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National Geographic : 1951 Dec
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775 National Geographic Photographer Willard R. Culver Hot Coffee and Ice Cream Test a Tooth Filling's Reaction to Heat and Cold If heat expands a filling too much, pain or breakage may result. If contracted by cold, the restoration may loosen and fall out. Research by the Bureau has improved both filling and denture materials (page 772). The wire entering this girl's mouth leads to a thermocouple imbedded in an experimental filling to measure temperature changes caused by hot and cold foods. out breaking the handle, and drop it five feet 50 times on all the faces, edges, and corners. Not long ago the Bureau invited some master plumbers to witness a unique kind of motion picture. As it unreeled, the audience grew more and more excited. They were see ing, for the first time, what actually happens inside the plumbing system of a house. Most plumbers thought they knew, but didn't all agree. American cities had more than 1,500 different plumbing codes. Bureau men built a complete plumbing system out of transparent plastic pipe, ran water through it, and took movies. These showed that many pipes were un necessarily large, and systems often had more traps than were needed, adding to the cost. Today local plumbing codes are gradually adopting these findings, saving money for the home builder. Brick manufacturers didn't like it at first when the Bureau reported that an 8-inch wall was just as safe for the average house as the 12-inch ones used for many years. But they soon found this enabled more people to afford to build brick houses, resulting in greater sales of brick. Care and Repair of the House, a book written by Bureau men, sold nearly 140,000 copies this past year. It gives expert advice on everything from fireproof shingles to leaky basements and can be bought from the Gov ernment Printing Office for 50 cents. Rebuilding the White House Decision to rebuild the inside of the White House, while preserving its original outer shell, was based on Bureau tests. Gauges put on interior cracks showed these were growing, while borings into the sandstone walls revealed no damage either from the fire during the War of 1812 or from the passage of time. Years ago confusion reigned on American railroads in the checking of carload weights. A load that weighed 100,000 pounds on one road's scale might weigh only 80,000 on another's. Today, in cooperation with the Association of American Railroads, two National Bureau of Standards test cars, equipped with stand-
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