I had the roof boards run with the slope, not 
across it; also there was an eave trough to carry 
the water off to one end. This made a total over¬ 
hang of 10 in. or more, sufficient to keep out all or¬ 
dinary rains. 
KEEPING OUT RAIN.—To prevent driving 
storms of rain or snow I made two frames of stuff 
2 y 2 in. wide, tacked cloth over them and hinged 
them at the top. Ordinarily they were swung up 
against the roof and held by a hook. When dropped 
they covered the openings, and were kept from blow¬ 
ing inward by wooden buttons at the bottom. But 
of course there are storms that come in the night, 
when there is no one to drop the curtains. In these 
cases some rain would blow in, but the hens, scratch¬ 
ing usually with their heads toward 
the light, kept the litter away from the 
front, and the dry earth floor absorbed 
it so rapidly that there was not any 
noticeable dampness. That is one of 
the reasons why I prefer an earth floor 
to anything else. Another reason is 
that dry earth is one of the best pos¬ 
sible absorbents. The droppings of the 
daytime do not remain on the floor, as 
in case of cement floor, but are ab¬ 
sorbed and deodorized. 
THE RAT QUESTION.—But what 
about rats? I settled that question by 
digging a trench 15 to 18 in. deep and 
filling it with stones and cement, where 
the foundation wall was to be, and 
making the wall a foot higher than the 
ground outside, filled the inside with 
garden soil so that it was 6 in. above 
the outside level. Rats seldom dig 
under that foundation wall, so far as 1 
know. 
A PRACTICAL EXAMPLE.—George 
II. Wraight, to whom 1 sold my farm, 
has five long open-front poultry houses and nearly 
a thousand White Leghorns in them. He boards up 
about 2 ft. of front, leaving the upper 3 ft. of the 
front covered only with the wire netting, and he has 
the healthiest lot of fowls that I have ever seen. 
With a single-slope roof and high opening in front, 
say 8 ft., I would board it down from the top for 
2 ft., then use windows considerably wider than the 
openings, hinged at the top so the bottoms could be 
swung outward and fastened at any desired angle, 
which would keep out practically all the rain, and 
yet allow plenty of ventilation. There should always 
be some windows on the east side, if the house faces 
south, to let in the morning sun. In a long house 
this is not possible, but in a square house, like mine, 
20x20 ft., the row of windows on the east end, let¬ 
ting the sunshine into the space boarded off for a 
dust bath, was greatly enjoyed by the birds. It is 
easy to have the roof boards run with the slope 
by nailing pieces of studding between the rafters 
for the boards to rest on and be nailed to, then by 
using the best matched stuff without a split or loose 
knot for the roof boards. The roof will not leak, 
even if some gale tears the roofing paper all off. 
Whereas, under the same circumstances, with the 
roof boards nailed on crosswise of the slope, in the 
usual way, every joint would be leaking a stream of 
water down into the coop. 
GLASS CLOTH.—'With relation to modern glass 
cloth over the front, I do not see how it would let 
any ventilation in. Possibly part of the dampness 
of Mrs. J. B. M.’s coop was due to condensation of 
moisture inside, because there were not sufficient 
openings to let in enough of the outside air. Damp¬ 
ness is far worse for the fowls than cold dry air. In 
Mr. Wraight’s long houses he has the roosting part 
divided by partitions every 10 or 12 ft., the parti¬ 
tions extending about 3 ft. beyond the roosts, so as to 
prevent side drafts on the hens at night. In his 
open-front houses, with the thermometer showing 
4 to 10 degrees below zero every Winter, there is 
A Tree Wrecked by a Lightning Stroke 
