The Birmingham age-herald., 1906-12-16
clay or gravel which takes the place oi
Sinkinu the Foundations.

IOth.
 Sinking the Foundations.
 To reach rock bottom in excavating for the Trust eompany's building it was nee essary to sink the foundations far below the tidewater level which was reached at point about thirty feet below the curb. At that level there was constructed, as the first step in sinking each caisson, working chamber for the "sand-hogs,' or laborers. employed in the excavation. This working chamber consisted of box like structure, minus top and bottom, made of the stoutest timber and caulked to prevent water from entering through it's sides. Into this chamber was pumped compressed air, which also served to keep out the water. As the men inside dug away the earth the chamber sank steadily towards rock bottom, forced down by the ever-ihcreasing weight of the great concrete column which was being nodded on top of it. Through the center of this column ran a cylindrical steel shaft about three feet in diameter. This shaft gave the workmen access to the gradually sinking chamber, and also served as a passage for removing the ex- cavated material.
 When at last the working chamber had reached the solid rock, it filled with concrete. the sand hogs" working up as DeIOTb they Hdu WOfkeu uON0, anu lIt termination of their task left a complete shaft of a material as solid as rock and capable of bearing an enormous weight The average depth of one of these cais- sons in Manhattan is from 75 to 80 feet below the water level and a result most of the work of excavation must be done under a considerable air pressure. Much has been written about the heroism of the men who bore tunnels under river beds sink caissons to support massive bridges. but the 'sand-hog' in the build ing trade shows nerve equally as great and runs equally as great a risls-consid- erably more, in fact, than the average citizen would care to take in earning a living.
 The trade of the sand hog" has grown to such importance that it's members are bound together by a union, which has drawn up, with experience a basis, a set of rules, the most important of which regulates the length of time a man may work under various degrees of air press ure. The normal pressure of the atmos- phere is approximately sixteen pounds to the square inch. In caisson sinking the pressure is artifcially increased onehalf pound to every foot added to the depth of the excavation. In ratio to the pressure the strain of human endurance increases. Thus, while the sand hogs may work for eight hours under more than twen- ty pounds pressure when the pressure rises as high twenty-five, four shifts of men work in every twenty-four hours, and the working periods decrease with the increasing pressure until fifty pounds is reached, which is the limit beyond which no man could work with safety.
 The immediate welfare of the sand hogs is guarded by a lad who sits just
 
 for hours at time on an air gauge. on the dial of which is registered the slight est fluctuation, of the pressure inside. It is his business by means of valves, to keep the pressure steady and to notice and give warning of any unusual conditions.
 Hot in the Caisson.
 Inside the caisson the heat is so great that it would be uncomfortable for men not hardened to the work The sand hogs,~ in shifts of four. under the orders of a hour, day after day. in an atmosphere in which hot moisture drps from the walls and an occasional draft of cooler air fills the chamber and caisson shaft with blind ing steam Like guomes. stripped to the waist, they dig on stolidly. with appar- enty no thought of their dependence on the lad outside. or upon the timbers of the chamber which might give way under some unexpected pressure and bring about wild scramble up the caisson shaft in mad race with the inrushng water.
 Many caissons must be sunk to support single building. But the work has been so systematized and safeguarded that the foundation company which. in addition to sinking the cassons for the Trust Com pany of Americas new building. was en- gagged at the same time in a number of other foundation problems in the city, re- ports but two fatalities within the last six years. both of which occurred to men engaged on work preliminary to the actual caisson sinking. The occupation Is one which seems to have a fascination for the sand hogs" Otherwise it would be hard to explain mans return to such a job after an accident like that which be- fell the workman who when engaged in the tunnelng work under the Hudson river. blown through a number of feet of river bed and then up through the water into the air above He was picked up by some boatmen and has since been holding the position of foreman in a shift of sand hogs" at work sinking caissons on lower Broadway.
 When the first of the Wall street sky scrapers are completed the work which has been done during the past year will be largely hidden from sight but it is the process of sinking the great concrete