Pare the potatoes, boil them well, beat them to a pulp, and knead with double their weight of wheat flour, adding a sufficient quantity of yeast and salt; ferment, make up, and bake. The introduction of potatoes in moderate quantity into the best wheaten bread is by no means prejudicial to its quality. We believe that most persons find such bread, when well made, more palatable than that which contains none. It is not quite so dry, when new as wheat flour alone; it retains its moisture much longer, and will keep for ten days without any trace of sourness. The following is the process employed by most bakers for introducing them: A cask is prepared by boring holes in its bottom; and the bottom made to fit into the mouth of a boiler containing water of the quantity of flour to be baked be four cwt., the quantity of potatoes that can be properly used is five stone. The potatoes are thrown into the cask, a cover is applied, the water is made to boil, and the steam ascending through the holes of the cask boils the potatoes. The boiling is continued until the potatoes crack and become mealy.

They are then withdrawn, and are pounded with a wooden instrument until they become quite fine.

While this potatoe-meal is still very hot, cold water is added in such quantity as to reduce the whole to the thickness of butter milk. To this liquid, still warm, a gallon of yeast is to be added. A fermentation commences; and after it has continued sufficiently long, during which the potatoe-meal rises to the top and forms a tough mass, the whole is to be well mixed; and being now a homogeneous liquid, it is to be strained, first through a coarse hair sieve, and afterwards through a finer. To this strained matter, one half of the whole quantity of flour is to be added, and well worked up with the hands so as to form sponge. When the sponge has duly fermented, the other half of the flour is to be added, along with some more water holding salt dissolved: this mixture is to be worked up into dough, and treated in the usual manner. An extremely light and beautiful bread is made by the introduction of the pure starch of the potatoe, in various proportions (to the extent of one fifth part), to wheaten flour. The best mode of separating this starch from the root with which we are acquainted, is by the employment of a simple machine that we contrived for the purpose many years ago, engravings of which are given in the next page. Fig. 1 represents a vertical section of the machine.

Fig. 2 is a perspective view of the grinding cylinder, with a part of the perforated covering turned back, to show the internal construction; a a is a strong square frame or stand, made of wood; b, a square cistern containing water, under which the grinding cylinder c is partly immersed; this cylinder, shewn separately in Fig. 2, is 11 inches in diameter, and 24 inches long; it is covered with a sheet of iron e, perforated throughout with small holes, produced by means of a steel punch, having a quadrangular pyramidical point, which raises four distinct burs or teeth, particularly adapted to the purpose of rasping; this perforated plate is nailed to the peripheries of four turned discs of wood, which thus produce the cylindrical figure, and each disc has a series of large holes d made through it, for the free passage of the water throughout the cylinder. The axis is mounted in plummer blocks, fixed on the frame, (not seen in the drawing,) and is turned by a winch handle f, or any other convenient means. G is a fly wheel, to equalise the motion. The potatoes are put into a hopper h, the lower extremity of which is formed into a square frame which encompasses the upper half of the cylinder in an exact manner, but not so as to touch it, in order that it may turn round freely.

The hopper is also provided with a movable curved portion i, turning upon a joint, and serves to press the potatoes r against the cylinder, as the latter is turned round by the agency of a lever k, on which a weight is suspended, - a traversing weight to vary the pressure. The curved side of the hopper is made of sheet iron, and has a long slit in the middle to allow the lever k to traverse, and as a guide to it. In setting this machine to work, the hopper is to be filled with potatoes washed perfectly clean, and the cistern is to be about two thirds filled with water, or so that the cylinder dips two or three inches into it. The weight being then applied to the lever k, the operation of grinding is commenced, and continued until the cistern is nearly filled with the pulp; but before this takes place, the water in the cistern rises so much that a portion of it must be run off, or ladled out into another vessel, as the water which is not then clear contains a portion of the finest starch, that takes an hour or more to subside. The grinding of a bushel of potatoes into pulp by a machine of this size takes a man about a quarter of an hour, from which fact it will be seen, that one horse power is adequate to the reduction of about 24 bushels per hour.

The next process to grinding down is the separation of the starch from the fibre, and other extraneous parts. For this purpose, the cistern, which is upon rollers, is drawn forward out of its situation about 6 inches, which allows sufficient room for the pulp being emptied out by means of a bowl into a sieve; or instead of the latter, into a piece of lawa stretched over a tall tub, (the best form of which is, that of the inverted frustrum of a cone;) the lawn being tied down by a cord passing round beneath a hoop on the top of the tub. The operation is thus performed; a bowlful of the pulp is first thrown on the strainer, (which is rendered concave by the pressure,) and immediately another bowlful of clear water, from a reservoir at hand, is dashed down upon the former; the dilution which it thus receives causes the starch to pass rapidly through the strainer, this effect being increased by the operator continually stirring up the mixture with his left hand. A small portion of starch remains after the first affusion, but which is entirely removed by a second dose; the fibrous remains are then cleared off the strainer, and a fresh portion of the pulp from the cistern is thrown on the filter, and treated as the former, and the operation thus continued until the cistern is emptied.