Other famous Loyd puzzles include his Hoop-Snake Puzzle, the Get Off the Earth Puzzle, and perhaps his most famous mathematical puzzle, The 15-15 Puzzle in Puzzleland, which he is credited with inventing. It led to the invention of many other sliding-block puzzles. It consisted of a square base in which 15 blocks were arranged in regular order, but with the 14 and 15 reversed. The object was to move the blocks around, one at a time, and to return them to their starting positions, except with the 14 and 15 tiles switched. In the words of Loyd, the puzzle drove the entire world crazy, and he offered a prize of $1,000 for the first correct solution.
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The money was never claimed, however, because, as Loyd already knew, there was no possible solution. He had realised that half the starting positions do not lead to a solution because rearrangement of the blocks by sliding them only gives rise to an equal number of exchanges. As Loyd himself put it, the original problem is impossible to solve except by such skullduggery as turning the 6 and 9 blocks upside down. One of the puzzle’s peculiarities is that any such interchange involving two blocks immediately converts the puzzle to a solvable one. In fact, any odd number of interchanges has the same effect, whereas an even number leaves the puzzle unsolvable as before.
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On this occasion, however, Loyd did not have the last laugh. There was an amusing twist in the tail when Loyd applied to patent the puzzle. In those days it was necessary to present a working model of a device, but when the patent commissioner was told that no solution existed he retorted, Then you can’t have a patent. If the thing won’t work, how can you file a working model of it!
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Sam Loyd became a full-time professional puzzlemaker in the 1890s, working with his son Sam Loyd Jr. After the death of his father, Sam Loyd Jr continued publishing puzzles that were mainly compilations of his father’s work and in 1914 issued a now out-of-print and much sought-after mammoth collection of his father’s puzzles called Cyclopedia of Puzzles.
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The above biography is extracted from Mind Sharpening IQ Tests by Philip J. Carter & Kenneth A. Russell, published in 1998 by Sterling Publishing Co., Inc., New York.
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