CHAPTER X 

 THE HORIZON MOON 



MOST people have been struck with the weird bigness 

 of the moon on the horizon, and, I dare say, the great 

 majority of them take it for granted that our satellite 

 is actually larger when it is rising or setting than 

 when it has got well up in the sky. I have myself 

 seen it appear from the Channel as large as six 

 meridian moons rolled into one. But it is all a decep- 

 tion. 



A few years ago Mr. Chas. Macnamara, of Arnprior, 

 Ontario, told me of a simple photographic experiment 

 which he had made, whereby this appearance of 

 horizontal enlargement was graphically shown to be 

 purely illusory. One fine September evening, at his 

 Canadian home, he focussed an ordinary whole-plate 

 camera on that part of the horizon where the full 

 moon was about to rise. Just as the upper limb 

 appeared the shutter was opened, and an exposure of 

 half an hour was given. The moon described a broad 

 path on the plate, which path was exactly of the same 

 width throughout. Yet to the eye, said Mr. Mac- 

 namara, our satellite looked enormous as it rose above 

 the distant trees, whilst at the end of the half-hour it 

 had dwindled to the usual size it appears when high 

 in the heavens. 



75 



