As to advertise, exercise, Detonize, and recognize, which I have noted among the exceptions, it is not easy to discover by which method we ought to suppose them to have been formed; but with respect to nearly all others, the distinction is very plain; and though there may be no natural reason for founding upon it such a rule as the foregoing, the voice of general custom is as clear in this as in most other points or principles of orthography, and, surely, some rule in this case is greatly needed.
"The Grammar of English Grammars"
Goold Brown
