Contrary to creationist Barnes' totally discredited claims, which I've covered in Topic 11, the earth's magnetic field (dipole moment) has, indeed, increased and decreased over time.
Now, the fuller that barrel gets the more water is going to leak out the thoroughly perforated sides, just as more carbon-14 will decay if you have more of it around.
Finally, when the water reaches a certain level in the barrel, the amount of water going into the barrel is equal to the amount leaking out the perforated sides.
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.
Sometimes it slows down to a trickle so that much more water is leaking out the barrel than is coming in; sometimes it goes full blast so that a lot more water is coming into the barrel than is leaking out. Lingenfelter's paper was written in 1963, before the cycles of C-14 variation we described had been fully documented.
Thus, the mere fact that the present rate of water coming in exceeds that of the water leaking out cannot be extrapolated back to a starting time. The point is that fluctuations in the rate of C-14 production mean that at times the production rate will exceed the decay rate, while at other times the decay rate will be the larger.To that end, he quoted some authorities, including Richard Lingenfelter.Having accomplished that, Morris concluded that the barrel was still in the process of being filled up and that, given the present rate of water coming in and leaking out, the filling process began only 10,000 years ago.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!(Strahler, 1987, p.158) Lingenfelter actually attributed the discrepancy between the production and decay rates to possible variations in the earth's magnetic field, a conclusion which would have ruined Morris's argument.