This section is from the "A Complete Dictionary of Dry Goods" book, by George S. Cole. Also available from Amazon: A complete dictionary of dry goods and history of silk, cotton, linen, wool and other fibrous substances,: Including a full explanation of the modern processes ... together with various useful tables.
Castor. The beaver, and by extension the fur or hide of a beaver. The fur of the Castor beaver is used in the manafacture of fur hats. Also, a heavy quality of broadcloth used for making overcoats is sometimes termed castor. [See Gloves]