On Thanksgiving Day 2006, I was once again reading Henry Dudeney's solution to "The Haberdasher's Puzzle" in his book The Canterbury Puzzles, when some of his wording struck me in a funny way. Here's the whole paragraph:I exhibited this problem before the Royal Society, at Burlington House, on 17th May 1905, and also at the Royal Institution in the following month, in the more general form:—" A New Problem on Superposition: a demonstration that an equilateral triangle can be cut into four pieces that may be reassembled to form a square, with some examples of a general method for transforming all rectilinear triangles into squares by dissection." It was also issued as a challenge to the readers of the Daily Mail (see issues of 1st and 8th February 1905), but although many hundreds of attempts were sent in there was not a single solver. Credit, however, is due to Mr. C. W. M`Elroy, who alone sent me the correct solution when I first published the problem in the Weekly Dispatch in 1902.A number of years before, I had read that passage and had thought that "credit" was an unusual word to use in that way. Yet I did not think too much about it, just ascribing that to different usage on the other side of the Atlantic a hundred years ago. But this time, the word "credit" caught my eye first, and I read that last sentence alone before reading the whole paragraph.
So I wondered: If Dudeney had appropriated the 4-piece solution from McElroy, but felt guilty enough to acknowledge McElroy, but yet could not bring himself to confess directly to the misappropriation, would this not be a quibbling way to slip in an acknowledgement, so that it could nevertheless be misread by his readers as acknowledging McElroy merely as a solver, rather than as the creator, of the 4-piece solution?
When one thinks further about how Dudeney made such a big deal about the 4-piece dissection by presenting it at the Royal Society and the Royal Institution, one wonders why he didn't make a bigger deal when he originally presented this puzzle to his Weekly Dispatch readers. Unless of course he had only a 5-piece dissection then.
It's always interesting how one's recollection of events can change over time. Here is Dudeney's recollection of the triangle-square episode in the Weekly Dispatch, fifteen years later in his book Amusements in Mathematics (page 28):At the time of the publication in the Weekly Dispatch, in 1902, of a method of cutting an equilateral triangle into four parts that will form a square (see No. 26, "Canterbury Puzzles"), no geometrician would have had any difficulty in doing what is required in five pieces: the whole point of the discovery lay in performing the little feat in four pieces only.Okay. Then why describe the 5-piece solution first, delaying the description of the 4-piece solution for two additional weeks?
Copyright 2006, Greg N. Frederickson.
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Last updated November 24, 2006.