Ragnarok : the age of fire and gravel

THE CHARACTERISTICS OF THE DRIFT, 5

In the next place, this “ till” differs from the rest of the Drift in its exceeding hardness :

“This till is so tough that engineers would much rather excavate the most obdurate rocks than attempt to remove it from their path. Hard rocks are more or less easily assailable with gunpowder, and the numerous joints and fissures by which they are traversed enable the workmen to wedge them out often in considerable lumps. But till has neither crack nor joint ; it will not blast, and to pick it to pieces is a very ‘slow and laborious process. Should streaks of sand penetrate it, water will readily soak through, and large masses will then run or collapse, as soon as an opening is made into it.”

Tint ovERLAID wirn BowrpEr-Ciay, Rrver Srmcnar. r, Rock; ¢, Till; g, Bow!der-Clay ; x, Fine Gravel, ete.

The accompanying cut shows the manner in which it is distributed, and its relations to the other deposits of the Drift.

Tn this “till” or “hard-pan” are found some strange and characteristic stones. They are bowlders, not waterworn, not rounded, as by the action of waves, and yet not angular—for every point and projection has been ground off. They are not very large, and they differ in this and other respects from the bowlders found in the other portions of the Drift. These stones in the “till” are always striated—that is, ent by deep lines or grooves, usually running lengthwise, or parallel to their longest diameter. The cut on the following page represents one of them,