I noticed that the vapour so produced is elastic,--that is, that as it expands, it presses against what opposes it; it has a force applicable everywhere force is needed by man's labour.

Behold a second agency of gigantic resources! And then, still studying this, I perceived that the vapour thus produced can be reconverted into water, shrinking necessarily, while so retransformed, from the space it filled as vapour, and leaving that space a vacuum.

But Nature abhors a vacuum; produce a vacuum, and the bodies that surround rush into it.

Thus, the vapour again, while changing back into water, becomes also a force,--our agent.

And all the while these truths were shaping themselves to my mind, I was devising and improving also the material form by which I might render them useful to man; so at last, out of these truths, arose this invention!" "Pardie," said Edward, with the haste natural to royalty, "what in common there can be between thy jargon of smoke and water and this huge ugliness of iron passeth all understanding.