Science: Sun Power in the Pyrenees

A simple magnifying glass, focusing the sun's rays, can scorch a piece of wood or set a scrap of paper on fire. Solar radiation can also be concentrated on a much more awesome scale. It can burn a hole through thick steel plate, for example, or simulate the thermal shock of a nuclear blast. It can, that is, with the aid of a super reflector of the sort that has been set up by French scientists high in the Pyrenees. Ten years in the building, the world's largest solar furnace is a complex of nearly 20,000 mirrors and can concentrate enough sunlight to create temperatures in excess of 6,000° F.

Harnessing solar energy is hardly a new accomplishment. Nearly 22 centuries ago, the Greek mathematician Archimedes is said to have temporarily saved Syracuse from Roman conquest by setting the invading fleet aflame with numerous large mirrors. In the 18th century, the pioneer French chemist Lavoisier produced enough heat with 52-inch-wide lenses to power his experiments. Though Lavoisier's work was cut short by the French Revolution (he was guillotined), his history has not discouraged contemporary French scientists—notably Physical Chemist Felix

Trombe. 64, a research director of France's National Center for Scientific Research and its premier experimenter with the sun's energy.

For more than 20 years, Trombe has championed solar furnaces as an ideal source of intensive heat for both industrial uses and scientific experimentation. In 1946 he fashioned his first sun stove out of a captured German antiaircraft searchlight mirror at an observatory near Paris. Moving to the old Pyrenean citadel town of Mont-Louis, where the sun shines as many as 200 days a year, he has since built five larger solar furnaces. Now, in masterly style, he has created his piéce de résistance on a hillside in the nearby ski resort of Odeillo. Compared with similar devices in several other countries, such as the U.S. Army's 30-kilowatt stove at Natick, Mass., Odeillo's 1,000-kilowatt structure is easily the Mount Palomar of solar furnaces.

Delicate Adjustment. The furnace's appearance is as spectacular as its power. Its glittering eight-story-high parabolic reflector (roughly half the size of a football field) towers over Odeillo's centuries-old houses. Anchored against a reinforced concrete office and laboratory building, the huge concave mirror consists of 8,570 individual reflectors. For the furnace to operate efficiently, these small (18 inches square) mirrors must be precisely adjusted so that their light will converge exactly at the parabola's focal point 59 ft. in front of the giant reflector. Only half of the mirrors have been aligned thus far, although the structure has been finished for more than a year. Reason: the work is so delicate that technicians can usually adjust no more than a few dozen even on the sunniest of days.