Considering the tools which dug them they were rather symmetrical craters, not jagged and gouged, but with smooth walls and each in shape a perfect funnel.

We measured roughly a typical specimen.

Across the top it was between fifty and sixty feet in diameter, and it sloped down evenly for a depth of eighteen feet in the chalky soil to a pointed bottom, where two men would have difficulty standing together without treading upon each other's toes.

Its sides were lined with loose pellets of earth of the average size of a tennis ball, and when we slid down into the hole these rounded clods accompanied us in small avalanches.
We were filled with astonishment, first, that an explosive grenade, weighing upward of a ton, could be so constructed that it would penetrate thus far into firm and solid earth before it exploded; and, second, that it could make such a neat saucer of a hole when it did explode.

But there was a still more amazing thing to be pondered.