(1) Deyelopment of coal washing jig.(2) A theory for coal washing by jig without preliminary sizing.(3) Devices to discharge the refuse layer from a jig.(4) Features of coal washing jigs.(5) The closing remarks.<BR>About 120 years ago a fixed sieve jig was introduced in the field of coal washing, and then Berard, a French engineer, developed a cotinuous working, fixed sieve jig for coal washing. This is the first cotinuous workig jig in general. The Hartz jig for mineral dressing could realize an uniform pulsation over all the sieve area by giving the same area to the sieve and plunger section. The principle of the bed jig was introduced to the Hartz district from Cornwall where a movable sieve jig with an artificial bed was practiced. This principle was adapted by Luhrig to wash tine coal with success. The artificial bed is very useful to get the uniform pulsation over all the sieve area and to moderate the suction. Rittinger wrote his book in 1867. Fritz Baum invented his air pulsated jig in 1892, developed his principle to wash a raw coal without preliminary sizing in a jig, and designed the air pulsated jig with 2 cells in series which is now the conventional type. With a large jig it is very difficult to get an uniform pulsation all over the sieve area with the most ingenious device. The newly developed TACUB jig solved this long pursued and basic probrem. There are various theories proposed for the conventional practice to wash a raw coal without preliminary sizing in a jig. The author understands it as follows: at the charging end the raw coal fed is separated according to the law of falling velocity, and the larger pieces of shale are arranged at the bottom forming a sole for the coal bed. On the following way the bed flows in a mass as a whole as it is expanded moderately by the pulsion. The bed in such a state is specified by the author as a “crowding and flowing” bed. In a crowding and fiowlng bed of a raw coal the larger plecesof coal areforced to roll upword into the top byer of the bed, “reversed classification”, and the smaller pieces of shale pass through the coal bed into the bottom layer of the bed replacing the coal particles according to their sizes and specific gravities. There are various devices to discharge the bottom layer of the refuse at the discharging end. It is controlled automatically according to the thickness of the bed of the refuse. The efficiency of the work of “coal washing by jig” can be evaluated practically as high as the H. M. S. The simplicity of a plant of “coal washing by jig” must not be neglected in the field of productive engineering.