One fall afternoon — red leaves, silver drizzle — a friend and I were given a tour of Canterbury Shaker Village in New Hampshire. We learned many things: how the Shakers believed in a life of unceasing prayer, for instance, with prayer defined as everything one did, said and thought. All activity was an homage to God. As such, since God is perfect, any homage to Him must also strive for perfection. Craftsmanship must not be profaned by inutility. In other words, a snug-fitting, non-squeaking hinge is a prayer. A fence that doesn't warp, because the posts are sunk in stone, is a kind of psalm.
This all sounded quite beautiful, if stern. But then our guide let on about the piano-violin. Here, it seemed, the Shaker drive toward harmonic efficiency had gotten endearingly out of hand. The piano-violin was an odd instrument, combining both keys and strings, patented by a particularly enthusiastic Shaker named Elisha D. Blakeman in 1871. I liked Brother Elisha; he'd also set up a butter-churning system activated by children on swings.
The piano-violin caught on for a while. Brother Elisha received letters from would-be agents and advertisers. He began to think it might operate as a handy tool of evangelization; fewer people were entering the Shaker community, but if they heard the instrument's sweet sound, they might long to join. The Elders, however, didn't concur, and it seems that their disapproval led to Elisha's leaving the community. He eventually married, published a book of riddles, kept inventing and died an octogenarian. As for the piano-violin, it fell into a probably well-deserved obscurity. There will never be an Isaac Vladimir Stern-Horowitz.
Brother Elisha's invention got me wondering about things that perform two functions at once. Remember that old Saturday Night Live advertising parody: "It's a floor wax — and a cake topping!" Think of Maxwell Smart's shoe phone, Skin So Soft as mosquito repellent, a clock radio.
I decided to see what other piano-violin-ish stuff might be out there. My local library's stacks offered up a children's book called Weird and Wacky Inventions, which profiled, among other things, the portmanteau-bathtub: you unpack your clothes, open up the sides, put in a stopper, then soap up. Another page pictured a little cylindrical contraption that grated cheese and, after you put a tiny screen inside, worked as a mousetrap.
Fifty Years of Popular Mechanics described how, in 1906, in London, fingernails served as display surfaces for tiny cameo photographs. Meanwhile, in Paris, umbrellas acted as foils in female fencing classes.
But the more I dueled with duality, the more I realized it wasn't, well, black and white. How do you define dual use? Does something have to do both things at once (the clock radio)? Or does it just have to be capable of two functions, even if they unfold at separate times (the cheese grater/mousetrap)?
Usually something that does two things does one of them better. You just know the portmanteau-bathtub was better at holding your clothes than you. Slept on a convertible sofa lately? It doesn't want to be a bed.
Inventors have yet to learn this lesson, however, to judge from a recent issue of the Official Gazette of the U.S. Patent and Trademark Office. Take the "Combined Refrigerator Water Heater," which sounds like an accident waiting to happen. Then there's the fact that, ever since Murphy, tinkerers can't seem to leave beds alone. One Catherine V. Grander, of Austin, Texas, patented the "Convertible Easel and Bed." Now, to be fair, maybe Ms. Grander's garret didn't have enough room for one easel and one bed. Flimsy as the idea sounds, the Gazette's no-nonsense prose lends it a certain workmanlike plausibility.
Duality is sometimes called for out of necessity. Take Prohibition, that era of violin cases used as gun-toters. In those days, pig carcasses made excellent whisky transporters.