Question for Jack Finney fans (TIME AND AGAIN spoilers)

[pseudotriton ruber ruber]

I just reread TIME AND AGAIN, and something puzzles me so much, it must be that I'm misreading something:

When Si decides to visit 1882 because he knows of a letter being mailed that describes "the destruction of the World [building] by fire"--how can that letter allude to the fire that's GOING to happen in a few days? Plainly the fire takes place AFTER the letter is mailed, but neither the recipient of the letter nor the receiver knows or even thinks the World building is going to go up in flames until a few seconds before it happens. So how can the letter describe the fire?

[DrFidelius]

The reference to the fire was added to the letter in the years after "Carmody" moved out West. The phrasing was along the lines of "I cannot believe that this letter started the chain of events culminating in the Destruction by Fire of the entire World (illegible)."

[DrFidelius]

(The part that was sent by mail was the blackmail threat against Carmody regarding the imported Italian marble. The phrasing was obscure enough to pique Si's antique-shopkeeper girlfriend's curiosity.)

[pseudotriton ruber ruber]

Thanks. Upon re-re-re-reading, the text specifies that there are two distinct handwritings on the letter, though the point is made rather delicately. It's there if you're looking for it.