By way of introduction to the subject of this paper, I will very briefly describe the physical features of the country drained by the River Calder. We shall thereby gain a clear idea of the present configuration of the Calder valley and better understand how the forces have operated which have produced the grand diversity of hill and valley, of moorlands bleak and wild, of precipitous crag, and steep, wooded slopes, and of the lower lands, rich and fertile, which extend along their base. To know clearly what has been done, is more than half to understand how it has been done.