 Work continued during 1841 – 42 , a crane being used to hoist the huge blocks as the tower rose . The last one was raised to the parapet in July 1842 . Robert Stevenson , then aged 70 , visited the site on his last annual voyage of inspection . The walls at the base are 9 @.@ 5 feet ( 2 @.@ 9 m ) thick , and 2 feet ( 0 @.@ 61 m ) thick at the top . The lightroom and lantern sit above nine apartments 12 feet ( 3 @.@ 7 m ) in diameter . The total cost of the works undertaken by the Northern Lighthouse Board was £ 86 @,@ 977 , including the cost of establishing the shore station at Hynish , estimated at £ 13 @,@ 000 . It is a credit to Stevenson , his foreman Charles Stewart , and Captain Macurich the landing master , that not a single life was lost during the construction . 
