These exceptions must be overruled on the authority of Locke v. Wood, 16 Mass. 317. In that case it was decided that after a cause is opened to the jury, and is begun to be proceeded in before them, the plaintiff has not a right, of his mere pleasure, to discontinue his suit or to become nonsuit. Mr. Justice Jackson had previously expressed an opinion to the like effect in Haskell v. Whitney, 12 Mass. 48, 49. Such therefore is now the law of this commonwealth, whatever it may be elsewhere, or may have been here under the colonial ordinance *573of 1641, which is found in Anc. Chart 46. And this law seems to us to be eminently just. As a nonsuit.is no bar to another suit for the same cause of action, a plaintiff might harass a defendant by unlimited litigation, if the court had no authority, in any case, to prevent a nonsuit.
The action of the judge, at the trial of this case, having been an exercise of his judicial discretion, cannot be supervised by as. Nor is the question before us whether he rightly decided that there was not sufficient proof of the loss of the plaintiff’s mortgage to warrant paroi proof of its contents. A nonsuit was refused, and a verdict taken, solely — so far as the exceptions show — because the plaintiff did not produce legal proof of the mortgage which was necessary to the maintenance of his action, although the court had granted him all the time that he asked for to procure such proof. jExceptions overruled.