How can man combat part of the continent on the move, driven by the ceaseless powers of the air?  By a humble plant or two.  The movement of the sand hills that threaten to destroy the marvelous beauty of the grounds of the Hotel del Monte at Monterey is stopped by planting dwarf pines.  The sand dunes that prevent much of Holland from being reconquered by the sea are protected with great care by willows, etc., and the coast sands of parts of eastern France have been sown with sea pine and broom.

The tract of a thousand acres on Cape Cod had been protected by humble beach grass.  Some careless herder let the cows eat it in places, and away went part of a township.  It is now a punishable crime on Cape Cod to destroy beach grass.

GAS HELP

This refers to more than stump speech-making.  The old Romans drove through solid rock numerous tunnels similar to the one for draining Lago de Celano, fifty miles east of Rome.  This one was three and a half miles long, through solid rock, and every chip cost a blow of a human arm to dislodge it.  Of course the process was very slow.

We do works vastly greater.  We drive tunnels three times as long for double-track railways through rock that is held down by an Alp.  We use common air to drill the holes and a thin gas to break the rock.  The Mont Cenis tunnel required the removal of 900,000 cubic yards of rock.  Near Dover, England, 1,000,000,000 tons of cliff were torn down and scattered over fifteen acres in an instant.  How was it done?  By gas.

There are a dozen kinds of solids which can be handled—­some of them frozen, thawed, soaked in water, with impunity—­but let a spark of fire touch them and they break into vast volumes of uncontrollable gas that will rend the heart out of a mountain in order to expand.

Gunpowder was first used in 1350; so the old Romans knew nothing of its power.  They flung javelins a few rods by the strength of the arm; we throw great iron shells, starting with an initial velocity of fifteen hundred feet a second and going ten miles.  The air pressure against the front of a fifteen-inch shell going at that speed is 2,865 pounds.  That ton and a half of resistance of gas in front must be much more than overcome by gas behind.

But the least use of explosives is in war; not over ten per cent is so used.  The Mont Cenis tunnel took enough for 200,000,000 musket cartridges.  As much as 2,000 kegs have been fired at once in California to loosen up gravel for mining, and 23 tons were exploded at once under Hell Gate, at New York.

How strong is this gas?  As strong as you please.  Steam is sometimes worked at a pressure of 400 pounds to the inch, but not usually over 100 pounds.  It would be no use to turn steam into a hole drilled in rock.  The ordinary pressure of exploded gas is 80,000 pounds to the square inch.  It can be made many times more forceful.  It works as well in water, under the sea, or makes earthquakes in oil wells 2,000 feet deep, as under mountains.