The barrel represents the earth's atmosphere in which the carbon-14 accumulates.The water leaking out the sides of the barrel represents the loss (mainly by radioactive decay) of the atmosphere's supply of carbon-14.
When the dipole moment is strong, carbon-14 production is suppressed below normal; when it is weak, carbon-14 production is boosted above normal.
What the magnetic field does is to partially shield the earth from cosmic rays which produce carbon-14 high in the atmosphere.
It's a great argument except for one, little thing.
The water is coming out of the hose at a steady rate as our model assumed!
We stick the garden hose in and turn it on full blast.
The water coming out of the hose is analogous to the continuous production of carbon-14 atoms in the upper atmosphere.
Creationists don't want their readers to be distracted with problems like that -- unless the cat is already out of the bag and something has to be said.
Tree-ring dating (see Topic 27) gives us a wonderful check on the radiocarbon dating method for the last 8000 years.
(The barrel is made deep enough so that we don't have to worry about water overflowing the rim.) Henry Morris argued that if we started filling up our empty barrel it would take 30,000 years to reach the equilibrium point.