The money-value of bay horses, as compared to white, was again discussed, and each announced his certainty that nothing less than "a good ole hunderd dollars" would be offered for the return of Whitey.
But immediately after so speaking they fell into another silence, due to sinking feelings.

They had spoken loudly and confidently, and yet they knew, somehow, that such things were not to be.

According to their knowledge, it was perfectly reasonable to suppose that they would receive this fortune; but they frightened themselves in speaking of it.
They knew that they COULD not have a hundred dollars for their own.

An oppression, as from something awful and criminal, descended upon them at intervals.
Presently, however, they were warmed to a little cheerfulness again by Penrod's suggestion that they should put a notice in the paper.

Neither of them had the slightest idea how to get it there; but such details as that were beyond the horizon; they occupied themselves with the question of what their advertisement ought to "say".