CHAPTER XVIII 

 PNEUMATIC DREDGES 



COMPRESSED air has been used for dredging purposes. Although 

 in the form used it proved to be more expensive than any other 

 process, yet there are cases in which it might be found economical. 

 For this reason the writer has collected all the information possible 

 on this subject, having obtained it from the Scientific American, 

 Engineering News and Compressed Air Magazine. 



Pneumatic dredging was done at Uleaborg, Finland, with a 

 dredge designed by M. Jandin of Lyons, France. This dredge 

 was used to excavate a canal 20 ft. deep from the city of Uleaborg 



FIG. 42. Jandin Method for Sinking Tubular Piers. 



to the Gulf of Bothnia at the mouth of the River Ulea, where the 

 depth of water had been reduced to about 13 ft. by accumulations 

 of sand. 



M. Jandin applied in this dredge an apparatus which he had 

 successfully employed in sinking tubular piers for the Palma del 

 Rio bridge over the Guadalquivir River. The apparatus (see Fig. 

 42) consisted of a tube 8 in. in diameter and connected at the bottom 



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