A turbine is a wheel usually placed horizontally to the water. The wheel is provided with curved internal buckets against which the water is led by outer curved pa.s.sages, the guides and the buckets both curved in such manner that the water shall enter the wheel as nearly as possible without shock, and leave it with the least possible velocity, thereby utilising the greatest possible amount of energy.

In the chapter on Electrical inventions reference is made to the mighty power of Niagara used to actuate a great number of electrical and other machines of vast power. This utilisation had long been the dream of engineers. Sir William Siemens had said that the power of all the coal raised in the world would barely represent the power of Niagara. The dream has been realised, and the turbine is the apparatus through which the power of the harnessed giant is transmitted. A ca.n.a.l is dug from the river a mile above the falls. It conducts water to a power house near the falls. At the power house the ca.n.a.l is furnished with a gate, and with cribs to keep back the obstructions, such as sticks. At the gate is placed a vertical iron tube called a penstock, 7 feet in diameter and 160 feet deep. At the bottom of the penstock is placed a turbine wheel fixed on a shaft, and to which shaft is connected an electric generator or other power machine. On opening the gate a ma.s.s of water 7 feet in diameter falls upon the turbine wheel 160 feet below. The water rushing through the wheel turns it and its shaft many hundred revolutions a minute. All the machinery is of enormous power and dimensions. One electric generator there is 11 feet 7 inches in diameter and spins around at the rate of 250 revolutions a minute. Means are provided by which the speed of each wheel is regulated automatically.

Each turbine in a penstock represents the power of 5,000 horses, and there are now ten or more employed.

After the water has done its work on the wheels it falls into a tunnel and is carried back to the river below the falls. Not only are the manufactures of various kinds of a large town at the falls thus supplied with power, but electric power is transmitted to distant towns and cities.

Turbine pumps of the Forneyron type have an outward flow; but another form, invented also by a Frenchman, Jonval, has a downward discharge, and others are oblique, double, combined turbine, rotary, and centrifugal, embodying similar principles. The term _rotary_, broadly speaking, includes turbine and centrifugal pumps. The centrifugal pump, invented by Euler in 1754, was taken up in the nineteenth century and greatly improved.

In the centrifugal pump of the ordinary form the water is received at the centre of the wheel and diverted and carried out in an upward direction, but in most of its modern forms derived from the turbine, the principle is adopted of so shaping the vanes that the water, striking them in the curved direction, shall not have its line of curvature suddenly changed.

Among modern inventions of this cla.s.s of pumps was the "Ma.s.sachusetts"

of 1818 and McCarty's, in 1830, of America, that of some contemporary French engineers, and subsequently in France the Appold system, which latter was brought into prominent notice at the London Exposition of 1851. Improvements of great value were also made by Prof. James Thompson of England.

Centrifugal pumps have been used with great success in lifting large bodies of water to a moderate height, and for draining marshes and other low lands.

Holland, Germany, France, England and America have, through some of their ablest hydraulic engineers and inventors, produced most remarkable results in these various forms of pumps. We have noted what has been done at Niagara with the turbines; and the drainage of the marshes of Italy, the lowlands of Holland, the fens of England and the swamps of Florida bear evidence of the value of kindred inventions.

That modern form of pump known as the _injector_, has many uses in the arts and manufactures. One of its most useful functions is to automatically supply steam boilers with water, and regulate the supply.

It was the invention of Giffard, patented in England in 1858, and consists of a steam pipe leading from the boiler and having its nozzle projecting into an annular s.p.a.ce which communicates with a feed pipe from a water supply. A jet of steam is discharged with force into this s.p.a.ce, producing a vacuum, into which the water from the feed pipe rushes, and the condensed steam and water are driven by the momentum of the jet into a pipe leading into the boiler. This exceedingly useful apparatus has been improved and universally used wherever steam boilers are found. This idea of injecting a stream of steam or water to create or increase the flow of another stream has been applied in _intensifiers_, to increase the pressure of water in hydraulic mains, pipes, and machines, by additional pressure energy. Thus the water from an ordinary main may be given such an increased pressure that a jet from a hydrant may be carried to the tops of high houses.

