There came to him gradually dawning thoughts. First, that of Latent Heat. Again, that a small quantity of water in the shape of steam heats a large quantity of cold water. Yet, again, that at 212° water is elastic, and that steam heats six times the weight of cold water to a temperature of 212°, the temperature of steam. And so he went on step by step, till one day the thing burst on him, full-fledged, as it were--complete, dazzling, a perfect inspiration. It was a Sunday afternoon in the spring of 1765. He was taking a stroll in a quiet part of Glasgow, now a paved and busy thoroughfare called the Green. A Sunday calm brooded over what was on weekdays a scene of busy life--of washing and drying clothes. His thoughts, as usual, hovered about his beloved theme. It inspired him with a very passion as a child of his own. The key to his engine--long sought--suddenly flashed before his mind's eye. The thing had been waiting incomplete for want of it. It came to him then--the idea of a Separate Condenser. A great uprising of his mind followed. In his solitary walk the flashing thought filled the man with rapture. Two drawbacks--waste of steam and waste of fuel--had been the ruin of former inventions. "Ye need not fash yourself about that, man," Watt said to a friend, answering some objection that he had made, "I have now made an engine that shall not waste a particle of steam." And so, though it was but the beginning, though years of weary labour and disappointment and discouragement waited him before the end was reached, the Condensing Steam Engine, as we have it now, first sprang into being that spring afternoon on the Green in Glasgow. And now the young inventor set himself with eager enthusiasm to make a model. There were no skilled workmen to be had, no self-acting tools, as in our day, and so the first model was only partly successful. But not a whit discouraged, he went on. "My whole thoughts are bent on this machine," he said. "I can think of nothing else." And now there remains but to tell in a few words--for it is the record of his manhood--the "ups and downs" just beginning, the disappointments, the failures, the hopes and fears that waited on this offspring of his brain. He was poor, and money was the first thing that was needed. Who would risk thousands on such a vague and shadowy thing? Meantime the pot had to be kept boiling! He looked into the future, and he saw great things steam might yet be made to do, but there was bread and butter needed for the present. So he went bravely in for surveying, though there was little enough to be made by that. He had still ill-health to struggle against. "I am still plagued with headaches," he wrote about this time, "and sometimes heartaches."