As for the palace of Solomon, it should be easy to find the foundations, for Jerusalem has been rebuilt several times upon the ruins of earlier periods and vast ancient remains must be still buried there. The work is being pushed vigorously at present and the future should bring to light many interesting relics. At last the real site of the Crucifixion may be found with many mementoes of the Saviour, and the Apostles.

Professor Flinders Petrie, the famous English archaeologist, has recently explored the Sinaitic peninsula and has found many relics of the Hebrews' pa.s.sage through the country during the Exodus and also many of a still earlier period. He found a remarkable number of altars and tombs belonging to a very early form of religion. On the Mount where Moses received the tables of the law is a monastery erected by the Emperor Justinian 523 A.D. Although the conquering wave of Islam has swept over the peninsula, leaving it bare and desolate, this monastery still survives, the only Christian landmark, not only in Sinai but in all Arabia. The original tables of stone on which the Commandments were written, were placed in the Ark of the Covenant and taken all through the Wilderness to Palestine and finally placed in the Temple of Solomon. What became of it when the Temple was plundered and destroyed by the Babylonians is not known.

Clay tablets have been found at Nineveh of the Creation and the Flood as known to the a.s.syrians. These tablets formed part of a great epic poem of which Nimrod, the mighty hunter, was the hero.

Explorers are now looking for the palace of Nimrod, also that of Sennacherib, the a.s.syrian monarch who besieged Jerusalem. The latter despoiled the Temple of many of its treasures and it is believed that his palace, when found, may reveal the Tables of the Law, the Ark of the Covenant, the Seven-branched candlestick, and many of the golden vessels used in Israelitish worship.

Ur of the Chaldees, birthplace of Abraham, father and founder of the Hebrew race, is a rich field for the archaeologist to plough. Some tablets have already been discovered, but they are only a mere suggestion as to future possibilities. It is believed by some eminent investigators that we owe to Abraham the early part of the Book of Genesis describing the Creation, the Tower of Babel and the Flood, and the quest of archaeologists is to find, if not the original tablets, at least some valuable records which may be buried in this neighborhood.

Excavators connected with the American School at Jerusalem are busy at Samaria and they believe they have uncovered portions of the great temple of Baal, which King Ahab erected in honor of the wicked deity 890 B.C. When the remains of this temple are fully uncovered it will be learned just how far the Israelites forsook the worship of the true G.o.d for that of Baal.

The Germans have begun work on the site of Jericho, once the royal capital of Canaan, and historic chiefly from the fact that Joshua led the Israelites up to its walls, reported to be impregnable, but which "fell down at the blast of the trumpet." Great piles have been unearthed here which it is thought formed a part of the original masonry. One excavator believes he has unearthed the ruins of the house of Rahab, the woman who sheltered Joshua's spies. Another thinks he has discovered the site of the translation of Elijah, the Prophet, from whence he was carried up to heaven in a fiery chariot.

Every Christian will be interested in learning what is to be found in Nazareth where Jesus spent his boyhood. Archaeologists have located the "Fount of the Virgin," and the rock from which the infuriated inhabitants attempted to hurl Christ.

In the "Land of Goshen" where the Israelites in a state of servitude worked for the oppressing Pharaoh (Rameses II), excavators have found bricks made without straw as mentioned in Scripture, undoubtedly the work of Hebrew slaves, also glazed bead necklaces. They are looking for the House of Amran, the father of Moses, where the great leader was born.

The site of Arbela, where Alexander the Great won his mightiest victory over Darius, has been discovered. It is a series of mounds on the Western bank of the Tigris river between Nineveh and Bagdad. All the treasures of Darius were taken and Alexander erected a great palace.

Bronze swords, cups and pieces of sculpture have been unearthed and it is supposed there are vast stores of other remains awaiting the tool and patience of the excavator. The famous Sultan Saladin took up his residence here in 1184 and doubtless many relics of his royal time will be discovered.

The remains of the city of Pumbaditha have been identified with the immense mound of Abnar some twenty miles from Babylon, on the banks of the Euphrates. This was the centre of Jewish scholarship during the Babylonian exile. One of the great schools in which the Talmud was composed was located here. The great psalm, "By the waters of Babylon, we sat down and wept." was also composed on this spot, and here, too, Jeremiah and Isaiah thundered their impa.s.sioned eloquence. Broken tombs and a few inscribed bowls have been brought to light. Probably the original scrolls of the Talmud will be found here. Several curiously wrought vases and ruins have been also unearthed.

Several monuments bearing inscriptions which are sorely puzzling the archaeologists have recently been unearthed at the site of Boghaz-Keni which was the ancient, if not original capital, of the mysterious people called the Hitt.i.tes who have been for so long a worry to Bible students. Archaeology has now revealed the secret of this people. There is no doubt they were of Mongolian origin, as the monuments just discovered represent them with slant eyes and pigtails. No one as yet has been able to read the inscriptions. They were great warriors, great builders and influenced the fate of many of the ancient nations.

