In State v. Lane, 301 N.C. 382, 271 S.E.2d 273 (1980), the Supreme Court stated: "Prior statements of a witness which are inconsistent with his present testimony are not admissible as substantive evidence because of their hearsay nature. Even so, such prior inconsistent statements are admissible for the purpose of impeachment. . . . '. . . If the former statement fails to mention a material circumstance presently testified to, which it would have been natural to mention in the prior statement, the prior statement is sufficiently inconsistent.'" Id. at 386, 271 S.E.2d at 276.