L 1 G II T N I N G. 
•606 
coat of ruft, which will continually increafe till the 
whole is converted into ruit ; but rult of iron, and in¬ 
deed the calx of al) metals, is a ?ion-condu&or, or atinoft 
but a very imperfect conduftor, of the eleCIric fluid. 
Hence it is eafy to fee, that, in a few years after a 
lightning-rod has been ereCted, that part of it which is 
under-ground will contribute little or nothing towards 
the fafety of the building. Befldes, the furface of this 
.part of the rod is too final 1 to afford an eafy and copious 
discharge of the electric fluid into the furrounding earth, 
when this is hut an imperfect cqnduCtor. As a remedy 
for thefe defeCfs, I would propofe that the part of the rod 
under-ground be made of tin or copper, which are far 
lefs liable to corrolion or ruft, by lying under-ground, 
than iron ; or, which perhaps would anfwer the purppfe 
better, let this part of the rod, of whatever metal it be 
made, be coated over with a thick cruft of black-lead, 
■previoufly formed into the confiftence of pafte, by being 
-pulverized and mixed with melted fulphur, (as in the 
manufactory of the ordinary kind of black-lead pencils,) 
and then applied to the rod while hot. By this means, 
the lower part of the rod would, I apprehend, retain its 
conducting power forages, without any diminution. I11 
order to increafe the furface of the lower part of the con¬ 
ductor, let a hole or pit of f'ufRcient extent be dug as 
deep as convenient, and into this pit let there be put a 
quantify of charcoal, roll (id the lower extremity of the 
rod. Charcoal poffeffes two properties, which in a pecu¬ 
liar manner fit it for anfweiing the purpofe here in view. 
Firft, it is a very good conductor of electricity ; and fe- 
condly, it will undergo little or no change of property by 
lying ever fo long in the earth. Thus might the furface 
of that part of the conductor in contact with the earth be 
kicreafed, with little trouble or expenle, to any extent at 
pleafure ; a circumftance which every one acquainted with 
electrical experiments mult acknowledge to be of great 
importance to the end here propofed.” For thefe pro- 
pofed improvements, the Magellanic gold medal was voted 
to Mr. Patterfon by the American Philofophical Society ; 
and the account was publifhed in their TranfaCtions. 
The editor of the London Philofophical Journal makes 
light of thefe improvements, being of opinion, that the 
place where lightning ftrikes feems to be governed in a 
great meafure by certain conducting mafles lying within 
the earth, which have an influence far beyond the coun¬ 
teracting power of any metallic rod, even fuppoling this 
laft to be inferted into the mafs itfelf. For this and other 
reafons, deduced from the greatnefs of the fcale on which 
eleftric phenomena are produced by atmofpheric evapo¬ 
rations and condenfations, he thinks that conduCting-rods 
.cannot effectually modify the courfe of thefe effects ; and, 
in fupport of his opinion, ftates the cafe of the poor-houfe 
at Heckingham, which about thirty years ago was fet on 
fire by lightning, without its touching any one of the 
eight elevated metallic conductors attached to the build¬ 
ing. Phil. Journal, vol. xxix. 
If, however, the objections ftated againft eleCtrical con¬ 
ductors were fo ftrong as the editor of the Philofophical 
Journal feems to think, it is manifelt that they would 
not have been found to he of that benefit which experi¬ 
ence has decided them to be of wherever they have been 
ufed, but particularly in America ; and we farther ima¬ 
gine, that, if the difpofltion of the internal mafles of the 
earth abfolutely decided the place of the eleCfric ftroke, 
that then certain places mull be oftener ftruck than others, 
(which has never been proved to be the cafe;) and that 
the praftice of the Romans, in marking by a public mo¬ 
nument the (pot ftruck by lightning, would appear to be 
a wife precaution. See p. 69+. On this fubjeCt the faireft 
decifion feems to be, that though conductors, like moft 
other human means, are not abfolutely perfeCt, yet they 
increafe the chance of protection lb much, as to make 
their adoption extremely advifeable; and, inftead of reject¬ 
ing them on account of a few failures, that thefe latter 
fliould rather excite to fucli an examination of the caufes. 
as might fuggeft farther improvements in their confiruc- 
tion and ufe. The event at Heckingham, for inftance, 
might have been caufed by the very defects in the rods 
which Mr. Cook mentions ; the rods might have been put 
up without making them terminate in water at all; or the 
water might at that time have been dried up; they might 
even have been fo injudicioufiy placed, as to conduCt the 
lightning to the building, inftead of drawing it off; and 
that this has been often the cafe, feems probable, from 
the precaution ufed of late years, in ereCIing conductors 
for gunpowder-magazines, by placing them at fome little 
diftance from the building, inftead of attaching them to 
it, as formerly. 
