_Pintsch Gas_ is another special application. It is a gas made from oil and compressed in storage cylinders by means of pumps for portable use.

It is stored under a pressure sometimes as high as 150 pounds to the inch, its pressure being reduced at the burners through the agency of pressure regulators. It is used for lighting railway cars, buoys, and lightships.

Gas making has probably been the most extensive and important of all the commercial chemical operations of the Nineteenth Century, and with it has come a great array of minor inventions as accessories. Among these first came the gas meter and pressure regulator. With the introduction of gas into houses some means of determining the amount consumed as a basis of payment was required, and for this purpose the gas meter was devised. The first gas meters were known as wet meters, and effected a measurement by pa.s.sing the gas through a liquid and rotating a wheel therein. The wet meter was invented by Clegg (British patent No. 3,968, of 1815), and the dry meter, by Malam (British patent No. 4,458, of 1820), and improved by Defries (British patent. No. 7,705, of 1838). The gas regulator is simply a little automatic apparatus whereby the variation of pressure in the gas main is reduced and the flow rendered perfectly uniform at the burner. It effects a saving of gas by preventing it from blowing when the pressure is too great, and also gives a more steady and uniform light.

Among the great number of mechanical devices which have grown out of the use of gas may be mentioned the gas range for heat, the gas engine for power, and the Welsbach burner for light. The gas range has contributed much to the domestic economy of the city house. It gives an immediate heat in the kitchen for all culinary and domestic purposes, without the incidental objections of having to transport fuel and remove ashes. It is put into or out of action in an instant, saves labor and time, and avoids the heat and discomfort of a coal stove during the hot months of summer. It is organized in principle after the Bunsen burner, whereby a perfect combustion of the carbon is obtained with maximum heating effect and without smoke or deposits of lampblack.

[Ill.u.s.tration: FIG. 226.--OTTO GAS ENGINE.]

The Otto gas engine, seen in Fig. 226, is a pioneer and representative type of a great number of explosive gas engines, which in recent years have become active compet.i.tors of the steam engine where only small power is required. The Otto engine is covered by patent No. 194,047, August 14, 1877. Patents No. 222,467, 297,329, 336,505, 358,796, 320,285, 386,211 and 549,160 represent important developments in this art.

[Ill.u.s.tration: FIG. 227.--WELSBACH GAS BURNER.]

_The Welsbach burner_ for improving the quality of gaslight, and economizing its consumption, is also well and favorably known. It utilizes the Bunsen burner principle to make a very perfect combustion of the gas, with the greatest possible heat and the least smoke, and then directs its great heat on to a refractory body which will not burn, but glows with a brilliant white incandescence. The Welsbach burner was brought out in 1885. The United States patent therefor was granted October 7, 1890, to Carl Auer Von Welsbach, No. 438,125. The Welsbach light is a development of the Drummond, or limelight, invented by Lieut.

Drummond, of England, in 1826. This latter exposed a piece of quick lime to the intensely hot flame of the oxy-hydrogen blow pipe, which was invented by Dr. Robt. Hare in 1802. The piece of lime glows with an intense brilliancy approximating that of the electric light. The Welsbach burner, see Fig. 227, operates on the same general principle, except that the refractory body, which is heated to incandescence, is a tubular sleeve of netted fabric first steeped in a solution of the salts of refractory earths, and then incinerated by heat to burn out the textile fibre and leave the refractory earthy oxides as a skeleton of the fabric, and which is called a "mantle." This mantle is suspended above the flame arising from a proper admixture of air and gas, and is heated thereby to a brilliant incandescence which furnishes the light.

In the Welsbach burner the light seen does not proceed directly from the combustion of the gas, but from the white hot mantle. The light is a very pure white one, does not distort or falsify colors, and effects a great saving of gas. An important improvement upon the mantle is covered by Rawson's patent, July 30, 1889, No. 407,963, for coating the mantles with paraffine or a.n.a.logous material to toughen them and prevent them from breaking in packing and transportation.

