122 THE WORK OF PLANTS 
The gas now, as it 1s given off from the water plant, 
rises through the funnel and into the test tube where 
it accumulates in the upper end and gradually displaces 
the water. In several days so much gas has accumu- 
lated that perhaps the tube is full of it and empty of 
water. We are now ready to test for the kind of gas, 
How to test for the gas. We wish now to bring a 
glowing splinter into the end of the test tube before 
the gas escapes, and without wetting the splinter in 
, water. We light 
a long, soft pine 
. splinter and hold 
y it in one hand, 
while with the 
other we grasp 
the upper end of 
the test tube, which 
should be freed if 
it was tied down. 
Blow out the flame 
on the splinter, 
leaving the coal 
glowing. Quickly 
lift the tube from 
the water and thrust the glowing end of the splinter 
into the test tube. It flames again! The gas, then, 
is oxygen, for we know that the oxygen of the air 

Fia. 154. Ready to see what the gas is. 
