. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 1846.] THE CIVIL ENGINEER AND ARCHITECPS JOURNAL. 337 uncertainty and difficiilly I have mentioned as besetting the use of the common dial and that of the Briefly to illustrate its use, permit me to refer you to the sketch, sup. posing it requisite to take the angle formed by the two lines joining re- gpeclively A B, BC, the instrument is placed at the angle, and the limb x y z, which is flat, circular, and divided on the outer edge into 720 or half degrees,
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. 1846.] THE CIVIL ENGINEER AND ARCHITECPS JOURNAL. 337 uncertainty and difficiilly I have mentioned as besetting the use of the common dial and that of the Briefly to illustrate its use, permit me to refer you to the sketch, sup. posing it requisite to take the angle formed by the two lines joining re- gpeclively A B, BC, the instrument is placed at the angle, and the limb x y z, which is flat, circular, and divided on the outer edge into 720 or half degrees, each indicating in an observation a whole degree—this limb is then turned on a joint below, admitting horizontal motion, until the candle A is reflected from the mirror B, to the eye of the observer placed any- where opposite the vertical line D E—this mirror B is fixed vertically on the lower limb, with the silvered surface exactly in the centre. Then the upper limb is so adjusted (hat the candle C is also reflected from the mirror G (which is fixed vertically to this limb, and whose centre of motion is in the plane of the mirror B,) to the eye of the observer on the line d c, of the sight D E, during this adjustment if any movement occurs in the instru- ment, it is instantly detected and adjusted by the observer without change of place, witJKjut difficulty, and in the leaU imaginable time. The angle required is then indicaied by the vernier at either end of the limb 7, ?•, s, /, at 1/ or t. To test the efficiency of the instrument, I made the subjoined survey wiih it, of a small but very hilly sloping piece of ground, of which I subjoin the plotting showing the error, which considering the iuiperfec- tion of the model, will be considered, I think, very Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original
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Keywords: ., boo, bookcentury1800, booksubjectarchitecture, booksubjectscience
