FRANK CEPOLLINA TALKS ENTHUSIASTICALLY ABOUT HIS favorite subject. “Someday we’ll be doing this in orbit around Mars,” he says. This is the technology of satellite servicing, which is his specialty. You probably haven’t heard his name, but you certainly have heard of some of his projects; they include the historic mission to correct defects in the Hubble Space Telescope back in 1993.

I ENJOYED DAVID PLOW den’s article “The Bridges I Love” (Winter 2003), especially the comments on the High Bridge here in central Kentucky. I’ve always wanted to walk across it but have been afraid an oncoming train would catch me in the middle. The article says it last saw traffic in 1985, but I know I was on the tracks in 1988 or 1989 when a train came along. Can you confirm that it no longer sees traffic?

CHEMICAL WEAPONS, THE BANE OF MOD ern warfare, saw their first battlefield use in World War I. And as the historian Kathryn Steen writes in a recent issue of Chemical Heritage , when that war was over, chemistry played a role in the peace as well.

THE “POSTFIX” FOR SPRING 2003 describes a neverbuilt concept for a railroad that would have hauled ships across the Isthmus of Tehuantepec, in Mexico, as an alternative to a Panama Canal (“The Most Gigantic Railroad,” by Joseph E. Vollmar, Jr.). Some ideas never die. The Mexican government is now floating a scheme, at the urging of President Vicente Fox, to create a sort of railroad of heavy trucks that would haul yachts across Baja California between the Sea of Cortés and the Pacific Ocean.

THE PICTURES BEGIN AS STREAMS OF DIGI tal data beamed from space down to receiving stations on the ground. Computers transI late the data into images on high-resolution screens for analysis by highly trained CIA and military photo interpreters. It’s a synergy of satellites, computers, and human eyes and minds that has been honed to a keen edge since the relatively primitive early days of photoreconnaissance. Now this technology is confronting a new enemy that kills about 46,000 Americans every year: breast cancer.

I ESPECIALLY ENJOYED “Holography: The Whole Picture,” by Tim Palucka, in the Winter 2003 issue. I knew most of the people involved, and I can relate a tale about Dennis Gabor’s naiveté concerning social issues. In the early 1970s he told me that money would someday be replaced by electronic transactions. Almost the case. He also said this would mean an end to crime. No comment.

ONE MORNING IN MAY 1994, A PAIR OF LETTERS ROLLED OFF a fax machine in the offices of Calgene, a start-up company located in Davis, California, amid the lush agricultural country of the Central Valley. The letters came from the federal Food and Drug Administration(FDA), and they granted regulatory approval for Calegene’s first product, a genetically modefied tomato. Anticipating this decision, company officials had already laid in a supply of their new Flavr Savr variety, which combined vine-ripped taste with firmness for ease in transport.

WHEN I WAS A LITTLE BOY, THE WINDOW OF MY BEDROOM looked out on New York’s East River, and my view was framed by three of America’s great bridges. Downriver to my right was the awesome Queensboro Bridge; to my left were the Triborough and the Hell Gate. On winter afternoons, the light was cold and clear, as in Charles Sheeler’s paintings. I learned from what I saw through my window of the effect of light and shadow on objects, of architecture and magnificent structures. I contemplated the bridges. They made sense to me.

NATURE CANTILEVERED those boulders out over the fall,” said Frank Lloyd Wright about the site of his most famous house, Fallingwater. “I can cantilever the house over the boulders.” As it turned out, however, Wright did not entirely meet the challenge set by nature. From the very beginning, Fallingwater has been falling down.

At the Spring 1964 meeting OF THE OPTICAL SOCIETY OF America, in Washington, D.C., Emmett Leith and Juris Upatnieks, from the University of Michigan, gave a presentation about their work in holography. When Upatnieks concluded his address, he announced that one of these images, a hologram of a toy train, was on display in a suite in the conference hotel.

