Statistics for occurrence #1 of “Island No.10” in chapter 11, page 204 of The Photographic History of The Civil War: in ten volumes, Thousands of Scenes Photographed 1861-65, with Text by many Special Authorities, Volume 5: Forts and Artillery.:
In the rear of such hasty works, heavier lines often were constructed by large forces working with spades.
Semi-permanent works were used both in the East and in the West.
Island No.10 , Forts Henry and Donelson, and other small works were all of a permanent or semi-permanent character, having more or less of the scientific touch that followed the old school of fortification.
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