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the whole expanse of the firmament ; then, when at 

 length the mountains come into view, we perceive how 

 insignificant is the space they occupy in comparison 

 to the expanse above them. Moreover, small as the 

 space they occupy actually is, it appears to be even 

 smaller, for, owing to the indistinctness of the light, the 

 line of horizon is but vaguely defined. Much, conse- 

 quently, of the lower portions of the mountains appears 

 merged in the surface of the ground. 



While on the subject of the mountains, I will 

 mention another optical illusion connected with them, 

 which is still more singular, and also less easy to 

 explain. 



The plains immediately below the outer ranges of 

 the Himalaya slope upwards, and at a considerable 

 angle ; nevertheless the impression conveyed to the 

 traveller approaching the mountains, always provided 

 that he is mounted, either riding or driving, is that he 

 is descending. This impression is the strongest when 

 the road is straight and is bordered by trees. 



The first time that I witnessed this illusion was in 

 approaching the line of mountains around Nynee Tal. 

 The road was straight ; it ran through the forest in a 

 direct line towards the mountains. I was not then 

 aware of the illusion, nor of the upward slope of the 

 ground. Judging from appearances, I was under the 

 impression that the road descended, and, moreover, that 

 the descent was steep. 



Presently we came to a little stream ; it flowed along 

 the margin of the road. To my amazement, the water 

 was running towards us, racing and foaming, so it 



