410 DUANE— SIGHT AND SIGNALLING IN THE NAVY. 



Flag signals, being necessarily intermittent, make no great de- 

 mands on the eyesight. 



Factors in the Signalman Himself. 

 The factors that may affect a signalman's'-" efficiency are : 



1. Faulty vision. 



2. Defective color vision. 



3. Refractive errors, including defective accommodation. 



4. Muscular errors. 



5. Slow reaction time. 



6. Slow adaptation. 



7. Effect of after-images. 



8. Fatigue from prolonged, excessive strain of eyes and body. 



7. Faulty Vision. — Fortunately in our navy, owing to the in- 

 sistence of the medical officers, the visual requirements are high, 

 so that seamen generally, and hence the signalmen also, must have 

 good vision in each eye without the aid of glasses. ^° It is very im- 

 portant that this standard be maintained. I may add that it is a 

 great pity that the same standard has not been maintained in the 

 army. In the conditions of naval service and of army service too, 

 acute vision is important, and glasses are a considerable handicap. 

 Readily fogged by moisture, smoke, or grease, they may obscure the 

 vision just when it is most needed. For in quick signalling, when 

 a second or two lost may mean the loss of a message and the conse- 

 quent delay of a whole squadron in some important evolution, one 

 has not time to clean glasses or replace them when broken. And 

 if one pulls the glasses off and goes on without them, the sudden 

 change in visual acuity and the sudden strain on the accommodation 

 thereby produced may, even with no very great refractive error, 

 reduce the sight below service requirements. I myself had a good 

 example of this during a week's cruise on the San Francisco in 1896. 

 Without glasses I had a vision of some |^to|^. Soon after the 

 cruise started my glasses were broken. When it came my turn to 

 act as gun-pointer, I could not see the target ; when I took my place 



^ What is said here about signahnen appHes in general to gun-pointers 

 and others doing similar work making special demands on the eyesight. 



10 The requirements are \1 in each eye and for gun-pointers f " in the 

 eye used for sighting. 



