The daily morning journal and courier., 1905-01-02
WONDERFUL TUNNEL.
ENGINEERING MIRACLE USDER
 THE HUDSON.

Hole in After 1t, But Pushes the Hole
 Ahead.
 The rapid progress made in the con struction of the trolley tunnel under the Hudson at New York is exciting the wonder and admiration of engineers. The records of fast tunnel-driving have not only been broken, but left out of sight. Ad yet the extreme simplicity the ease with which a task formerly abandoned as all but impossible is be ing pushed ahead at so great speed.
 Every one has heard Of the person who. for the purpose of escaping from the observation of his fellowmen, crawled into a hole and pulled the hole in after him. That mythical feat is now equalled by the achievement of well-known New York engineer who is driving tunnel under the Hudson riv- CT and actually pushing the hole ahead of him. The work on the south tube for the Hudson river tunnel represents method Of tunnel-driving which, we risk little in saying. has never been carried on or attempted before in the world. That it is successful is attested by the rate at which the tunnel is being driv- en, which far exceeds all records of fast tunnel-driving ever made.
 What is being done is to push the hylraulic shield right into the soft mud, which is forced to either side and upward into the bed of the river. The tunnel is thus not. being excavated at alB but it is actually bored in the same manner that an awl bores hole in
 wood or leather. Of course, in driving a tunnel in this manner. nearly all the difficulties and dangers usually attend an tupon submarine tliiineling are elim- mated The workmen are protected by the iron walled tunnel around them and
 .ile shield in front So long as the shield can shove its way ahead without |encountering any boulders or other ob- stacle, necessitating the opening of the bulkhead doors and work in front of the shield, the worknen are as safe as If they were in the open air. Moreover,
 when the shield is pushed forward in
 this manner there Is actually na tun- |neling work to be done. All the work men have to do is to place ring after ring of the cast-iron lining as the shield moves ahead. Hydraulic power makes the hole that is ordinarily dug by |pick and shovel and dynamite.
 It will be evident, of course, that this
 method of working is only made possi
 ble by the exceeding softness of the
 seni-fluid silt underlying the Hudson
 river and through which the tunnel is
 being driven. This ser1tfiuid silt. has defeated every engineer who has hith- erto attempted to penetrate 1t by ordf- nary tunneiing methods. De Witt Has kins spent years of time and a large slice of aTrenor w. Parks fortune in driving two thousand feet of the north
 tunnel, and the enterprise was then abandoned by both engineers and capi-
 talists. After lying idle for half dog
 en years on English corporation under took to complete 1t with the famous firm of s. Pearson & Son as the con tractor, and the distinguished Sir Ben jarnii1 Baker as consulting engineer. But the million and half of money
 raised proved Insufficient to complete even the one river tunnel, and again
 the work was abandoned and lay un- touched for thirteen years. It was in November, 1874, that work on the Hudson river tunnel was begun,
 So that thirty years have now elapsed since MT Haskins first undertook the work It had come to be universally
 regarded by engineers and contractors as the most difficult work ever attempt- | ed. And now comes forward Charles M. Jacobs, and. by simply putting on
 force enough to push his shield right through the soft silt, discovers that in stead of beingtl1e most difficult tun- neling proposition ever undertaken, it ! is really the easiest, and he drives his
 south tunnel along at the astonishing rate of nearly fifty feet per day!
 It is doubtless true that the condi- l tions under the Hudson river are ex- tremely unusual Probably in no other submarine tunnel ever attempted has | the material penetrated been soft enough to do with it what is being done now under the Hudson. There is, how ever, another piece of tunnel work In connection with the same enterprise which represents conditions only toc common. The engineer Is. often asked I to drive a tunnel beneath street sur face through soft material loaded over
 head by buildings often of great value
 If he judges by the records of past ex-
 perience, he will probably advise thai | the probabilities are exceedingly strong that settlement of the building founda tions will occur. In driving the How I ard street tunnel in Baltimore, for ex
 ample, building after building along ths I line of the tunnel was injured or rtl' Il ined. Tn Brooklyn, numerous cases O
 settlement have occurred along tn, \ streets where sewer tunnels have beer driven; and other instances might eas
 fly be cited. .@. N.
 But the approach to the north tub, of the Hudson river tunnel is beint built through a coarse, easily moved sand, loaded above by high brick build ings, and the work is being done witl such care as to confine the excavatet
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