空気を封じ込めるものならなんでもいいから用意します。たとえばこの膜は、伸び縮みして空気の弾力性を示してくれます。そしてこの袋に、空気を少し閉じこめます。それからそのまわりの空気を取り除いてみましょう。さっきの例で空気を入れたのとは逆です――圧力をのぞくと、ほら、ごらんのようにどんどんふくれていきます。そしてこの広口びんいっぱいにまで広がります。これで空気の弾性というすばらしい性質や、そのすさまじい膨張性がわかりますね。これはものづくりを効率よく行うにあたって、きわめて重要になる性質なんです。

If I take anything that confines the air properly, as this membrane, which also is able to contract and expand so as to give us a measure of the elasticity of the air, and confine in this bladder a certain portion of air; and then, if we take the atmosphere off from the outside of it, just as in these cases we put the pressure on—if we take the pressure off, you will see how it will then go on expanding and expanding, larger and larger, until it will fill the whole of this bell-jar, shewing you that wonderful property of the air, its elasticity, its compressibility, and expansibility, to an exceedingly large extent, and which is very essential for the purposes and services it performs in the economy of creation. - Michael Faraday『ロウソクの科学』