As the tooth rotates, the pebbles drop.
In the ancient world's hodometer, a calibrated system of wheels and gears makes a new chip drop into a bowl of bronze for every 400 rotations by a wheel whose circumference is 1/400th of a mile. The number of pebbles told you how much you owed the cisium driver, for instance, and the sound of stone on bronze could make one cringe, I gather.
Now, in Yahoo! Mail moving messages is accompanied by the sweet sound of keyboard, trackpad or mouse — and costs little time no matter how far down the folder list you go:
›› Here's a swift way to move one message or even multiple messages at once from one Yahoo! Mail folder to another.