Complex sentence: In modern candles, the wick is constructed so that it curves over as it burns, so that the end of the wick gets oxygen and is then consumed by fire--a self-trimming wick.
Split into simpler sentences: In modern candles, the wick is constructed so that it curves over as it burns. This insures that the end of the wick gets oxygen and is then consumed by fire--a self-trimming wick.