SCIENCE. 



197 



THE CUPRIFEROUS SERIES IN MINNESOTA.* 



The paper of Prof. N. H. Winchell, State Geologist, of Min- 

 nesota, was a brief statement of the relations of that formation 

 to the ranges of crystalline rock that form the northwestern 

 border of the Lake Superior Basin. He concluded, by two 

 lines of investigation, that the Cupriferous series is of the 

 age of the New York Potsdam, and that it falls within the 

 horizon of some part of that group which the Canadian ge- 

 ologists have designated the Quebec. 



One line of argument related to an examination in the field 

 of the stratigraphy, in which the sedimentary beds are seen 

 to pass by metamorphic changes through various forms to 

 fully crystalline rocks styled granite and gneiss. These 

 crystalline rocks, whicli are spread over large areas, are in- 

 timately associated with the igneous rocks of the Cuprif- 

 erous Series, from which, however, they are constantly dis- 

 tinguished by certain mineralogical differences The writer 

 also parallelized the igneous beds of the northwestern coast 

 ranges with the Labradorite, or Norite, rocks of Canada, 

 and suggested the possibility that the " Laureutian " Eozoon, 

 said to occur in this terrane, may be of the age of the Low- 

 er Silurian. 



w> 



ON COLOR BLINDNESS.* 

 By Dr. B. Joy Jeffries. 



Dr. Jeffries first described the natural condition of the 

 color-sense, and illustrated some of its peculiarities relating 

 to color-blindness. The complimentary after-image of a 

 color can be readily seen by gazing at the red setting sun, 

 when, if we turn our eyes to the east, we shall see a green 

 rising one. Looking steadily at a yellow spot on white, 

 and turning away, we see a blue one, etc. After looking 

 intently at the red or green light on a railroad or vessel, one 

 cannot help momentarily seeing the reverse color. The 

 centre of the retina has the greatest power of form-percep- 

 tion; we must fix our eye steadily to see anything very dis- 

 tinctly. The same with color. All colors fade in intensity 

 outward from the centre of the retina. In a central zone 

 we can distinguish all three of the colors now considered 

 primary, viz., red, green, and violet. In a zone outside of 

 this our red perception fails, and in the outer portions still 

 of the retina green fails, and we see blue or violet only. 

 Now, we have red, green, and violet blindness, resembling, 

 so to speak, the conditions of these zones. This must not, 

 however, be too strictly construed. Color-blindness may 

 be best described thus: Those who are red or green Cone 

 involving the other) or violet-blind see all objects having 

 these colors as gray or grayish in the proportion in which 

 they are color-blind and the depth of the pigment. A color 

 mixed with their faulty one will be, so to speak, muddy: 

 Many thousands of examinations have been made all over 

 the world, with the same result. He has tested 17,695 males, 

 finding 739 color-blind in greater or lesser degree, viz., 

 about 4 per cent. In females it is very rare, which, how- 

 ever, their familiarity with the colors does not account for. 

 He tested 13,893 females, finding only ten color-blind. 

 Age, race, color, education, condition of civilization — all 

 seem to have no effect, as tests have been now made from 

 the north pole to the equator, and throughout Europe and 

 America. It is congenital, and largely hereditary, It may 

 be artificially produced by putting a person in a cataleptic 

 or hypnotic state; also those color-blind who can be put 

 in this state can be temporarily relieved of their defect. 

 It may be cured by tobacco and alcohol poisoning, by in- 

 juries affecting the head, and by disease. It is a symptom 

 of some brain disease of constitutional origin. 



It can be palliated by gas light, or by looking through 

 pale lemon-colored glass, or by looking through a solution 

 of the aniline dye called fuchsine. All this does not cure, 

 but simply changes the relations of light and shade for the 

 color-blind, by which alone they distinguish their faulty 

 colors. The reader briefly described how difficult it was 

 formerly to detect color-blindnes, and referred to his man- 

 ual in explanation of the manner in which persons affected 

 escape. Thanks to recent observers and workers in the 

 field we now have methods which are simple, and readily 

 and quickly carried out by competent experts. 



