Self-ignition catapult bolts?

[Tormenta]

In the Appian's History of Rome: The Illyrian Wars I noticed, that in the attack on the town of Delminium by consul Marcius Figulus in 156 BC, the author is speaking of a self-ignition bolts:

Then, returning to Delminium, he hurled sticks of wood, two cubits long, covered with flax and smeared with pitch and sulfur, from catapults into the town. These caught fire from friction and, flying in the air like torches, wherever they fell caused a conflagration, so that the greater part of the town was burned. This was the end of the war waged by Figulus against the Dalmatians.
(the whole text on the internet http://www.livius.org/ap-ark/appian/appi...ian_3.html)
It is possible to catch fire just from friction?
Is there some other source that is mentioning the same thing?

[PhilusEstilius]

I wonder if the friction was not caused by the catapult as the bolts were leaving it in the firing process, and there would be no damage to the machine as the ignition was beginning just after the bolt was leaving it.

[M. Demetrius]

It sure seems like a lot of heat from very little time spent on the move while still in the catapult. But I wasn't there, so what do I know?

[Forty-One]

Galen in de temperamentis mentions a substance concocted from sulfur and bitumen that is ignited by friction: "Everything smeared with it catches fire when heat strikes it. It is prepared from sulfur and liquid bitumen and is ignited with friction."

I suspect there may have been more to it than just sulfur and bitumen, though. Some substances are extremely volatile in combination. The constituents of strike-anywhere matches will spontaneously violently combust unless separated with some kind of binder (the PIRA in Northern Ireland used to use exactly the same stuff to make improvised incendiary bombs). Maybe the Romans stumbled onto that chemistry without any historian noticing?

[Tormenta]

If I checked the right chemistry book, sulphur auto ignition temperature is over 250° C. I don't believe, that the bolt can fly through the air at such speed that this will ignite it. But is possible that the friction caused by the projectile going through the loading channel can light it like a match(sulphur is also one of the main element for it). Like Harry suggested I believe, that there is a small trick behind it, or in the process or in the unmentioned element/s.

[Sean Manning]

It is possible to catch fire just from friction?
Is there some other source that is mentioning the same thing?

It was a popular ancient "factoid" that sling bullets would melt from speed, so I wonder if the original bolts were ignited some other way and Appian (or his source) just assumed they were ignited by friction. I'm not enough of a chemist to reject Appian's story out of hand, but the sling story is impossible. For sources on the sling story, see Lucretius 6.178-9 or Virgil, Aeneid, 9.586-9.

[Epictetus]

Pliny's Natural History has a section on fire, including some rather bizarre properties. He mentions fires starting - perhaps spontaneously - by friction.

[M. Demetrius]

I have made fire by friction with a "fire-bow" and board, but it's a) not at all like you see in the movies, and b) not as easy as it sounds. You really don't make fire, though, just a glowing ember that can be blown against tinder to make a fire.

Without chemicals to help with the combustion, I agree with those who have said they doubt it could be done just by air friction, of the 1/100 of a second the bolt is in contact with the ballista as it moves off the launcher.

[D B Campbell]

... the author is speaking of a self-ignition bolts:
Then, returning to Delminium, he hurled sticks of wood, two cubits long, covered with flax and smeared with pitch and sulfur, from catapults into the town. These caught fire from friction and, flying in the air like torches, wherever they fell caused a conflagration, so that the greater part of the town was burned. This was the end of the war waged by Figulus against the Dalmatians.

The sentence in question actually reads: "These were kindled by the rush ...", which translator Horace White sensibly glossed as "These were fanned into flame by the draught ..." It seems that they were simply incendiary arrows of the usual sort. (Sorry to spoil a good story! :wink: )

[Tormenta]

(Sorry to spoil a good story! :wink: )

Not at all, I like the simple solution.

I have made fire by friction with a "fire-bow" and board, but it's a) not at all like you see in the movies, and b) not as easy as it sounds. You really don't make fire, though, just a glowing ember that can be blown against tinder to make a fire.

I know this from experience, I have given up after 15 fails.