DUGDALE'S UNIVERSAL CLOTHES' WASHER. BLOWING ORGANS. boxhead come into use and easily carry the box round The ingenuity of the inventor has, perhaps, been MEAN DISTANCE OF THE SUN. SIR,-By the application of Kepler's third law, as to the square of the periodical times being proportional to the cube of the mean distance of the sun, and in deducing by that law the mean distance of Venus from the Sun at 67,301,800 miles, that of the Sun being 93,014,100 miles, and the distance of Venus from the centre of the earth being the difference between these two distances, or 25,742,300 miles, the mean horizontal parallax of Venus being 31" 69854, which equals 3956-06 miles, divided by 25742300 miles. Now, the mean distance of the Sun is to the mean distance of Venus from the earth, so is the mean herizontal parallax of Venus to the mean horizontal parallax of the Sun-viz., 93044100 miles: 25742300 miles :: 31" 69854: 877 very nearly. By Logarithms-7.9686890: 7-41064866: 1:50103934: 09429990 = 8769988. VERITAS. THE WIRE TRAMWAY AT BRIGHTON. SPECIMEN OF A LINE 60 MILES LONG ABOUT TO BE ERECTED IN CEYLON.-(Described on page 228.) bring up a family comfortably. I will conclude by, RENOVATING OLD FILES. SCALE ON STEAM BOILERS. SIR,-Having charge of a number of steam boilers, I feel anxious for some information on the following important results (the boilers used are single-flued Cornish boilers):-For a lengthened period of time we have used cold water feed. The result has been, in those parts of the boilers least accessible to hand labour being for cleaning, a gradual formation SIR, I notice an article in your last publication on and increase of thick. hard, stony scale on the renovating old files by the use of the battery, I here boiler plates. In order to increase the steaming capa-with give you a simpler and cheaper method, which I city of the boilers, the owners adopted Barton's have used for a long time, and found to be a great patent self-acting feed water heater," changing the saving in the mechanics' shop. Clean the files with a feed water to a temperature of 2129. I may here men- hand brush and a concentrated solution of soda or tion that the feed water is heated by the exhaust caustic lye, placing them in a dish or water-tight steam. Since the change to hot water feed, the scale wooden box containing water, adding to the latter has fallen away from the boiler plates, relieving itself one-eighth part concentrated nitric acid, and mixing in large flakes, leaving the boilers quite free from well by agitation, then leaving them at rest for fiveincrustation or scale of any kind. I am quite at a loss and-twenty minutes; next, withdrawing them, and to understand how this occurs, and am very anxious washing them with water and a brush, replacing them for information as to cause and effect, as resulting in the dilute acid, to which is under my own particular notice. I would deem it a added a second eighth of nitric great favour to have the opinion of any one of your acid, and letting them lie for correspondents on what I consider a very important fifty minutes, then again washsubject in reference to future management of steaming and brushing, and replacing boilers. S. C., Birkenhead. in the bath, to which is added THE "ENGLISH" VELOCIPEDE. SIR-I perceive there are one or two of your correspondents that seem puzzled as to the way in which the "English" velocipede is guided, I believe this may in some measure be owing to the printer's mistake in my letter, where the fourth property of this machine In my communication about making fishing rods, is described. As it stands it reads, "the driving I made an error in stating the weight of the salmon wheels not slipping." It should be, "the driving | rod, it should have been 27oz. VIVIS SPERANDUM. wheel not slipping." In answer to "C. T. W.." p. 142, No. 2583, the machine is not guided by the hind wheel. but it is driven by the hind wheel exclusively. The guiding wheels are the front ones, on each side of the driver. In answer to "Garibaldi," p. 190, No. 3735, there is a connecting rod from the guiding wheel axle to the guiding lever. It is jointed at each end. The fulcrum of the guiding levers may be above or below the connecting rod. I have preferred it below. The cranks are set at the quarter circle. I would recommend four alterations:-Make the crank lin. longer, place the lever bar lin. further from the seat, raise the seat 2in., and bend the hand lever about 3in. towards the seat. A THINKER. DARK LINES IN SOLAR SPECTRUM. SIR,-Permit me to assure Mr. Proctor of my firm belief in the earnestness and honesty of our physicists; it is not there they fail; but I believe very obvious considerations are being constantly overlooked, simply because of their familiarity. What is more commonly observed than the gradual fading of the light of the sky after sunset; but can Mr. Proctor affirm that the received explanation of its cause is supported by a solitary observed fact? Yet Kirchhoff, patient, cautious, and clear-sighted though he was, seemed completely blind to the unsatisfactory character of the evidence sustaining it; for if he had only suspected this was something more than simply reflected solar light, he would readily have understood how our atmosphere could contain such a widely diffused element as iron in sufficient quantity to score the solar spectrum with dark lines through the light generated by its chemical combination with oxygen. The same remark applies to calcium, magnesium, sodium, hydrogen, carbon, and other elements, whose chemical combinations with oxygen are known to evolve light, and which are also