408
��Popular Science Monthly
��put in from the outside by the 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
�� �
