so far stills the ripple, leaving the reflections. Our eminent engineer, Mr Robert Stevenson, made use of the water-telescope more than 30 years ago, in works connected with harbour improvement in the north of Scotland; it has also been used to examine the sand-banks, &c., at the bottom of the River Tay, but in this case the mud prevented its use in any considerable depth of water. To obviate this difficulty, the construction was modified thus: by making the tube of considerable length, and placing the glass at the lower end, this tube was thrust through the water till within a few feet of the bottom, acting as a cofferdam to set aside the dirty water, and enable the bottom to be seen; but in this method of application it was found very difficult to hold the tube down in the water from its buoyant power, and we are informed by Mr Thomas Stevenson, C. E., that, he understood from this cause its use had been discontinued. He suggested a simple remedy; viz., to fill up the empty tube with pure water. We are indebted to Mr Mitchell, the gentleman already mentioned, for having brought this instrument into notice in the public prints, under the name of Norwegian water-telescope, on the shores of which country it is stated to be much used in fishing--in particular, that of the herring; but the herring-fishers on the east coast of Scotland inform us, that they require no such auxiliary, as, from the surrounding elevated grounds, they can tell the position of the shoal, and, from their motions seen from such situations, they know where they are to be found when they go out a-fishing.[50] Footnote 49: Leslie's Elements of Nat. Phil., p. 19. Footnote 50: _Norwegian Water-Telescope._ The water-telescope is thus noticed in a very promising periodical, the American Annual of Scientific Discovery, just published, of which a copy reached us a few days ago.--ED. _Phil. Journal_.