408 



Popular Science Monthly 



put in from the outside by tlie divers. 

 As the sand-hogs on the inside removed 

 the wooden plugs from the rivet holes, 

 they also put in the nuts and bolts. In 

 the vicinity of the injury, the frames of 

 the ship were entirely destroyed, and 

 they were supplanted by a new structure 

 of heavy timbers. To make all this bolt- 

 ing tight, gaskets of red lead and lamp 

 wick were used. Also, due to irregular 

 contour of the hull plating, in many 

 places it was necessary to fill in with 

 concrete. Once before this method had 

 been utilized, and by the same man, Air, 

 W. W. Wotherspoon, and that was when 

 the Royal George went down in the St. 

 Lawrence River. 



Thus patched and plugged, the Pro- 

 greso was finally pumped dry. She was 

 then able to make a sea voyage to Vera 

 Cruz under her own steam. After an 

 examination it was decided that the 

 patches would be allowed to remain as 

 they had been placed, until a slight 

 amount of work could be done to put 

 her into excellent condition while in a 

 New York drydock. 



The Progreso is a vessel of fifteen hun- 

 dred and sixty-five tons displacement, 

 measures two hundred and thirty feet in 

 length by thirty-four foot beam, has en- 

 gines of 1,380 horsepower, and mounts 

 four-inch guns. 



The method by 

 which the Pro- 

 greso was raised 

 1 s substantially 

 the same in prin- 

 c i p 1 e as that 

 used in driving 

 tunnels under 

 the bed of a riv- 

 er. W h e n the 

 tunnels under 

 the Hudson Riv- 

 er were con- 

 structed, a 

 "shield" was 

 driven forward 

 by hydraulic 

 jacks. The men 

 who dug and 

 blasted the earth 

 and rock en- 

 countered by the 

 shield passed 

 through air- 



locks ; in other words, chambers in which 

 air was forced at such high pressure that 

 the river water was held back and pre- 

 vented from inundating the workmen. 

 Some conception of this air pressure may 

 be obtained when it is considered that 

 during the construction of the Pennsyl- 

 vania railway tunnel under the East 

 River a man was actually blown up 

 through the mud of the river, arriving at 

 the surface none the worse for his ex- 

 perience. 



It is evident that a kind of air-lock 

 was created in the forward hold of the 

 Progreso and air at such high pressure 

 was forced in that the sea water could 

 not push its way in. 



After the 

 holes in the 

 hull of the 

 steamer had 

 been patched 

 with sheets of 

 steel, and the 

 forward com- 

 partments 

 filled with 

 compressed 

 air, the pow- 

 erful salvage 



When the "Progreso" was pumped dry, she was able to steam to 

 Vera Cruz, where she was dry-docked and thoroughly examined 