In connection with pumping it may be said that a great deal has been discovered and invented during this century concerning the force and utilisation of jets of water and the force of water flowing through orifices. In the art of mining, a new system called _hydraulicising_ has been introduced, by which jets of water at high pressure have been directed against banks and hills, which have crumbled, been washed away, and made to reveal any precious ore they have concealed.

To a.s.sist this operation _flexible nozzles_ have been invented which permit the stream to be easily turned in any desired direction.

Returning to the idea of raising weights by hydraulic pressure, mention must be made of the recent invention of the _hydraulic jack_, a portable machine for raising loads, and which has displaced the older and less efficient screw jack. As an example of the practical utility of the hydraulic jack, about a half century ago it required the aid of 480 men working at capstans to raise the Luxor Obelisk in Paris, whilst within 30 years thereafter Cleopatra's Needle, a heavier monument, was raised to its present position on the Thames embankment by four men each working one hydraulic jack.

By the high pressures, or stresses given by the hydraulic press it was learned that cold metals have plasticity and can be moulded or stretched like other plastic bodies. Thus in one modification a machine is had for making lead pipes:--A "container" is filled with molten lead and then allowed to cool. The container is then forced by the pump against an elongated die of the size of the pipe required. A pressure from one to two tons per square inch is exerted, the lead is forced up through the die, and the pipe comes out completed. Wrought iron and cold steel can be forced like wax into different forms, and a rod of steel may be drawn through a die to form a piano wire.

By another modification of the hydraulic press pipes and cables are covered with a coating of lead to prevent deterioration from rust and other causes.

Not only are cotton and other bulky materials pressed into small compa.s.s by hydraulic machines, but very valuable oils are pressed from cotton seed and from other materials--the seed being first softened, then made into cakes, and the cakes pressed.

If it is desired to line tunnels or other channels with a metal lining, shield or casing, large segments of iron to compose the casing are put in position, and as fast as the tunnel is excavated the casing is pressed forward, and when the digging is done the cast-iron tunnel is complete.

If the iron hoops on great casks are to be tightened the cask is set on the plate of a hydraulic press, the hoops connected to a series of steel arms projecting from an overhanging support, and the cask is pressed upward until the proper degree of tightness is secured.

In the application of hydraulic power to machine tools great advances have been made. It has become a system, in which Tweddle of England was a pioneer. The great force of water pressure combined with comparatively slow motion const.i.tutes the basis of the system. Sir William Fairbairn had done with steam what Tweddle and others accomplished with water.

Thus the enormous force of men and the fearful clatter formerly displayed in these huge works where the riveting of boilers was carried on can now be dispensed with, and in place of the noisy hammer with its ceaseless blows has come the steam or the hydraulic riveting machine, which noiselessly drives the rivet through any thickness of metal, clinches the same, and smooths the jointed plate. The forging and the rolling of the plates are performed by the same means.

