2 
Mr. Home’s Lecture 
deration, were made upon the eye, and were in some measure 
connected with the observations contained in the former Lec- 
tures : they were instituted with a view to ascertain the cause 
of the luminous appearance frequently observed in the cat's 
eye. 
The illumination so conspicuous in the eye of the cat, and 
of many other animals, when seen in an obscure light, has at- 
tracted the attention of every common observer. Philosophers 
also have paid particular attention to it, and have endeavoured 
to investigate the cause. On this subject there have been two 
opinions : one, that the illumination arises from the external 
light collected in the eye, and reflected ; the other, that there 
is a quantity of light generated in the organ itself. 
Professor Bohn, at Leipsick, made experiments which proved, 
that when the external light is wholly excluded, none can be 
seen in the cat’s eye. 
These experiments were favourable to the first opinion ; but 
the brightness of the illumination is so great, that it appeared 
to exceed any effect which could be produced through the 
medium of the retina ; so that some other source of light was 
thought necessary to account for the phenomenon : this cir- 
cumstance gave support to the second opinion. 
To determine which of the two opinions was just, several ex- 
periments were instituted, under the direction of Mr. Ramsden, 
who likewise assisted in making them. The truth of Professor 
Bohn’s experiments was readily ascertained; it therefore only 
became necessary to inquire, whether the external light was of 
itself capable of producing so great a degree of illumination as 
that seen in the cat’s eye. 
This was attended with difficulty ; for, when the apartment 