_Natural Gas._--No review of gas lighting would be complete without some reference to the development incident to the use of the natural gas flowing from the internal reservoirs of the earth. Such gas has been known and utilized for centuries in China, and was conveyed by the Chinese in bamboo pipes to points of utilization. The discovery of coal oil in the United States in 1859, and the great advances made in the methods and apparatus for sinking oil wells, have resulted in the discovery of numerous wells of natural gas, whose values were quickly perceived and utilized by their owners. The village of Fredonia, N. Y., was probably the first to be lighted by natural gas, and a flow from a well at West Bloomfield, N. Y., opened in 1865, was carried in a wooden main more than twenty miles to the city of Rochester. Many wells of natural gas have since been found at various points, and so extensive has been its use for cooking, heating, lighting and metallurgical processes, that thousands of patents have been taken for various forms of burners, pressure regulators and other appliances for utilizing the same. The annual production of natural gas in the United States for 1888 was valued at $22,629,875. There has, however, been a steady decrease in the past ten years. The amount produced in 1897 was $13,826,422. The insatiable demands of modern civilization must some day exhaust the supply, and what will take place when the subterranean chambers are relieved of their burden is a question for the geologists to answer.

CHAPTER XXVII.

CIVIL ENGINEERING.

GREAT BRIDGES--PNEUMATIC CAISSONS--TUNNELS--THE BEACH TUNNEL SHIELD --SUEZ Ca.n.a.l--DREDGES--THE LIDGERWOOD CABLEWAY--Ca.n.a.l LOCKS-- ARTESIAN WELLS--COMPRESSED AIR ROCK DRILLS--BLASTING--MISSISSIPPI JETTIES--IRON AND STEEL BUILDINGS--EIFFEL TOWER--WASHINGTON'S MONUMENT--THE UNITED STATES CAPITOL.

Almost entirely of an outdoor character, and necessarily on public exhibition, the engineering achievements of the Nineteenth Century have always been conspicuously in evidence, challenging the admiration of the public eye. They represent man's attack upon the obstacles presented by nature to his irrepressible spirit of progress. Difficulties apparently insuperable have confronted him, only to melt away under his persistent genius until nothing seems impossible. He has connected continents with the telegraph, has crosshatched the land with railroads, penetrated the bowels of the earth with artesian wells, opened communication between oceans with the Suez Ca.n.a.l, reclaimed territory from the sea in Holland, pierced mountain ranges with tunnels, drained marshes, irrigated deserts, reared lofty structures of masonry and steel, spanned waters with magnificent bridges, opened channel-ways to the sea, built beacons for the mariner, and breakwaters for the storm beaten ship.

Probably the most important branch of engineering work is railroad construction, already considered under steam railways. Closely related to the railroad, however, is bridge building, and many of these n.o.ble structures hang between heaven and earth, conspicuous monuments of the engineer's skill.

[Ill.u.s.tration: FIG. 228.--THE FORTH BRIDGE. LARGEST VIADUCT IN THE WORLD. FROM A PHOTOGRAPH WHEN IN PROCESS OF CONSTRUCTION. LENGTH, 8,290 FEET; HEIGHT ABOVE WATER, 361 FEET; MAIN SPANS, 1,710 FEET LONG, 150 FEET HIGH.]

_The Forth Bridge._--This ma.s.sive structure, of the cantilever type, is shown in Fig. 228. It was begun in 1882 and finished in 1890, and is the largest and most costly viaduct in the world. It is built across the Firth of Forth, and is the most important link in the direct railway communication of the North British Railway, and a.s.sociated roads, between Edinburgh on the one side, and Perth and Dundee on the other.

