The detection of colour-blindness and imperfect eyesight : with a table of coloured Berlin wools and sheet of test-types / by Charles Roberts.

  • Roberts, Charles, 1836-1901.
Date:
1884
Catalogue details

Licence: Public Domain Mark

Credit: The detection of colour-blindness and imperfect eyesight : with a table of coloured Berlin wools and sheet of test-types / by Charles Roberts. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    8/26 (page 4)
    method. All the test-colours are placed on the left of the table, at the beginning of each row of wools, which makes them easily found by the person who undertakes the examination; and strands, or threads, of the test-colours are worked in between each of the confusion-colours, thus bring- ing them into immediate apposition, as they would be if held in loose skeins in the hand by Holmgren's plan. The colours are arranged in rows, as if they were different shades of the test-colours as colour-blind persons see them; and the rows in which the same test-colour is used are placed together, in order to show more clearly the different confusion-colours which the test elicits from green- red- and violet-blind persons. The table of wools is useful, therefore, for teaching the examiner the principles on which the various methods of testing the colour-sense are based. Practice shows that it is impossible to draw a line between colour-blindness and colour-ignorance; and the chief difficulties attending the examination of the colour-sense is the ignorance of colom-s and their ordinary names displayed by imperfectl}' educated persons, and the careless ajjplication by educated persons of the common names of colours, or the employment of what may be called draper's and dress-maker's names for shades which can be easily defined by compound words. To simplify this, and to make the wool-card avail- able for teaching purposes, a row of wools is introduced showing the primary and secondary colours, and some of the compounds derived from them; and two rows, one of reds and one of greens, are also given to show the difference between the word shade and colour. The first row consists of different colours; the second row of different shades of one colour. The entire value of the table of wools as a test for colour-blindness depends on this distinction being observed.