资料题：The Statue of Liberty was constructed of（　）。

As soon as his plan had been approved by the men who had sent him to America, the young sculptor, Frederic Augunte Bartholdi , started working on the designs of the Statue of Liberty.By 1875, he bad already made several small study models.The most difficult problems were involved in the details of building.In solving them the sculptor had no guide but his own genius.The material must be light, easily worked, and of good appearance.It had to be strong enough to stand the stress of 8 long ocean voyage.It had to withstand the effects of the salty air of New York Harbor.Copper was chosen as the material.The framework would be of iron and steel.To get the form for the statue, Bartholdi made a study model measuring about nine feet in height.Another model four times lager was made, giving the figure a height of 36 feet.This model was correct in every detail.Then the statue was divided into sections.Each of these was also to be made four times its size.These pieces when jointed together, would form the huge statue in its finished shape.Only a small part of such a gigantic statue could be worked on at a time.Section by section, the36-foot model was enlarged to four times is size.For each section of the enlarged model it was necessary to take about 9,000 separate measurements.When a section was finished, the carpenters made wooden molds.On these molds, thin copper sheets were pressed and hammered into shape.More than 300separate sheets of copper, each hand-hammered over a single mold, went into the statue to form the figure.The framework, too, is worthy of attention.It was designed and built by the great French engineer, Gustave Eiffel, who afterwards constructed the famous Eiffel Tower in Paris.Four huge iron posts mun from the base of the statue to the top, forming a pyramid which bears the weight of the whole structure.Out of this central tower is built a maze of smaller beams, each supporting many outer copper sheets.Each sheet is backed by an iron strap to give it stiffness.These iron straps are fastened to the supporting framework in such a way that each section is supported separately.