Any roughness was levelled by polishing with ivory or a smooth shell.
The roughness of the surface of the cavity serves to retard it.
Indeed, the velocity must be far greater than this where the edge or corner of one lump touches the side of another, and the only room for the passage of this enormous quantity of gas is that left by the roughness and irregularity of the individual lumps.
In the school of Wolgemut Diirer learned much, by his own account, but suffered not a little from the roughness of his companions.
Fascinated by the texture of his palm, she took and held his hand up until she was able to see the roughness of his calloused palm.