Accessory farm buildings, windmills, belfries, chimneys, cooling towers, elevator bulkheads, fire towers, monuments, silos, scenery lofts, tanks, water towers, ornamental towers, spires, wireless television or broadcasting towers, masts or aerials, public water towers, telephone, telegraph and power transmission poles and lines, microwave radio relay structures and necessary mechanical appurtenances are herein exempted from the height regulations of this chapter.