“If the solid material in any liquid is agitated, so that it is virtually in suspension, it cannot add to the pressure, and if allowed to subside it acts as a solid, independently of the water contained with it, although the water may change somewhat the properties of the material, by increasing or changing its cohesion, angle of repose, etc.”

On the other hand, it is believed that the author’s statement, as to “the tendency of marbles to arch,” a few lines above the one last quoted, should be qualified by the addition of the words, “only when a certain amount of deflection has taken place so as to bring the arch into action.”  Again, on the following page, a somewhat similar qualification should be added to the sentence referring to the soft clay arch, that it would “stand if the rods supporting the intrados of the arch were keyed back to washers covering a sufficiently large area,” by inserting the words, “unless creeping pressures (such as those encountered by the writer in his experiments) were exceeded.”

The writer considers as very doubtful the formula for D{x}_, which is the same as that for W{1}_, already discussed.  The author’s statement that “additional back-fill will [under certain circumstances] lighten the load on the structure,” is considered subject to modification by some such clause as the following, “the word ‘lighten’ here being understood to mean the reduction to some extent of what would be the total pressure due to the combined original and added back-fill, provided no arch action occurred.”

The writer is in entire agreement with the author as to the probability that water is often “cut off absolutely from its source of pressure,” with the attendant results described by the author (p. 378); and again, that too little attention has been given to the bearing power of soil, with the author’s accompanying criticism.

The writer cannot see, however, where the author’s experiments demonstrate his statement “that pressure is transmitted laterally through ground, most probably along or nearly parallel to the angles of repose,” or any of the conclusions drawn by him in the paragraph (p. 381), which contains this questionable statement.  Again the writer is at a loss as to how to interpret the statement that the author has found that “better resistance” has been offered by “small open caissons sunk to a depth of a few feet and cleaned out and filled with concrete” than by “spreading the foundation over four or five times the equivalent area.”  The writer agrees with the author in the majority of his statements as to the “bearing value and friction on piles,” but believes that he is indulging in pure theory in some of his succeeding remarks, wherein he ascribes to arch action the results which he believes would be observed if “a long shaft be withdrawn vertically from moulding sand.”  These phenomena would be due rather to capillary action and the resulting cohesion.