KNEADING MILL. finding the sum of the infinite series nt. + + 1 + &c.) (1). I have not, however, been n2 2 + 20 n° to + 30 fortunate enough to assign the sum of this elegant series in finite terms, though its simplicity is such as to hold out the hope, that this "consummation, most devoutly to be wished," may, perhaps, be accomplished by abler hands at some future period. (To be continued in our next.) SIR, Seeing in your Magazine an inquiry by A. B. C. (p. 54, vol. III.), for a Machine for Kneading Dough, I beg leave to inform him, that in the public baking-houses of Genoa, bread has been long manufactured in this manner, with a great saving both of time and labour. with your leave, attempt a descrip tion of the machine. I remain, Sir, Description. the distance of 21 palms. D, the axis, 30 palms in length, and one palm and wheel fixed to the said axis, between one-third in thickness. E, the great 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 I will, turn the wheel very from each other, and one-third of a smartly; they are two palms distant palm in height. G, a small wheel, with cogs fixed almost at the further extremity of the axis; its diameter is 121 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 axiş; its length is 14 palms, and its thickness one and a third; there is likewise a transverse Fig. 1. A 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, 3 palms thick, through which the aforesaid axis passes. C, another wall similar to the former, and facing it, to 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 14 palms, and its thickness 1. Z is a trundle of 5 palms in diameter, and 14 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 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 a palm and a half, its breadth 1 1-6th palms. The wooden sheath of this part of the axis is fixed to the bottom of the tub by means of three screws with 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 7-12ths of a palm, and their breadth one palm. O, four pieces of wood, called beaters, of a triangular shape, fixed vertically into the extremities of, and underneath the arms of the forementioned cross; they are one and three-quarters palms in length, and half a palm in thickness, and beat or knead the dough in the tub at equal distances from the centre. P is a stout wooden tub, about a quarter of a palm thick, well hooped with iron; its diameter is six palms, its height 1 in the clear. Fig. 2 is a box or trough of wood, four palms long, and three wide, in which the leaven is formed (in about an hour) in a stove, and in which it is afterwards carried to the tub, P. Fig. 3 exhibits a view of the trundle, cross, &c. with a section of the tub. Fig. 4 is a bird's-eye view of the cross and tub, with the upper ends of the triangular beater. This tub, P, will contain about 18 rubbi (about 19 bushels) of flour, which is carried to it in barrels; the leaven is then carried to it in the box or trough, and when the whole is tempered with a proper quantity of warm water, the men work in the wheel till the dough is completely and properly kneaded. In general, a quarter of an hour is sufficient to make very good dough; but an experienced baker, who superintends, determines that the opera tion shall be continued a few minutes more or less, according to circumstances. The measures in the preceding description are given in Genoese palms, each of which very nearly equals 9.85 of our inches. The machinery may be varied in its construction according to circumstances, and the energy of the first mover much better applied than by men walking in a common wheel. [In November, 1811, a patent was granted to Mr. Joseph Baker, navy-contractor, for a method of kneading dough by means of machinery, which is thus described :-An upright shaft, turning on a pivot, is fixed in the centre of a circular trough, so that the dough placed in such trough may be kneaded by a stone or iron roller on its edge, which passes over it in a rotatory motion, being fixed at a due distance by an horizontal bar or axle to the shaft, which is to be turned by means of one or more horizontal bars also fixed thereto, and worked, like a capstan, by a proportionate number of bipeds or quadrupeds. These horizontal bars have small shares fixed to them, so as to run in the trough, and acting like a plough, they cause the dough to present fresh surfaces for each successive revolution.-EDIT.] WARM BATHING. SIR-Should Warm Baths be established contiguous to any of the great gas-works, upon the principle recommended by Mr. Bell, in your 92d Number, I would beg leave to inquire of your medical readers how far it may be made to imitate, in efficacy, the saline springs, or sea water, as a bath, by the addition of common salt (muriate of soda); and if so, what proportion of salt should be added to the water for that purI would also wish to inquire, pose. if it could be improved by the addition of any other substance? would also be desirable to be imformed, to what degree of temperature the bath should be heated for general use. It There appear some obstacles in the way to the general adoption of warm baths upon Mr. Bell's principle, which may prevent their becoming "co-extensive with gas illu CABINET-MAKER'S GUIDE. mination," as he rather sanguinely expresses it. To mention one of these, is it likely to obtain, in every situation where gas-works are established, a sufficient supply of water, of that degree of purity which is necessary for the purpose of filling the baths? Still, however, I thank him for the hint, and hope the Mechanics' Magazine will be the means of informing that important part of the community (the labouring classes) how they may derive that advantage from tepid bathing at home, and at an expense within their means, which has hitherto been enjoyed, at established watering-places, almost exclusively by the fashionable and opulent. 