According to Fowler 1926 the distinguishing features of magic and magical are that (1) magic is almost always used attributively and (2) magic is used literally and in fixed phrases while magical is used with extended meaning. Shaw 1975 objects to figurative uses of magic and magical because he believes they are overused; he also advises using magical when magic cannot be used attributively. Chambers 1985 assigns literal uses to magic and figurative uses to magical. We agree to some extent with Fowler and Shaw, but not with Chambers. Here is what we have found in the evidence we have collected.
The adjective magic is almost exclusively an attributive adjective, partly because the word magic after a linking verb can be construed either as a noun or an adjective. Magical can be either an attributive or a predicate adjective, but attributive uses are about three times as common as the others. So nonattributive uses of either word are relatively uncommon. Attributive uses that are part of fixed phrases (as magic carpet, magic square, and magic number) call for magic, not magical.
Both words are used with literal force to refer to the supernatural.
... bulls and stags represented a greater magic potency —Katharine Kuh, Saturday Rev., 20 Nov. 1971
The practice of using human fat as a powerful magical ingredient —A. W. Howitt, in A Reader in General Anthropology, ed. Carleton S. Coon, 1948
And both are commonly used with extended meanings, though their connotations may differ. Magic often implies some kind of instant effect, while magical often involves a feeling such as enchantment. These are only tendencies, however, because the figurative uses of the two words overlap quite a bit.
... the magic solution to the defense problem in Europe —J. F. Golay, New Republic, 19 Apr. 1954
... a man who really had the magic touch —Leonard Bernstein, Atlantic, April 1955
... the magic plainness of La Fontaine's language — Richard Wilbur, N. Y. Times Book Rev., 14 Oct. 1979
... looked more and more magical and silvery as it danced away —G. K. Chesterton, The Innocence of Father Brown, 1911
... its magical mornings and its incomparable sunsets —Paul Bowles, Holiday, March 1957
... the magical ease with which they are summoned forth —Daniel Menaker, Harper's, October 1972
Whether or not the figurative meanings are, as Shaw and Nickles 1974 say, overused to the point of weakening the strength of the words, is a matter of opinion and a matter beyond anyone's control. One problem here is that, having become sensitive to a word or turn of phrase, one tends to think of it as more frequently used than a careful statistical count would warrant. From a practical point of view, since many writers of quality find that magic and magical serve them well in figurative uses, there is no good reason for you to feel they are forbidden to you. As with any other word, however, avoid overusing magic or magical within the context of your own writing.(資料出處：韋伯斯特英語用法詞典)