The Straight Dope 01/05/2007

The Straight Dope -- By Cecil Adams
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THE STRAIGHT DOPE 01/05/2007

Dear Cecil:

How come if you dig a well far down enough, you hit water? Where does that
water come from, and how did it get so far underground? How did people
first figure out that digging in the ground would get you water?--Will,
Washington, DC

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Cecil replies:

Ever hear of gravity, nudnik? Water in the form of rain, snowmelt, and
seepage from lakes and rivers soaks into the ground until it hits an
impermeable layer, typically rock or consolidated soil called hardpan,
whereupon it collects in what's known as an aquifer. A well merely has to
reach down past the upper surface of this buried water, known as the water
table, and you're up to your knickers in the stuff. Granted, the subject
has its infrequently explored aspects. Here's one: Water dowsers claim
they can detect underground rivers, the idea being that groundwater flows
in narrow channels and not elsewhere (which is why you need a dowser).
That flies in the face of the commonsensical view that, barring some
peculiarity of local geology, the water beneath your feet is distributed
pretty uniformly and you can find it digging most anywhere. But you know
what? Underground rivers actually exist.

First let's finish answering your question. 

For more, see:
http://www.straightdope.com/columns/070105.html

STRAIGHT DOPE CLASSIC #1 - 12/21/1990

Dear Cecil:

Why do the spouters on some water fountains produce two streams of water
that merge into one before reaching your parched lips? Why not just one
stream to start with?--Steven Palkovitz, Alexandria, Virginia

Dear Steven:

In an age when you can't even fix your Chevy without having to fool with
microchips, Cecil is always cheered by examples of low-tech ingenuity. The
twin-stream water fountain is a perfect example. But first we need to put
things in proper historical perspective. Let me quote from a brochure for
Halsey Taylor water fountains, one of the leading names in the industry:

"In 1896, Halsey W. Taylor lost his father to an outbreak of typhoid fever
caused by a contaminated water supply. This personal tragedy led the young
Halsey Taylor to dedicate his life to providing a safe, sanitary drink of
water in public places....The historic Double Bubbler projector [spouter]
was designed by Halsey Taylor himself, and still ranks as the most
important innovation in the industry's history. It projects two separate
streams of water, which converge to provide an abundant `pyramid' of water
at the apex of the stream. This gives the user a fuller, more satisfying
drink."

The folks at Halsey Taylor are being polite here. 

For more, see: 
http://www.straightdope.com/classics/a3_279.html

STRAIGHT DOPE CLASSIC #2 - 08/21/1992

Dear Cecil: 

Why don't freight trains have cabooses anymore?--George, Dallas  

Dear George:  

Don't need 'em, and besides, it's cheaper this way. There used to be two
guys in the caboose: the conductor and a brakeman. The conductor did
paperwork, the brakeman threw switches, and they both watched for
"hotboxes" (overheated freight car wheel bearings). They also radioed
useful tidbits of information about the train (e.g., there's been a little
accident) to the engineer. Today virtually all mainline switch-throwing is
done electrically from the central office, roller bearings have eliminated
most hotboxes and trackside infrared sensors catch the rest, the conductor
can do his paperwork in the locomotive, and the useful tidbits of
information are provided to the engineer by a soulless machine (see
below). So it's curtains for the caboose.

What you see instead on the end of the train is a gizmo called an
"end-of-train device" (ETD) that (1) senses motion, (2) monitors the
pressure in the air brake line, and (3) automatically radios its findings
to a receiving unit in the locomotive. Unlike car brakes, trains brakes
are released by increasing (not decreasing) the pressure in the brake
line. This can take a while in a mile-long freight. When the engineer
wants to start the train, she pumps air into the brake line until the
rear- end gauge reaches a certain level. That tells her all the brakes
throughout the train have been released and she can give that puppy some
gas.

For more, see:
http://www.straightdope.com/classics/a3_282.html
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