The total length of the viaduct is 8,296 feet, or nearly 1? miles. The extreme height of the structure is 361 feet above the water level, and the foundations extend 91 feet below the water level. The two main spans are 1,710 feet, and these both give a clear headway for navigation of 150 feet height. There are over 50,000 tons of steel in the superstructure, and about 140,000 cubic yards of masonry and concrete in the foundation piers. The three main piers consist each of a group of four masonry columns faced with granite, 49 feet in diameter at the top, and 36 feet high, which rest on solid rock, or on concrete carried down in most cases by means of caissons of a maximum diameter of 70 feet to rock or boulder clay.

No intelligent conception of the enormous size of this great structure can be obtained except by comparison. Estimating from the bottom of the masonry piers to the towering heights of the cantilevers, it reaches above the dome of St. Peter's at Rome, and is only a little short of the height of the greatest of the pyramids of Egypt. The cost of the bridge is given as 3,250,000 or nearly $16,000,000.

_The Brooklyn Bridge._--Having for its successful construction and maintenance the same foundation principle upon which the spider builds its web, this magnificent bridge of steel wires spans the East River between New York and Brooklyn, with a total length of 5,989 feet, and in length of span and cost is second only to the great Forth Bridge. It is shown in Fig. 229, and among suspension bridges it ranks first. It has a central span of 1,595 feet between the two towers, over which the suspension cables are hung, and has a clear headway beneath of 135 feet.

It has two side spans of 930 feet each between the towers and the sh.o.r.e.

[Ill.u.s.tration: FIG. 229.--THE BROOKLYN BRIDGE. LONGEST SUSPENSION BRIDGE IN THE WORLD. TOTAL LENGTH, 5,989 FEET; SPAN BETWEEN TOWERS, 1,595 FEET 6 INCHES.]

The suspension towers stand on two piers founded in the river on solid rock at depths of 78 and 45 feet below high water, and they rise 277 feet above the same level. There are four suspension cables 15 inches in diameter, each composed of 5,282 galvanized steel wires, placed side by side, without any twist, and arranged in groups of 19 strands bound up with wire. These cables have a dip in the center of the large span of 128 feet, rest on movable saddles on the top of the towers to allow for slight movement of the cables due to expansion and contraction, and are held down at the sh.o.r.e ends by ma.s.sive anchorages of masonry. The bridge has a width of 85 feet, and has two roadways, two lines of railway, and a foot way. It was begun in 1876 and opened for traffic in 1883, and its cost was about $15,000,000. It fulfills a great function for the busy metropolis, and it hangs in the air a monument in steel wire to the genius of the Roeblings.

_Masonry Bridges._--The largest and finest single span of masonry in America, and believed to be the largest in the world, is to be found about 9 miles northwest of the city of Washington. It is known as the Washington Aqueduct or Cabin John Bridge, and is seen in Fig. 230. It extends across the small stream known as Cabin John Creek, and carries an aqueduct 9 feet in diameter, that supplies the National Capital with water, its upper surface above the water conduit being formed into a fine roadway. It is 450 feet long. Its span is 220 feet, the height of the roadway above the bed of the stream is 100 feet, and the width of the structure is 20 feet 4 inches. Gen. Montgomery C. Meigs was the engineer in charge of its construction. It was begun in 1857 and finished in 1864, with the exception of the parapet walls of the roadway, which were added in 1872-3. Its cost was $254,000. Only one other masonry arch has ever been built which equalled this in size. The Trezzo Bridge, built in the fourteenth century, over the Adda in North Italy, and subsequently destroyed, is said to have had a span of 251 feet, but the Washington Aqueduct Bridge at Cabin John is a n.o.ble work in masonry, and when standing beneath its majestic sweep, and viewing the regular courses of masonry hanging nearly a hundred feet high in the air, and springing more than a hundred feet from the embankment upon either side, one loses sight of the principles of the arch, and the fear that the ma.s.s may fall upon him gives way to the impression that nature has bowed to the genius of man, and suspended the law of gravity.