* Read before the A. A. A. S., Boston, 1880. 



These facts have led the United States Government to 

 undertake its control in the arm}', navy, and marine hospi- 

 tal service. Unusual examination of seamen is not yet 

 compulsory. Its great value to the sailor was particularly 

 explained. Standard tests and standard powers of sight 

 and color-perceptions are not yet determined by the United 

 States. An International Commission to determine these 

 has been proposed in a bill now before Congress. The 

 future value of such a commission was explained, and the 

 audience urged to assist in having the system carried out. 



As to the railroads of the country, Dr. Jeffries quoted 

 from his book, now a United States manual ; "The diffi- 

 culties are very great. Here the interests and the safety of 

 the community have to contend with ignorance, prejudice, 

 pecuniary considerations and incredulity born of supposed 

 immunity from danger." This has proved most true, and 

 even at this date, three years and a half since he, in this 

 same room, called public attention to the danger from color- 

 blindness, but one State, Connecticut, has passed laws con- 

 trolling color-blindness and visual defects among railroad 

 employes. And here in this State most violent attempts 

 have been made to prevent the action of the law in protect- 

 ing the community, even politics being introduced. 



The practical tests, approved of over the world and rec- 

 ommended at the International Medical Congress at Amster- 

 dam, September, 1879, and directed by the Connecticut 

 Board of Health in charge of the control, were then thor- 

 oughly shown and explained. Practical illustration was 

 also given the audience by a color-blind gentleman who 

 kindly consented to exhibit his infirmity in the cause of sci- 

 ence. These tests were Holmgren's with the colored wors- 

 teds (used by Dr. Jeffries in our public schools and the as- 

 sociation), Donders and Daae's modification of this method, 

 Stilling's pseudo-chromatic cards, Woinow's disk, Pfiiiger's 

 letters, and finally Donders' method with reflected light and 

 transmitted light, and Holmgren's with colored shadows, — 

 these last two being for the purpose of determining the 

 quantitative color-sense so necessary in deciding the fate of 

 a railroad employe or pilot. The simple, practical use of 

 these methods in the hands of competent experts was 

 shown and proved in testing thereby the color-blind present. 

 Dr. Jeffries explained in detail how theoretical was the at- 

 tempt to decide the color-sense by lanterns and flags used 

 on land or sea, and how readily mistakes would thus be 

 made. The worsted test can, by competent experts, be 

 quickly made in the paymaster's car, for instance, whereby 

 no man is taken from his duty. The color-blind can thus 

 be sorted out, and subsequently re-examined with these ad- 

 ditional tests as a means of control, and to exhibit their 

 precise defect to those in authority. During and after the 

 reading of the paper color-blind gentlemen present were ex- 

 hibited, to their astonishment and to that of the bystanders. 

 All present were asked if convinced by what was shown of 

 the danger, to exert their influence in the cause of control of 

 color-blindness. Dr. Jeffries stated in conclusion that he had 

 hoped to have been able to touch upon the most interesting 

 point of the development of the color-sense and the educa- 

 tion of our color-perception. He was, however, only able 

 to briefly refer to the work going on of the study of color 

 development, and particularly the contributions to it by his 

 friend Dr. Hugo Magnus, of Breslau. Dr. Jeffries' work 

 in testing all the Boston school-children showed, as it 

 has elsewhere, the great ignorance on the part of males of 

 color-names, aside from color-blindness. He exhibited 

 Dr. Magnus' color-chart for teaching children colors and 

 their names, which received a diploma of honor from the 

 International Medical Society at Amsterdam. The use of 

 this he explained, and said he was engaged with Mr. Prang 

 in its introduction into this country among our schools, both 

 private and public. The great purpose of this special work 

 being to teach the child to associate with the word the color 

 and the color sense, as well as the mere color names. 



Occurrence of Ozone on Evaporation of Different 

 Liquids. — A few drops of ether or alcohol are let fall upon 

 a paper equally moistened with cadmium iodide-starch so- 

 lution, and the volatile liquids set on fire. After their co- 

 operation the paper is found to be turned blue from the 

 formation of ozone. — Polyt, Notizblatt. 



