Original sentence: Geokaun Mountain and Fogher Cliffs : the highest mountain on Valentia Island and the seacliffs of 600ft.Prior to the transatlantic telegraph, American longitude measurements had a 2800 foot uncertainty with respect to European longitudes.The permanent population of the island is 650, and the island is approximately 11 km long by 3 km wide.on its northern face
Edited sentence: Geokaun Mountain and Fogher Cliffs : the highest mountain on Valentia Island and the seacliffs of  on its northern face.Prior to the transatlantic telegraph, American longitude measurements had a  uncertainty with respect to European longitudes.The permanent population of the island is 650, and the island is approximately 7 miles (11 km) long by almost 2 miles (3 km) wide