Note
Evaluation of current methods of measuring turbidity in estuaries indicates a need to calibrate rapid, in situ optical measurements of beam transmittance with the units specified in water quality standards and with quantitative and qualitative data on the composition of suspended matter. Our results include curves relating per cent light transmission to Formazin Turbidity Units and the concentrations of monotnineralic suspensions of Ca-montmorillonite and kaolinite.