The greatest invention of all, the condenser, is fully covered by the first patent of 1769. The best engine up to this time was the Newcomen, exclusively used for pumping water. As we have seen, it was an atmospheric engine, in no sense a steam engine. Steam was only used to force the heavy piston upward, no other work being done by it. All the pumping was done on the downward stroke. The condensation of the spent steam below the piston created a vacuum, which only facilitated the fall of the piston. This caused the cylinder to be cooled between each stroke and led to the wastage of about four-fifths of all the steam used. It was to save this that the condenser was invented, in obedience to Watt's law, as stated in his patent, that "the cylinder should be kept always as hot as the steam that entered it"; but it must be kept clearly in mind that Watt's "modified machines," under his first patent, only used steam to do work upon the upward stroke, where Newcomen used it only to force up the piston. The double-acting engine--doing work up and down--came later, and was protected in the second patent of 1780. Watt knew better than any that although his model had been successful and was far beyond the Newcomen engine, it was obvious that it could be improved in many respects--not the least of his reasons for confidence in its final and more complete triumph. To these possible improvements, he devoted himself for years. The records once again remind us that it was not one invention, but many, that his task involved. Smiles gives the following epitome of some of those pressing at this stage: Various trials of pipe-condensers, plate-condensers and drum-condensers, steam-jackets to prevent waste of heat, many trials of new methods to tighten the piston band, condenser pumps, oil pumps, gauge pumps, exhausting cylinders, loading-valves, double cylinders, beams and cranks--all these contrivances and others had to be thought out and tested elaborately amidst many failures and disappointments. There were many others. All unaided, this supreme toiler thus slowly and painfully evolved the steam engine after long years of constant labor and anxiety, bringing to the task a union of qualities and of powers of head and hand which no other man of his time--may we not venture to say of all time--was ever known to possess or ever exhibited. When a noble lord confessed to him admiration for his noble achievements, Watt replied, "The public only look at my success and not at the intermediate failures and uncouth constructions which have served me as so many steps to climb to the top of the ladder."