370 Historical 



until the digging is finished; then there is nothing more to do but 

 fill the whole cylinder with masonry and the pier is finished. 



It is by this method, which is so simple and yet which is much 

 more complicated in practice than the preceding description seems 

 to indicate, that a great many bridges have, been constructed since 

 1851. 



The idea of this application of his system of drainage to the 

 foundation of bridge piers belongs to M. Triger 14 himself. But this 

 idea was not put into execution until 1851, by an English engineer 

 Hughes, in the construction of the Rochester bridge over the 

 Medway in the county of Kent. 



An engineer of French descent, Brunei, constructed by this 

 system the bridge of Chepstow, over the Wye (1849-1851) and that 

 of Saltash (1854-1859) ; for the latter, the maximum depth reached 

 was 26.68 meters below high water. Only in connection with this 

 one did a fatal accident occur; a man died on leaving the cylinder 

 in which he had remained a very short time. I could not get 

 detailed information on these facts, however. 



In 1856, M. Cezanne 15 was charged with the construction of a 

 bridge at Szegedin (Hungary), to permit the Austrian railroad 

 from the south-east to cross the Theiss, a tributary of the Danube. 



He used the system of caissons with compressed air. The work 

 of excavating was "stopped at about 20 meters below high water, 

 so as not to expose the men to the pressure of 3 atmospheres, 

 beyond which work is very difficult." (P. 355) 



A special section of the memoir of my regretted colleague is 

 devoted to the study of the physiological effects of compressed air: 



There are three phases to be distinguished: the entrance, the stay, 

 and the exit. 



When the cock admitting the air is opened, the ears are immediately 

 attacked by a violent buzzing accompanied by pains the intensity of 

 which varies with the individuals .... 



The stay at the bottom of the caisson, in a pressure of three 

 atmospheres, may be prolonged for several hours without ill conse- 

 quences; the tone of the voice is somewhat impaired, and the 

 respiration hastened as if by rapid walking; if a cigarette is waved 

 about, it burns with a flame; candles burn rapidly, but with smoky 

 flame 



The time of exit, though not very painful for the great majority 

 of individuals, is the most dangerous for the workmen .... Sometimes 

 there is an issue of blood from the nose and the throat; some persons 

 experience violent, but brief neuralgia; others have headaches and 

 toothaches for several days 



Laborers who usually work in the caissons look ill; however, they 

 resist the ill effects very well. (P. 369.) 



