wide driveways have one or two broad sidewalks. The same rule of
making the slow-moving vehicles keep near the outside prevails,
though the rate of increase in speed on approaching the middle is
more rapid than in cities, and there is usually no dividing
ridge. On reaching the top of a long and steep hill, if we do
not wish to coast, we convert the motors into dynamos, while
running at full speed, and so change the kinetic energy of the
descent into potential in our batteries. This twentieth-century
stage-coaching is one of the delights to which we are heirs,
though horses are still used by those that prefer them.

We have been much aided in our material progress by the facility
with which we obtain the metals. It was observed, some time ago,
that when artesian and oil wells had reached a considerable
depth, what appeared to be drops of lead and antimony came up
with the stream. It finally occurred to a well-borer that if he
could make his drill hard enough and get it down far enough,
keeping it cool by solidified carbonic acid during the
proceeding, he would reach a point at which most of the metals
would be viscous, if not actually molten, and on being freed from
the pressure of the crust they would expand, and reach the
surface in a stream. This experiment he performed near the hot
geysers in Yellowstone Park, and what was his delight, on
reaching a depth scarcely half a mile beyond his usual stopping-
place, to be rewarded by a stream of metal that heralded its
approach by a loud explosion and a great rush of superheated
steam! It ran for a month, completely filling the bed of a
small, dried-up river, and when it did stop there were ten
million tons in sight. This proved the feasibility of the
scheme, and, though many subsequent attempts were less