Figure 37. — The giant Roots lobe-type blower 

 used for propelling the car. 



air sufficiently above atmospheric pressure to prevent 

 the water from entering and to support the earth. In 

 this, and his description of air locks for passage of men 

 and materials between the atmosphere and the pres- 

 surized area, Cochrane fully outlined the essential 

 features of pneumatic excavation as developed since. 

 In 1839, a French engineer first used the system in 

 sinking a mine shaft through a watery stratum. From 

 then on, the sinking of shafts, and somewhat later the 

 construction of bridge pier foundations, by the pneu- 

 matic method became almost commonplace engineer- 

 ing practice in Europe and America. Not until 1879 

 however, was the system tried in tunneling work, and 

 then, as with the shield ten years earlier, almost 

 simultaneously here and abroad. The first appli- 

 cation was in a small river tunnel in Antwerp, only 

 5 feet in height. This project was successfully com- 

 pleted relying on compressed air alone to support the 

 earth, no shield being used. The importance of the 

 work cannot be considered great due to its lack of 

 scope. 



Figure 38. — Testing alignment of the Broadway 

 Sulnvdx .11 niehl bv driving a jointed rod up to 

 street level. {Scientifit American, March 5, 1870.) 



In 1871 Dewitt C. Haskin (1822-1900), a west 

 coast mine and railroad builder, became interested 

 in the pneumatic caissons then being used to found 

 the river piers of Eads' Mississippi River bridge at 

 St. Louis. In apparent total ignorance of the Coch- 

 rane patent, he evolved a similar system for tunneling 

 water-bearing media, and in 1873 proposed construc- 

 tion of a tunnel through the silt beneath the Hudson 

 to provide rail connection between Xew Jersey and 

 New York City. 



It would be difficult to imagine a site more in need 



232 



BULLETIN 240: CONTRIBUTIONS FROM III1'. MUSEUM OF HISTORY AND TECHNOLOGY 