William George Armstrong of England, afterward Sir William, first a lawyer, but with the strongest bearing toward mechanical subjects, performed a great work in the advancement of hydraulic engineering. It is claimed that he did for hydraulic machinery, in the storage and transmission of power thereby, what Watt did for the steam engine and Bessemer did for steel. In 1838 he produced his first invention, an important improvement in the hydraulic engine. In 1840, in a letter to the _Mechanics' Magazine_, he calls attention to the advantages of water as a mechanical agent and a reservoir of power, and showed how water pumped to an elevated reservoir by a steam engine might have the potential energy thus stored utilised in many advantageous ways. How, for instance, a small engine pumping continuously could thus supply many large engines working intermittently. In ill.u.s.tration of this idea he invented a crane, which was erected on Newcastle quay in 1846; another was constructed on the Albert dock at Liverpool, and others at other places. These cranes, adapted for the lifting and carrying of enormous loads, were worked by hydraulic pressure obtained from elevated tanks or reservoirs, as above indicated. But as a subst.i.tute for such tanks or reservoirs he invented the _Acc.u.mulator_. This consists of a large cast-iron cylinder fitted with a plunger, which is made to work water-tight therein by means of suitable packing. To this plunger is attached a weighted case filled with one or many tons of metal or other coa.r.s.e material. Water is pumped into the cylinder until the plunger is raised to its full height within the cylinder, when the supply of water is cut off by the automatic operation of a valve. When the cranes or other apparatus to be worked thereby are in operation, water is pa.s.sed from the cylinder through a small pipe which actuates the crane through hydraulic pressure. This pressure of course depends upon the weight of the plunger. Thus a pressure of from 500 to 1,000 pounds per square inch may be obtained. The descending plunger maintains a constant pressure upon the water, and the water is only pumped into the cylinder when it is required to be filled. With sensitive acc.u.mulators of this character hydraulic machinery is much used on board ships for steering them, and for loading, discharging and storing cargoes.

_Water Pressure Engines_ or _Water Motors_ of a great variety as to useful details have been invented to take advantage of a natural head of water from falls wherever it exists, or from artificial acc.u.mulators or from street mains. They resemble steam engines, in that the water under pressure drives a piston in a cylinder somewhat in the manner of steam.

The underlying principle of this cla.s.s of machinery is the admission of water under pressure to a cylinder which moves the piston and is allowed to escape on the completion of the stroke. They are divided into two great cla.s.ses, single and double acting engines, accordingly as the water is admitted to one side of the piston only, or to both sides alternately. Both kinds are provided with a regulator in the form of a turn-c.o.c.k, weight, or spring valve to regulate and control the flow of water and to make it continuous. They are used for furnishing a limited amount of power for working small printing presses, dental engines, organs, sewing machines, and for many other purposes where a light motor is desired.

The nineteenth century has seen a revolution in _baths_ and accompanying _closets_. However useful, luxurious, and magnificent may have been the patrician baths of ancient Rome, that system, which modern investigators have found to be so complete to a certain extent, was not nor ever has been in the possession of the poor. It is within the memory of many now living everywhere how wretched was the sanitary accommodations in every populous place a generation or two ago. Now, with the modern water distribution systems and cheap bathing apparatuses which can be brought to the homes of all, with plunger, valved siphon and valved and washout closets, air valve, liquid seal, pipe inlet, and valve seal traps, and with the flushing and other hydraulic cleaning systems for drains and cesspools, little excuse can be had for want of proper sanitary regulations in any intelligent community. The result of the adoption of these modern improvements in this direction on the health of the people has been to banish plagues, curtail epidemics, and prolong for years the average duration of human life.

How multiplied are the uses to which water is put, and how completely it is being subjected to the use of man!

Rivers and pipes have their metres, so that now the velocity and volume of rivers and streams are measured and controlled, and floods prevented.

The supplies for cities and for families are estimated, measured and recorded as easily as are the supplies of illuminating gas, or the flow of food from elevators.

Among the minor, but very useful inventions, are _water scoops_ for picking up water for a train while in motion, consisting of a curved open pipe on a car, the mouth of which strikes a current of water in an open trough between the tracks and picks up and deposits in a minute a car load of water for the engine. _Nozzles_ to emit jets of great velocity, and ball nozzles terminating in a cup in which a ball is loosely seated, and which has the effect, as it is lifted by the jet, to spread it into an umbrella-shaped spray, are of great value at fires in quenching flame and smoke.