[Ill.u.s.tration: FIG. 230.--CABIN JOHN BRIDGE, NEAR WASHINGTON, D. C.

LARGEST MASONRY ARCH IN THE WORLD. LENGTH, 450 FEET; SPAN OF ARCH, 220 FEET; HEIGHT, 100 FEET.]

Among the patents granted for bridges the most important are those relating to the cantilever type, among which may be mentioned those to Bender, Latrobe, and Smith, No. 141,310, July 29, 1873; Eads, No.

142,378 to 142,382, September 2, 1873, and Clarke, No. 504,559, September 5, 1893.

_Caissons._--For submarine explorations the ancient diving bell, which was said to have been used more than 2,000 years ago, has given place to diving armor, while for more extensive local work the pneumatic caisson is employed. The latter was invented by M. Triger, a French engineer, in 1841. An early example of it is also given in Cochrane's British patent No. 3,226, of 1861. It consists of a vertical cylinder divided into compartments, its lower open end resting on the river bottom. Compressed air forced into the lower compartment forces the water back, while the men are at work, the intermediate chamber forming an air lock, by which entrance to, or egress from, the lower working chamber is obtained. The pneumatic caissons of Eads (patents Nos. 123,002, January 23, 1872, and 123,685, February 13, 1872) and Flad (patent No. 303,830, August 19, 1884) are modern applications of the same principle. The sinking of shafts through quicksand, by artificially freezing the same and then treating it as solid material, is an ingenious modern method shown in patents to Poetsch, No. 300,891, June 24, 1884; and Smith, No. 371,389, October 11, 1887.

_Tunnels._--Less conspicuous than bridges, by virtue of their underground character, but none the less important, are these mole-like means of communication. Especially difficult of construction for the reason that the nature of the soil or rock is largely unknown, and for the reason also that the work may have to encounter faults in rocks, and springs or quicksands in the earth; nevertheless the demands of the railroads for shortening the distance of travel and economizing time have stimulated the engineer to expend millions of dollars in piercing the earth with these great underground pa.s.sageways.

_The Mont Cenis Tunnel_ was constructed to establish railway communication between France and Italy through the Alps. It was begun in 1857, and after having been in progress of construction for thirteen years, was opened for traffic in 1871. This tunnel was commenced by hand borings, being for the most part through solid rock, and its progress up to 1862 was so slow that it was estimated that thirty years would be required for its construction. Its earlier completion was due to the introduction of rock drills operated by compressed air, which trebled the rate of advance, and which device made a new epoch in all rock-boring and mining operations. This tunnel was cut from both ends at the same time, and so accurate were the surveys in establishing the alignment of the two headings through the mountain ma.s.s, that, although the tunnel was more than 7 miles long, when the two headings came together in the middle, only a difference of one foot in level existed between them. When it is remembered that most of the 7 miles of tunnel was cut through solid rock, by boring and blasting, the immensity of the undertaking can be appreciated. As completed the tunnel is 8 miles long, and wide enough for a double track railway.

_The St. Gothard Tunnel_ is another tunnel through the Alps, which involved even a longer and deeper cut through the mountains than the Mont Cenis Tunnel. This is 9 miles long, and it was begun in 1872, the headings joined in 1880, and the tunnel opened for traffic in 1882.

Although by far the largest undertaking yet made, the improvement in rock-boring machinery enabled it to be constructed much more rapidly and at less expense.

The Arlberg is still another Alpine tunnel. It is 6 miles long, was commenced in 1880, and opened for traffic in 1884.

Tunneling under rivers presents many more difficulties than driving through the hardest rock. This is so by reason of the inflow of water.

Among successful tunnels of this kind may be named the Mersey and Severn tunnels in England, opened in 1886, and the St. Clair tunnel between the United States and Canada. The histories of the abandoned Detroit and Hudson river tunnels are object lessons of the difficulties encountered in this cla.s.s of work.

