See also 2 Wigmore, Evidence § 657 (3d ed. 1940); McCormick on Evidence § 15 (hornbook series 1954); 31 Am.Jur.2d Expert and Opinion Evidence § 42 (1967); 19 A.L.R.3d 1008. But it is true also that an expert witness who has heard the entire testimony in a case and who assumes the truth of it all, where it is not conflicting, may base his opinion upon facts testified to by other witnesses, or upon facts contained in reports or examinations made by third parties. Wilhelm v. Burke, 235 Md. 412 [ 201 A.2d 835] (1964); State ex rel. Solomon v. Fishel, 228 Md. 189 [ 179 A.2d 349] (1962); Ihrie v. Anthony, 205 Md. 296 [ 107 A.2d 104] (1954); Bethlehem-Sparrows Point Shipyard, Inc. v. Scherpenisse, 187 Md. 375 [ 50 A.2d 256] (1946); Langenfelder v. Thompson, 179 Md. 502 [ 20 A.2d 491] (1941). Admittedly it is often hard to draw the line between fact and opinion.

State v. Peterson, 315 Md. 73, 79-82, 553 A.2d 672, 675-77 (1989); Mercy Hosp., Inc. v. Jackson, 306 Md. 556, 561, 510 A.2d 562, 564 (1986); Hagerstown Reproductive Health Services v. Fritz, 295 Md. 268, 271, 454 A.2d 846, 848, cert. denied, 463 U.S. 1208, 103 S.Ct. 3538, 77 L.Ed.2d 1389 (1983); Attorney Gen. v. Anne Arundel County School Bus Contractors Assoc., 286 Md. 324, 327, 407 A.2d 749, 751 (1979); Reyes v. Prince George's County, 281 Md. 279, 291-92, 380 A.2d 12, 19 (1977); State v. Ficker, 266 Md. 500, 506-07, 295 A.2d 231, 234-35 (1972); Potts v. Governor v. Maryland, 255 Md. 445, 448-49, 258 A.2d 180, 182 (1969); Lloyd v. Board of Supervisors, 206 Md. 36, 39, 111 A.2d 379, 380 (1954), and, therefore, subject to dismissal, pursuant to Maryland Rule 8-602(a)(10). Although this Court has discretion to decide a question which has become moot — Maryland Rule 8-602(a)(10) authorizes, rather than mandates the dismissal of a moot appeal, see Reyes, 281 Md. at 296, 380 A.2d at 21; Wilhelm v. Burke, 235 Md. 412, 416, 201 A.2d 835, 837 (1964) — as this issue is not likely to recur, and there is, in this case, no "imperative and manifest urgency to establish a rule of future conduct," Attorney Gen. v. Anne Arundel County School Bus Contractors Assoc., 286 Md. at 327-28, 407 A.2d at 752-53; see also State v. Peterson, 315 Md. at 82, 553 A.2d at 677; Reyes v. Prince George's County, 281 Md. at 297, 380 A.2d at 22; State v. Ficker, 266 Md. at 507, 295 A.2d at 235; Area Dev. Corp. v. Free State Plaza, Inc., 254 Md. 269, 271, 254 A.2d 355, 356 (1969); Lloyd v. Board of Supervisors, 206 Md. at 43, 111 A.2d at 382, we decline the invitation extended by the appellants nevertheless to address the merits. Instead, we dismiss the appeal.

See also 2 Wigmore, Evidence § 657 (3d ed. 1940); McCormick on Evidence § 15 (hornbook series 1954); 31 Am. Jur.2d Expert and Opinion Evidence § 42 (1967); 19 A.L.R.3d 1008. But it is true also that an expert witness who has heard the entire testimony in a case and who assumes the truth of it all, where it is not conflicting, may base his opinion upon facts testified to by other witnesses, or upon facts contained in reports or examinations made by third parties. Wilhelm v. Burke, 235 Md. 412 (1964); State ex rel. Solomon v. Fishel, 228 Md. 189 (1962); Ihrie v. Anthony, 205 Md. 296 (1954); Bethlehem-Sparrows Point Shipyard, Inc. v. Scherpenisse, 187 Md. 375 (1946); Langenfelder v. Thompson, 179 Md. 502 (1941). Admittedly it is often hard to draw the line between fact and opinion.

The Court of Appeals held that "it is within the discretion of [the appellate courts] whether to dismiss an appeal or not." Wilhelm v. Burke, 235 Md. 412, 417 (1964). In Anderson v. Hull, 215 Md. 476 (1958), the appellees filed a motion to dismiss the appeal because the appellant failed to supply appellee with a designation of the proposed record extract and omitted certain required items.

To dismiss the appeal is within our sound discretion. E.g., Wilhelm v. Burke, 235 Md. 412, 417, 201 A.2d 835 (1964). The Court, having vacated the Motion, left it to the present panel to decide whether to grant it. Between appellant's first Motion to Correct the Record and now, appellant has provided a transcript of the missing portion of the trial, certified as accurate by Deborah H. Powers of Gore Reporting Company.

An expert witness who has heard the entire testimony in a case and who assumes the truth of it all, where it is not conflicting, may, however, base his opinion upon facts testified to by other witnesses, or upon facts contained in reports or examinations made by third parties. Wilhelm v. Burke, 235 Md. 412, (1964), cited in Consol. Mech. Contractors v. Ball, 263 Md. 328, (1971).

See also 2 Wigmore, Evidence § 657 (3d ed. 1940); McCormick on Evidence § 15 (hornbook series 1954); 31 Am.Jur.2d Expert and Opinion Evidence § 42 (1967); 19 A.L.R.3d 1008. But it is true also that an expert witness who has heard the entire testimony in a case and who assumes the truth of it all, where it is not conflicting, may base his opinion upon facts testified to by other witnesses, or upon facts contained in reports or examinations made by third parties. Wilhelm v. Burke, 235 Md. 412 (1964); State ex rel. Solomon v. Fishel, 228 Md. 189 (1962); Ihrie v. Anthony, 205 Md. 296 (1954); Bethlehem-Sparrows Point Shipyard, Inc. v. Scherpenisse, 187 Md. 375 (1946); Langenfelder v. Thompson, 179 Md. 502 (1941). Admittedly it is often hard to draw the line between fact and opinion.