the air, and the churches were crowded by the populace. The relics of San Januarius-his skull among them-were carried in procession through the streets. Thirty years later, a stream of lava one mile wide and containing 300,000,000 cubic feet burst from the mountain side. The next notable eruption was that of 1760, when new cones formed at the side. Seven years later the King of Naples hastily retreated into the capital from the palace at Portici, threatened by a fresh outburst, and found the Neapolitans again in confusion. A frenzied mob set fire to the Cardinal Archbishop's gate because that functionary refused to bring out the relics of the patron saint. Finally, forcing him to produce the skull, they carried it in a procession alleged to

ing in frequency is attested by the record of the nineteenth century. The first of note occurred in 1822, when the top of the great cone fell in and a lava stream a mile in width poured out. Altogether 800 feet of the cone was blown away, leaving a hole 938 feet deep in the crater. Twelve years later a river of lava nine miles long wiped out a town of 500 houses. One stream threatened Pompeii with another interment. Lava flowed almost to the gates of Naples in 1855, and caused a deplorable loss of property to the cultivated region above. Twelve years later a new cone was raised to a height greater than that attained by any in historic times.

Great Outburst in 1872

Blocks of stone forty-five feet in cir

have immediately quieted the demon of the mountain. Twenty-two years later, while our patriot fathers were in the midst of their struggle for freedom, a column of liquid fire burst from the crater, and rose to three times the height of the mountain. This was followed by a black cloud emitting flashes of lightning and advancing toward Naples, where the theaters were immediately closed and the sacred relics again paraded. An eruption lasting a year and a-half commenced in 1793. Lava was emitted for fifteen hours, and the sea boiled 100 yards from the coast.

Gaining in Frequency
That the Vesuvian eruptions are gain-

cumference were hurled down the mountain by the spectacular outburst of 1872. Two lava floods rushed down the valley on two sides, ashes were shot thousands of feet in the air, and the sea rose for miles. More than 20,000,000 cubic feet of lava was ejected in a single day. A cloud of smoke enveloped parties of tourists escorted by guides. They were caught under a hail of burning projectiles and close to a lava torrent. An unknown number, including eight medical students, were buried beneath this seething stream.

Since 1879 Vesuvius has been variously active, there being two eruptions of note in 1900; two others in 1903. But

that of the autumn of 1904, commencing quietly on September 1, and reaching its maximum on the 25th, has been more violent than any since 1872. Red hot stones hurled 1,600 feet above the cone, have dropped down the flanks of the mountain with deafening sound. One stone thrown out weighed two tons, while 1,844 violent explosions have been

PANORAMA OF RUINS OF POMPEII.

recorded in a single day by the instruments of the seismic observatory.

Observatory Near Cone

This institution has been a scene of activity during the present eruption. It is situated about a mile and a-half from the cone, near the foot of the rope railway ascending that troubled apex. It is a handsome edifice of white stone, and can be seen at a great distance against the black background of lava. It stands on the side toward Naples, on the top of a

conspicuous ridge 2,080 feet above the level of the sea. On each side of this ridge flows a river of lava during eruptions; but the building has withstood all, unscathed as yet. An observer is on duty, night and day, even during the most violent outbursts. During that of 1872, when a sheet of red-hot lava glowed on either side of the ridge, and when fiery projectiles fell all about, the post was not deserted. Inside, mounted upon piers penetrating the ground, are delicate instruments, whose indicating hands, resting against record sheets of paper, trace every movement made by the shuddering mountain. One sign by which these great outbursts may almost always be forecast, is the falling of water in the wells of the neighboring villages.

The rope tramway, or "funicular railway," which ascends the great cone from a station of white stone near the Observatory, is now disabled for the first time since it was erected in 1880. Lava from the crater has melted its metal rails, destroyed the upper station, and burned the wooden huts in which the guides at the upper cone have lived. During the three months to be required for the repair of the railroad, all tourists venturing up the cone must resort to the old-fashioned vehicle the sedan chair carried by port

ers.

The railway up the smokestack of the fiery furnace is to be rebuilt. But who can say when it may be suddenly blown into the clouds, or when it may fall into the bottomless pit? And let it be repeated-how soon will the thin ledge beneath the fair City of the Siren give way, offering a tragic theme for a future story, "The Last Days of Neapolis ?"

Recovery of Waste Gases-The Gas
Engine

In the first group-the recovery of waste gases we have the remarkable development of the gas engine, which has been constructed to utilize furnace and flue gases as well as the ordinary commercial gas of our cities. The gas engine, a few years ago, was of small unit power, and adapted to only a few uses; but within the past two years engines of this type have been constructed with outputs of 4,000 to 5,000 horsepower. In 1870, gas engines were limited to twenty horse-power, and an engine of 1,000 horse-power was then con

sidered a brilliant dream of the enthusiast.

