There was indeed something which appeared long, like two green Weeds lying among the Grass, and there was something like a large Spot of dryed Grass or Flags a little before them.
While I was looking at the Place, the Dog, being out of Patience, seized Hold of this Phœnomenon, which proved to be no other than the Bittern itself. Those Things which seemed to be green Weeds, were it's Legs extended at the full Length, behind the Bird, as it lay quite flat upon it's Belly; and that broad Spot of brown or dried Grass was the Body, with the Wings extended to their full Stretch, quite flat upon the Ground, which, I believe, formed as compleat a Deceptio Visus as any Thing in Nature.
Thus we see how wonderfully these Animals are formed for their Self-Preservation; so wonderfully, that though they are near as large as a Heron, and much of the same Shape, it must be a keen Eye that distinguishes their long green Legs from Weeds, and their brown Backs from dried Grass; but this Deceptio Visus is so notorious in Partridge, and many other Species of Game, that there is no Occasion to dwell any longer upon that; only what has been said may serve to convince the Reader of the Truth of what has been observed in the foregoing Section, concerning the Posture of a Heron and a Bittern on their Nests.
IV.
That the Tone of a Violin is to be brought out, by laying on like a Blacksmith.
Before we can convince such of our Readers as have no Knowledge in that
Part of Pneumatics which is called Harmonics, of this Mistake, it will be necessary just to give a short Account of the Cause of Sound in stringed Instruments.
In the first Place, all Sound proceeds from Undulations in the Air, which is an elastic Fluid; and with regard to these Undulations, is much of the same Nature as Water, which is another Fluid, but differs from Air in many Respects. Now when a Person throws a Stone into Water, these Undulations or Waves are raised in the Fluid for some Distance, by the Force and Action of one Wave upon another. This is the Case with regard to Sound; only the Air being an elastic Fluid, these Undulations are more quick and brisk in their Motions than in Water. So much for Sound itself. Now for the Cause of this Sound, or of these Undulations.