is appalling. About 65 per cent. of the heat energy of coal can be put into the steam boiler, and from this only 15 per cent. of mechanical power is obtained. Thus about nine-tenths of the original heat in coal is wasted. Proceeding further and putting mechanical power into electricity, only from 2 to 5 per cent. is turned into light; or, in other words, from coal to light we get on an average only about one-half of 1 per cent. of the original energy, a wastage of ninety-nine and one-half of every hundred pounds of coal used. The very best possible with largest and best machinery is a little more than one pound from every hundred consumed.

When Watt gave to the steam-engine five times its efficiency by utilising the latent heat, he only touched the fringe of the mysterious realm which envelops man.

Burbank, of the spineless cactus and new fruits, who has been delving deep into the mysteries, tells us:

The facts of plant life demand a kinetic theory of evolution, a slight change from Huxley's statement that, “Matter is a magazine of force," to that of matter being force alone. The time will come when the theory of "ions" will be thrown aside, and no line left between force and matter."

Professor Matthews, he who, with Professor Loeb at Wood's Hole, is imparting life to sea-urchins through electrical reactions, declares "that certain chemical sub'stances coming together under certain conditions are "bound to produce life. All life comes through the

"operation of universal laws." We are but young in all this mysterious business. What lies behind and probably near at hand may not merely revolutionise material agencies but human preconceptions as well. "There are more things in Heaven and Earth than "are ever dreamt of in your Philosophy."

Latent Heat was a find indeed, but there remained another discovery yet to make. Watt found that no less than four-fifths of all the steam used was lost in heating the cold cylinder, and only one-fifth performed service by acting on the piston. Prevent this, and the power of the giant is increased fourfold. Here was the prize to contend for. Win this and the campaign is won. First then, what caused the loss? This was soon determined. The cylinder was necessarily cooled at the top because it was open to the air, and also cooled below in condensing the charge of steam that had driven the piston up in order to create a vacuum, without which the piston would not descend from top to bottom, to begin another upward stroke. A jet of cold water was introduced to effect this. How to surmount this seemingly insuperable obstacle was the problem that kept Watt long in profound study.

Many plans were entertained, only to be finally rejected. At last the flash came into that teeming brain like a stroke of lightning. Eureka! he had found it. Not one scintilla of doubt ever intruded thereafter. The solution lay right there and he would invent

the needed appliances. His mode of procedure, when on the trail of big game, is beautifully illustrated here. When he found the root of the defect which rendered the Newcomen engine impracticable for general purposes, he promptly formulated the one indispensable condition 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° 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 (he was always Jamie to his friends), for such self-abnegation, but the truth of history must be vindicated for all that. It proclaims, Thou art the man; go up higher and take your seat there among the immortals, the inventor of the greatest of all inventions, a great discoverer and one of the noblest of men!

In this one change lay all the difference between the

Newcomen engine, limited to atmospheric pressure, and the steam engine, capable of development into the modern engine through the increasing use of the tremendous force of steam under higher pressures, and improved conditions from time to time.

Watt leads the steam out of the cylinder and condenses it in a separate vessel, leaving the cylinder hot. He closes the cylinder top and sends a circular piston (hitherto all had been square) through it, and closely stuffs it around to prevent escape of steam. The rapidity of the "strokes" gained keeps the temperature of the cylinder high; besides, he encases it and leaves a space between cylinder and covering filled with steam. Thus he fulfils his law: "The cylinder is kept as hot as the "steam that enters." "How simple!" you exclaim. “Is "that all? How obviously this is the way to do it!" Very true, surprised reader, but true, also, that no condenser and closed cylinder, no modern steam engine.

On Monday morning following the Sabbath flash, we find Watt was up betimes at work upon the new idea. How many hours' sleep he had enjoyed is not recorded, but it may be imagined that he had several visions of the condenser during the night. One was to be made at once; he borrowed from a college friend a brass syringe, the body of which served as a cylinder. The first condenser vessel was an improvised syringe and a tin can. From such an acorn the mighty oak was to grow. The experiment was successful and