1884... 
On Thunderbolts. 
723 
first is a very important one, and consists of a dictum by the 
famous Dr. Joseph Priestley, F.R.S., in his “ History of 
Electricity,” 4th edition, London, 1775. Speaking of the 
analogy between a lightning flash and the eleCtric spark, he 
observes : “ It was Dr. Franklin who first proposed a 
method of verifying this hypothesis, entertaining the bold 
thought . . . “ that pointed iron rods fixed in the air, 
when the atmosphere was loaded with lightning, might 
draw from it the matter of the thunderbolt, and discharge it 
without noise or danger into the immense body of the 
earth. [Hist. p. 164]. It is clear that the “ matter” here 
alluded to is the electricity causing the lightning stroke, or 
thunderbolt. The other case is the account of a lightning 
stroke at Holbeck, near Leeds, on September 1st, 1672, 
when a child (playing with others) was killed, his com- 
panions being badly burnt. The narrative is supplied to 
the “Philosophical Transactions of the Royal Society” (xxii., 
578) by Mr. R. Thoresby, F.R.S., who quotes the parish 
register which records that the child was “ slain by a 
thunderbolt” It is abundantly clear from the context that 
there was no stone or material bolt present, and that neither 
Mr. Thoresby nor the parish authorities had the faintest 
idea of any other agency than that of an ordinary lightning 
stroke. 
But perhaps the most curious circumstance connected 
with the mistaking of thunderbolts for thunderstones is the 
complete manner in which the expressions employed by the 
French are ignored. It is hard to imagine that any man 
should allow himself to be accepted as an authority on the 
science of lightning strokes who had not studied French 
works on the subject, but it is certain that any such student 
could not but have noticed that the French almost invariably 
use the term la foudre to designate a stroke of lightning, 
whilst for lightning itself they employ a totally different 
word, viz., Veclair. They thus differ entirely from the 
slip-shod English practice of the present day of adopting 
the term lightning both for the stroke and also for its flash 
or luminous accompaniment. But what is the English 
translation of la foudre — the translation given by every 
French dictionary ? Why, nothing else than thunderbolt. 
It would appear then that, whilst originally in both lan- 
guages a scientific distinction was maintained between the 
stroke and its accompanying light, such distinction has in 
recent years been permitted in the less scientific country to 
drop, and that, on the strength of this negligence, English 
men of science have lapsed into a complete ignorance of the 
