582 
Proceedings of the Royal Society 
In the beginning of the session Professor Tait read a paper on 
Mirage, and exhibited to the Royal Society of Edinburgh an enlarged 
representation of an aerial phenomenon described by Professor Yince. 
The Professor of Mathematics inquired of me my opinion as to the 
explanation offered; and I now reply to Mr. Chrystal’s inquiry 
indirectly, not by discussing in any way Mr. Tait’s analysis, but by 
examining the major proposition, the reality of the phenomenon. 
The sight of the enlarged representation recalled to my mind 
matters connected with my college and even with my school days. 
The name of Yince is to me a familiar one ; his elementary treatise 
on Astronomy was our text-book at school and I had read, with not 
less pleasure than profit, his little work on Hydrostatics ; his large 
work on Astronomy stands on my book-shelf for frequent reference. 
Any observation made by Yince thus naturally arrested my attention 
and pre-secured my confidence. Nevertheless, there were features 
in that drawing which awakened a long-confirmed distrust, and 
which seemed to me to need a careful examination. 
We boys of twelve or thirteen years, had determined the latitude 
by our own observations made with the school sextant and artificial 
horizon. We knew of the augmentation of the moon’s diameter, and 
by actual measurement had satisfied ourselves that the enlargement 
of the horizontal moon is only an error in judgment due to the 
seeming increase of distance. The stories of phantom ships and 
giant spectres were classed among those of ghosts and hobgoblins. 
During my first session at college, an incident occurred to intensify 
this chronic distrust. One misty morning, while going to class 
from my lodgings in Gayfield Square, and when at Picardy Place, I 
was startled by the apparition of enormous spectres walking in the 
sky. The first momentary astonishment being over, the apparition 
had to be scrutinised. The outline of the Calton Hill was with 
difficulty traced through the mist; the spectres were walking 
thereon; it was therefore a case of atmospheric magnification 
analogous to the seeming enlargement of the horizontal moon ; so 
by moving so as to bring the figures to contrast with the houses near, 
it was easy to see that the angular magnitude was that of human 
beings on the hill. The illusion was due to the false idea of dis- 
tance, but the vividness of the first impression showed how readily 
a mistake may be made, and left on my mind a deep conviction of 
the absolute need for a close scrutiny of all such appearances. 
