The ballast used in ships was being changed from shingle to pigs of iron, which could be moved and cleaned in a way not possible with shingle.
Izinto ezinzima ezilayishwe enqanaweni ukuyizinzisa zantshintshwa ukusukela kumaplanga ukuya kwiihagu zentsimbi, ezinokusunduzwa kwaye zicocwe ngendlela elula kunaleyo yamaplanga.