Section 3. Within Such Parts of District B As May Be Designated by the

commission as aforesaid (which may, except as hereinafter provided, include any parts of said district B affected by prior acts limiting the height of buildings) buildings may be erected to the height fixed by the commission as aforesaid, exceeding eighty feet but not exceeding one hundred feet, or one hundred and twenty-five feet as hereinbefore provided, and subject to such conditions as may be fixed as aforesaid by the commission; but within the following described territory, to wit:—Beginning at the corner of Beacon street and Hancock avenue, thence continuing westerly on Beacon street to Joy street, thence continuing northerly on Joy street to Myrtle street, thence continuing easterly on Myrtle street to Hancock street, thence continuing southerly on Hancock street and Hancock avenue to the point of beginning, no building shall be erected to a height greater than seventy feet, measured on its principal front, and no building shall be erected on a parkway, boulevard or public way on which a building line has been established by the board of park commissioners or by the board of street commissioners, acting under any general or special statute, to a greater height than that allowed by the order of said boards; and no building upon land any owner of which has received and retained compensation in damages for any limitation of height or who retains any claim for such damages shall be erected to a height greater than that fixed by the limitation for which such damages were received or claimed.