What Does "Transported" Mean In This Usage?

“…* thought of an old bridge that I know in Sturminster Newton in Dorset. It still has a cast-iron notice bolted to it that warns anybody thinking of damaging or defacing the bridge in any way that the penalty is transportation. To Australia. Now, Sturminster Newton is a lovely town, but it astonishes me that the bridge is still standing.”

– Douglas Adams, from ‘Riding the Rays’, reprinted in “The Salmon of Doubt.”

I shared that here as a reference to the use of ‘transportation’ as a penalty. (And because I like the punch line.)

A not entirely wild guess is that Miss Saunders and Miss Bryant were both young and nubile - eg: potential assets in Australia - and hanging them could also have been ‘unpopular’

Acting under orders would also contribute, if they had disobeyed they would have received a thorough beating from Mrs Tonney