KANSAS ACADEMY OF SCIENCE. 37 



ing the duties assigned to them? That color-blindness is the source of acci- 

 dents and calamities on railroads, in which property and life are sacrificed, 

 is as apparent as any fact in pure mathematics. 



How shall railway accidents and dangers be prevented ? Simply by see- 

 ing that no men who have this visual defect be employed as train-men; that 

 is, in the capacity of engineer, stoker, brakeman, conductor, or switch-man. 

 This result can be secured by examinations, as first suggested by Wilson in 

 1855. It is accomplished, according to Prof Holmgren's method, by having 

 the person to be tested match colored worsteds. For the purpose of making 

 the examinations, colored worsteds are procured, and placed in a pile on a 

 table or large plane surface. The examinations are made in daylight. "The 

 selection of worsteds includes red orange, yellow, yellow green, pure green, 

 blue; violet, purple pink, brown, gray; several shades of each color, and at 

 least five gradations of each tint, from the deepest to the lightest. Green 

 and gray, several kinds each of pink, blue and violet, and the pale-gray 

 shades of brown, yellow, red and pink, must especially be well represented.* 

 The colors are divided into sample colors, consisting of green, purple and 

 red, and confusion colors, made of every shade and tint of the solar spec- 

 trum. The first test consists in matching the sample green color. He who 

 places besides the sample color one of the colors of confusion — that is to 

 say, finds that it resembles the test color — is color-blind. He who, without 

 being quite guilty of this confusion, evinces a manifest disposition to do so, 

 has a feeble chromatic sense. Second test : A purple skein is presented. The 

 color chosen must be between the deepest and lightest shades of the scale. 

 Diagnosis : He who in the second test selects with purple only blue and vio- 

 let, or one of them, is completely red-blind. He who in the second test 

 selects with purple only green and gray, or one of them, is completely green- 

 blind. Test third : The red skein is presented to the subject. It is necessary 

 to have a vivid red color, like the red flag used as signals on railways. This 

 test, which is applied only to those completely color-blind, should be con- 

 tinued until the person examined has placed beside the specimen all the 

 skeins belonging to this shade, or the greater part, or else, separately, one or 

 several colors of confusion. The red-blind then chooses, besides the red, 

 green and brown shades, which to the normal sense seem darker than red. 

 On the other hand, the green-blind selects opposite shades which appear 

 lighter than red. Violet-blindness will be recognized by a genuine confusion 

 of purple, red and orange, in the second test." (See "Color-Blindness," by 

 F. Holmgren, page 185 — Report of Smithsonian Institution, 1878.) 



In conclusion, Mr. President, permit me to say that the principal object I 

 have had in view in preparing this paper has been to interest this Academy 

 in the subject of color-blindness, and through it the Legislature and his 

 Excellency the Governor of the great commonwealth of Kansas. I believe 

 that when this subject is properly presented to the legislators of your State, 



*The word purple here does not designate the color that has that name in this country. It is known 

 to us as Victoria rose, and is said to be carmine diluted with white. 



