ing an establishment so unjustly calumniated in its day, and the premature destruction of which, by fire, in 1791, was, not improbably, imputed to design. So far from being, as misrepresented, a monopoly injurious to the public, it was the means of considerably reducing the price of flour while it continued at work.

The "double-acting" engine was followed by the compound" engine, of which Watt says:

A new compound engine, or method of connecting together the cylinders and condensers of two or more distinct engines, so as to make the steam which has been employed to press on the piston of the first, act expansively upon the piston of the second, etc., and thus derive an additional power to act either alternately or cojointly with that of the first cylinder.

We have here, in all substantial respects, the modern engine of to-day.

Two fine improvements have been made since Watt's time: first, the piston-rings of Cartwright, which effectively removed one of Watt's most serious difficulties, the escape of steam, even though the best packing he could devise were used-the chief reason he could not use high-pressure steam. In our day, the use of this is rapidly extending, as is that of superheated steam. Packing the piston was an elaborate operation even after Watt's day.

It was not because Watt did not know as well as any of our present experts the advantages of high pressures, that he did not use them, but simply because of the mechanical difficulties then attending their adoption. He was always in advance of mechanical practicalities rather than behind, and as we have

seen, had to retrace his steps, in the case of expansion. The other improvement is the cross-head of Haswell, an American, a decided advance, giving the piston rod a smooth and straight bed to rest upon and freeing it from all disturbance. The drop valve is now displacing the slide valve as a better form of excluding or admitting steam.

Watt of course knew nothing of the thermodynamic value of high temperature without high pressure, altho fully conversant with the value of pressures. This had not been even imagined by either philosopher or engineer until discovered by Carnot as late as 1824. Even if he had known about it the mechanical arts in his day were in no condition to permit its use. Even high pressures were impracticable to any great extent. It is only during the past few years that turbines and superheating, having long been practically discarded, show encouraging signs of revival. They give great promise of advancement, the hitherto insuperable difficulties of lubrication and packing having been overcome within the last five years. Superheating especially promises to yield substantial results as compared with the practice with ordinary engines, but the margin of saving in steam over the best quadruple expansion engine cannot be great. Lord Kelvin however expects it to be the final contribution of science to the highest possible economy in the steam engine.

In the January (1905) number of "Stevens Institute

"Indicator," Professor Denton has an instructive résumé of recent steam engine economics. He tells us that Steam Turbines are now being applied to Piston Engines to operate with the latter's exhaust, to effect the same saving as the sulphur dioxide cylinder; and adds

that the Turbine is a formidable competitor to the Piston Engine is mainly due to the fact that it more completely realizes the expansive principle enunciated in the infancy of steam history as the fundamental factor of economy by its sagacious founder, the immortal Watt.

Watt's favorite employment in Soho works late in 1783 and early in 1784 was to teach his engine, now become as docile as it was powerful, to work a tilt hammer. In 1777 he had written Boulton that

Wilkinson wants an engine to raise a stamp of 15 cwt. thirty or forty times in a minute. I have set Webb to work to try it with the little engine and a stamp-hammer of 60 lbs. weight. these battering rams will be wanted if they answer.

Many of

The trial was successful. A new machine to work a 700 lbs. hammer for Wilkinson was made, and April 27, 1783, Watt writes that

it makes from 15 to 50, and even 60, strokes per minute, and works a hammer, raised two feet high, which has struck 300 blows per minute.

The engine was to work two hammers, but was capable of working four of 7 cwt. each. He says, with excusable pride,

I believe it is a thing never done before, to make a hammer of that weight make 300 blows per minute; and, in fact, it is more a

matter to brag of than for any other use, as the rate wanted is from 90 to 100 blows, being as quick as the workmen can manage the iron under it.

This most ingenious application of steam power was included in Watt's next patent of April 28, 1784. It embraced many improvements, mostly, however, now of little consequence, the most celebrated being "parallel motion," of which Watt was prouder than any other of his triumphs. He writes to his son, November, 1808, twenty-four years after it was invented (1784):

Though I am not over anxious after fame, yet I am more proud of the parallel motion than of any other mechanical invention I have ever made.

He wrote Boulton, in June, 1784:

I have started a new hare. I have got a glimpse of a method of causing a piston-rod to move up and down perpendicularly, by only fixing it to a piece of iron upon the beam. . I think it one of the most ingenious simple pieces of mechanism I have contrived.

October, 1784, he writes:

The new central perpendicular motion answers beyond expectation, and does not make the shadow of a noise.

He says:

When I saw it in movement, it afforded me all the pleasure of a novelty, as if I had been examining the invention of another.

When beam-engines were universally used for pumping, this parallel motion was of great advantage. It has been superseded in our day, by improved piston guides and cross-heads, the construction of which in

Watt's day was impossible, but no invention has commanded in greater degree the admiration of all who comprehend the principles upon which it acts, or who have witnessed the smoothness, orderly power and "sweet simplicity" of its movements. Watt's pride in it as his favorite invention in these respects is fully justified.

A detailed specification for a road steam-carriage concludes the claims of this patent, but the idea of railroads, instead of common roads, coming later left the construction of the locomotive to Stephenson.*

Watt's last patent bears date June 14, 1785, and was

for certain newly improved methods of constructing furnaces or fire-places for heating, boiling, or evaporating of water and other liquids which are applicable to steam engines and other purposes, and also for heating, melting, and smelting of metals and their ores, whereby greater effects are produced from the fuel, and the smoke is in a great measure prevented or consumed.

The principle, "an old one of my own," as Watt says, is in great part acted upon to-day.

So numerous were the improvements made by Watt at various periods, which greatly increased the utility of his engine, it would be in vain to attempt a detailed recital of his endless contrivances, but we may mention

* Sinclair's "Development of the Locomotive" tends to deprive Stephenson of some part of his fame as inventor. Much importance is attached to Hedley's "Puffing "Billy," 1813, which is pronounced to have been a commercial success. Sinclair, however, credits Stephenson with doing most of all men to introduce the Locomotive. As the final verdict may admit Hedley and cannot expel Stephenson from the temple of fame, we pass the sentence as written, leaving to future disputants to adjust rival claims.