arithmetical proportion
Webster's Dictionary (GCIDE)
Arithmetical \Ar`ith*met"ic*al\, a. Of or pertaining to arithmetic; according to the rules or method of arithmetic. [1913 Webster]
Arithmetical complement of a logarithm. See Logarithm.
Arithmetical mean. See Mean.
Arithmetical progression. See Progression.
Arithmetical proportion. See Proportion. [1913 Webster]