¶1Pennie, Edmonds, Morton & Barrows, of New York City, for petitioner.
¶2Herbert C. Smyth, Jr., of New York City, for respondent.
¶3Before AUGUSTUS N. HAND, CPIASE and FRANK, Circuit Judges.
¶5The judge erred in striking the jury demand, despite the fact that more *500than ten days had elapsed from the service of the last pleading directed to the issues as made by the original complaint and amended answer. For, under that complaint, the plaintiff was not entitled to de.mand a jury, since the relief he then sought was exclusively “in equity,” so that there was then no “issue triable of right by a jury.” When, by amending his complaint, he abandoned his prayer for such “equitable” relief, he then, for the first tim.e, was in a position to demand a jury, for only then did there come into being an issue “triable of right by a j-qry.” He made his demand well within ten days thereafter.
¶6Defendant seems to suggest that tlie Rules have completely obliterated, for substantive as well as procedural purposes, the historic differences between “law” and “equity.” We cannot agree.1 Those who favor it should have in mind that such obliteration, as to substantive rules, might deprive us of the inestimably valuable flexibility and capacity for growth and adaption to newly emerging problems which the principles of equity have supplied in our legal system. The procedural merger is undoubtedly desirable. A transplanted civilian, however, has shown us the djsadvantages of a system in which “law” and “equity” are fused not only as to procedure but also as to substantive rules ;2 and another writer has pointed to the danger that, if the courts are not watchful, the procedural fusion may cause a hardening of equity3 in its substantive aspects. But our decision here involves no issue of “substantive” equity.3a
¶7We consider inapposite Clark v. Wooster, 119 U.S. 322, 328, 7 S.Ct. 217, 30 L.Ed. 392, and Rice & Adams Corporation v. Lathrop, 278 U.S. 509, 515, 49 S.Ct. 220, 73 L.Ed. 480. For, in each of those cases, the defendant — not the plaintiff— sought to have the action discontinued in equity after the patent had expired, although suit had been begun before that expiration; consequently, as the plaintiff had not elected to substitute a' law action for his equity action, the court, which had originally obtained equity “jurisdiction,” had discretion to retain such “jurisdiction.” It is of no moment that we believe that trial by a jury of a patent suit is usually undesirable, since it is well settled that such a trial may be demanded where the sole claim is for money, if the demand be timely, as we hold it was here.4
¶8*501There can be no doubt of our power in such a case to issue a writ of mandamus, as it is in aid of our appellate jurisdiction.5
¶9The writ will issue directing the respondent to vacate the order striking the jury demand.