We had, the year before deciding that case, sustained the constitutionality of a subdivision (numbered subd. 4, par. a) of section 309 of the Multiple Dwelling Law which provided that, if an owner of an old law (pre-1901) tenement house desired to continue the structure as a tenement or multiple dwelling, he was obliged to make those changes in the building found necessary for the public health and welfare and that, if the owner refused to make the alterations, the city was authorized to do so, the cost becoming a lien upon the property subject to taxes, assessments and prior mortgages. (See Adamec v. Post, 273 N. Y. 250, supra.) A year later, as just noted, the court was called upon, in the Central Sav. Bank case (279 N. Y. 266, supra), to consider the effect of a 1937 amendment (to the statute sustained in Adamec) which declared that the cost of the alterations was to be assessed against the property and that the assessment was to be a lien upon the property having ‘ priority over all other liens and encumbrances, including [previously recorded] mortgages ”. In holding that the provision rendered the statute unconstitutional insofar as the mortgagee was concerned, the court stated that his property was “ taken without due process of law * * * and the obligation of his contract with the mortgagor impaired ” (279 N. Y., at p. 275).