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09 Dec 2010 [07:35]
So the plot thickens. I went in at 07h30 to see what is responsible for this amplitude glitch at 07h35 every morning [link] , it happened again today. Is it the strike silencer? No, this releases at around 07h20. Is it the sun at sunrise? No, the sun does not shine on the clock tower until about 08h10, and it is not until 08h45 that the window into the clock case is out of the shadow of the S-E turret. Is it the central heating switching on? Well, not sure, but the event is so sudden and short-lived that the heating switch-on cannot really be responsible. But at precisely 07h35 I heard a noise. It was the cleaning lady opening the door of Dr Hopkinsons room below. I went down to see her and asked if she came in at this time every day and she said yes, exactly this time - not on weekends. How long does she stay? About 10 minutes. Now, when she cleans she leaves the door wide open.
09 Dec 2010 [07:34]
This might explain why Dr Hopkinsons comings and goings have no effect. So I asked her if she would leave the door open again tomorrow but next week she will close the door when she cleans. We will see if it makes a difference. But I am still really puzzled: the pendulum chamber is now (since Tuesday) fully taped up and I cannot see any obvious places for draughts to get anywhere near the clock. Maybe there is a non-draught-related explanation - perhaps the cleaning lady is attractive to long swinging objects? Next week will be interesting. (By the way, this glitch is small by comparison to others eg pigeons and spiders, but it is curious all the same)

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