By the enclosed from an old friend, a worthy clergyman at Carlisle, whose great learning and extensive knowledge in most sciences would have more distinguished him had he been placed in a more conspicuous point of view, You will find that he had heard of your experiment on Derwent Lake, and has thrown together what he could collect on that subject; to which I have subjoined one experiment from the relation of another Gentleman.

I sometime ago met with Mr. Dun, who surprised me with an account of an experiment you had tried upon the Derwentwater, in Company with Sir J. Pringle and Dr. Franklin. According to his representation, the water, which had been in great agitation before, was instantly calmed, upon pouring in only a very small quantity of oil, and that to so great a distance round the boat as seems a little incredible. I have since had the same accounts from others, but I suspect them all of a little exaggeration. Pliny mentions this property of oil as known particularly to the Divers, who made use of it in his days, in order to have a more steady light at the bottom.* The sailors, I have been told, have observed something of the same kind in our days, that the water is always remarkably smoother in the wake of a ship that had been newly tallowed, than it is in one that is foul. Mr. Pennant also mentions an observation of the like nature made by the Seal Catchers in Scotland: Brit. Zool. Vol. IV. Article Seal. When these Animals are devouring a very oily fish, which they always do under water, the waves above are observed to be remarkably smooth, and by this mark the fishermen know where to look for them. Old Pliny does not usually meet with all the credit I am inclined to think he deserves. I shall be glad to have an authentic account of the Keswick Experiment, and if it comes up to the representations that have been made of it, I shall not much hesitate to believe the old Gentleman in another more wonderful Phenomenon he relates of stilling a Tempest only by throwing up a little Vinegar into the Air.

Sir Gilfred Lawson who served long in the army, at Gibraltar, assures me that the Fishermen in that place are accustomed to pour a little oil on the sea in order to still its motion that they may be enabled to see the Oysters lying at its bottom; which are there very large, and which they take up with a proper instrument. This Sir Gilfred had often seen there performed, and said the same was practised on other parts of the Spanish Coast.