116 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



pose lie uses two Becquerel actinometers, one opposed to the 

 other. The strength of the current produced appears to be 

 in exact proportion to the intensity of the light. 



Bezold has contrived a convenient method for comparing 

 pigment colors with spectrum colors. It consists simply in 

 replacing the scale of an ordinary spectroscope by a vertical 

 slit a millimeter wide, before which the color to be studied 

 is placed. The eye sees then the spectrum color by refrac- 

 tion and the pigment color by reflection, and by a movement 

 of either slit the two colors may be brought into exact coin- 

 cidence. 



Holmgren, at the request of the direction of the Swedish 

 railway between Upsala and Gefle, has examined the entire 

 staff of officials with reference to color-blindness. Out of 

 the 260 persons examined, no fewer than eighteen were found 

 who could not distinguish color, and were therefore utterly 

 useless and unfit for railway service. An investigation of 

 this sort on some of the leading American railways would 

 undoubtedly be of service. 



Thompson has submitted to the test of experiment the 

 common impression that objects appear brighter when seen 

 with two eyes than with one, using an ingenious apparatus 

 by which two beams of light (one polarized, the other unpo- 

 larized) give to two Nicol prisms, one in front of each eye, 

 the same quantity of light. It appears from these experi- 

 ments that light is more powerful in producing an effect 

 when concentrated upon one eye than when equally distrib- 

 uted to the two ; but the light so concentrated on one eye 

 does not produce the sensation of twice as much illumina- 

 tion as the half of the light viewed by both eyes at once. 



Rood has called attention to and confirmed an observation 

 made by Tait which bears on Young's subjective color the- 

 ory. Tait observed that on awaking from a feverish sleep a 

 lamp flame assumed a red color, lasting for a second. Rood 

 first noticed the same result twenty years ago, in Munich, on 

 recovering from anaesthesia by chloroform, when the face of 

 the operator appeared ruddy and his hair purplish red. lie 

 now has observed a chronic condition of the same sort, last- 

 ing for a couple of weeks, during convalescence from typhoid 

 fever. White objects appeared orange yellow. On Young's 

 theory this result is explained by supposing that the nerve 



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