an unusual horizontal Refraction of the Air. 15 
sultry; the sky was clear, with a few flying clouds. I shall 
describe the phenomena as I observed them with a terrestrial 
telescope, which magnified between 30 and 40 times; they 
were visible, however, to the naked eye. The height of the 
eye, above the surface of the water, at which most of the obser- 
vations were made, was about 25 feet ; some of them, however, 
were made at about 80 feet from the surface; and it did not 
appear that any of the phsenomena were altered from varying 
the height of the eye, the general effect remaining the same. 
The first unusual appearance which I observed, was that 
which is represented in Tab. I. fig. 1. Directing my telescope 
at random, to examine any objects which might happen to be 
in view, I saw the top of the masts of a ship A, above the ho- 
rizon, xy, of the sea, as shown in, the figure; at the same time 
also, I discovered in the field of view, two complete images,, 
B, C, of the ship in the air, vertical to the ship itself, B being 
inverted, and C erect, having their hulks joined. The pheno- 
menon was so strange, that I requested a person present to look 
into the telescope, and examine what was to be seen in it, who 
immediately described the two images, as observed by myself ; 
indeed they were so perfect, that it was impossible we could 
differ in our description. Upon this, I immediately took a 
drawing of the relative magnitudes and distances of the ship 
and its images, which, at that time, were as represented in the 
figure, as near as it was possible for the eye to judge ; and it was 
very easy to estimate them to a very considerable degree of ac- 
curacy. As the ship was receding from the shore, less and less 
of its masts became visible ; and, continuing my observations, 
in order to discover whether any, or what variations might 
take place, I found that, as the ship descended, the images B, C 
