Federalist 55 is attributed to Madison. In conjunction with those observations, Federalist 55 also promised that, at the rate of 1 for every 30,000, we would have 400 Reps by 1840. Can we assume that 400 is below that unknown "certain limit"?

Believe me, Madison's ultimate position was quite different than is commonly known. In fact, he later elaborated on his position in a most conspicuous way. First, as one of his amendments to the Bill of Rights, he proposed changing the maximum population size of congressional districts to 30,000 (rather than that being the minimum). In defending his proposal, Madison stated the following on on August 14, 1789:

"I do not consider it necessary, on this occasion, to go into a lengthy discussion of the advantages of a less or greater representation. I agree that after going beyond a certain point, the number may become inconvenient; … but it is necessary to go to a certain number, in order to secure the great objects of representation. Numerous bodies are undoubtedly liable to some objections, but they have their advantages also; if they are more exposed to passion and fermentation, they are less subject to venality and corruption; and in a Government like this, where the House of Representatives is connected with a smaller body [the Senate], it might be good policy to guard them in a particular manner against such abuse."

Note that Madison says that a large House "may become inconvenient". That's the sort of inconvenience that I believe would be good for the country. Anyway, he made several more such statements similar to this, but too many for a posting. Anyone interested in seeing those quotes (and their citations) should download the 70-page report (PDF) from this webpage:
http://www.thirty-thousand.org/pages/QHA-04.htm

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It was supposed to be our House.
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