200 THE FRIENDLY ARCTIC 



a tent. The attack was not severe, but it is true with snowblind- 

 ness if it is true with anything that an ounce of prevention is worth 

 a pound of cure. As soon as we realized what had happened we put 

 up again the inner cover of the tent, spread some canvas over the 

 outside to make it darker, and then put on our amber-colored 

 glasses and sat or slept inside until our eyes were normal again. 



Through great care of my eyes I have never in ten winters spent 

 north of the arctic circle become completely snowblind, though one 

 of my eyes has been frequently affected. When one eye is better 

 than the other, as is the case with most people, the poorer eye is 

 the one affected. The glare of the snow appears brighter to the 

 eye of keener vision, and that eye is instinctively closed or shielded. 

 When you have once begun to shield one eye, it becomes increas- 

 ingly difficult to keep it open, for the reason that an eye which 

 has been in darkness is blinded by a light which does not blind an 

 eye that has been continually exposed to it. The whole strain of 

 seeing thus falls upon the weaker eye and it accordingly is at- 

 tacked first. Those who become snowblind in both eyes simul- 

 taneously have either used their will power to keep both eyes open 

 or else have eyes of nearly equal quality. 



From this it might be inferred that snowblindness is most 

 likely to occur on days of clear sky and bright sun. This is not 

 the case. The days most dangerous are those when the clouds 

 are thick enough to hide the sun but not heavy enough to produce 

 what we call heavily overcast or gloomy weather. Then light is 

 so evenly diffused that no shadows can be seen anywhere. The sea 

 ice is not level; if there are no actual snags of broken ice sticking 

 up, there are at least snowdrifts. Wlien the sun is shining in a 

 clear sky all these unevennesses are easily seen, because shadows 

 lie in the low places, but on a day of diffused light everything looks 

 level, as was observed in respect to travel under cloudy skies. 

 You may collide against a snow-covered ice cake as high as your 

 waistline and, far more easily, you may trip over snowdrifts a foot 

 or so in height, because without the assistance of shadows every- 

 thing that is pure white seems to be perfectly level. Knowing the 

 danger, your eyes are continually strained for its detection. Here 

 amber-colored glasses are of use, for unevennesses imperceptible 

 to the bare eye can sometimes be seen by the aid of these "ray 

 filters," as they are called in photography. This is one of the 

 advantages of the amber glass over all other forms of protection 

 against snowblindness. Glass of "chlorophyll green" is excellent 

 when the sun is shining, and seems to be easier on the eye than dark 



