53 
jgSo.' On Water and Air. 
one globe and air to enter the other, you will find that the globe 
into which the carbonic acid enters will sink down. (Fig* •) 
Why is that ? Because the carbonic acid is heavier than 
Fig. i. 
the air ; and it is so heavy that .if you put 1 .into a vessel t 
will lie at the bottom. Here is a vessel which is now full 
of it, and if Mr. Cottrell gives me a match I will jee 
whether the gas is not there ; for, as many of you no doubt 
are aware, it is a peculiarity of this gas that it will n 
support a flame. You see that the flame goes out very soon 
when I dip it into the gas. ... , , 
Now, in order to show the weight of the gas, I will 
a soap-bubble, and throw the soap-bubble into this invisible 
gas The gas is there at the present time ike a liquid, and, 
although nobody can see it, I think you will find that when 
I blow the bubble and throw it into the gas, ^J le 
sufficiently heavy to support the weight of the bubble. 
[The ledturer blew a soap-bubble from a thistle-headed g ass 
tube and allowed the bubble to fall into a large glass vessel 
of ck, Tonic acid gas. The bubble floated about midway 
down the vessel.] You see that it does not sink 
Well, now, in order to show you again the heaviness ot 
this gas, I will pour it out before you, although, as it stands 
there, it is perfedtly invisible. I want you to have a per- 
fedtly distindt idea about it. [The vessel in which t 
soap-bubble had been floating was then tipped up in front 
of the electric light, so that its shadow was received on 
a white screen. The carbonic acid streamed gently down- 
wards from the lip of the vessel and cast a ^adow upon 
the screen.] There you see the gas falling, although it is 
perfedtly invisible under ordinary circumstances. This 
heavy gas falls down before you like a liquid. 
This, then, is one of the constituents of our carbonate o 
lime The other constituent is this ordinary lime. If you 
