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CERAMICS OF GUMBO SOILS 
problem to be attacked by the state survey. It is also the very first 
of the topics to receive attention by the same organization 30 years 
ago, when it was first inaugurated. The conclusions reached in 
the early day appear unshaken by any later considerations. Cal¬ 
vin’s very last effort was on this very theme, in connection with his 
report on the Geology of Taylor County, the field work of which 
was completed but the notes of which were not fully written out 
when stayed by the hand of death. The Calvin idea is clearly 
epitomized in the use of the term “Blue silt,” by which he designat¬ 
ed the upland gumbo. 
From a strictly geological angle it is manifest that the association 
of gumbo with the Glacial till is purely a fortuitous relation, and 
not a genetic connection. Restriction of the gumbo to the drift 
is an unfortunate attempt at too broad generalization from too 
slender basis. There might be some mitigation from the blunder 
by a geologist working alone and hampered by political boundaries 
and a lack of moderate experience could be under the circumstances 
overlooked. In the present instance the geologist had the very 
great advantage of chemical check, which, however, seems to have 
not only availed him nothing but to have actually helped to lead 
him astry. Certainly modern colloid chemistry is not too new a 
theme to have escaped the laboratory of a state university. On 
gumbo soil origin Kay and Pearce will certainly have to guess 
again. 
Gumbo has particular interest to the clay-worker. Its remark¬ 
able plasticity is unlike that possessed by any other clays. This 
property makes it undergo in burning an unusual amount of 
shrinkage. Because of such property it breaks up intp strong 
clinker. In highway betterment burnt gumbo thus forms an ideal 
road-metal. It is superior to any other form of MacAadam. It 
has many advantages over concrete and other hard pavements, of 
which cheapness is not the least. Not an unimportant feature is 
the seemingly strange circumstance that wherever the country 
roads are most impassible it is on account of the presence of 
gumbo. Thus by throwing up and simply burning the ordinary 
dirt road-bed the worst roads become the best roads. 
The fundamental problem of highway improvement in prairie 
country becomes closely linked with the location of the gumbo 
