In To Kill a Mockingbird, what does it mean while they're waiting for the verdict that, "The courthouse clock suffered its preliminary strain"?
What does this mean in Chapter 21 (though a minor point)?
Consider the context of this description. Scout is sitting in a packed courtroom, marvelling at how quiet and still it is. Except for the occasional baby crying or child scurrying out, the place is as still as a "church."
The courthouse clock is the one noise to really break the silence and its "preliminary strain" likely refers to the Westminster Chimes it plays before bonging out the hours. If you have ever been inside a cathedral or heard a grandfather clock inside a house, you know that on the hour, such a clock plays a preliminary "song" that signifies the hour, quarter past, half-hour, and quarter-till times. Each has the same beginning but depending on what time it is, the "song" is the shortest at 15 minutes past the hour and longest when chiming the full hour.
This "preliminary strain" is familiar enough to Scout that she can anticipate exactly what time it is before counting the full eight bongs. Aside from her father, Mr. Gilmer, and Judge Taylor, the sound of the clock is the only normal thing in the courthouse that night. It is also an important legal allusion to a court's preliminary procedures.