In many other places throughout these lands, deep students of Biblical lore are pushing on the work of excavation and daily adding to our knowledge concerning the peoples and nations in whom posterity must ever take a vital interest.

A short time ago, Professor Doerpfeld announced to the world that he had discovered on the island of Ithaca, off the west coast of Greece, the ruins of the palace of Ulysses, Homer's half-mythical hero of the _Odyssey_. The German archaeologist has traced the different rooms of the palace and is convinced that here is the very place to which the hero returned after his wanderings. Near it several graves were found from which were exhumed silver amulets, curiously wrought necklaces, bronze swords and metal ornaments bearing date 2,000 B.C., which is the date at which investigators lay the Siege of Troy.

If the ruins be really those of the palace of Ulysses, some interesting things may be found to throw a light on the Homeric epic. As the schoolboys know, when Ulysses set sail from Troy for home, adverse winds wafted him to the coast of Africa and he beat around in the adjacent seas and visited islands and spent a considerable time meeting many kinds of curious and weird adventures, dallying at one time with the lotus-eaters, at another braving the Cyclops, the one-eyed monsters, until he arrived at Ithaca where "he bent his bow and slew the suitors of Penelope, his hara.s.sed wife."

In North America are mounds, earthworks, burial sites, sh.e.l.l heaps, buildings of stone and adobe, pictographs sculptured in rocks, stone implements, objects made of bone, pottery and other remains which arouse the enthusiasm of the archaeologist. As the dead were usually buried in America, investigators try to locate the ancient cemeteries because, besides skeletons, they usually contain implements, pottery and ornaments which were buried with the corpses. The most characteristic implement of early man in America was the grooved axe, which is not found in any other country. Stone implements are plentiful everywhere. Knives, arrow-points and perforators of chipped stone are found in all parts of the continent. Beads and sh.e.l.ls and pottery are also found in almost every State.

The antiquity of man in Europe has been determined in a large measure by archaeological remains found in caves occupied by him in different ages, but the exploration of caves in North America has so far failed to reveal traces of different degrees of civilization.

CHAPTER IX

GREAT TUNNELS OF THE WORLD

Primitive Tunneling--Hoosac Tunnel--Croton Aqueduct--Great Alpine Tunnels--New York Subway--McAdoo Tunnels--How Tunnels are Built.

The art of tunnel construction ranks among the very oldest in the world, if not the oldest, for almost from the beginning of his advent on the earth man has been tunneling and boring and making holes in the ground. Even in pre-historic time, the ages of which we have neither record nor tradition, primitive man scooped out for himself hollows in the sides of hills, and mountains, as is evidenced by geological formations and by the fossils that have been unearthed. The forming of these hollows and holes was no indication of a superior intelligence but merely manifested the instincts of nature in seeking protection from the fury of the elements and safety from hostile forces such as the onslaughts of the wild and terrible beasts that then existed on the earth.

The Cave Dwellers were real tunnelers, inasmuch as in construction of their rude dwellings they divided them into several compartments and in most cases chose the base of hills for their operations, boring right through from side to side as recent discoveries have verified.

The ancient Egyptians built extensive tunnels for the tombs of their dead as well as for the temples of the living. When a king of Thebes ascended the throne he immediately gave orders for his tomb to be cut out of the solid rock. A separate pa.s.sage or gallery led to the tomb along which he was to be borne in death to the final resting place.

Some of the tunnels leading to the mausoleums of the ancient Egyptian kings were upwards of a thousand feet in length, hewn out of the hard solid rock. A similar custom prevailed in a.s.syria, Mesopotamia, Persia and India.

The early a.s.syrians built a tunnel under the Euphrates river which was 12 feet wide by 15 high. The course of the river was diverted until the tunnel was built, then the waters were turned into their former channel, therefore it was not really a subaqueous tunnel.

The sinking of tunnels under water was to be one of the triumphs of modern science.

Unquestionably the Romans were the greatest engineers of ancient times.

Much of their masonry work has withstood the disintegrating hand of time and is as solid and strong to-day as when first erected.

The "Fire-setting" method of tunneling was originated by them, and they also developed the familiar principle of prosecuting the work at several points at the same time by means of vertical shafts. They heated the rock to be excavated by great fires built against the face of it. When a very high temperature was reached they turned streams of cold water on the heated stone with the result that great portions were disintegrated and fell off under the action of the water. The Romans being good chemists knew the effect of vinegar on lime, therefore when they encountered calcareous rock instead of water they used vinegar which very readily split up and disintegrated this kind of obstruction.

