Scott Kim

Clip Joints

Henry Petroski, professor of civil engineering at Duke University, writes about the fascinating histories behind everyday objects. He devoted a whole chapter of his book Invention by Design (Harvard University Press, 1996) to the paper clip. The invention of the classic Gem clip, in 1899, spawned numerous competitors. Above are drawings of just a few that have been patented over the years. Can you match each clip with the description of its advantages at right?

1. The classic Gem paper clip

2. Holds more, easier to apply

3. Patented around the time of the Gem clip’s invention

4. A Gem clip competitor that uses less wire

5. Librarians like it because the long legs reduce tearing

6. Slides onto paper without the need to first spread the loops

7. Slips on from either end; endless wire eliminates tearing

8. Similar to the Gem clip, but lengthened legs eliminate tearing

9. Slides on easily from either end; whichever way it is applied, the clip always protrudes beyond the edge of the paper

See My Point?

In Petroski’s The Pencil [Knopf, 19901, he reports that in 1981 the Engineering News-Record printed a large, colorful drawing of a pencil on its cover. Unfortunately the drawing contained several errors, which the readers gleefully pointed out in a deluge of mail. Here is a modified version of that drawing. Can you spot four errors? Assume you are looking at a typical number 2 pencil directly from the side.

Accidental Inventions

Can you match the 10 famous inventions below with the surprising circumstances that led to their discovery? For the full stories, along with other serendipitous breakthroughs, see Accidents May Happen by Charlotte Foltz Jones (Delacorte Press, 1996) and They All Laughed by Ira Flatow (HarperCollins, 1992).

1. In 1825, Jean-Baptiste Jolly spilled an oil lamp containing distilled turpentine on his wife’s tablecloth.

2. In the mid-1800s, Swedish chemist Alfred Nobel was transporting a sensitive material in glass flasks packed in soil when one of the flasks broke.

3. In 1859, Robert Chesebrough watched oil-field workers scrubbing a waxy substance off their machinery.

4. In the early 1900s, French scientist Rene-Antoine Ferchault de Reaumur paused to study a wasp’s empty nest.

5. In the early 1920s, businessman Donald Duncan saw a weapon from the Philippines that could be quickly retrieved if the hunter missed the target.

6. In 1938, DuPont research chemist Roy J. Plunkett was surprised when an experimental refrigerant turned from a gas into an oily white powder.

7. In 1942, Percy Le Baron Spencer was working with radar equipment at Raytheon when he noticed that a candy bar had melted in his pocket.

8. In the 1950s, George de Mestral came home from a walk in the woods to find his jacket covered with cockleburs.

9. In 1965, Dr. James Schlatter was developing a new drug to treat ulcers when he spilled some on his fingers.

10. In 1982, researchers at a Japanese laboratory used superglue to fix a crack in a fish tank.

a. Yo-yo

b. Velcro

c. Teflon

d. Vaseline

e. Dynamite

f. NutraSweet

g. Dry cleaning

h. Modern paper

i. Microwave oven

j. Modern fingerprinting



1 b, 2i, 3h, 4a, 5f, 6e, 7g, 8c, 9d


The four mistakes: The line where the lead joins the wood should appear straight across; the exposed wood area should be smooth, without edges; the scallops where the paint meets the wood should arch up instead of down; the middle panel of the hexagonal part of the pencil should appear twice as wide as the two side panels. In addition, most pencil sharpeners create an angle that is about twice as sharp as the one shown here, but some sharpeners do produce blunter angles.


1g. When Jolly tried to rub out the stain, the tablecloth got cleaner. Turpentine smells bad and is flammable, so modern dry cleaners now use other liquids.

2e. By mixing nitroglycerin with a special soil, Nobel created an easy-to-handle explosive. He later used his fortunes to found the Nobel prize.

3d. Oil-field workers often took the waxy residue from the machinery and used it to help heal wounds. It took 10 years for Chesebrough to develop this substance into a colorless, odorless petroleum jelly.

4h. Modern paper is made from wood, not cotton rags, as are wasp’s nests.

5a. The weapon was tied to a string for quick retrieval.

6c. The powder turned out to be surprisingly inert and slippery. Teflon remained a military secret until after World War II.

7i. The second thing Spencer held in front of the equipment was a bag of unpopped popcorn.

8b. De Mestral put the cockleburs under a microscope and saw that the spikes ended in little hooks.

9f. Schlatter licked his fingers and noticed the substance tasted sweet. Other artificial sweeteners have been discovered through similar accidents.

10j. The fumes from the superglue (cyanoacrylate) condensed on the fingerprint oils, making them visible.

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