PRINCIPIA.
"Stilling Waves by means of Oil." This wonderful property, though well known to the ancients, as appears from the writings of Pliny, was for ,many ages either quite unnoticed, or treated as fa bulous by succeeding philosophers. By means of Dr...Franklin, the subject again attracted the attention of the learned ; though it appears from some anecdotes, that seafaring people have always been acquainted with It: Mr. Pennant, in his British Zoology, vol. iv. under the article Seal, takes notice that when these animals are devouring a very oily fish, which they always do under water, the waves above are remarkably smooth ; and by this mark the fishermen know where to find them. Sir Gilbert who served long in the army at Gibraltar, assured Dr. Frank lin, 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 instru ment. A similar practice obtains among fishermen in various other parts; and Dr.
Franklin was informed by an old sea-cap tain, that the fishermen of Lisbon, when about to return into the river, if they saw too great a surf upon the bar, would empty a bottle or two of oil into the sea, Which would suppress the breakers, and allow them to pass freely.
The doctor having revolved in his mind all these pieces of information, be came impatient to try the experiment himself At last, having an opportunity of observing a large pond very rough with the wind, he dropped a small quan tity of oil upon it. But having at first ap plied it on the lee-side, the oil was dri ven back again upon the shore. lie then went to the windward side, and poured on about a tea-spoon full of oil ; this pro. ducedain instant calm over a space seve ral yards square, which spread amazing ly, and extended itself gradually till it came to the lee-side; making all that quarter of the pond, perhaps half an acre, as smooth as glass. This experiment was often repeated in different places, and always with success.