THE OPERATIVE MECHANIC Look in the tables under a 20 feet water-wheel, and opposite 808 gallons will be found 24 bolls of corn ground per hour. EXAMPLE II-If a stream of water producing 808 gallons, ale measure, per minute, can be applied to an undershot water-wheel 20 feet diameter, what quantity of corn can it grind per hour? It is found by the tables, that, if applied on an overshot water-wheel 20 feet diameter, the stream will grind 24 bolls per hour; and from page 156, the power required by the undershot to that of the overshot water-wheel, to produce an equal effect, is as 2-4 to 1; therefore, as 2-4: 1:25:104 bolls of corn ground per hour by means of the stream. EXAMPLE III.-If a stream of water, producing 808 gallons, ale measure, per minute, can be applied on a breast water-wheel 20 feet diameter, what quantity of corn can it grind per hour? It is found by the tables, that, if applied to an overshot water-wheel of equal size, 24 bolls of corn will be ground per hour; and from page 156, the power of a breast water-wheel to that of an overshot water-wheel, to produce an equal effect, is as 175 to 1; therefore, as 1·75 : 1 :: 2·5 : 1·42 bolls of corn ground per hour by the stream. EXAMPLE IV. Of what diameter must the cylinder of a common steamengine be made, to grind 10 bolls of corn per hour? By looking on the table, page 157, opposite 10 bolls ground per hour, the diameter of the steam cylinder will be found to be 36 inches. FAMILY MILL AND BOLTER. As a family mill and bolter cannot but be highly useful in many situations, we shall give a description of one or two, beginning with that invented by Mr. T. Rustall, of Purbrookheath, near Portsmouth, who received a premium of forty guineas from the Society of Arts for his invention. In fig. 157, A is the handle of the mill; B one of the mill-stones, which is about 30 inches in diameter, and five inches in thickness, moving with its axis C; D is the other mill-stone, which, when in use, is stationary; but which may be placed near to or at a distance from the movable stone B, by means of three screws passing through the wooden block E, that supports one end of the axis C, after it has been put through a hole or perforation in the-bed stone. perforation, from the hopper F, into the mill. F represents the hopper. The grain likewise passes through this which is agitated by two iron pins on the axis C, that alternately raise the vessel containing the grain, which again sinks by its own weight. In consequence of this motion the corn is conveyed through a spout that passes from such hopper into the centre of the mill behind, and through the bed-stone D. G, a paddle, regulating the quantity of corn to be delivered to the mill, and by raising or lowering which, a larger or smaller proportion of grain may be furnished; H, the receptacle for the flour, into which it falls from the mill-stones, when ground; I represents one of the wooden supporters on which the bed-stone, D, rests. These are screwed to the block E, and likewise mortised into the lower frame-work of the mill at K, which is connected by means of the pins or wedges, L, L, L, that admit the whole mill to be easily taken to pieces; M, a fly-wheel, placed at the farthest extremity of the axis C, and on which another handle may be occasionally fixed; N, a small rail, serving to keep the hopper in its place, the furthest part of such hopper resting on a small pin, which admits of sufficient motion for that vessel to shake forward the corn; O, a spur-rail, for strengthening the frame-work of the mill; P, the front upright, that is mortised into the frame-work, and serves as a rest for the end of the iron axis C, which is next to the handle. On each extremity of such axis there is a shoulder, which keeps it steady in its place. Lastly, there is a cloth hood fixed to a broad wooden hoop, which is placed over the stones while working, to prevent the finer particles of flour from escaping. Fig. 158 represents the bolter, with its front removed, in order to display its interior structure; the machine being 3 feet 10 inches in length, and 194 inches in breadth, and 18 inches in depth. A is a movable partition, sliding about four feet backwards or forwards from the centre of the box, upon two wooden ribs, which are fixed to the back and front of the box, and one of which is delineated at the letter B; C, the lid of the bolter, represented open; D, a slider, which is movable in a groove made in the lid, by means of two handles in the back of such lid; E, a forked iron, fixed in the slider D, and which, when the lid is shut, takes hold of the sieve F, and moves it backwards and forwards on the wooden ribs B, according to the agitation of the slider; G represents a fixed partition in the lower centre of the box, which it divides into two parts, in order to separate the fine from the coarse flour; from this partition the slider A moves each way about four inches, and thus affords room for working the sieve; H, a board that is parallel to the bottom of the bolter, and forms part of the slider A ; this board serves to prevent any of the sifted matter from