The Century of Inventions of the Marquis of Worcester / from the Original MS., with Historical and Explanatory Notes and a Biographical Memoir

by Marquis of Edward Somerset Worcester

No. LXXVI.

How to write in the dark, as straight as by day or candle-light.

NOTE.

Two planes of ebony of equal length and breadth, similar to the parallel ruler, and joined at each end by racks, the side of which being graduated to the width of the line intended will serve as a certain guide, and by the use of this instrument a blind person may write with the greatest accuracy. If ivory tablets or a slate is used, a fine wire drawn with a steel point may be readily felt by the point of the pencil.