I can tell. The gritlets are starting to feel the strain of geology.
Really, I find that extraordinary, given that this is beautiful Kimmeridge bay. And the Purbecks! My goodness, Eden fell down here and no-one told me.
I think I could go on with my geology tour. Yes, my knees are becoming quite sore, what with the kneeling on rocks to scrutinise beaches, and my back is probably broken, thanks to the megaliths that Squirrel drops casually into my handbag as she passes.
But Shark is pissed off. She realises there are people at Kimmeridge bay who will run kayaking and snorkeling sessions, and I have miserably failed to organise something for her. She snaps that this is a marine reserve and what else did I expect? She wants to see it.
Now she's not forgiving me. Look, here she is in the marine centre, and she's not talking to me.
I say what I always say. Where ever you visit, you should depart leaving something undone. Not your trouser zip or shoelace, obviously. I mean something by which you can think how better you can approach this place in future years. Except Weymouth. Just avoid that place altogether, that's my advice.
Shark ignores me and slopes off to sulkily adopt the rockpooling and geology postures we know so well.
Tiger is becoming fatigued with geology, and so gives up on the fossil hunting to amuse herself inflating a plastic glove to gesture in rude and deniable fashion to other holidaymakers.
Squirrel? There aren't any pictures of her, thanks to the stomping off routine. I merely said you cannot dig up the cliffs here, they are protected. And no, I am not putting that boulder in my handbag. Then off she went, with as much stomping off as you can do over a boil of slimy seaweed. (Memo: do not smile at an outraged Squirrel with no balance.)
So I give in. About 3pm I take everyone over to Corfe Castle to cheer up.
Castles are always guaranteed to raise a laugh. Especially when we can imagine the sieges, poisoned wells, projected sheep carcasses, murder holes and battering rams.
I say yes, on the remaining days of our week, we'll visit Brownsea Island, which is on everyone's list of places to enjoy, and we'll take the history tour of Lyme Regis with a quick turn round Blackbury iron age camp.
I think I have to give up the very opposite tips of our geology tour, Old Harry and Exmouth, but they'll stay. And I should always leave something undone. (Not belt buckles or bra straps, as I said.)