434 Transactions. — Miscellaneous. 



Art. LIII. — An Optical Illusion. 



By G. W. Tiffen. 



[Read before the Hawke's Bay Philosophical Institute, 10th September, 



1900.] 



Some time in March lasfc the following clipping appeared in 

 the Poverty Bay Herald : — 



" A friend, known to us as trustworthy, sends us the 

 following account by a relative of hers of a remarkable phe- 

 nomenon of light which she recently observed at Gisborne. 

 Sbe savs, ' As we were coming up the hill on the Whatau- 

 poko side of the footbridge, the sun, which was just setting, 

 being at our backs, we, of course, saw our shadows walking 

 up the hill in front of us. But, instead of being black, as 

 they should have been, our dresses were white, with a very 

 faint black rim round the hem and up the sides, and were 

 perfectly transparent. Now, I had on my last winter dress, 

 which is long and very thick indeed, and Lu had on a navy- 

 blue serge ; but, in spite of that, we could see through skirts, 

 petticoats, and everything else, our limbs, black, shapeless, 

 and exaggerated in thinness, reaching right from our shoes 

 to our waists. We were so astonished that we thought we 

 must have been mistaken, and went away back to the bridge 

 and walked up the hill again, with exactly the same result. 

 Did you ever hear anything so queer ? It was a very stuffy, 

 close" day, and just at that precise time there was a rainbow 

 over Kaiti Hill, which was also peculiar, being thick in the 

 middle and thin at both ends, and with some of its colours 

 bright and others very dull. As soon as we reached the top 

 of the hill our shadows became black again, and continued so 

 till the sun had set.' Will some experienced scientific friend 

 explain this affair for the benefit of our readers'? Mr. J. L. 

 Holland writes to the Auckland Herald, stating that the same 

 atmospheric effect was discovered by members of his family 

 two years ago in front of his own residence, Grafton Road. 

 The conditions under which it has been observed are : The 

 pavement thoroughly wet and the night fairly dark, with the 

 gas-lamp on the opposite corner alight, the shadow of a 

 person thrown on the fence in front of the house gives the 

 exact result described by the ladies in the paragraph — 

 namely, a modification of the Rontgen rays, the limbs being 

 distinctly seen through the dresses or clothing." 



The nature of the above-mentioned clipping is so very 

 startling that the reader's first thought is one of incredulity, 



