The facts that the plaintiff has had the use and enjoyment of the premises under the lease for several years and that as matter of general knowledge there has been depreciation in real estate values, do not preclude equitable relief. Rackemann v. Riverbank Improvement Co. 167 Mass. 1. Equitable adjustment of fair rental of the premises may be allowed if the facts disclosed at the trial require that result. See Hall v. Ryder, 152 Mass. 528. The case at bar is distinguishable from Crowley v. Holdsworth, 264 Mass. 303, where reformation of the transaction rather than rescission was required by the facts. It cannot rightly be ruled that laches on the part of the plaintiff is disclosed on the face of the bill.

Since this defence must be based upon rescission of the contract of lease, it fails for the further reason that the defendant has not proved that it rescinded or attempted to rescind on discovery of the alleged concealment. Milliken v. Thorndike, 103 Mass. 382. Hall v. Ryder, 152 Mass. 528. See Stevens v. Pierce, 151 Mass. 207, 209-210. It is not necessary to consider whether other essential elements of this defence are lacking. Compare Cutter v. Hamlen, 147 Mass. 471, 474; Stumpf v. Leland, 242 Mass. 168, 174-175.