Complex sentence: By 9:00 PM on the night of the 16th, the work of the protesters was done--they had demolished 342 chests of tea worth about ten thousand pounds--today's equivalent of about $1 million.
Split into simpler sentences: By 9:00 PM on the night of the 16th, the work of the protesters was done. They had demolished 342 chests of tea worth about ten thousand pounds, today's equivalent of about $1 million.