582 
The professor advocated the theory of Dr. Young as to the 
perception of colour, who supposes that the eye is provided 
with three distinct sets of nervous fibres, each set extending 
over the whole sensitive surface of the eye. Each of these 
three systems of nerves, when excited, gives us a different sen¬ 
sation. One of them, which gives us the sensation we call red, 
is excited most bj r the red rays, but also by some others; 
another is acted on by the green rays and some others ; 
while the third is acted on by the blue and violet rays. He 
stated that he had tested more than 100 different pig¬ 
ments and mixtures, and found the results agree with the 
theory of these three primaries in every case, and he had also 
examined all the colours of the spectrum, with the same 
result. 
THE COLOURING MATTER OE LEAVES. 
When leaves are extracted by alcohol, a green oil is 
obtained, which is called chlorophyll . Fremy has ascertained 
that this consists of a Hue and a .yellow principle, which he 
has succeeded in isolating. To the blue principle he has 
given the name phyllocyanine , and to the yellow the name 
phylloxanthine. Leaves which become yellow in autumn contain 
onlv the latter. 
A NEW ARTIFICIAL LIGHT. 
It is stated that Professor Bunsen has ascertained that the 
brightest artificial light known may be obtained by burning 
a piece of magnesium wire in the flame of a common spirit 
lamp. A wire fine enough to be wound on a cotton-reel thus 
heated will yield a light equal to seventy-four stearine 
candles, five in the pound. Its brilliancy is only 525 times 
less than that of the sun. 
The cost of the wire is at present great; the price of a 
gramme thereof being nine shillings. Should it, however, 
come into use, doubtless other means to develop it will be 
discovered than at present exists, as has been the case with 
other rare metals. 