Next to pure air to breathe we need pure water to drink, and modern discoveries and inventions have done and are doing much to help us to both. Pasteur and others have discovered and explained the germ theory of disease and to what extent it is due to impure water. Inventors have produced _filters_, and there is a large cla.s.s of that character which render the water pure as it enters the dwelling, and fit for all domestic purposes. A specimen of the latter cla.s.s is one which is attached to the main service pipe as it enters from the street. The water is first led into a cylinder stored with coa.r.s.e filtering material which clears the water of mud, sediment and coa.r.s.er impurities, and then is conducted into a second cylinder provided with a ma.s.s of fine grained or powdered charcoal, or some other material which has the quality of not only arresting all remaining injurious ingredients, but destroys organisms, neutralises ammonia and other deleterious matter. From thence the water is returned to the service pipe and distributed through the house. The filter may be thoroughly cleansed by reversing the movement of the water, and carrying it off through a drain pipe until it runs clear and sweet, whereupon the water is turned in its normal course through the filter and house.

In a very recent report of General J. M. Wilson, Chief of Engineers, U.S.A., the subject of filtration of water, and especially of public water supplies in England, the United States, and on the Continent, is very thoroughly treated, and the conclusion arrived at there is that the system termed "the American," or mechanical system, is the most successful one.

This consists, first, in leading the water into one or more reservoirs, then coagulating suspended matter in the water by the use of the sulphate of alumina, and then allowing the water to flow through a body of coa.r.s.e sand, by which the coagulated aluminated matter is caught and held in the interstices of the sand, and the bacteria arrested. All objectionable matter is thus arrested by the surface portion of the sand body, which portion is from time to time sc.r.a.ped off, and the whole sand ma.s.s occasionally washed out by upward currents of water forced through the same.

By this system great rapidity of filtration is obtained, the rate being 120,000,000 gallons a day per acre.

The English system consists more in the use of extended and successive reservoirs or beds of sand alone, or aided by the use of the sulphate.

This also is extensively used in many large cities.

CHAPTER XII.

PNEUMATICS AND PNEUMATIC MACHINES.

"The march of the human mind is slow," exclaimed Burke in his great speech on "Conciliation with the Colonies." It was at the beginning of the last quarter of the 18th century that he was speaking, and he was referring to the slow discovery of the eternal laws of Providence as applied in the field of political administration to distant colonies.

The same could then have been said of the march of the human mind in the realms of Nature. How slow had been the apprehension of the forces of that kind but silent Mother whose strong arms are ever ready to lift and carry the burdens of men whenever her aid is diligently sought! The voice of Burke was, however, hardly silent when the human mind suddenly awoke, and its march in the realms of government and of natural science since then cannot be regarded as slow.

More than fifteen centuries before Burke spoke, not only had Greece discovered the principles of political freedom for its citizens and its colonies, but the power of steam had been discovered, and experimental work been done with it.

Yet when the famous orator made his speech the Grecian experiment was a toy of Kings, and the steam engine had just developed from this toy into a mighty engine in the hands of Watt. The age of mechanical inventions had just commenced with the production of machines for spinning and weaving. And yet, in view of the rise of learning, and the appearance from time to time of mighty intellects in the highest walks of science, the growth of the mind in the line of useful machinery had indeed been strangely slow. "Learning" had revived in Italy in the 12th and 13th centuries and spread westward in the 14th. In the 15th, gunpowder and printing had been discovered, and Scaliger, the famous scholar of Italy, and Erasmus, the celebrated Dutch philosopher, were the leading restorers of ancient literature. Science then also revived, and Copernicus, the Pole, gave us the true theory of the solar system. The 16th century produced the great mathematicians and astronomers Tycho Brahe, the Dane, Cardan and Galileo, the ill.u.s.trious Italians, and Kepler, the German astronomer, whose discovery of the laws of planetary motion supplemented the works of Copernicus and Galileo and illuminated the early years of the 17th century.

In the 17th century appeared Torricelli, the inventor of the barometer; Guericke, the German, inventor of the air pump; Fahrenheit, the inventor of the mercurial thermometer bearing his name; Leibnitz, eminent in every department of science and philosophy; Huygens, the great Dutch astronomer and philosopher; Pascal of France and Sir Isaac Newton of England, the worthy successors of Kepler, Galileo and Copernicus; and yet, with the exception of philosophical discoveries and a few experiments, the field of invention in the way of motor engines still remained practically closed. But slight as had been the discoveries and experiments referred to, they were the mine from which the inventions of subsequent times were quarried.

