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APPENDIX

A GLOSSARY OF RHEOLOGICAL TERMS

The exact defmition of many of the terms used in theological work is still at a controversial stage, and no attempt will be madę to enter into these controversies. The list given below is intended to provide the reader with a generał idea of the meaning of some of the current rhfeological expressions. ..Terms in generał use in physics and colloid science will not be included.

Although there is, as yet, no recognised set of symbols, certain coiiventions are usua!, and the symbok given in brackets will be found frequently in the literaturę,

Coefficient of Viscous Traction. Ratio of tensile Itress to ratę of shear. For materials having a Poisson ratio of o^-5, this is nnmerically equal to three times the yiscosity. {Jfide p. 22.)

_t Consistency. “ That property of a materiał by which ft resists permanent change of shape . . . defined by the complete flow-force rdation.” Sometimes used to define elastic, as well as plastic deformability. No definite ditnensions.

Cybotaxis. The orientation of moleculęs in liquids into temporary groups (Cybomas).¹ [Vide p, 6.)

Elastic Fore- and After-effects. The phenoraena shown when elastic deformations take effect and recover slowly, due to interna! yiscosity or some similar cause.

Flow-elastidty. The condition under which, when a materia! is flowing under an applied stress, and the stress iś suddenly reduced to zero, the streaming materiał not only stops flowing, but actually recoils slightly.

¹ For criticisms of the Cyboma theory vide Seoond Report on Viscoaity and Plasticity. Academy of Sciences, Amsterdam

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