INCH (O. Eng.ywce from Lat. uncia, a twelfth part ;cf. "ounce," and see As), the twelfth part of a linear foot. As a measure of rainfall an " inch of rain " is equivalent to a fall of a gallon of water spread over a surface of about 2 sq. ft., or 100 tons to an acre.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)