“For instance, the author’s well-known theory that the pressures against retaining walls are a maximum at the top and decrease to zero at the bottom, is in absolute contradiction to the results of experiments conducted on a large scale by the writer on the new reinforced concrete retaining wall near the St. George Ferry, on Staten Island.”

The writer’s “well-known theory that pressures against retaining walls are a maximum at the top and decrease to zero at the bottom” applies only to pressures exerted by absolutely dry and normally dry material, and it seems to him that this so-called theory is capable of such easy demonstration, by the simple observation of any bracing in a deep trench in material of this class, that it ought to be accepted as at least safer than the old theory which it reverses.  As to this “well-known theory” in material subject to water pressure, a careful reading of the paper, or an examination of Fig. 12 and its accompanying text, or an examination of Table 1, will convince Mr. Goodrich that, under the writer’s analysis, this pressure does not decrease to zero at the bottom, but that in soft materials it may be approximately constant all the way down, while, in exceptionally soft material, conditions may arise where it may increase toward the bottom.  The determination should be made by taking the solid material and drying it sufficiently so that water does not flow or seep from it.  When this material is then compacted to the condition in which it would be in its natural state, its angle of repose may be measured, and may be found to be as high as 60 degrees.  The very fine matter should then be separated from the coarser material, and the latter weighed, to determine its proportion.  Subtracting this from the total, the remainder could be credited to “aqueous matter.”  It is thus seen that with a material when partially dried in which the natural angle of repose might be 60 deg., and in which the percentage of water or aqueous matter when submerged might be 60%, there would be an increase of pressure toward the bottom.

The writer does not know the exact nature of the experiments made at St. George’s Ferry by Mr. Goodrich, but he supposes they were measurements of pressures on pistons through holes in the sheeting.  He desires to state again that he cannot regard such experiments as conclusive, and believes that they are of comparative value only, as such experiments do not measure in any large degree the pressure of the solid material but only all or a portion of the so-called aqueous matter, that is, the liquid and very fine material which flows with it.  Thus it is well known that, during the construction of the recent Hudson and North River Tunnels, pressures were tested in the silt, some of which showed that the silt exerted full hydrostatic pressure.  At the same time, W.I.  Aims, M. Am.  Soc.  C. E., stated in a public lecture, and recently also to the writer, that in 1890 he made