What did Montmorency do at sonning?

He was burnt by the kettle water. He proceeded to attack the boiling kettle,

"And he rushed at that poor little kettle, and seized it by the spout.

Then, across the evening stillness, broke a blood-curdling yelp, and Montmorency left the boat, and did a constitutional three times round the island at the rate of thirty-five miles an hour, stopping every now and then to bury his nose in a bit of cool mud."