2. For a reference source, I am relying on Lure of the Limerick, Baring-Gould, current edition, Barnes and Noble 1993 (orig. 1967). This book is well-known and covers a broad spectrum of clean, obscene, and in-between. Also, the author discusses style to some extent, although not systematically.
3. In most of the limericks given in Lure, the beat patterns are as follows:
1,2,5 w [w] S w w S w w S [w] [w]
3,4 w {w] S w w S [w]
4. Here w is a weak beat and S is a strong beat. The brackets indicate that the beat is optional and is often omitted. I checked Lure, A and B, and found that 53 out of 56 fit the general framework given above for all five lines. Most of them failed to fit the 8-8-5-5-8 pattern mentioned in the letter to Eric, because at least one of the five lines had two weak beats in front of the first strong beat. Also many had an extra weak beat at the end of either lines 125 or 34 or both. As Eric indicates, the crucial requirement is for the number of feet and hence the number of strong beats to be correct: 3-3-2-2-3. True, it can be done by ear, but counting helps if one is learning.
5. Just as Eric has explained, the last strong beat rhymes and any weak beats following the strong beats must be present and have the same sound for rhyming lines. The first w after the last S is quite common (nearlly half the time), but the second one is fairly rare (only 3 of 56). Also lines 3 and 4 can possibly have two weak beats at the end, but it is rare enough that I (like Eric) will omit it. My explanation here is basically the same as Eric's.
6. Next, consider the optional second w in front of the first S. This beat is clearly allowed, and its presence or absence may be vary over all lines and they do not have to match. For example the lady from Niger (or Riga) gets two weak beats at the start of lines 3, 4, and 5, even though she did not enjoy them nearly as much as the young lady of Kent who gets them only for lines 3 and 4. Readers may want to check out the following examples from Lure.
Tiger: (12)wSwwSwwSw (34)wwSwwS (5)wwSwwSwwSw
83: Star: (125)wwSwwSwwS (3)wwSwwSw (4)wSwwSw
117:antigue (1)wSwwSwwS (25)wwSwwSwwS (3)wSwwS (4)wwSwwS (5)wwSwwSwwS
120:Baker (15)wSwwSwwSw (2)wwSwwSwwSw (34)wSwwSw
123:Benin (125)wSwwSwwSw (3)wSwwSw (4)wwSwwSw
125:Birmingham (12)wSwwSwwSww (34)wSwwS (5)wwSwwSwwSww
178 Kent: (125)wSwwSwwS (34)wwSwwS
7. For the 53 of 56 strictly conforming cases, the break-downs were as follows:
Weak syllables at start:
Line 1: 44 with 1; 9 with 2
Line 2: 32 with 1; 21 with 2
Line 3: 23 with 1; 32 with 2
Line 4: 25 with 1; 28 with 2
Line 5: 26 with 1; 27 with 2
Extra weak syllables at end
Lines 1,2,5: 30 with none; 21 with 1; 2 with 2
Lines 3,4: 44 with none; 9 with 1
8. Note that the vast majority had just one leading weak beat at the start of line one, Much of this is due to the stock phrase "There was a[n]," but it probably goes further than that. The basic anapestic rhythmn is two shorts and a long, but one can imagine a pause at the start of a line (replacing a beat), and this effect may be stronger in in line 1.
9. The three exceptional cases were:
(a) 115:Algiers. Lines 3 and 4 have two weak repeated beats at the end.
Also with these lines I had some difficulty getting the second beats to be stronger than the third. The pattern appears to be: (12)wwSwwSwwS (34)wSwwSww (5)wSwwSwwS, but I would not want to push my views of lines 3 and 4.
(b) 116:Amazon. This is not really a limeric, since the beat is iambic, rather than anapestic. The pattern is (125)wSwSwSwS (34)wSwS. Nifty poem though.
(c) 121:Bates. (125)wSwwSwwS (3)wSwwSw (4)SwwSw. Everything conforms except that Line 4 has no weak beats before "rend," which is obviously strong. I assume that a justification would be that "rend" is not merely strong, but awesome and needs no buildup.
10. Although this might seem to some like just the sort of thing a pedant might do to spoil the fun, I thing it might prove to be illuminating to some of the less experienced. Please let me defend my emphasis as follows:
My limericks disparage Japan,
Insult frogs and the first nation man.
They depict girls as just
Things for masculine lust,
But, by jingo, they rhyme and they scan!
(H.P. Fletcher)