Transactions . ber, 1882. The quadrant is rotated by a wooden hand-wheelattached to its axis, and is balanced by a weight uponthe hand-wheel, so that it will stand in any position with-out being fixed. The chart is placed upon the hinder surface of thehand-wheel, and a horizontal scale is fixed immediatelybehind it, the divisions of w^hich correspond with thecircles on the chart. As the quadrant rotates the chartrotates with it, and in whatever position the quadrantstands the corresponding meridian lies against the scale. A NKW UEUlSTEIilNQ IKK1M MTKIf. 295 This arrnngcmout onablcs the operato
Transactions . ber, 1882. The quadrant is rotated by a wooden hand-wheelattached to its axis, and is balanced by a weight uponthe hand-wheel, so that it will stand in any position with-out being fixed. The chart is placed upon the hinder surface of thehand-wheel, and a horizontal scale is fixed immediatelybehind it, the divisions of w^hich correspond with thecircles on the chart. As the quadrant rotates the chartrotates with it, and in whatever position the quadrantstands the corresponding meridian lies against the scale. A NKW UEUlSTEIilNQ IKK1M MTKIf. 295 This arrnngcmout onablcs the operator to finish off liisobservations witli the greatest ease, and has the furtheradvantage tliat the cliart is constantly under inspection,so that any part of the field can be immediately broughtunder examination or re-examination at any time, byturning the corresponding point on the chart round tothe scale. The test object is a square of paper gummed upon alight vulcanite wand ; this the operator holds in his left. hand, while with the right he rotates the hand-wheel andpricks the readings upon the chart. The charts are of two kinds, A and b, correspondingrespectively to the whole visual field, and to its centralarea on a larger scale. The scale of the perimeter isgraduated accordingly on its two sides ; the A side isused with the A charts, the B side with the B charts. There are cases in which the field is mapped moreaccurately by moving the test object in circles concentricwith the fixation point than by moving it in meridians. 296 NEW INSTRUMENTS. hemiauoplc, sector-like, and all other defects in whichthe boundary line runs in a meridional direction. Insuch cases the test object should be placed in the clipwhich slides upon the quadrant, and carried round thefield in successive circles, every point at which it entersor leaves the sentient field being pricked upon the chart. (May 10th, 1883.) 3. Description of a new ophthalmoscope^ designed especiallyfor the use of artists.
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Keywords: ., bookcentury1800, bookdecade1880, bookpu, booksubjectophthalmology
