BINGHAM: PLASTIC FLOW 



177 



On the basis of the data it would be hazardous to attempt any 

 generalizations; but the regular sequence of the figures suggests 

 that in spite of the individual variation of the observations the 

 averages are more or less reliable, and that the warming of the 

 abyssal water from the California!! coast toward the mid-Pacific 

 may be accepted as a fact. 



In this connection it is well to call attention to the relatively 

 high abyssal temperatures on the South and Central American 

 coasts, as contrasted with those from southern California north- 

 ward, especially off southern California and in the Gulf of Alaska. 



5 

 5 



PHYSICS.— Plastic flow. 1 E. C. Bingham, Richmond College. 

 (Communicated by C. W. Waidner). 



Bingham and Durham 2 showed experimentally that the fluidity 

 of a suspension is a linear function of the concentration. The 

 zero of fluidity is reached at a comparatively low volume con- 

 centration, as is shown in 

 figure 1. The concentra- 

 tion which has zero fluidity 

 serves to sharpty demarcate 

 viscous from plastic flow. 

 All concentrations less than 

 this are viscous and any 

 shearing force, no matter 

 how small, will produce a 

 permanent deformation if 

 exerted long enough. Con- 

 centrations greater than 

 this are plastic and it is 

 necessary to use a shearing- 

 force of definite magnitude 

 in order to produce a per- 

 manent deformation. The 

 laws of plastic flow have never been studied. The method of 

 attack was to force suspensions of clay in water under known 



1 This work has done at the Bureau of Standards. 



2 Amer. Chem. Journ. 46: 278. 1911. 



200 



o 



H 



o 



01 

 100^ 



so 



25 SO 75 



VOLUME PERCENTAGE CLAY 



100 



Fig. 1. 



Relation of fluidity and friction to 

 concentration. 



