CERAMICS OF GUMBO SOILS 
407 
gumbo is sometimes really water-laid cannot be denied by anyone 
who has ever had very much to do with the gumbo clays. 
So accurate are the records of these several workers in this field, 
so clever and logical are their arguments, and so harmonious are 
their independent conclusions, that the latter do not in any way 
conflict with one another, because they refer to entirely different 
aspects of the same problem, and because they happen to be most 
appealing in the respective localities. Far from demolishing the 
conclusions of these investigators, and thus clearing the stage for 
the presentation of a new hypothesis, the objections of Kay and 
Pearce tremendously strengthen the views of their predecessors, 
and at the same time they greatly weaken their own claims. It 
may be concluded that Kay and Pearce’s criticisms of their fellow 
workers constitute the strongest possible evidence against their own 
position. Of their own citadel scarcely one stone is left upon an¬ 
other so completely is it razed. 
Since gumbo silts are the most plastic clays known, it is because 
of this high degree of plasticity which they possess that they are 
subject of such exhaustive experimentation and examination con¬ 
cerning the cause of plasticity of clays generally. When the Miss¬ 
ouri Geological Survey ^ undertook a special investigation of the 
clays of that state it was from an industrial rather than from the 
geological angle. One of the main themes for determination was 
the cause of the plasticity property. Prof. H. A. Wheeler ® found 
that fine grinding of clays increased this property. Some of the 
clay plants put the matter to test, on a large scale, and were quite 
well satisfied with the partial results. Prof. E. Haworth,® who 
made extensive microscopic examinations, noted that size of grain 
had an important bearing upon the perfection of the plasticity, as 
did also the lamellar form of the particles. This latter feature 
corroborated early contentions of Johnson and Blake.’’ It was 
fully recognized, however, in the Missouri work that there must also 
be other factors involved that were not understood. The gumbo 
clays of Missouri, because of their high plasticity thus came in for 
special consideration. 
At the time that the Missouri investigations were made colloid 
4 Missouri Geol. Surv., Vol. XI, 622 pp., 1896. 
5 Ibid., p. 106. 
6 Ibid., 104. 
7 Am. Jour. Sci., (2), Vol. XLIII, p. 351, 1867. 
