An Act amending the act of June 15, 1939 (P.L.346, No.203), entitled "An act to promote uniformity in the assessment and taxation of properties and persons within the territorial limits of cities of the second class by providing that city taxes within such territorial limits shall be assessed, levied and collected upon the basis of the county assessments; imposing duties on county assessing authorities; abolishing the department of assessors in cities of the second class and transferring certain property to county taxing authorities," authorizing assessment of buildings and improvements at rates lower than that of land.