Mark Hotz writes:

To read the a New York Times article on the fire, see:
The Great Fire in Boston.; DESTRUCTION OF THE WINTHROPHOUSE AND FREEMASON'S HALL. - The New York Times (https://www.nytimes.com/1864/04/10/archives/the-great-fire-in-boston-destruction-of-the-winthrop-house-and.html)

For a post-fire photo from the Boston Public Library, see:
Ruins of the Winthrop House, cor. Tremont and Boylston Sts. Burned 1864(https://www.flickr.com/photos/boston_public_library/5579838288)

To read the earlier E-Sylum article, see:
NEWMAN PORTAL ADDS NENA NEWS (https://www.coinbooks.org/v22/esylum_v22n03a12.html)