I LOOK FORWARD TO READ ing Invention & Technology , but when I openec the most recent issue, I knew I’d be in trouble. I agree with guitarists that tube-sound distortion is what they’re after (“The Tube Is Dead. Long Live the Tube,” by Mark Wolverton, Fall 2002), but I wince when people say they prefer tube sound over solid state when it concerns the reproduction, not production, of music.

WHEN STEPHANIE LOUISE KWOLEK RECEIVED HER B.S., WITH a major in chemistry, from the Carnegie Institute of Technology (now Carnegie Mellon University) in 1946, she didn’t have enough money to pursue her dream of going on to medical school. So she accepted a research job with DuPont, hoping to eventually get a medical degree. But she discovered that she liked the work so much, with its constant challenges and the university-like atmosphere, that she decided to stay.

The Great Tube Debate

I LOOK FORWARD TO READ ing Invention & Technology , but when I openec the most recent issue, I knew I’d be in trouble. I agree with guitarists that tube-sound distortion is what they’re after (“The Tube Is Dead. Long Live the Tube,” by Mark Wolverton, Fall 2002), but I wince when people say they prefer tube sound over solid state when it concerns the reproduction, not production, of music.

DO YOU BELIEVE IN MAGIC? I DO. THIS MAY SEEM A strange thing to say in a magazine like Invention & Technology , but I suspect that after you read this, you’ll find you believe in it too. The occasion of my conversion to faith in magic is the 200th anniversary of the United States Patent and Trademark Office, the greatest repository of intellectual property in history.

IN 1991 HARRY BARRY FOUND THE NOISEMAKER OF HIS DREAMS: a huge air-raid siren from the 195Os. It weighed more than .S1OOO pounds and was powered by a .33 I-cubic-inch V-8 Chrysler industrial gasoline engine. Barry, who has been collecting sirens, horns, and whistles since he was 15, had his latest treasure hauled from Detroit to his home in northeastern Pennsylvania. Might years later, in 1999, he invited Mric Larson, a professional pipeorgan restorer and fellow siren collector, to hear it in full song.

ON MONDAY AFTERNOON, AUGUST 5, 2002, A CRANE ON a barge 16 miles off Cape Hatteras pulled up a rusting 160-ton prize from the ocean floor. It was the fabled turret of the Civil War ironclad Monitor , seeing daylight for the first time since the ship had sunk in December 1862. During her 10-month career, indeed in the first days of that career, the Monitor had changed warfare more than any other ship in history.

A Bridge Too Few

DAVID PLOWDEN WROTE an engaging and beautifully illustrated article on American bridges (“The Bridges I Love,” Winter 2003), saying a lot in a small space, but in common with other surveys of bridge design where the text emphasizes the tallest, fastest, and longest, no mention was made of the very long railroad bridge across Lake Pontchartrain, in Louisiana. It is the ultimate stepchild of bridge history. I suppose this is because it is so very low and thus not photogenic.

AS THOMAS HUNT ington details elsewhere in this issue, three-dimensional movies experienced their first brief boom in the 1920s. Last fall the Museum of Modern Art’s film division showed a test reel made with that era’s Plastigram process, giving modern viewers a chance to experience 3-D just as those in 1921 did. Sure enough, the initial images of baseballs being thrown at the audience, a long line of marchers parting around the camera, and a whip uncoiling toward viewers’ eyes elicited moans, self-conscious shrieks, and nervous laughter.

DAVID PLOWDEN WROTE an engaging and beautifully illustrated article on American bridges (“The Bridges I Love,” Winter 2003), saying a lot in a small space, but in common with other surveys of bridge design where the text emphasizes the tallest, fastest, and longest, no mention was made of the very long railroad bridge across Lake Pontchartrain, in Louisiana. It is the ultimate stepchild of bridge history. I suppose this is because it is so very low and thus not photogenic.

AT 8:15 A.M. EASTERN TIME ON SATURDAY, FEBRUARY 1, THE space shuttle Columbia , 175 miles above the Indian Ocean, fired its engines to begin its hour-long descent to Cape Canaveral. With its onboard computers closely monitored by the Mission Control Center in Houston and directing its maneuvers perfectly, the seven men and women aboard had little to do but watch their instrument panels.