One of the earliest, if not the first of pneumatic machines, was the bellows. Its invention followed the discovery of fire and of metals. The bladders of animals suggested it, and their skins were subst.i.tuted for the bladders.

The Egyptians have left a record of its use, thirty-four centuries ago, and its use has been continuous ever since.

Mention has been made of the cannon. It was probably the earliest attempt to obtain motive power from heat. The ball was driven out of an iron cylinder by the inflammatory power of powder. Let a piston be subst.i.tuted for the cannon ball, as was suggested by Huygens in 1680 and by Papin in 1690, and the charge of powder so reduced that when it is exploded the piston will not be thrown entirely out of the cylinder, another small explosive charge introduced on the other side of the piston to force it back, or let the cylinder be vertical and the piston be driven back by gravity, means provided to permit the escape of the gas after it has done its work, and means to keep the cylinder cool, and we have the prototype of the modern heat engines. The gunpowder experiments of Huygens and Papin were not successful, but they were the progenitors of similar inventions made two centuries thereafter.

Jan Baptista van Helmont, a Flemish physician (1577-1644), was the first to apply the term, _gas_ to the elastic fluids which resemble air in physical properties. Robert Boyle, the celebrated Irish scholar and scientist, and improver of the air pump, and Edwin Mariotte, the French physicist who was first to show that a feather and a coin will drop the same distance at the same time in a reservoir exhausted of air, were the independent discoverers of Boyle's and Mariotte's law of gases(1650-1676). This was that at any given temperature of a gas which is at rest its volume varies inversely with the pressure put upon it. It follows from this law that the density and tension, and therefore the expansive force of a gas, are proportional to the compressing force to which it is subjected. It is said that Abbe Hauteville, the son of a baker of Orleans, about 1678 proposed to raise water by a powder motor; and that in 1682 he described a machine based on the principle of the circulation of the blood, produced by the alternate expansion and contraction of the heart.

The production of heat by concentrating the rays of the sun, and for burning objects had been known from the time of Archimedes, and been repeated from time to time.

Thus stood this art at the close of the 17th century, and thus it remained until near the close of the 18th.

In England Murdock, the Cornish Steam Engineer, was the first to make and use coal gas for illuminating purposes, which he did in 1792 and 1798. Its utilisation for other practical purposes was then suggested.

Gas engines as motive powers were first described in the English patent to John Barber, in 1791, and then in one issued to Robert Street in 1794. Barber proposed to introduce a stream of carbonated hydrogen gas through one port, and a quant.i.ty of air at another, and explode them against the piston. Street proposed to drive up the piston by the expansive force of a heated gas, and antic.i.p.ated many modern ideas.

Phillipe Lebon, a French engineer, in 1799 and in 1801 antic.i.p.ated in a theoretical way many ideas since successfully reduced to practice. He proposed to use coal gas to drive a piston, which in turn should move the shaft that worked the pumps which forced in the gas and air, and thus make the machine double-acting; to introduce a charge of inflammable gas mixed with sufficient air to ignite it; to compress the air and gas before they entered the motor cylinder; to introduce the charge alternately on each side of the piston; and he also suggested the use of the electric spark to fire the mixture. But Lebon was a.s.sa.s.sinated and did not live to work out his ideas.

At the very beginning of the 19th century John Dalton in England, 1801-1807, and Gay-Lussac in France began their investigations of gases and vapours. Dalton was not only the author of the atomic theory, but the discoverer of the leading ideas in the "Const.i.tution of Mixed Gases." These features were the diffusion of gases, the action of gases on each other in vacuum--the influence of different temperatures upon them, their chemical const.i.tuents and their relative specific gravity.