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WHY SOME ANIMALS ARE ENABLED TO SEE IN 
COMPARATIVE DARKNESS. 
It has been proved that there exist rays of light of far 
higher refrangibility than those seen in the ordinary New¬ 
tonian spectrum. They are called by Chevreul lavender and 
fluorescent rays. Mr. Hunt considers it probable that these 
highly refrangible rays, although under ordinary circum¬ 
stances invisible to the human eye, may produce the necessary 
degree of excitement upon which vision depends in the optic 
nerves of night-roaming animals. The bat, the owl, and the 
cat, may see in the gloom of the night by the aid of rays 
which are invisible to, or inactive on, the eyes of man and 
those animals which require the light of day for perfect 
vision. 
EEEECT OE CARBONIC ACID ON THE SKIN. 
Carbonic acid, M. Boussingault informs us, has a calorific 
action. During a late vintage at the Liebfrauenberg, he was 
told that the fermentation of the grapes had caused a very high 
temperature. Introducing his arm into the atmosphere around 
the wort, he felt, as he thought, a heat of about forty or forty- 
five degrees centigrade ; but he found, by the thermometer, 
that the sensation was a pure delusion, the heat not being 
really more than about twelve degrees above that of the 
cellar. The sensation, which may become an actual irri¬ 
tation, is due to the action of carbonic acid on the skin. 
This discovery M. Boussingault made many years since when 
travelling in New Granada. He found, on descending into a 
fissure, near an extinct crater, that his face became flushed, 
and he felt a painful feeling of heat; but, to his great surprise, 
the temperature of the fissure was actually three degrees 
lower than that of the atmosphere outside it. The air of the 
excavation was proved, by analysis, to consist of 95 per cent, 
of carbonic acid.— Medical News. 