falling into the other partition; I represents two of the back feet which support the bolter. Fig. 159 is a view of the top or upper part of the lid of the bolter; R the slider that moves the lengthwise of the bolter; LL the handles by which the slider is worked; M, a screw, serving to hold the fork, which imparts motion to the sieve. Fig. 160 represents the forked iron, E, separately from the lid. Both the mill and bolter may be constructed at a moderate expense, and they occupy only a small space of ground. The former may even be worked in a public kitchen, or within a room in a farm-house, without occasioning any great encumbrance. The particular excellence of this mill consists in this circumstance, that, from the vertical position of its stones, it may be put in action without the intervention of cogs or wheels. It may be employed in the grinding of malt, the bruising of oats for horses, and for making flour, or for all these purposes: it likewise may be easily altered, so as to grind either of those articles to a greater or less degree of fineness. Another advantage peculiar to Mr. Rustall's contrivance is, that one man is sufficient to work it; though, if two persons, namely, a man and a boy, be employed, they will be able to produce, in the course of two hours, a quantity of flour sufficient to serve a family, consisting of six or eight persons. for a whole week:-repeated satisfactory trials have proved that this mill grinds the corn completely, and at the rate of one bushel of wheat within the hour. Besides, the industrious farmer will thus be enabled to make comparative experiments on the quality of his grain, and may furnish himself, at a trifling expense, with flour from his own wheat, without apprehending any adulteration, or without being exposed to the impositions or caprice of fraudulent and avaricious millers. Lastly, though Mr. Rustall's bolter be more particularly calculated for sifting flour, it may also be applied to various other useful purposes, and especially with a view to obviate the inconveniences necessarily attendant on the levigation of noxious substances, and to prevent the waste of their finer particles. In order to reduce the labour in grinding, and to adjust the power to the acquired force, and also to simplify millmaking and grinding, and to reduce the expense attendant upon them, so as to enable the farmer and housekeeper to be independent of the miller's system of grinding, Mr. George Smart, of the Ordnance-wharf, Westminster-bridge, in April 1814, obtained a patent for certain improvements in machinery for grinding corn, and various other articles, by means of which every article required to be broke or ground is exposed to the application of rubbers or crushers, resting on their fulcrums, and pressed against the revolving body by means of levers, weights, or springs. The rubbers, or crushers, each acting on a separate axle, will admit of any irregular surface, from a square to a circle, to revolve against them, as each can be loaded more or less, by moving the weights on the levers further from, or nearer to, the fulcrum; or, if with springs, by screwing them more or less down. The rubbers or crushers may be plain, grooved, circular sided, concave, or any other figure best adapted for the substance to be broke or ground. The square or octagon are best adapted for breaking cement-stones, bones for manure, chalk, mixing clay, mortar, &c. For breaking malt, beans, &c. one crusher only is wanted; but for wheat, oats, barley, rice, or any flour, or meal, the more rubbers or crushers the finer the article will be ground; and the more flats there are on the revolving body, the more crushers can be applied to advantage. HAND-MILLS ARE most commonly used in grinding coffee and spices; but they are sometimes made of a larger size, and used to grind wheat, malt, &c.; in such cases the hand is generally applied to a winch handle. In Bockler's Theatrum Machinarum there is a description of a mill, in which the effort of a man is applied to a lever moving to and fro horizontally, nearly as in the action of rowing: as this is a very advantageous method of applying human strength, the effort being greatly assisted by the heaviness of the man in leaning back, we shall give a brief description of it. It is represented in fig. 161. The vertical shaft E G carries a toothed wheel C, and a solid wheel F; the latter being intended to operate as a regulating fly. Upon the crank AB hangs one end of an iron I, the other end of which hangs upon the lever H K, the motion being pretty free at both ends of this bar I. One end of the lever H K hangs upon the fixed hook K, about which, as a centre of motion, it turns. Then, while a man, by pulling at the lever H K, moves the extremity H from H to N, the bar I acting upon the crank A B gives to the wheels C and F half a rotation; and the momentum they have acquired will carry them on, the man at the lever suffering it to turn back from N to H, while the other half of the rotation of the wheels is completed. In like manner another sufficient pull at the lever H K gives another rotation to