OBS. 28.—­The term not but is equivalent to two negatives that make an affirmative; as, “Not but that it is a wide place.”—­Walker’s Particles, p. 89. “Non quo non latus locus sit.”—­Cic.  Ac., iv, 12.  It has already been stated, that cannot but is equal to must; as, “It is an affection which cannot but be productive of some distress.”—­Blair’s Rhet., p. 461.  It seems questionable, whether but is not here an adverb, rather than a conjunction.  However this may be, by the customary (but faulty) omission of the negative before but, in some other sentences, that conjunction has acquired the adverbial sense of only; and it may, when used with that signification, be called an adverb.  Thus, the text, “He hath not grieved me but in part.” (2 Cor., ii, 5,) might drop the negative not, and still convey the same meaning:  “He hath grieved me but in part;” i.e., “only in part.”  In the following examples, too, but appears to be an adverb, like only:  “Things but slightly connected should not be crowded into one sentence.”—­Murray’s Octavo Gram., Index.  “The assertion, however, serves but to show their ignorance.”—­Webster’s Essays, p. 96.

   “Reason itself but gives it edge and power.”—­Pope.

    “Born but to die, and reasoning but to err.”—­Id.

OBS. 29.—­In some constructions of the word but, there is a remarkable ambiguity; as, “There cannot be but one capital musical pause in a line.”—­Kames, El. of Crit., ii, 92.  “A line admits but one capital pause.”—­Ibid. Thus does a great critic, in the same paragraph, palpably contradict himself, and not perceive it.  Both expressions are equivocal.  He ought rather to have said:  “A line admits no more than one capital pause.”—­“There cannot be more than one capital musical pause in a line.”  Some would say—­“admits only one”—­“there can be only one.”  But here, too, is some ambiguity; because only may relate either to one, or to the preceding verb.  The use of only for but or except that, is not noticed by our lexicographers; nor is it, in my opinion, a practice much to be commended, though often adopted by men that pretend to write grammatically:  as, “Interrogative pronouns are the same as relative, ONLY their antecedents cannot be determined till the answer is given to the question.”—­Comly’s Gram., p. 16.  “A diphthong is always long; as, Aurum, Caesar, &c.  ONLY prae, in composition before a vowel is commonly short.”—­Adam’s Gram., p. 254; Gould’s, 246.