in the vessel or tank containing the slurry by utilizing the flow produced by the agitator or mixing impeller or pulper which circulates the slurry within a region of the vessel the flow is preferably detected by a sonic flow sensor which responds to the velocity of the particles of material while the flow thereof is induced by shift in frequency between transmitted and received waves due to the doppler effect this velocity signal obtained from the sensor is used to vary the dilution of the slurry thereby controlling the consistency thereof the addition of make up material such as dilutant the outlet slurry of controlled consistency as well as the measurement of consistency are all made in the same region of the tank where flow is occurring the measurement and contol of consistency is closely coupled and is carried out without delay thereby resulting in maximum accuracy downstream dilution and trimming to obtain desired consistency can be eliminated in that lower consistencies of the material in the tank result in a reduction of size in the motor and drive for operating the agitator with the attendant conservation and saving of power accordingly it is a principal object of the present invention to provide an improved method and apparatus for the measurement and control of consistency in slurries which may be contained in a chest or tank it is a further object of the present invention to provide an improved method and apparatus for the measurement and control of consistency at low cost and with high accuracy the foregoing and other objects features and advantages of the invention as well as the best mode known for practicing the invention and a.