At first the gas engine could use only high-grade gas, but even with that as fuel it became an important factor in the industrial revolution. Meanwhile the millions of cubic feet of waste gas of blast furnaces and factories were utilized in only a very small way. Efforts were

made to burn it under boilers for auxiliary purposes, and air blasts and fans were operated by this method. It was not, however, until the large gas engines were constructed to utilize furnace gases that the problem appeared anywhere near a practical solution. To-day the big blast furnaces are being converted into enormous gas generators, while the manufacture of pig iron promises to become of relatively small importance. To illustrate-a blast furnace capable of producing 150 tons of cast iron a day will furnish 21,000,000 cubic feet of gas. The greater percentage of this enormous gas production was formerly wasted, and represented a fuel that was real and potent for good if it could be recovered and burnt for commercial uses. Possibly half of this gas was available under the old methods, for heating the air blast and for other minor auxiliary purposes. If the other half were burnt in gas engines, 3,500 effective horse-power would be ready for electrical production and transmission. If this same amount of gas were burnt under the boiler for steam purposes, not more than 1,000 horsepower could be obtained.

Blast-furnace gas is comparatively very poor, averaging not more than 27 calories per cubic foot; while some flue and furnace gases are much better, and results are correspondingly more satisfactory.

burning of the gases in specially constructed gas engines, these products of combustion are made to contribute toward the operation of a mill or factory through the employment of fuel economizers. These are placed in the flue in the form of coils or tubes for heating the feed water. About 9.4 per cent of the heat value of coal can in this way be saved. Reclaiming the gases for heating the air before it is admitted to the furnacewhich greatly facilitates combustionrepresents a further saving of about 7.4 per cent. The recovery of the waste gas for use in the gas engine represents a saving of fully twenty per cent. Thus the waste of heat energy is reduced almost to a minimum.

Possibilities of the Gas Turbine

Now that the merits of the steam turbine have been well established, the best

rocating gas engine of to-day, designed to utilize waste flue and blast-furnace gases, is the most efficient machine in existence; but the perfect gas turbine would convert the stored energy of carbon into mechanical energy almost directly, and with the least possible amount of waste. This is the dream of scientists, and the goal toward which they are working. It would represent something more precious than the discovery of new coal mines with their millions of tons of stored energy. The saving of waste through the utilization of the last heat unit, is worth more to the manufacturing industries of the world than the discovery of new fuels. Mechanical genius is thus laboring successfully to make amends for any shortcomings of nature in failing to store sufficient fuel for the world's use.

But science is discovering that the world's supply of fuel is not so limited

as earlier judges estimated. The demands upon the coal pile have multiplied rapidly in the past decade of industrial expansion, and the fear of exhausting the supply of fuel has perennially caused some anxiety. The mining of coal is steadily increasing in all parts of the world; but the low grades of bituminous coals, which formerly were little used in this country, are being utilized now so that the consumption of anthracite is not so rapidly increasing. The waste at the coal pile is being abolished also, which represents an item of considerable importance. This is accomplished through the briquetting of the coal dust or culm.

Coal Briquettes

In

A distinctly new fuel is thus created and brought into common use. In Europe some 22,000,000 tons of coal briquettes are annually produced and used. America the output of coal briquettes has until recently been almost nothing. The Silesian and lignite or brown coal used for the German briquettes is inferior for steam plants, to the ordinary bituminous coals found so abundantly in the United States. Yet these coal briquettes are burnt with little smoke, and with far better combustion than the soft coal used in American furnaces. The waste attendant upon the burning of raw bituminous coals in steam plants is so great that special machinery has been invented to re/cover a part of it.

Thus we have machinery constructed to briquette flue dust in the larger factories. The immense amount of soot and dust that goes up the chimney from soft coal, represents imperfect combustion of a high order. This accumulates in flues and chimneys, and clogs them so that frequent cleaning is necessary. Machinery for scraping the flues, and collecting the flue dust for briquetting purposes, has of late been in successful operation. dust is carried away to hoppers, and mixed with a binder containing certain percentages of lime, soda ash, salt, and pitch. The compound is hydraulically pressed into briquettes of convenient size. When dried properly in ovens, the bri

The

quettes furnish a high grade of combustible fuel, which burns better, and gives a more uniform heat, than raw soft coal.

The waste flue dust of our factories represents from ten to fifteen per cent of the total amount of soft coal consumed, while the culm of coal dust of the anthracite mines represents five per cent or more of the total production of hard coals. The utilization of both wastes through briquetting them in commercial forms, diminishes our extravagant use of fuel, which for years has been an American sin. Europeans have decried our waste of coal as much as our foolish waste of wood and timber. In both cases we are gradually coming to a reforming sense of our guilt, which will immeasurably add to the manufacturing wealth of the country.

The briquetting of waste material of all kinds that can be burnt under the furnace represents an economy in fuel practice of considerable importance. In our cities the garbage that is now incinerated

CARTING PEAT TO THE CONVERTER.

to produce steam must be burnt with other fuel to produce good combustion. It is a question whether this waste material could not be briquetted so that it would prove of commercial value. At present it is burnt at low commercial returns.