BIOLOGY. 241 



ences researches on this subject in connection with colors, and 

 the conclusions to which they lead are very curious. He has 

 found that the retina decomposes the rays of light in a manner 

 different from that either of the prism or the double-refracting 

 crystal. These disperse the rays with reference to different points 

 of space ; the retina disperses them with reference to different 

 points of time. 



In the experiments which were made, the light of the sun was 

 received on a mirror, which reflected it horizontally through a 

 chink formed in the shutter of a darkened chamber. This chink 

 was about the tenth of an inch wide, and the fifth of an inch high. 

 Very near it, and within the chamber, was placed a metallic disk, 

 around the edge of which were formed openings corresponding 

 with, and of nearly the same dimensions as, that in the darkened 

 chamber. These openings were at considerable intervals ; the 

 disk was made to revolve by clock-work, and a means by which 

 the operator, though at a distance, could moderate, accelerate, or 

 arrest the revolution of the disk was provided. Across the path 

 of the luminous ray, and at the distance of about 3 feet, was fixed 

 a plate of roughened glass, behind which the experimentalist ob- 

 served the modifications of the light. The disk being set in mo- 

 tion, the luminous ray reappeared at certain known intervals. 

 When it was made to reappear slowly, it seemed of a' uniform 

 white color ; but when it reappeared at shorter intervals, the edges 

 began to be colored, and as the velocity of rotation was increased, 

 the image passed successively through the following tints : blue, 

 green, rose-color, white, green, blue. After the latter blue no in- 

 crease of velocity produced an}'thing but white. 



It thus appears that some of the colored rays cause a more last- 

 ing impression on the retina than others. The Scientific Review. 



TEACHING THE DUMB TO SPEAK. 



It is well known that there is a school for teaching articulation 

 to deaf-mutes, in successful operation at Chelmsford, Mass., under 

 the instruction of Miss II. B. Rogers. At a meeting of the edu- 

 cational department of the "American Social Science Associa- 

 tion," in Boston, in March, 1867, Mr. F. B. Sanborn presented a 

 paper on this subject. The folio wing are extracts from the " Pro- 

 ceedings" of this meeting: 



Why the Deaf are catted Dumb. The only impossibilities Miss 

 Rogers has done are those which incredulity or ignorance first 

 created. There is nothing miraculous about her art. She has 

 simplj' applied common sense and patience, and a gift for teach- 

 ing, to the unfortunate circumstances of these children. 



The dumb taught to speak ! But who are these dumb, these 

 deaf-mutes, as they are called? They are simply persons who 

 have lost the sense of hearing, and consequently have forgotten, 

 or have never learned, the practice of speaking. That is the 

 whole story. Let me state the case in the quaint language of a 

 good old man, who has had some experience in teaching the deaf 

 to speak. He says, "Here is a smart, intellectual child, having 



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