155 Al an Appendix of very useful Tables, which show, by inspection, the superficial content of any board or plank, without having recourse to duodecimals, or cross multiplication. together the work leaves little to be desired; and being as cheap as it is complete, ought to be in the hands of every cabinet-maker, chair-maker, japanner, gilder, and lackerer. We shall quote, as a specimen of the original matter it contains, the following useful directions to workmen, with respect to the choice and management of their tools : "With respect to choosing the tools used in the trades to which I have alluded, the most necessary, and in which all may be comprehended, are planes, saws, and chisels; and we will consider them with respect to the wood they are manufactured from, and the steel which form the cutting part of them. And, first, beech is in general, and ought to be always used, for the purpose of the stocks, handles, &c., as it is of a tough texture, and not liable to split or warp so much as any other. Now there are two kinds New Edition, 95 pp. 16mo. price 1s. 6d. of beech, usually known by the names of Every Carpenter is acquainted with a little work under this title, which has been published for some years, and held deservedly in considerable estimation. It must be admitted, however, that it was open to much improvement, particularly in the practical application of the rules and cautions necessary to be observed by the workman to ensure success in his operations, and that it left many subjects connected with the general plan wholly untouched. In the present edition these deficiencies have been very ably supplied, by a hand evidently well and practically acquainted with the art of cabinet-making in all its branches. It not only embodies all that was useful in the original Cabinet-Maker's Guide, and adapts to practice the rules there contained, but contains a great deal of new matter of the most valuable description. We would particularly instance the additions under the head of Varnishing, French Polishing, Gilding, and Buhl Work; as also black or red beech, and the white beech; the former is by far the best in every respect, and may be always known by its colour and texture, which is darker and more hard in substance; the white is also more apt to warp, and soon wears with use; it should therefore always be rejected as improper. Again, if you examine a piece of beech endways, you will perceive the grain run in streaks, which, among workmen, is called the beat of the wood; and in all planes this grain or beat, which is the hard fibrous particles of the wood, should run in a direction perpendicular to the face of the plane, which in that case appears full of little hard specks; whereas, if the beat runs parallel to the face, it will appear in irregular streaks, which situation of the grain should always be avoided, as the face will be apt to wear uneven, and more subject to warp and twist. Again, in saw-handles and stocks for bits, the beat should run in the same direction as the saw-blade, or in the same direction as the stock, when laid on its side. In moulding - planes it is very frequently the case, that pieces of box are let into 156 EFFECT OF SCIENTIFIC READING. that part of the face that forms the quirk of the mouldings; but that, when possible, should be avoided, as the texture of the two woods are very different, and the different temperature of the atmosphere will cause a difference in their contraction, and consequently the plane will be liable to cast. If it is at any time introduced, I would recommend only a small piece just at the mouth of the plane, firmly dovetailed in, which will not be so apt to derange the accuracy of the plane. ness, and that the hairs are sufficiently mixed, so that taking hold of one hair, it will not pull out or separate from the rest. The larger brushes are usually made of bristles, the smaller of camel's hair; the former must be firmly tied to the handle, and the string well glued. The latter are best put into a tin case, and after being used must always be cleaned according to the directions given in the course of this work. "By paying proper attention to these directions, and a little care, the workman will be enabled to keep his tools in order, and to select such as are proper for the purpose they are intended." EFFECT OF SCIENTIFIC READING. SIR,-Although there is now such a general strike for an advance in wages among workmen of almost every trade, I feel the greatest pleasure and satisfaction in giving you the gratifying intelligence, that not one of my men who is in the habit of taking your valuable little work, is among the disorderly. On the contrary, they endeavour, by whatever means lie in their power, to prevail upon their fellow-men to return to their duty. I confess, that at one time I had a strong prejudice against the mechanics attending to such a thing as science; how my views of the case are altered, I need not tell you; I can only say, you may now reckon me as one of your greatest admirers and constant readers. From yours, truly, With respect to saws, chisels, and other edge-tools, their goodness depends upon the quality of the steel, which should be uniform throughout, and it is always better to have them tempered rather too hard than soft, for use will reduce the temperature: or if at any time it is necessary