A cross bill is a bill brought by a defendant in a suit in equity, who seeks some affirmative relief against some other party to the suit. It may be brought either against the complainant, or against some other defendant. Thus if a bill is brought for the specific performance of a contract the defendant may file a cross bill asking for the cancellation of the contract; or if in a bill to foreclose on a first mortgage, a second mortgagee is made a defendant, he may file a cross bill against the mortgagor.

A cross bill may be brought for the purpose merely of obtaining discovery.

Cross bills are thus discussed by the Supreme Court of the United States 8 in the case of Morton's Louisiana & Texas R. & S. Co. vs. Texas Central R. Co.:

"A cross-bill,' says Mr. Justice Story (Eq. PL, No. 389), 'ex vi terminorum, implies a bill brought by a defendant in a suit against the plaintiff in the same suit, or against other defendants in the same suit, or against both, touching the matters in question in the original bill. A bill of this kind is usually brought, either (1) to obtain a necessary discovery of facts in aid of the defense to the original bill, or (2) to obtain full relief to all parties, touching the matters of the original bill.' And as illustrative of cross-bills for relief, he says (No. 392): 'It also frequently happens, and particularly if any question arises between two defendants to a bill, that the court cannot make a complete decree without a cross-bill, or cross-bills, to bring every matter in dispute completely before the court, to be litigated by the proper parties, and upon the proper proofs.'

"It seems to us that in order that a decree might be made upon the whole matter in dispute, brought completely before the court, the bill in question was necessary and was correctly styled a cross-bill. In no proper sense were new and distinct matters introduced by it, which were not embraced in the original and amended and supplemental bills, and while it sought equitable relief, it was such as, in point of jurisdiction over the subject matter, the court was competent to administer. It may be that, so far as it sought the further aid of the court beyond the purposes of defense to the original bill, it was not a pure cross-bill, but that is immaterial. The subject matter was the same, although the complainant in the cross-bill asserted rights to the property different from those allowed to it in the original bill, and claimed an affirmative decree upon those rights. A complete determination of the matters already in litigation could not have been obtained except through a cross-bill, and different relief from that prayed in the original bill would necessarily be sought. This bill was filed, on leave, before the testimony was taken, and though there should be as little delay as possible in filing bills of this kind, yet that was a matter entirely within the discretion of the court, which could have directed it to be filed even at the hearing. And whether this bill be regarded as a pure cross-bill, as an original bill in the nature of a cross-bill, or as an original bill, there is no error in calling for the disturbance of the decree because the court proceeded upon it in connection with the other pleadings. The jurisdiction of the Circuit Court did not depend upon the citizenship of the parties, but on the subject matter of the litigation. The property was in the actual possession of that court, and this drew to it the right to decide upon the conflicting claims as to its ultimate possession and control.

8 137 U. S., 171.

"Milwaukee & M. R. Co. vs. Soutter, 69 U. S., 2 Wall., 609 (17, 886); People's Bank vs. Calhoun, 102 U. S., 256 (26, 101); Krippendorf vs. Hyde, 110 U. S., 276 (28, 145)."