Marvels of Modern Science

Hoosac Tunnel-Croton

way-McAdoo Tunnels-H

hich 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

they divided them into several compartments and in most cases chose the base of hills for t

his tomb to be cut out of the solid rock. A separate passage 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

5 high. The course of the river was diverted until the tunnel was built, then the waters

r water was to be one of th

mes. Much of their masonry work has withstood the disintegrating ha

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

s, shovels and scoops, but for rock work they had a greater variety. The ancient Egyptians besides the hammer, c

in the 17th century when gunpowder came into use as an explosive in blasting rock. The first application of gunpowder was probably at Ma

ering. In 1803 a tunnel was built through very soft soil for the San Quentin Canal in France. Timbering or strutting was employed to support the walls and roof of the excavation as fast as the earth was rem

ansportation of coal. It was several hundred feet long, 22 feet wide and 15 feet high. The first railroad tunnel in America was

rought 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 18

chievement 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

ating 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

ne 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

esent 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

e case of solid rock the work is slow but simple; dry, hard, firm earth is much the same as rock. The difficulties of tunn

e sections depends upon the kind of rock and upon the time allotted for the job and several other circumstances known to the engineer. If the first section attacked be at the top immediately beneath t

ple of thousand feet ahead of the other sections. In soft rock it is often necessary to use timber props

oglycerine 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 int

f steel of the diameter of the excavation to be made. This was provided with a cutting edge of cast steel made up of assembled segments. Within the shell was arranged a vertical bulkhead provided with a number of doors to permit the passage of workmen, tools and explosives. Th

en had excavated the material in front of the shield it was passed through the heavy steel plate diaphragm in center of the shell 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 shell 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

the shields acts as a bulkhead and the openings in it are so devised as to be quickly closed if necessary. The extension of t

rough 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. Men in normal health should be

ting first of a small central tunnel to be used as a refrigerating chamber or ice box in freezing the surrounding material soli

son to Hoboken. This was begun in 1880 and continued at intervals as funds could be obtained until 1890, when the work was abandoned after about two thousand feet had been constructed. For a number of years the tunnel remained full of water until it was finally acquired by the Hudson Companies who completed and opened it to the public in 1908. Another tunnel to the foot of Cortlandt Street was c

ected proposals through fear that such a tunnel would afford a ready means of invasion from a foreign enemy. However, it is almost sure to be built. Another projected British tunnel is one wh

. Water gave much trouble in its construction which occupied thirteen years from 1873 to 1886. Pumps were employed to raise the water through a side heading connecting with a shaft twenty-nine f

miles below the surface. The St. Gothard also connecting Switzerland and Italy under the lofty peak of the Col de St. Gothard is nine and one-fourth miles in length. The third great Alpine tunnel, the Arl

n the Atlantic and Pacific railway. It begins near Georgetown, will pass under Gray's peak and come out near Decatur, Colorado, in all a length o

of tunnel engineering Uncle Sam is not