It not being feasible to fire a lot of holes electrically, the limit being about thirty, the simultaneous explosion of perhaps hundreds has to be brought about in some other manner, and usually it is accomplished by the simple device of putting the holes fairly near together and firing one with a fuse. The commotion set up by this one causes the nearest ones to "go off," they in turn detonating those farther on, with the result that explosion follows explosion all along the line so rapidly as to be almost instantaneous. A farmer who is troubled by a winding stream passing through his land, cutting it up into awkward shapes, can straighten it by blasting a ditch across a loop in the manner just described. In the case of low-lying land, however, ditches are obviously no use, since water would not flow away along them. In that case the principle suggested just now for dealing with an inconvenient pond can sometimes be used, for if the subsoil be blasted through at several points it is very likely that water will find a way downwards by some means or other. And the list of possible uses is by no means exhausted yet. A man opening up virgin land often finds old tree stumps his greatest bother. He can dig round them and then pull them out with a team of horses, but by far the simpler way is with a few well-placed dynamite cartridges, for they not only throw up the stump for him, but they break it up, shake the earth from it, and leave it ready for him to cart away or to burn. Boulders, too, can be blown to pieces far more easily than one would think. The charges may be put underneath them as with the tree stumps, but in many cases that is not necessary, all that is needed being some dynamite laid upon the top of the rock and covered with a heap of clay. So sudden is the action of the explosive that its shock will break up the stone underneath it. Yet another way, perhaps the most effective of all, is to drill a hole into the stone and fire a charge inside it. It behoves the onlooker then to keep away, for the fragments may be thrown three or four hundred feet, a fair proof that the stone will be very thoroughly demolished. Even in the digging of wells explosives may be useful. In that case the holes are made in a circle, and they slant downwards and inwards, so that their lower ends tend to meet. The result of simultaneously exploding the charges in these holes is to cut out a conical hole a little larger in size than the ring and a little deeper than the point at which the explosion took place. The bottom of that hole can be levelled a little and the operation repeated, and so stage by stage the well will proceed to grow downwards.