This paper describes the detailed assembly of an X-ray automatic analyzer for the continuous estimation of elemental contents in flowing pulp streams as applied in a concentrator of the Northern Rhodesian Copperbelt. Arguments are given for the selection of electronic components, the programming of operations, mechanical movements, and other aspects concerned with the consecutive analysis of a number of pulp streams of widely different composition and elemental concentration. Details are given of a method of automatic compensation for pulp density and matrix variations using X-ray absorption.