"The candle fell and a fire started."
Translation:Thit an choinneal agus thosaigh tine.
That would be 'let a fire start', the imperative. thosaíodh would be 'a fire used to start' (past habitual)
"thosaíodh" would be the past habitual, but "tosaíodh" is past tense autonomous/passive person, so "tosaíodh tine" would be "a fire was started", which would seem to me to be equivalent to "a fire started" in english. Imerative would be "tosaigh tine" = "start a fire", wouldn't it. I did see (after posting this) a comment on another thread that "thosaigh tine" can be used intransitively, so used that way "thosaigh tine" would seem correct for "a fire started". I wasn't familiar with this usage.
Wow, oops. Forgot about the past autonomous (cause it is also the imperative). So. There's two things:
It's not really a passive; it'd equate more to 'one started a fire'
Based on samples in FGB, it's fine as it is. They have thosaigh an chluiche for 'the game started'.
Oh fooey. The lenition on candle. I forgot direct objects lenite. Somebody lenite my candle? ;)
Unless I'm mistaken, "candle" is the subject and it lenites because it's a feminine noun following "an."