A bill of discovery is one brought against the opposite party in an action at law, for the purpose of obtaining evidence as to facts within the knowledge of the defendant, (i. e., in the bill of discovery, who may be the plaintiff in the original action) or to secure the production of deeds or other written instruments in his presence.

"Under the existing practice in courts of law in this State, a plaintiff can obtain the evidence of a defendant upon the trial by examining him as a witness, and can obtain a production of books and papers both before and upon the trial. He can also compel a sworn answer to his complaint and thus require the defendant to admit or deny under oath all the material allegations of fact in his complaint. The practice which thus prevails is the practice of the federal courts also, by force of sections 724, 858, 914, Rev. St. He cannot obtain the testimony of the defendant before the trial in an action pending in this court, although he can do so in the state courts, because Section 861 of the Revised Statutes, as construed in Beardsley vs. Little, 14 Blacthf., 102, requires such testimony, unless taken de bene esse or by commission to be taken in the presence of the court and jury at the trial. See also Easton vs. Hodges, 7 Biss., 324.

"The jurisdiction in equity for discovery originated in the absence of power in courts of law to compel a discovery by their own process, either by means of the oath of a party or by the production of deeds, books and writings in his possession or control. But it does not follow, because courts of law now have power to extend such relief, that a court of equity should forego the exercise of an ancient and well-settled jurisdiction. No principle is more vigorously asserted by courts of equity than that they will not yield a jurisdiction once legitimately exercised, because an enlargement of the ordinary powers of courts of law has rendered a resort to equity no longer necessary. There can be no ebb and flow of jurisdiction dependent upon external changes. Being once legitimately vested in the court it must remain there until the legislature shall abolish or limit it; for without some positive act the just inference is that the legislative pleasure is that the jurisdiction shall remain upon its old foundations. Story, Eq., Sec. 64. Accordingly, it has been frequently held that a court of equity should not refuse to entertain a bill for discovery, although, by the enlargement of the jurisdiction and remedies exercised by courts of law, similar relief could be obtained by the complainant in his action at law. Lovell vs. Galloway, 17 Beav., 1; British Empire Shipping Co. vs. Somes, 3 Kay & J., 433; Shotwell's Admr. vs. Smith, 20 N. J. Ch., 79; Cannon vs. McNab, 48 Ala., 99; Millsaps vs. Pfeiffer, 44 Miss., 805.

"It is obviously desirable to ascertain the merits of a case at its outset, so far as may be practicable, when this can be done, with the formalities and safeguards of regular procedure, rather than to await the result of an elaborate trial. The saving of time and expense which may thus be effected is beneficial, not only to the immediate litigants but to the public also. There are, therefore, persuasive considerations why a party should be permitted to resort to a bill of discovery when the facts alleged in the bill reasonably indicate that such a remedy will conduce to the safe and convenient prosecution of bis action or defense at law. It is the rule of the English courts that a party may maintain a bill of discovery in equity, not only when he is destitute of other evidence than the oath of the adverse party to establish his case, but also to aid such evidence or to render it unnecessary. Montague vs. Dudman, 2 Ves. Sr., 398; Finch vs. Finch, Id., 491; Brereton vs. Gamul, 2 W. Atk., 241. In Earl of Glengall vs. Fraser, 2 Hare, 99, it was said by Vice-Chancellor Wygram: 'The plaintiff is, in this court, entitled to an answer from the defendant, not only in respect to facts which he cannot otherwise prove, but also as to facts, the admission of which will relieve him from the necessity of adducing proof from other sources.' There are many American authorities to the same effect, among which may be cited Marsh vs. Davison, 9 Paige, 580; Peck vs. Ashley, 12 Metc, 381; Stacy vs. Pierson, 3 Rich., Eq., 152; Williams vs. Wann, 8 Blackf., 477.

"Other authorities hold that in order to maintain such a bill it must appear affirmatively that the case of the party at law cannot be established by the testimony of other witnesses, or without the aid of the discovery he seeks. Such is the rule declared in Brown vs. Swann, 10 Pet., 497, where it is held that the complainant must show by his bill that he is unable to prove the facts sought to be discovered by other testimony than that of the defendant. That was a case, however, in which the complainant sought general relief as well as discovery, thus seeking to withdraw the whole jurisdiction from the court of law of a cause of action properly triable there and transfer it to a court of equity, and the decision is not applicable where the bill is for discovery merely. Story's Eq. PL, Sec. 324. The same observation applies to the case of Drexel vs. Berney, 14 Fed. Rep., 268, decided in this court." 4

4 Colgate vs. Compagnie Francaise du Telegraphe de Paris a New York, 23 Fed. Rep., 82.

In many of the states a somewhat different view is taken, and bills for discovery alone will be no longer maintained under any circumstance.