It may not appear foreign to the Purpose, when I say that I have heard a Bittern make the Noise abovementioned, and that I have gone to the Spot, which was coarse Grass or Flags, just mowed, where there were no Reeds; and the Bird rose up before me. Here I must beg Leave to put in a Word or two, by way of corroborating what has been said about the Heron and the Bittern lying flat upon their Nests, with their Legs parallel to the Plain of the Horizon. When the aforesaid Bittern rose up, I shot, and wounded him slightly, and marked him down again in the same Kind of Grass or short mowed Flags. As the Grass was not higher than one's Shoes, and it was wounded, I was in Hopes of having the Pleasure of seeing him lie on the Ground very plain. However I let my Pointer go first, knowing that he would stand at the Place. Accordingly made a dead Point at it. I came up as silent as possible, to take a View of it, but to my great Surprize, nothing was to be seen. 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 Phoenomenon, 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.