The land base for the construction of the light was Erraid near Iona. Fourteen miles distant from Dhu Heartach across open sea, the little island provided a granite quarry and a shore station once the work on the lighthouse was completed. Initial construction on the rock, which began on 25 June 1867 under the supervision of Alan Brebner, required a barrack for the workmen made of iron. Summer gales brought high seas, which resulted in breaking water falling on the roof above sea level. It held firm, although fourteen men including Brebner were trapped there for five days, and at one point seawater poured in through the trapdoor, swirled around them and exited with their remaining food supplies. Describing a similar occasion, R. L. Stevenson wrote: