Page:The Formation of Vegetable Mould through the Action of Worms (1881).djvu/322

 of a year, a horizontal line one yard in length; so that 240 cubic inches would cross a line 100 yards in length. This latter amount in a damp state would weigh 11½ pounds. Thus a considerable weight of earth is continually moving down each side of every valley, and will in time reach its bed. Finally this earth will be transported by the streams flowing in the valleys into the ocean, the great receptacle for all matter denuded from the land. It is known from the amount of sediment annually delivered into the sea by the Mississippi, that its enormous drainage-area must on an average be lowered .00263 of an inch each year; and this would suffice in four and half million years to lower the whole drainage-area to the level of the sea-shore. So that, if a small fraction of the layer of fine earth, .2 of an inch in thickness, which is annually brought to the surface by worms, is carried away, a great result cannot fail to he produced within a period which no geologist considers extremely long.

Archæologists ought to be grateful to worms, as they protect and preserve for an