which alone met the problem,
and which the successful steam-engine must possess. He abandoned all
else for the time as superfluous, since this was the key of the
position. This is the law he then laid down as an axiom--which is
repeated in his specification for his first patent in 1769: "To make a
perfect steam engine it was necessary that the cylinder should be always
as hot as the steam which entered it, and that the steam should be
cooled below 100 deg. to exert its full powers."

Watt describes how at last the idea of the "separate condenser," the
complete cure, flashed suddenly upon his mind:

I had gone to take a walk on a fine Sabbath afternoon, early in
1765. I had entered the green by the gate at the foot of
Charlotte Street and had passed the old washing-house. I was
thinking upon the engine at the time, and had gone as far as the
herd's house, when the idea came into my mind that as steam was
an elastic body it would rush into a vacuum, and if a
communication were made between the cylinder and an exhausted
vessel it would rush into it, and might be there condensed
without cooling the cylinder. I then saw that I must get rid of
the condensed steam and injection-water if I used a jet as in
Newcomen's engine. Two ways of doing this occurred to me. First,
the water might be run off by a descending pipe, if an offlet
could be got at the depth of thirty-five or thirty-six feet,
and any air might be extracted by a small pump. The second was
to make the pump large enough to extract both water and air ...
I had not walked farther than the golf-house when the whole
thing was arranged in my mind.

Professor Black says, "This capital improvement flashed upon his mind at
once and filled him with rapture." We may imagine

"Then felt he like some watcher of the skies
When a new planet sweeps into his ken."

A new world had sprung forth in Watt's brain, for nothing less has the
steam engine given to man. One reads with a smile the dear modest man's
deprecatory remarks about the condenser in after years, when he was
overcome by the glowing tributes paid him upon one occasion and hailed
as having conquered hitherto uncontrollable steam. He stammered out
words to the effect that it came in his way and he happened to find it;
others had missed it; that was all; somebody had to stumble upon it.
That is all very well, and we love thee, Jamie Watt (h