90 A. STEADLING — ANNIVEESAET ADDEESS : 



our reason revolts at the assertion that the image and present- 

 ment which fall upon the retina are of precisely the same 

 dimensions whether the satellite be at the zenith or upon the 

 horizon. Nevertheless, this may be demonstrated to be the case 

 by placing a disc of cardboard the size of a shilling at the 

 extremity of a straight stick, forty inches long, at which 

 distance such a disc will exactly extinguish that of the moon, 

 whatever its situation may be. The explanation of the anomaly 

 lies in the circumstance that we can never get rid of the im- 

 pression that the vault of the heavens assumes the form of a 

 flattened dome, that the horizon is farther away from us than 

 the vertex, and that consequently a body ought to appear smaller 

 to us at the greater distance ; we therefore intuitively magnify 

 the moon's image in our receptivity to compensate for the dis- 

 crepancy of its equality of diameter in both positions. In a 

 somewhat similar manner, the gas-lamps in the street, which we 

 know to be close at hand, convey when looming through a fog 

 an irresistible impression of distance to our easily -deluded ocular 

 appreciation. In fact, the eye can never be depended upon to 

 give a correct perception of distance unless there be something 

 to mark the interval ; a light in the air may be an expiring 

 caudle a few feet off, or a planet at millions of miles. A curious 

 illusion of a small character affects myself in connection with 

 the constant use of spectacles. (If I quote myself and the 

 phenomena of my own life-history from time to time in the course 

 of the evening, please do not set it down to inordinate vanity on 

 my part, or misjudge me as offering myself as a remarkably fine 

 example of the Wonderful Animal we have under consideration. 

 I do so simply because I happen to be the specimen which comes 

 most immediately within the sphere of my personal observation. 

 If I were lecturing on cats or dogs or serpents, you would 

 naturally expect that I should select for illustration those in my 

 own collection as most familiar to me, and it is on precisely the 

 same principle that I allude to myself in the present instance. 

 However, other people wear spectacles, and may perhaps have 

 noticed a similar deception.) For me of course the world is 

 framed in a somewhat narrow oval ; I don't employ the whole 

 capacity of my extent of vision, that being bounded by the rim 

 of my glasses. The result is that pictures of landscapes always 

 seem unnatural to me — they all have too much sky, more, that 

 is to say, than I am accustomed to see in proportion to the 

 amount of groiind. This shows that it does not do to accept 

 eveiything as viewed through one's own spectacles. 



