All street monuments shall be either of granite
or iron and granite. If of granite, the street monument shall be not
less than four feet in length, not less than one foot square at the
bottom and not more than six inches square at the top and shall be
marked with the letter "H." If of iron and granite, the street monument
shall be a granite post not less than 2 1/2 feet in length, and
an iron rod firmly fixed into the same, and extending to the surface
of the ground. All of said monuments shall be located, set and reset
by the City Engineer and placed perpendicularly in the earth and not
less than four feet deep.