Or, perhaps, we may be watching one of the many loading machines. There is a certain suggestiveness in the way the machines are separated by partitions. The man in charge takes a small carrier of powder from a case in the outside wall and shuts the door, then carefully empties it into the reservoir of his machine, and watches alertly while it packs the proper portions into the waiting shells. He looks like a careful man, and needs to be. You do not stand too close.
The empty carrier then passes through a little door at the side of the building, and drops into the yawning mouth of an automatic tube. In the twinkling of an eye it appears in front of the operator in one of the distributing stations, where it is refilled and returned to its proper loading machine, in order to keep the machine going at a perfectly uniform rate; while at the same time it allows but a minimum amount of powder to remain in the building at any moment. Each machine has but just sufficient powder in its hopper to run until a new supply can reach it. Greater precaution than this cannot be imagined, illustrating as it does, that no effort has been spared to protect the lives of the operators.
How does an Artesian Well Keep Up Its Supply of Water?
Artesian wells are named after the French Province of Artais, where they appear to have been first used on an extensive scale.
[Illustration: ARTESIAN WELL (_D_) IN THE LONDON BASIN]
They are perpendicular borings into the ground through which water rises to the surface of the soil, producing a constant flow or stream. As a location is chosen where the source of supply is higher than the mouth of the boring, the water rises to the opening at the top. They are generally sunk in valley plains and districts where the formation of the ground is such that that below the surface is bent into basin-shaped curves. The rain falling on the outcrops of these saturates the whole porous bed, so that when the bore reaches it the water by hydraulic pressure rushes up towards the level of the highest portion of the strata.
The supply is sometimes so abundant as to be used extensively as a moving power, and in arid regions for fertilizing the ground, to which purpose artesian springs have been applied from a very remote period. Thus many artesian wells have been sunk in the Algerian Sahara which have proved an immense boon to the district. The same has been done in the arid region of the United States. The water of most of these is potable, but a few are a little saline, though not to such an extent as to influence vegetation.