Thus would each mushroom represent, tolerably well, one of the innumerable flat asphalt bosses, which seem to have sprung up each from a separate centre, while the parting seams would be of much the same shape as those in the asphalt, broad and shallow atop, and rolling downward in a smooth curve, till they are at bottom mere cracks, from two to ten feet deep.

Whether these cracks actually close up below, and the two contiguous masses of pitch become one, cannot be seen.

As far as the eye goes down, they are two, though pressed close to each other.

Messrs.

Wall and Sawkins explain the odd fact clearly and simply.