However, having the size of the ca. 1812 hearth only provided part of the answer.  Still unknown was what type of material was used to finish the hearth.  In the period, brick and stone (including marble, sandstone, and limestone) were commonly laid over hearths to give them a decorative, and fireproof, finish.  Interestingly, a ca. 1816 letter was uncovered that gave a tantalizing clue to what Madison may have used for the hearth.  In the letter a Washington, DC merchant wrote to President Madison to say that "The nine marble slabs which you requested me to purchase for you were shipped on the 3rd…the size is 19 inches square."  Intriguingly, the ca. 1812 hearths in both Mr. Madison's Room and the Dining Room were found to be 19 inches deep.  However, the matching dimensions could have been a coincidence and the letter did not reveal what type or color of marble Madison had ordered.