Sentence:  [B]y what process, we would ask, could these sands have been sifted and separated agreeable to their grades, as they are now found? What circumstances could have effected such <WSD>comminutions</WSD>, such separations, such transpositions, and transportations of the several kinds, having all the same origin? 
Meaning of the word marked with <WSD> tags:  The breaking or grinding up of a material to form smaller particles.