to perform the operation yourself, the best method I can recominend, is to melt a sufficient quantity of lead to immerse the cutting part of the tool. Having previously brightened its surface, plunge it into the melted lead for a few minutes, till it gets sufficiently hot to melt a candle, with which rub its surface, then plunge it in again, and keep it there till the steel assumes a straw colour (but be careful not to let it turn blue); when that is the case, take it out, rub it again with the tallow, and let it cool; if it should be too soft, wipe the grease off, and repeat the process without the tallow, and when it is sufficiently hot, plunge it into cold spring water, or water and vinegar mixed. By a proper attention to these directions, and a little practice, every workman will have it in his power to give a proper temper to the tools he may use. If a saw is too hard, May 31st, 1825. it may be tempered by the same means; but as it would be not only expensive, but, in many cases, impossible to do it at home, a plumber's shop is mostly at hand, where you may repeat the process when they are melting a pot of lead. But here observe, that the temper necessary is different to other cutting tools; you must wait till the steel just begins to turn blue, which is a temper that will give it more elasticity, and, at the same time, sufficient hardness. "With respect to choosing your brushes for varnishing, it is necessary that they possess elasticity combined with soft A MASTER. [We are gratified by this testimony to the beneficial effect of our labours, but hope it will not hence be inferred, that we concur in the opinion which the words of our Correspondent seem calculated to convey, that all strikes for advances of wages are necessarily "disorderly," and a breach of duty." We can conceive cases in which workmen have no other means left of obtaining justice; but, to be fully justifiable, they must, of course, be unaccompanied by violence or intimidation.-EDIT.] THE LOG-LINE THE USE OF THE SLIDING RULE. THE LOG-LINE. SIR-The method commonly made use of for measuring a ship's way at sea, or how far she runs in a given space of time, is by the log-line and half-minute glass. It is clear to me, that a machine might be constructed with a dial-plate, similar to that of a perambulator, which might be divided agreeably to the rules of navigation. If such a machine has ever been made use of, any Correspondent will oblige me by giving a description of it in the Mechanics' Magazine. I am, Sir, THE USE OF THE SLIDING RULE. (Continued from page 132.) PROBLEM I. To multiply numbers together. RULE. Place unity or 1 on the upper line of the slide, marked B, to the multiplier on the line marked A on the rule; then against the multiplicand on B is the product, as A. EXAMPLE I. Let it be required to multiply 48 by 76. Set 1 on the line B to 76 on the line A, then against 48 on the line B will be the number 3648 on the line A, which is the answer required. EXAMPLE II. Multiply 498 by 82. Set 1 on the line B to 498 on the line A, then against 82 on the line B stands 40,836, the answer. NOTE. It may be here asked, How, in the First Example, I find the number 3648 opposite to 48 on the line B, which appears, by the inspection of the rule, to be at 3 of the large division of the right-hand scale of numbers marked at A, 6 of the small division, and about half another? This I will endeavour to explain as follows:-We know that, as we have two figures in the multiplier and 157 two figures in the multiplicand, the product must, of course, consist of three figures at least, and that the third figure from the right-hand to the left is, in numeration, accounted the place of hundreds; therefore I call the commencement of the lefthand scale at A 100, and, of course, the commencement of the right-hand one 1000; therefore our figures stand thus, 3000+600+50, nearly. Now, as the scale is not long enough to estimate the units or tens, I find, by multiplying the right-hand figure of the multiplicand by the right-hand figure of the multiplier (in my mind) that 48 is the product; hence I know that the last figure of the product (of 48 x 76) I am seeking is 8, and, therefore, instead of 50 I write 48; hence we have 3000+600+ 48=3648, the answer required. Now, with regard to Example the Second, where the product consists of five figures, they are thus found: -I place the I on the line B, as near as I can estimate, at 498, that is, 4 of the large divisions on the left-hand scale, 9 of the smaller ones, and, as near as I can guess, 8-10ths of a small division. I then find that, as there are three figures in the multiplicand and two in the multiplier, there must be at least four figures in the product, which is the place of thousands in numeration; I therefore call the beginning of the lefthand scale 1000, and therefore the beginning of the right-hand one 10,000, I then look opposite 82 on the slide B, and I find 4 large divisions, which is tens of thousands; therefore we have 40,000, and I find it does not reach quite to one of the small divisions; therefore the number stands 40,000, and not quite 1000. But I estimate it, as near as I can, to be about 2-10ths of a small division. Hence we have 40,000+800=40,800. But, if I wish to be very exact, I find, by multiplying the two last figures of the multiplicand by the last figure of the multiplier, the two righthand figures will be 96; hence I am certain that the last figure of the product will be 6 for the unit's place. I then again multiply the last figure of the multiplicand by the first figure of the multiplier, which gives me a |