AT the present time about 80 per cent of all the mixing at the Miller Rubber Company is done in internal mixers. All tires, tubes, heels and in fact all stocks with the exception of highly colored bath caps, water bottles and the like are mixed on these machines. The transition from mill to internal mixer has been gradual as there were many difficulties to iron out, both in the original mixer itself as well as in the operation. Our first experience with the internal mixer dates back to 1916 when we installed a small machine. The troubles encountered with this machine were largely due to the inability of getting rid of the heat generated during the mixing operation. In 1919 we installed the first mixer with which we mixed tire tread socks with some degree of success. Our biggest difficulty at this time was not the dispersing of the powders or pigments in order to meet gravity and tensile specifications, but was rather due to the fact that the mixed stock refused to run through the calendars and tube machines on account of being too stiff.