It must be taken from the terms of the exceptions, that the plaintiffs’ land was injured by water set back upon it in consequence of the obstruction by the defendant upon his land of an ancient watercourse, which flowed from the *80plaintiffs’ land through the defendant’s land. The declaration describes the watercourse as an ancient rivulet or stream, which had existed beyond the memory of man.

The exceptions state that the action was for damages for the obstruction of an ancient watercourse, and that the evidence showed that “ a ditch, with defined banks and bed, and of varying width, had for more than twenty years run across the land ” of the parties. No question is suggested in the exceptions as to the nature of the plaintiffs’ right, and it must be taken that it was not a mere easement derived by grant from the owner of the defendant’s land, but the right to have the water flow from his land in a natural watercourse.

The obstruction complained of was the filling up of the ditch, or watercourse, except so much of it as was occupied by a pipe for conducting water. The obstruction was made when Clarke was the owner of the plaintiffs’ land, and has been continued since. The plaintiffs’ title is from Clarke, in trust for himself and others. The declarations and admissions of Clarke made after his deed to the plaintiffs are not made competent by the fact that he is one of several cestuis que trust. Pope v. Devereux, 5 Gray, 409. Besides, the acts of Clarke which they were offered to prove were not competent; and the remaining exception, which is to the rejection of evidence offered to prove such acts, cannot be sustained.

So far as such acts tend to prove a license, whether by Clarke or by the plaintiffs, they are not competent, because a license is not set up in the answer. Pub. Sts. o. 167, § 20. Hollenbeck v. Rowley, 8 Allen, 473. Ward v. Bartlett, 12 Allen, 419.

If the defence of a right by grant or prescription to flow the plaintiffs’ land is open under an answer of general denial, the evidence offered was not competent to prove it. It is a right to an easement in the plaintiffs’ land which can be shown only by grant or prescription. The evidence was not competent to prove either. Cobb v. Fisher, 121 Mass. 169. Craig v. Lewis, 110 Mass. 377. Fitch v. Seymour, 9 Met. 462. Morse v. Copeland, 2 Gray, 302. Stevens v. Stevens. 11 Met. 251.

Exceptions overruled.