358 Historical 



then Rear-Admiral Bourgeois invented cigar-boats which might be 

 used in case of war. But since no observation of a physiological 

 nature has been made with the help of these contrivances, and 

 since I have no desire to write a history, no matter how short, of 

 the industrial applications of compressed air, I now come without 

 other transition to the numerous data relating to the digging of 

 mine shafts and to the sinking of bridge piers by the Triger 

 method. 



2. Apparatuses Constructed by the Triger Method. 



It is, in fact, to M. Triger, a French engineer, that we owe the 

 valuable invention of the use of air compressed to high pressures 

 for boring mine shafts and sinking bridge piers. It was a question 

 of working in the grant of Haye-Longue (Maine-et-Loire) coal- 

 bearing strata covered with alluvial deposits over which flowed 

 the waters of the Loire. It was impossible to drain off the water 

 which seeped through and prevented them from extending the 

 galleries: M. Triger conceived the simple but brilliant idea of 

 driving it back and holding it by pumping compressed air in 

 through the upper part of the shaft; protected by the drainage 

 thus secured, workmen could stop the leaks by vaults of masonry. 



M. Trouessart, whose report on this wonderful discovery we 

 shall quote later, comments that Denis Papin had already had an 

 idea of this sort, in 1691, and he quotes the following passage, 

 which is indeed very noteworthy: 



Fresh air could be injected constantly into the diving bell by- 

 means of a strong leather bellows furnished with valves, by a tube 

 passing under the bell and opening into its upper part. And so, since 

 the bell would always remain empty and rest entirely on the ground, 

 the bottom in this place would be almost dry and one could work 

 there just as if he were out of the water, and I have no doubt that 

 it would save much expense when construction must be carried on 

 under water. Moreover, in case the leather bellows were not strong 

 enough to compress the air as much as would be necessary at great 

 depths, one could always meet this difficulty by using pumps to com- 

 press the air. 



But from this idea to the complete invention of M. Triger is a 

 long way; in 1839, he solved the problem from a practical stand- 

 point, and listed the numerous applications which would later be 

 made of it. 



The complete explanation of this invention is in a Memoir 8 

 presented to the Academy of Sciences in 1841. 



We naturally omit all details of the construction of the appara- 



