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James Murray Spangler, a department-store janitor in Canton, Ohio, suffered from asthma. Sweeping the rugs every night stirred up dust and dirt, which left him gasping for breath. It was 1907, and agencies like the Occupational Safety and Health Administration did not yet exist, so Spangler was left to his own devices. He fashioned a machine from a tin soapbox, a sateen pillowcase, and a broom handle. Inside the box, an electric motor powered a fan and a rotating brush. The fan blew air out one end of the machine through the pillowcase.

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On July 16, 2005, Philadelphia celebrated the 200th anniversary of Oliver Evans’s Orukter Amphibolos.

Congress’s termination of the SST program did not ensure success for either the Anglo-French Concorde or the Soviet Tu-144. Both came into service in the mid-1970s and were plagued with their own misfortunes. The foreign supersonics required massive government subsidies in a race that ended up producing only 20 Concordes and 17 Tu-144s, and both types ultimately experienced horrific disasters.

Every year more than three million miles of dental floss are sold in the United States. That’s a lot, but the total should be much higher, since that amount works out to only about one flossing per week for the average American. Dentists recommend flossing at least once a day to prevent gum disease, which robs more adults of their teeth than all other oral problems combined. A recent study reported that almost half of Americans feel guilty because they don’t floss their teeth, and 32 percent feel even more guilty for lying to their dentists about it.

In a recent issue, one of our authors recalled the atom-bomb drills that his grade school held. Your columnist is barely old enough to have experienced a few of these in the late 1960s. By that time even young children had some inkling of how terribly destructive atomic bombs were, and every time we had a drill, someone was sure to express skepticism about whether kneeling with our heads against the wall would be of any use against a nuclear attack.

Polymerase is the chemical that a cell uses to replicate its DNA when it divides. The polymerase attaches to a single strand of DNA after the molecule splits and builds a complementary strand to re-create the double helix. Polymerase chain reaction (PCR) takes advantage of this mechanism to make many copies of a small DNA section.

In forensic analysis, the polymerase chain reaction makes identical copies of a specific short section of DNA. It targets and multiplies a repeating section of DNA, making it easy to measure. After extracting the small sample of DNA needed, the technician places it in a test tube with the cocktail of chemicals used for the steps below.

This is the year for halls of fame to play catch-up. This summer the National Baseball Hall of Fame inducted 17 previously neglected figures from the Negro Leagues. And in May the National Inventors Hall of Fame, in Akron, Ohio, inducted a record 78 members, including 57 long-overlooked inventors, mostly from the nineteenth century.