For the above reafons, we ftill think the ufe of con¬ 
ductors for lightning highly neceffary ; and agree with 
Mr. Cook and Mr. Patterfon that rods tipped with brals 
or black-lead would be much fuperior to any ufed for the 
purpofe at prefent. On the point of the propriety of ereCt- 
ing conductors all over the kingdom, in the manner the 
former propofes, we cannot, however, coincide with him; 
for, in the firft place, the diftance he mentions for them 
would be totally inadequate as a general protection ; and 
to have them much clol'er, would coft a fum too enor¬ 
mous to be applied to guard againft an evil, which, formi¬ 
dable as it is, ranks very low in the lift of thofe by which 
mankind in general are l'urrounded, or even of thofe which 
we peculiarly labour under in England. The ufe of con¬ 
ductors therefore, we imagine, muft be ftill confined to 
the defence of expenfive public buildings, or to the dwel¬ 
lings of thofe individuals who can afford them, and are 
fo happy as to have no greater evils to contend with. 
Dr. Franklin advifes perfons who are apprehenfive of 
danger from lightning, to fit in the middle of a room, pro¬ 
vided it be not under a metal lultre fufpended by a chain, 
fitting on one chair, and laying their feet on another. 
It is It ill fafer, he fays, to bring two or three mattrafies, 
or beds, into the middle of the room, and, folding them 
double, to place the chairs upon them ; for, as they arc 
not fo good conductors as the wall, the lightning will not 
choofe to pafs through them ; but the fafeft place of all is 
in a hammock hung with filken cords, at an equal dif¬ 
tance from all the fldes of a room. Dr. Prieftley obferves, 
that the place of moft abfolute fafety muft be the cellar, 
and efpecially the middle of it; for, when a perf'on is 
lower than the furface of the earth, the lightning muft 
ftrike it before it can poflibly reach him. In the fields, 
the place of fafety is within a few yards of a tree, but not 
quite near it. Neverthelefs, S. Beccaria cautions perl'ons 
not to depend upon the neighbourhood of a higher, or, in 
all cafes, a better conductor than their own body ; fince, 
according to his repeated obfervations, the lightning by 
no means defeends in one undivided track; but bodies of 
various kinds conduCt their (hare of it at the fame time, 
in proportion to their quantity and conducting power. 
See on this fubjeCt, Franklin’s Letters ; Beccaria’s Lettre 
dell’ Elettricil'mo ; Prieftley’s Hiltory, See. of IJleCtricity. 
Phofphorus, when newly made, gives a fort of artificial 
lightning , viftble in the dark, which would furprife thofe 
who are not ufed to fuch a phenomenon : the ufual me¬ 
thod of keeping this preparation is under, water; and, if 
the corrufcations are defired to be feen to the greateft ad¬ 
vantage, the glafs in which it is kept fhould be deep and 
cylindric, and not more than three-fourths filled with wa¬ 
ter. The phofphorus put into this water will fend up cor¬ 
rufcations at times, which will pierce through the incum¬ 
bent water, and expand themlelves with great brightnefs 
in the empty upper part of the bottle. If we compare 
this artificial corrufcation to the •real lightning, we (hall 
find, that, as in this the fire pafl’es unaltered through the 
water, fo in that the flafhes of lightning, which come at 
intervals, pafs uninterrupted through the moft aenfe 
clouds, and are not obftruCted by the heavieft ltorms of 
rain, but, like the beams of the fun, or any other fire, pafs 
uninterrupted through glafs and water. The feafon of 
the weather, as well as the newnefs of the phofphorus, 
mult 
