The illustrations are reproduced by the Grout Engraving Company.
Grout pipes were built into the masonry and later all voids were filled with grout.
Rubble masonry packing and grout ejected through pipes built into the arch were used to fill the voids above the roof.
On account of the unstable nature of the rock encountered throughout, the voids in the packing were afterward filled with grout.
The grout machines were of the vertical-cylinder, air-stirring type.
In the subgrade telephone and telegraph ducts east of the Manhattan Shaft, much trouble was caused by grout in the ducts.
All the grout hole plugs were examined, and the plugs in any leaking ones were taken out, smeared with red lead, and replaced.
Grout pipes were built in, as it was not likely that the concrete could be packed tightly into the upper part of the lining.
The first type of grout pipe arrangement is shown as Type A, in Fig. 23.
Even with 1:1 grout it must be constantly stirred and a steady flow into the pipe maintained.