Somehow I missed this fireplace when I was last at Monticello. The ones in the the house are not what I would call real Rumfords even though Jefferson credited Rumford for the design.

Perplexed and curious, I dug a little deeper. I found that the fireplaces at Monticello had been rebuilt since Jefferson's time - maybe several times. But even the originals that Jefferson had built were not exactly according to Rumford's prescription. Jefferson wrote a couple of letters and made some drawings in an effort to "improve" the Rumford design by making the fireback wider, but he didn't seem to understand streamlining (or "pneumatics" as Rumford would have put it) and neglected to round the breast. See http://www.monticello.org/site/research-and-collections/sir-benjamin-thompson-count-von-rumford#_ftnref5

(See the monticello.org article here in case the article is not kept on line.)

Best,
Jim