THE WEDGE. 251 



the stones, and sometimes to such an extent as to cover the 

 whole roadway with verdure. 



The force which is employed is simply marvellous, and can 

 only be appreciated by those who know the resisting power of 

 earth, however dry and loose it may be. Even sand has so 

 strong a resistance that tents can be pitched in the desert with- 

 out difficulty. Of course the ordinary tent-peg would be use- 

 less, but the desert dwellers can pitch their tents with perfect 

 security. They fasten the tent-rope to a branch or piece of 

 bush, scrape a hole in the sand, put the bush into the hole, 



GRASS-BLADES. 



cover it up again, and it will withstand almost any strain, 

 though it be only covered with a few inches of sand. 



When miners blast rocks with gunpowder, they take advan- 

 tage of the resisting power of sand. They bore a suitable hole, 

 place a charge of gunpowder at the bottom, and then merely 

 pour loose sand into the hole until it is filled. When the 

 powder explodes, the rock or coal is shattered to pieces, but the 

 sand is not blown out of the hole. This operation is called 

 " tamping." 



Every one, again, knows how firm are gate-posts, and how 

 they resist the weight, jarring, and leverage of a heavy gate, 

 all because they are sunk a little way into the earth. 



Considering, therefore, that such fragile things as young 

 grass-blades can force their way through the superincumbent 

 weight, we can but be amazed at the aggregate of active force 

 which is in full operation in every pasture field and garden 

 lawn. 



As far as I know, not being much of a botanist, every seed 

 that springs up does so on the wedge principle, though the form 

 of the wedge may be varied. 



