OBSERVATIONS.
OBS. 1.—The dash does not appear to be always a rhetorical stop, or always intended to lengthen the pause signified by an other mark before it. As one instance of a different design, we may notice, that it is now very often employed between a text and a reference;—i.e., between a quotation and the name of the author of the book quoted;—in which case, as Wm. Day suggests, "it serves as a connecting mark for the two."—Day's Punctuation, p. 131. But this usage, being comparatively recent, is, perhaps, not so general or so necessary, that a neglect of it may properly be censured as false punctuation.
OBS. 2.—An other peculiar use of the dash, is its application to side-titles, to set them off from other words in the same line, as is seen often in this Grammar as well as in other works. Day says of this, "When the substance of a paragraph is given as a side-head, a dash is necessary to connect it with its relative matter."—Ibid. Wilson also approves of this usage, as well as of the others here named; saying, "The dash should be inserted between a title and the subject-matter, and also between the subject-matter, and the authority from which it is taken, when they occur in the same paragraph."—Wilson's Punctuation, Ed. of 1850, p. 139.
OBS. 3.—The dash is often used to signify the omission of something; and, when set between the two extremes of a series of numbers, it may represent all the intermediate ones; as, "Page 10-15;" i. e., "Page 10, 11, 12, &c. to 15."—"Matt, vi, 9-14."