LIGHT AND LIFE. 115 
Biot relates that in 1807, while at Formentera, em- 
ployed in the work of extending the meridional arc, he de- 
voted his leisure hours to the analysis of the gas contained 
in the swimming-bladder of fishes living at different depths 
in the sea. The oxygen required for these analyses was fur- 
nished him by the leaves of the Cactus opuntia, which he 
exposed in water to sunlight, under hand-glasses, ingen- 
_iously applying the discovery of Ingenhousz and Senebier. 
It occurred to him one day to expose these leaves, in a 
dark place, to the illumination thrown by lamps placed in 
the focus of three large reflectors, used for night-signals in 
the great triangulation. He threw the light from three of 
these reflectors on the cactus-leaves. ‘The eye, placed in 
this concentration of light, must have been struck blind, 
Biot says. The experiment, kept up for an hour, did not 
cause the release of a single gas-bubble. The glass was 
then taken into the diffused light outside the hut. Thesun 
was not shining, but the evolution of gas took place at once 
with great rapidity. Biot is a little surprised at the result, 
and concludes that artificial light is impotent to do what 
solar light can. The labors of Prillieux and other contem- 
porary botanists have proved that all light acts on the res- 
piration of plants, provided only it is not too powerful. 
In Biot’s case artificial light had no effect, because it was 
far too intense. 
Il, 
Lavoisier somewhere says: “ Organization, voluntary 
movement, life, exist only at the surface of the earth, in 
places exposed to light. One might say that the fable of 
Prometheus’s torch was the expression of a philosophic 
truth that the ancients had not overlooked. Without light, 
Nature was without life; she was inanimate and dead. A 
benevolent God, bringing light, diffused over the earth’s 
surface organization, feeling, and thought.” These words 
