A new form of disintegrator has been recently brought out in America by the Williams’ Patent Crusher and Pulveriser Company, in which a series of discs are keyed to the main shaft, to the circumference of which a number of sets of “hammers” are suspended by means of hinge-bolts. Each of these steel bars, or hammers, has a free arc movement of 120°, and when the machine is in motion take a position divergent from the centre on account of the centrifugal force. After striking a blow against any material fed on to a plate serving as an “anvil,” the hammers recoil, and, after passing any material which is not shattered by the blow, again resume their normal position, leaving the next set of hammers to beat against the unground material. The hinged suspension of the hammers imparts a degree of flexibility to the mill which is not found in any other machine of this character, and lessens the risk of serious damage to the machine by the introduction of pieces of metal along with the bark. The makers claim that this machine can be repaired more rapidly and with less expense than any other disintegrator of equal power on the market. Considerable improvements have recently been made in the details of its construction. Fig. 72 shows a section of this mill. Of course only the end hammers of each set can be seen in the figure. [Illustration: FIG. 72.--Section of Williams’ Crusher.] When myrobalans or valonia is to be used for leaching, it is generally better to crush it between toothed or fluted rollers, rather than to grind it finely, as the cellular structure is just as completely broken up, and the flakes formed by crushing allow of much freer percolation than when the material is powdered by the disintegrator, while the consumption of power is also less. The general construction of the machine will be easily understood from Fig. 73, and it is only necessary to point out that the small upper roller acts mainly as a “feed” to the larger crushing rolls. In the best mills, the rollers are made up of a series of toothed steel discs on a square axis, and are on this account easily replaced or sharpened when they have become broken or worn. [Illustration: FIG. 73.--Myrobalans Crusher.]