The work of tunneling was very severe on the laborers, but the Romans did not care, for nearly all the workmen were slaves and regarded in no better light than so many cattle. One of the most notable tunnels constructed by the old Romans was that between Naples and Pozzuoli through the Posilipo Hills. It was excavated through volcanic tufa and was 3,000 feet long, 25 feet wide, and of the pointed arch style. The longest of the Roman tunnels, 3-1/2 miles, was built to drain Lake Fucino. It was driven through calcareous rock and is said to have cost the labor of 30,000 men for 11 years.

Only hand labor was employed by the ancient people in their tunnel work. In soft ground the tools used were picks, shovels and scoops, but for rock work they had a greater variety. The ancient Egyptians besides the hammer, chisel and wedges had tube drills and saws provided with cutting edges of corundum or other hard gritty material.

For centuries there was no progress in the art of tunneling. On the contrary there was a decline from the earlier construction until late in the 17th century when gunpowder came into use as an explosive in blasting rock. The first application of gunpowder was probably at Malpas, France, 1679-1681, in the construction of the tunnel on the line of the Languedoc Ca.n.a.l 510 feet long, 22 feet wide and 29 feet high.

It was not until the beginning of the nineteenth century that the art of tunnel construction, through sand, wet ground or under rivers was undertaken so as to come rightly under the head of practical engineering. In 1803 a tunnel was built through very soft soil for the San Quentin Ca.n.a.l in France. Timbering or strutting was employed to support the walls and roof of the excavation as fast as the earth was removed and the masonry lining was built closely following it. From the experience gained in this tunnel were developed the various systems of soft ground subterranean tunneling in practice at the present day.

The first tunnel of any extent built in the United States was that known as the Auburn Tunnel near Auburn, Pa., for the water transportation of coal. It was several hundred feet long, 22 feet wide and 15 feet high. The first railroad tunnel in America was also in Pennsylvania on the Allegheny-Portage Railroad, built in 1818-1821.

It was 901 feet long, 25 feet wide and 21 feet high.

What may be called the epoch making tunnel, the construction of which first introduced high explosives and power drills in this country, was the Hoosac in Ma.s.sachusetts commenced in 1854 and after many interruptions brought to completion in 1876. It is a double-track tunnel nearly 5 miles in length. It was quickly followed by the commencement of the Erie tunnel through Bergen Hill near Hoboken, N.J.

This tunnel was commenced in 1855 and finished in 1861. It is 4,400 feet long, 28 feet wide and 21 feet high. Other remarkable engineering feats of this kind in America are the Croton Aqueduct Tunnel, the Hudson River Tunnel, and the New York Subway.

The great rock tunnels of Europe are the four Alpine cuts known as Mont Cenis, St. Gothard, the Arlberg and the Simplon. The Mont Cenis is probably the most famous because at the time of its construction it was regarded as the greatest engineering achievement of the modern world, yet it is only a simple tunnel 8 miles long, while the Simplon is a double tunnel, each bore of which is 12-1/4 miles. The chief engineer of the Mont Cenis tunnel was M. Sommeiler, the man who devised the first power drill ever used in such work. In addition to the power drill the building of this tunnel induced the invention of apparatus to suck up foul air, the air compressor, the turbine and several other contrivances and appliances in use at the present time.

Great strides in modern tunneling developed the "shield" and brought metal lining into service. The shield was invented and first used by Sir M. I. Brunel, a London engineer, in excavating the tunnel under the River Thames, begun in 1825 and finished in 1841. In 1869 another English engineer, Peter Barlow, used an iron lining in connection with a shield in driving the second tunnel under the Thames at London. From a use of the shield and metal lining has grown the present system of tunneling which is now universally known as the shield system.

Great advancement has been made in the past few years in the nature and composition of explosives as well as in the form of motive power employed in blasting. Powerful chemical compositions, such as nitroglycerine and its compounds, such as dynamite, etc., have supplanted gunpowder, and electricity, is now almost invariably the firing agent. It also serves many other purposes in the work, illumination, supplying power for hoisting and excavating machinery, driving rock drills, and operating ventilating fans, etc. In this field, in fact, as everywhere else in the mechanical arts, the electric current is playing a leading part.

To the English engineer, Peter Barlow, above mentioned, must be given the credit of bringing into use the first really serviceable circular shield for soft ground tunneling. In 1863 he took out a patent for such a shield with a cylindrical cast iron lining for the completed tunnel. Of course James Henry Greathead very materially improved the shield, so much so indeed that the present system of tunneling by means of circular shields is called the Greathead not the Barlow system.

