What sparked the 1851 fire that devastated the collection at the US Library of Congress? |...

On December 24, 1851, a fire devastated the United States Library of Congress in Washington, destroying 35,000 volumes. From the article:

"What sparked the 1851 fire that devastated the collection at the US Library of Congress? | Grateful American® Foundation
December 24th

December 24, 1851 — As Americans celebrated Christmas Eve tonight, fire ripped through the US Library of Congress in Washington, DC, destroying 35,000 volumes. A faulty chimney flue set off the blaze, which took two-thirds of the collection, including most of Thomas Jefferson’s personal library that had been sold to the institution in 1815.

Initially established in 1800 when President John Adams approved legislation that appropriated $5,000 to purchase “such books as may be necessary for the use of Congress” — the first books, ordered from London, arrived in 1801. They were stored in the U.S. Capitol. Twelve years later, the British army invaded the city of Washington and burned the Capitol, including the 3,000-volume Library of Congress. Jefferson responded to that loss by selling his personal library of 6,487 volumes — the largest and finest in the country — to Congress to “recommence” the library.

After the fire of 1851, architect of the Capitol Thomas U. Walter presented a plan to repair and enlarge the Library room using fireproof materials throughout. The elegantly restored Library room was opened on August 23, 1853. Called by the press the “largest iron room in the world,” it was encircled by galleries and filled the west central front of the Capitol. A month before the opening, Pres. Franklin Pierce inspected the new Library in the company of British scientist Sir Charles Lyell, who pronounced it 'the most beautiful room in the world.'”