When using this odd sled one foot would rest on the runner with the toe in the strap, and by kicking out against the snow or ice with the other foot the rennwolf would be made to spin along at a rapid rate.  Of course, when coasting both feet would rest on the runners and the sled was steered by an occasional side push at the right or left.  Owing to the great length of the runners the rennwolf would easily ride over uneven surfaces and thin spots in the ice.

[Illustration:  Fig. 180.  The Rennwolf in Use.]

Ice Creepers.

In order to provide a better hold for the propelling foot, we fastened around the toe a strap of leather, through which a number of long tacks projected.  Their sharp points would stick into the ice, and prevent the foot from slipping.  The seat of the rennwolf was convenient for carrying a coat or any light luggage, and it was often used to give a friend a very exhilarating ride.

[Illustration:  Fig. 181.  The Ice Creeper.]

CHAPTER XV.

THE SUBTERRANEAN CLUB.

I am afraid we were not very glad to get back to school that fall.  It seemed very hard to give up the sport we had been having, and our heads were brimful of new schemes which we could hardly wait to put into practice.  But we soon learned that there are many things that could be done during recreation hours at school.  We had intended building a cave on our island that summer, but our vacation came to an end before we got around to it.  There seemed no reason why we shouldn’t dig one in the woods at the back of the schoolhouse.

A Cave-in.

Bill had read somewhere that if you dig a cave under a tree the roots of the tree will support the ground on top and make a natural and substantial roof.  It sounded very reasonable, we thought; in fact, we never questioned the truth of the statement, because we had somehow gotten the notion that books were never wrong, and that whatever was set up in type must surely be so.  But events proved that the man who wrote that book had never attempted to build a cave in the manner he described, at least not in the loose, sandy soil of south Jersey.  A large spreading cedar was selected as the tree which should support the roof of our cave.  It was situated on a mound at the edge of the woods.  First a passageway, or ditch, was dug at the bottom, and then we begun tunneling in the side of the mound under the roots of the tree.  For a while the ground above held, and our tunnel had reached a length of about four feet, when suddenly, without the slightest warning, the sandy soil gave way and we were engulfed.  Bill, who was furthest within the cave, was almost entirely covered, while I was buried to the shoulders.  A crowd of boys came to our assistance and dug us out.  Poor Bill was almost smothered before they scooped the sand away from around his mouth and nose.  The boys made slow work of it, having to dig with their hands and a couple of shingles, because the two spades we had were buried with us at the bottom of the cave.