An important engineering invention for tunneling through silt or soft soil is the so-called "shield." This was first employed by the engineer Brunel in the construction of the Thames tunnel, which was begun in 1825 and opened as a thoroughfare in 1843. The shield, as now used, is a sort of a cylinder or sleeve as large as the tunnel, which sleeve, as the excavation proceeds in front of it, is forced ahead to act both as a ring-shaped cutter and a protection to the workmen, its advance being effected by powerful hydraulic jacks or screws which find a back bearing against the completed wall of the tunnel. As the digging proceeds the shield is advanced, and a section of tunnel is built behind it which, in turn, furnishes a bearing for the jacks in the further advance of the shield.

This latter improvement was the invention of the late Alfred E. Beach, of the _Scientific American_, and was covered by him in patent No.

91,071, June 8, 1869, and was used in driving the experimental pneumatic subway constructed by him under Broadway, New York, in 1868-9, and also in the St. Clair River tunnel and the unfinished Hudson River tunnel and other works.

Subsequent improvements made upon the shield by J. H. Greathead of England and covered by him in United States patents Nos. 360,959, April 12, 1887; and 432,871, July 22, 1890, have greatly added to the value and efficiency of this device, and made it one of the leading instrumentalities in tunnel construction.

_Suez Ca.n.a.l._--It is said that the undertaking of connecting the Mediterranean and Red Seas was considered as long ago as the time of Herodotus, and a small channel appears to have been opened twenty-five centuries ago, but was subsequently abandoned. In 1847 the subject was again taken up for serious consideration, the work begun in 1860, and finished in 1869, at a cost of 20,500,000, or more than a hundred million dollars. The ca.n.a.l starts at Port Said, on the Mediterranean, a view of which with its ships of all nations and the ca.n.a.l reaching far away in the distance is seen in Fig. 231. The ca.n.a.l extends nearly due south to Suez on the Red Sea, a distance of about 100 miles, through barren wastes of sand and an occasional lake. It was originally formed with a bottom width of 72 feet, spreading out to 196 to 328 feet at the top, and of a depth of 26 feet, but has since been increased in transverse dimension to accommodate the great increase in travel.

[Ill.u.s.tration: FIG. 231.--PORT SAID ENTRANCE TO SUEZ Ca.n.a.l, SHOWING HARBOR WITH SHIPS OF ALL NATIONS, AND THE Ca.n.a.l REACHING AWAY IN THE DISTANCE.]

Sixty great dredges were employed on the work, and the dredged material was discharged in chutes on to the bank. The ca.n.a.l was the work of M. De Lesseps, the eminent French engineer, and has proved a great success from both an engineering and financial standpoint. The stock is mainly held in England, having been bought from the Khedive of Egypt. In 1898 the ships pa.s.sing through the ca.n.a.l during the year reached the remarkable number of 3,503. The rate of tolls is 10 francs (about $2) per net ton. The gross tonnage of ships pa.s.sing through in 1898 was 12,962,632, the net tonnage 9,238,603. The total receipts for the year were 87,906,255 francs (about $17,500,000), and the net profit 63,441,987 francs (about $12,500,000). An average size ocean liner pays about $5,000 for the privilege of sailing through this great ditch.

Admiral Dewey's ship, the "Olympia," returning from the Philippines, paid for her toll $3,516.04, and the "Chicago," $3,165.95. Going the other way, our supply ship "Alexander" paid $4,107.99, while the "Glacier" paid $5,052.38. Ships making the pa.s.sage through the ca.n.a.l move slowly on account of the washing of the banks, about 22 hours being required, but the shortening of the travel of ships going east and west, and the saving of life, property, and time, involved in avoiding the circuitous and stormy pa.s.sage around the Cape of Good Hope, has been of incalculable benefit to the world.

[Ill.u.s.tration: FIG. 232.--HERCULES DREDGER.]

