Heligoland
2 of the 7 encyclopedias on this shelf carry an entry for Heligoland. Both are reproduced below, so you can see where they agree and where they differ.
Collier's New Encyclopedia (1921)
or HELGOLAND (hel'ig-ä-land), a small island in the North Sea, formerly belonging to Great Britain. It is about 1 mile long from N. to S., and 1-3 of a mile from E. to W.; 1-5 of a square mile in superficial area, and about 2 2-3 miles in circumference. The island consists of an upper and a lower quarter, the Oberland and Sandy Island. A lighthouse stands on a cliff near the village. Heligoland is an important place in time of war, and commands the German trade in the North Sea. The island, which was taken by the English from the Danes in 1807, was formally ceded to Great Britain in 1814, and by Great Britain to Germany in 1890. Pop. about 3,000. The Germans made Heligoland an impregnable fortress and military base. In the Bight the British won a naval victory over the Germans, Aug. 28, 1914. By the terms of the Treaty of Versailles the fortifications of Heligoland were dismantled.
Aiton's Encyclopedia (1910)
or Helgoland, a small island in the North Sea , belonging to the province of Schleswig-Holstein. It is only a mile in length. Its population is about 2,000. It was taken from Denmark by Great Britain in 1807. Aside from lobster fishing the island has little value, except as a military station. Germany coveted it as commanding the entrance to the new Kiel Canal. Great Britain ceded the island to Germany in 1890. The island is crumbling away rapidly beneath the blows of the German Ocean. A cliff on which a portion of a new German wall is rising became undermined in 1905 and fell carrying the wall with it.