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relatively very large proportion of the total . faces of the stones. I have found by prac- tical demonstration that, by this construc- tion of the millstone dress, a much more uni- 5 form product is secured than where larger proportions of the faces of the stones are grooved or furrowed; the material may be ground without objectionable heating of the product; and the speed of the operation is 10 largely increased. Having thus fully described the invention, what I claim as new is: 1. A millstone having a grinding face com- prising a general surface lying. in a single 1.5 plane, and a dress consisting essentially of an annular depression or feed groove in its central region having exits in the form of leading or feeding furrows extending tan- gentially from said groove in a direction in- 20 dining backward from the direction of rota- tion, and of a length not greater than the diameter of the annular groove; said furrows having inclined bottoms shallowing. out-
wardly and rearwardly into the general plane or face of the stone, substantially as specified. 25 2. The combination of a pair of millstones each having a grinding surface lying in one general plane, a central annular depression or feeding groove, and feeding furrows lead- ing therefrom and tangential thereto, having 30 a length no greater than the diameter of said annular groove and dying rearwardly into the general plane of the surface whereby the grain as it is fed outwardly receives a shear- ing or preliminary grinding action from the 35 two sets of grooves, and a maximum pro- portion is. secured of coating grinding sur- faces each lying in one general plane, sub- stantially as specified. In testimony whereof, I affix my signature 40 in presence of two witnesses. JOHN L. DURHAM. Witnesses: JAMES CLEPPER, LEWIS PAYNE.