The grooves, which are the teeth of the millstone, radiate from the centre, but do not proceed direct to the edge: they slant slightly.
'There bean't many as can do this job,' he said, 'I can put in sixteen or twenty to the inch.

These old French burrs be the best stone; they be hard, but they be mild and takes the peck well.' Ponderous as the millstones appear, they are capable of being set so that their surfaces shall grind with extreme accuracy.

The nether, called the 'bed stone,' is stationary; the upper millstone, or 'runner,' revolves, and the grain crushed between the two works out along the furrows to the edge.
Now and then the miller feels the grain as it emerges with his pudgy thumb and finger, and knows by touch how the stones are grinding.

It is perceptibly warm at the moment it issues forth, from the friction: yet the stones must not grind too close, or they 'kill' the wheat, which should be only just cracked, so as to skin well.

To attain this end, first, the surfaces of the stones must be level, and the grooves must be exactly right; and, secondly, the upper stone must be hung at the exact distance above the other to the smallest fraction of an inch.