Youre right, Tiger. I've always read that the adjust the speed of the Big Ben clock by putting pennies on the pendulum(or taking them off). So I kind of imagined putting a penny on would slow it down, on the "more work to do principle".Now from what you say, putting the pennies on would speed it up, because they'd raise the centre of gravity of the pendulum weight, which would make effectively effectively shorter. Have I got that right? I'm finding it difficult to visualise.