With the construction of ca.n.a.ls and harbors, great improvements have been made in dredges. Some of these are of the clam-sh.e.l.l type, some employ the scoop and lever, others an endless series of buckets. An example of the latter, used on the Panama Ca.n.a.l, is seen in Fig. 232.

Still another form, and the most recent if not the most important is the hydraulic dredger, which, by rotating cutters, stirs and cuts the mud and silt, and by powerful suction pumps and immense tubes draws up the semi-fluid ma.s.s and sends it to suitable points of discharge. The best known of the latter type is the Bowers hydraulic dredge, covered by many patents, of which Nos. 318,859 and 318,860, May 26, 1885; 388,253, August 21, 1888; and 484,763, October 18, 1892, are the most important.

For surface excavations in solid earth the Lidgerwood Cableway is an important and labor saving device. A track cable is stretched from two distant towers, and a bucket holding well on to a ton of earth is made to travel on a trolley running on said cable track, rising at one end out of the excavation, and dumping at the other end to fill in the excavation as the cutting progresses, all in a continuous and economical manner. This device is made under the patent to M. W. Locke, No. 295,776, March 25, 1884, and comprehends many subsequent improvements patented by Miller, Delaney, North and others. The Chicago Drainage Ca.n.a.l is a work just completed, which largely employed these devices. This ca.n.a.l was designed to connect the Chicago River with the Mississippi River, so as to send the sewage of Chicago down the Mississippi instead of into Lake Michigan. Although it cost $33,000,000 and required seven years for completion, the labor-saving cableways greatly cheapened its cost and shortened the time of its construction.

Among the leading inventions relating to ca.n.a.l construction may be mentioned the bear-trap ca.n.a.l-lock gate (patents Nos. 229,682, 236,488 and 552,063), and the Dutton pneumatic lift locks. The latter provide ease and rapidity of action by a principle of balancing locks in pairs, and are covered by his patent No. 457,528, August 11, 1891, and others of subsequent date.

_Artesian Wells_ represent an important branch of engineering work, and they are so called from the province of Artois, in France, where they have for a long time been in use. Extending several thousand feet into the subterranean chambers of the earth, they have brought abundant water supply to the surface all over the world, from the desert sands of Sahara to the hotels of the modern city; they have contributed oil and gas in incredible quant.i.ties to supply light and heat, and have made valuable additions to the salt supply of the world.

They are driven by reciprocating a ponderous chisel-shaped drill within an iron tube, six inches more or less in diameter, which is built up in sections, and moved down as the cutting descends. The drill is reciprocated by a suspending rope from machinery in a derrick, and in order to give a hammer-like blow to the chisel a pair of ponderous iron links coupled together like those of a chain, and called a "_drill jar_"

connect the drill to the rope. As the sections of the link slide over each other they come together with a hammer blow at the moment of lifting that dislodges the drill from the rock, and on the descending movement they come together with a hammering blow immediately after the drill touches the rock to drive it into the same. The first United States patent for a drill jar is that to Morris, No. 2,243, September 4, 1841. When an oil well ceases to flow, it is rejuvenated by being "shot," which is quite contrary to the ordinary conception of prolonging life. For this purpose a dynamite cartridge is exploded at the lower end of the well, which shatters the rock, and, in opening up new channels of flow for the oil, renews the yield. Many patented inventions have been made in the field of well boring, and the discovery of coal oil in the United States in 1859 has developed a great industry and built up enormous fortunes. The amount of petroleum produced in the United States in 1896 was 60,960,361 barrels, the largest yield on record. In 1897 the amount was 60,568,081 barrels.

Of less consequence than the artesian well, but finding many useful applications, is the drive well. A metal tube with a perforated lower end is driven down by hammers into the ground, and furnishes a quick and cheap source of water supply. This was invented by Col. Green in 1861, in meeting the necessities of his military camp during the civil war, and was patented by him January 14, 1868, No. 73,425.