At the time, accounts blamed strong currents. Later it was discovered that "Apollo" had taken on board an iron tank, but that no one had adjusted her compass for the influence of this large magnetic mass. Consequently, a small error in direction accumulated over the course of the five days; at the time "Apollo" struck Dixon thought she was forty or so miles out to sea. Because the convoy had endured bad weather since leaving Cork, no one had taken sightings that would have enabled them to correct their estimates of their position. Instead, they had relied on an approximately known speed and a biased heading for their estimate.