168 POPULAE SCIENCE EE VIEW. 
by circumstantial evidence, to the conclusion that the discovery 
is traceable to what may be called the second grand historic 
period of the world's history. In law a great many human 
lives have been taken on evidence infinitely less reliable ; but 
men of science being naturally, from their love of the demon- 
strative, the antipodes of the lawyer, and having no legal 
subtleties, shams, and glib inferences from nothing in their 
hearts, despise so-called circumstantial evidence, as meaning 
what the cleverest sophist can best present from the smallest 
data, and as unworthy of all serious regard. They there- 
fore will go, I doubt not, as a man, with Gibbon, in 
believing nothing absolutely about Greek fire until they have 
clear knowledge of the time when the invention was actually 
used in warfare, which would bring it down to the ninth 
century. 
This much we know : that there was, under the Constan- 
tines, a liquid substance which, discharged from a catapult, 
bow, or sling, ignited in the air spontaneously. We know 
that the fire thus produced was very terrible in its effects, and 
we learn that, as the use of gunpowder came to be better 
known, Greek fire became of no importance : gunpowder blew 
it out of the field. 
It still remains an interesting question, — What was the 
nature of this Greek fire fluid ? On this point nothing posi- 
tive remains. The Princess Anna Comnena says it was com- 
posed of sulphur, resin, and oil. Roger Bacon is supposed to 
have given two of its constituents — viz., sulphur and saltpetre 
— but to have hidden the third in the absurd sentence (at 
least, to us absurd), “ Luru vopo vir Can utriet !" but in the 
sentence referred to, Bacon may be referring to gunpowder. 
In a word, it is hopeless, in the confusion surrounding the 
whole subject, to come to any decisive opinion. At the same 
time it is not improbable that, in the main, the formula of the 
Princess Anna Comnena is not far from the truth. Our diffi- 
culty in understanding her formula lies in the construction we 
put on the word “ resin." We are not departing a letter from 
what is known at the present day in chemical science to sup- 
pose that a so-called resin was used, which, on admixture with 
oil and sulphur, formed a compound that would spontaneously 
ignite on exposure to the air. In another way we sometimes 
have fire produced in these days, — when saw-dust and oil are 
admixed, and what is called spontaneous combustion ensues. 
The remarkable feature of the old Greek liquid is, that it 
must have been very safe in the mass, as safe as turpentine or 
common naphtha. Had not this been the case, it could never 
have been carried in wooden galleys or pumped through 
engines in torrents. It must have ignited in the air from the 