Greathead and Barlow entered into a partnership in 1869. They constructed the tunnel under the Tower of London 1,350 feet in length and seven feet in diameter which penetrated compact clay and was completed within a period of eleven months. This was a remarkable record in tunnel building for the time and won for these eminent engineers a world wide fame. From thenceforth their system came into vogue in all soft soil and subaqueous tunneling. Except for the development in steel apparatus and the introduction of electricity as a motive agent, there has not been such a great improvement on the Greathead shield as one would naturally expect in thirty years.

The method of excavating a tunnel depends altogether on the nature of the obstruction to be removed for the pa.s.sage. In the case of solid rock the work is slow but simple; dry, hard, firm earth is much the same as rock. The difficulties of tunneling lie in the soft ground, subaqueous mud, silt, quicksand, or any treacherous soil of a shifting, unsteady composition.

When the rock is to be removed it is customary to begin the work in sections of which there may be seven or eight. First one section is excavated, then another and so on to completion. The order of the sections depends upon the kind of rock and upon the time allotted for the job and several other circ.u.mstances known to the engineer. If the first section attacked be at the top immediately beneath the arch of the proposed tunnel, next to the overlying matter, it is called a heading, but if the first cutting takes place at the bottom of the rock to form the base of the tunnel it is called a drift.

Driving a heading is the most difficult operation of rock tunneling.

Sometimes a heading is driven a couple of thousand feet ahead of the other sections. In soft rock it is often necessary to use timber props as the work proceeds and follow up the excavating by lining roof and sides with brick, stone or concrete.

The rock is dislodged by blasting, the holes being drilled with compressed air, water force or electricity, and, as has been said, powerful explosives are used, nitroglycerine or some nitro-compound being the most common. Many charges can be electrically fired at the same time. If the tunnel is to be long, shafts are sunk at intervals in order to attack the work at several places at once. Sometimes these shafts are lined and left open when the tunnel is completed for purposes of ventilation.

In soft ground and subaqueous soil the "shield" is the chief apparatus used in tunneling. The most up-to-date appliance of this kind was that used in constructing the tunnels connecting New York City with New Jersey under the Hudson River. It consisted of a cylindrical sh.e.l.l of steel of the diameter of the excavation to be made. This was provided with a cutting edge of cast steel made up of a.s.sembled segments. Within the sh.e.l.l was arranged a vertical bulkhead provided with a number of doors to permit the pa.s.sage of workmen, tools and explosives. The sh.e.l.l extended to the rear of the bulkhead forming what was known as the "tail." The lining was erected within this tail and consisted of steel plates lined with masonry. The whole arrangement was in effect a gigantic circular biscuit cutter which was forced through the earth.

The tail thus continually enveloped the last constructed portion of this permanent lining. The actual excavation took place in advance of the cutting edge. The method of accomplishing this, varied with conditions. At times the material would be rock for a few feet from the bottom, overlaid with soft earth. In such case the latter would be first excavated and then the roof would be supported by temporary timbers, after which the rock portion would be attacked. When the workmen had excavated the material in front of the shield it was pa.s.sed through the heavy steel plate diaphragm in center of the sh.e.l.l out to the rear and the shield was then moved forward so as to bring its front again up to the face of the excavation. As the sh.e.l.l was very unwieldy, weighing about eighty tons, and, moreover, as the friction or pressure of the surrounding material on its side had to be overcome it was a very difficult matter to move it forward and a great force had to be expended to do so. This force was exerted by means of hydraulic jacks so devised and placed around the circ.u.mference of the diaphragm as to push against the completed steel plate lining of the tunnel. There were sixteen of these jacks employed with cylinders eight inches in diameter and they exerted a pressure of from one thousand to four thousand pounds per square inch. By such means the shield was pushed ahead as soon as room was made in front for another move.

The purpose of the shield is to prevent the inrush of water and soft material while excavating is going on; the diaphragm of the shields acts as a bulkhead and the openings in it are so devised as to be quickly closed if necessary. The extension of the shield in front of the diaphragm is designed to prevent the falling or flowing in of the exposed face of the new excavation.

The extension of the sh.e.l.l back from the diaphragm is for the purpose of affording opportunity to put in place the finished tunnel lining whatever it may be, masonry, cast-iron, cast-iron and masonry, or steel plates and masonry. Where the material is saturated with water as is the case in all subaqueous tunneling it is necessary to use compressed air in connection with the shield. The intensity of air pressure is determined by the depth of the tunnel below the surface of the water above it. The tunnelers work in what are called caissons to which they have access through an air lock. In many cases quick transition from the compressed air in the caisson to the open air at the surface results fatally to the workers. The caisson disease is popularly called "the bends" a kind of paralysis which is more or less baffling to medical science. Some men are able to bear a greater pressure than others. It depends on the natural stamina of the worker and his state of health.

The further down the greater the pressure. The normal atmospheric pressure at the surface is about fourteen pounds to the square inch.