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Tommy Trimble, age 10, of Spokane, Washington, for his question:

How did the Incas erect such huge buildings?

The Incas built stupendous pyramids and temples, splendid palaces and well planned cities, roads and terraces, bridges and fortresses. Most of their buildings were deserted centuries ago and many lie partly in ruins. Some visitors have thought that such magnificent buildings were not made by human hands and that the Incas used magic to haul those enormous stones and set them so securely in place. But actually those bygone builders used something better than magic.

When the Inca Empire was at its peak, it reached from Ecuador, southward through the lofty Andes to Argentina. Its capital city was Cusco, perched two miles high among the peaks of Peru. Roads stretched from end to end of the empire, more than 3,000 miles. And every ten miles or so there were sturdy Inca buildings  fortresses and villages, cities and shrines.

We know more or less how the Inca builders worked because they left their tools behind. None of their work was done by magic. Their secret was manpower    the skills of master builders, the cleverness of human hands and the strength of human muscles, all working together in teams.

They took their building blocks from quarries of limestone and other suitable rock. But they had no dynamite to blast off the chunks. Instead they found natural cracks in the rock and drove in wooden wedges. When the wedges were soaked with water, they expanded. The cracks became wider and great chunks were pried free. Some of the slabs weighed many tons and hauling them to the building site was a big fob.

The Incas had no modern building equipment to help them. They had no wheels and no horses. Instead, teams of strong men used ropes to haul the huge slabs to the building site. Perhaps they also used logs or round stones to help roll them along.

The architects did not depend on drawings or blueprints. Instead they made a small clay model of the planned building. The builders used a simple slide rule to copy the model on a larger scale. Pits were dug and the first row of building blocks was half buried in the ground. As a wall grew higher, piles of rubble were used to build a ramp beside it. The upper rows of building blocks were dragged up the slopes.

When a stone reached the top of the ramp, it was shaped and smoothed to fit perfectly in place. The tools for this work were made of hema¬tite or some other extra hard stone. No cement or mortar was used to stick the stone in place. But when the job was done, each stone fitted like a cork in a bottle.

The man made Inca buildings were handsome and very durable. In Cusco stood their great Temple of the Sun. When the Spanish arrived they remodeled this building and made it into a Christian church. In 1950, the region was struck by a major earthquake. The fancy front and all the stonework done by the Spanish crumbled to rubble. But the sturdy old Inca walls survived without damage.

 

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