Page:The chemical history of a candle.djvu/160

158 carbonic acid is; we will just try the depth, and see whereabouts is its level. There, you see, we have this bladder floating on the carbonic acid; and if I evolve some more of the carbonic acid, the bladder will be lifted up higher. There it goes—the jar is nearly full; and now I will see whether I can blow a soap-bubble on that, and float it in the same way. [The Lecturer here blew a soap-bubble, and allowed it to fall into the jar of carbonic acid, when it floated in it midway.] It is floating, as the balloon floated, by virtue of the greater weight of the carbonic acid than of the air. And now, having so far given you the history of the carbonic acid—as to its sources in the candle, as to its physical properties and weight—when we next meet I shall shew you of what it is composed, and where it gets its elements from.