the wheel C, and so on, at pleasure. The wheel C turns by its teeth the trundle D, the spindle of which carries the upper mill-stone, just as the spindle D carries round the upper mill-stone in fig. 156. In this mill the nearer the end of the bar I upon the lever HK is to the fixed hook K, the easier, cæteris paribus, will the man work the mill. If the number of teeth in the wheel C be six times the number of cogs in the trundle D, then the labourer, by making ten pulls at the lever H in a minute, will give sixty revolutions to the upper millstone in the same space of time. In the Transactions of the Society of Arts, may be seen a description of a mill, invented by Mr. Garnett Terry, of the City-road, for grinding hard substances, by means of a wheel turning upon a horizontal axis instead of a vertical one, as in the common construction. See fig. 162. THE FOOT-MILL Is used for grinding corn or any other substance, moved by the pressure of the feet of men or oxen. A judicious construction of the foot-mill is given in G. A. Bockler's Theatrum Machinarum. This mill is represented in fig. 163. A is an inclined wheel, which is turned by the weight of a man, and the impulsive force of his feet while he supports himself, or occasionally pushes with his hands at the horizontal bar H. The face of this wheel has thin pieces of wood nailed upon it at proper distances, to keep the feet of the man from slipping while he pushes the wheel round: and the under side has projecting teeth or waves which catch into the cogs of the trundle B, and by that means turn the horizontal shaft G with the wheel C: this latter wheel turns the trundle D, the axle of which carries the upper mill-stone E. This kind of foot-mill will answer extremely well to grind malt, &c. when no very great power is required. M THE OPERATIVE MECHANIC KNEADING-MILL. away THE business of grinding and baking is in one sense so closely connected, that we shall in this place present a description of the kneading-mill; which is meant to do with that disgusting practice among bakers of kneading the dough with their bare feet. It would be well if the legislature paid some attention to this, which is still carried on in some parts of the metropolis, and particularly in the kneading of dough for biscuits. In the public baking-houses of Genoa a machine is used which produces a great saving of time and labour. It was first described in the Atti della Societa Patriotica di Milano, vol. ii. A, in fig. 164, is a frame of wood which supports the axis of the machine : a wall 14 palms high from the ground may be made use of instead of this frame. B, a wall, 34 palms thick, through which the aforesaid axis passes. C, another wall, similar to the former, and facing it at the distance of 21 palms. D, the axis, 30 palms in length, and one palm and one-third in thickness. E, the great wheel, fixed to the said axis, between the frame and the wall; its diameter is 28 palms; and its breadth, which is capable of holding two men occasionally, is five palms. F, are steps, by treading on which, the men turn the wheel very smartly; they are two palms distant from each other, and one-third of a palm in height. G, a small wheel with cogs, fixed almost at the further extremity of the axis: its diameter is 12 palms. H, a beam of wood which extends from one wall to the other, being 21 palms in length, and one and a third in thickness. A similar beam, not seen in the figure, is on the opposite side of the axis. I, a transverse piece of wood, placed near the wall C; it is fixed into the two beams, and serves to support the further extremity of the axis; its length is 14 palms, and its thickness one and a third: there is likewise a transverse piece (which cannot be seen in the figure) 14 palms long, and half a palm thick, placed close to the wall B. K is a strong curved piece of oak, fixed transversely in the side beams H, to receive the axis of the trundle: its length is 14 palms, and its thickness 14. L is a trundle of 54 palms in diameter, and 1 in height, which is moved by the cog-wheel G. M is a trundle proceeding from the trundle L, and continued through the cross N to the bottom of the tub P; its centre is made of iron, partly square and partly round, and it turns in a socket of brass. The first part of this axis between the trundle L and the cross N is of square iron, surrounded by two pieces of wood, held together by iron hoops, which may be removed at pleasure to examine the iron within; its length is three palms, its diameter about one palm. The second part of the axis which is within the tube, is made like the first part; its length is 14 palm, its diameter 14. The wooden sheath of this part of the axis is fixed to the bottom of the tub, by the means of three screws with their nuts. This axis is distant one-third of a palm from the nearest triangular beater of the cross. N, the cross, formed of two bars of wood unequally divided, so that the four arms of the cross are of different lengths: one of the two pieces of wood of which the cross is made, is six palms in length, the other five; their thickness is of a palm, |