House-keeping: Of late, many of you have written in to note (i.e., complain) that cutting and pasting on TPM has become weirdly difficult. The reasons for this are too complicated to go into (i.e., I don't even understand it myself). But the short version is that it was a trade-off with changes that were made to make the site download more quickly. We're working on a fix. But for now, if you want to copy some text for whatever reason, click on the 'print' link up at the top right hand side of the post. That will take you to a version where cutting and pasting is as easy as, well ... cutting and pasting.