constituents of the surface matter of the globe. For I hold it to be a demonstrable truth that the earth is continually receiving matter from space, which, chemically combining under solar action, generates the diffused light of the sky. The geologist gives valuable testimony upon this point. With reference to the Editorial remarks on p. 183, I have further to observe that the ordinary employment of a photographer is nothing less than a series of very delicate investigations concerning the nature and properties of light. I enclose my card to satisfy our worthy Editor regarding the profession of his guessing correspondent. T. A. COTTON SPINNING. subject, but must confess my inability to understand why such is the fact. With all due deference to his opinion, it is stated that some of our most successful spinners in the country work them; and if it be not asking too much, will Mr. Slater kindly give us his reasons for condemning them, as it is a point which I am sure the spinners of the district would be glad to have explained. Scutcher Draught.-My experience goes to prove that a down draught is as good as an up one, and an up one equally so to a down one. I prefer a down draught, as the quantity of dust tins required at a large concern not only make a room look ugly, but are often in the way. MUTUAL IMPROVEMENT. 3PORIVER 2 DRIVER is! DRIVER worm terms as I cannot bear to see a rule put into a lad's head without the reason of it, I will try to make them understand the rules that are given in books "for finding speeds and draughts." If a lad knows a rule I admit he can work by rule, but if he knows the reason of it as well he can make the rule work also; and circumstances often occur that render such knowledge SIR.-" Harmonious Cotton Spinner" has not pene- necessary. A principle thoroughly understood is trated very deeply into the mysteries of cotton spin- easily applied. To the subject, then. I told you in ning if he has not yet discovered a draught between my last that the expression "a given time," which the feed roller and lap roller of a carding engine. He occurs so often in subjects of this kind, means nothing says there is not, nor ought there to be a draught here, more thau the length of time you fix upon during and asks "of what use a draught would be?" which a thing may act, so that you may know what it That there is a draught the letter of E. Slater, will do in a long time from what it does in a short Burnley, on the same page as his own, 183, will perhaps one. I remember the expression, simple as it may convince him; as to its use, I may tell him that it is seem to me now, bothered me a great deal when I was to keep the lap stretched between the two rollers to a lad. I dare say, from the example I gave you in my prevent its bagging, which it otherwise would do, last, you would fufer that the travelling speed of any causing irregularity in the feed. His other assertion point or mark you might make upon the diameter of about there being no draught, but a "contraction" be- a wheel would depend upon its distance from the tween doffer and delivery roller, is rather inconsistent centre of the wheel or the point around which it with a statement made by him to "Factory Lad" on revolves. If so, you were right; the travelling speed draughts in the same letter, in which he speaks of a increases in proportion to the distance from the centre, draught of 125 and 2 in the draw-box of engine, which, and it is to the advantage that is taken of this plain of course, is between doffer and delivery rollers. truth that we owe all the various speeds of revolution E. Halmshaw, Gomersal, is wrong in stating (p. 183) that we have in the cotton mill, froh that which gives that I said "it is immaterial whether the bobbin leads to the "fans" and "scutching beaters' their terrific the flyer, or the flyer leads the bobbin" in the roving roar, and to the "mule" or "throstle" spindles their frame. I offered no opinion on the two methods, as whirling buzz, to that of the slowly creeping there was none called for. I merely attempted to wheel." You will observe, too, that the describe the working of the cone, sun and planet "driving wheel," "driving strap," &c., are very wheels, and reversing motion, which was all that was suggestive. A thing that is driven must be occupying asked for by the correspondent who requested an some space or position continually that another is as explanation of these parts, and I said it was immate- continually taking from it by pushing it forward out rial to the description which of the two methods was of its way, so that from this circumstance you may taken to illustrate the matter, as the mechanism was properly infer that both "driving straps" and "driving alike in both cases, the only difference being in the wheels communicate their motion upon the same arrangement of the gearing; so that when the bobbin principle. I do not mean that you must call power led the flyer, the wheel D (p. 112) would revolve in the the principle, but that the power in the two cases same direction as the wheel b, and in a contrary direc-operates, not upon two distinct and separate principles, tion when the flyer led the bobbin (for "wheel a," in but upon an identical one only in a modified manner. the sentence "which in this case revolves in the same If you will, I call the hindmost pushing the foremost direction as the wheel a," read "wheel &"). the principle. It may also have occurred to you that the diameter of a wheel and the number of its teeth correspond to each other. So they do; not that every wheel of 6in. diameter will be found to have the same number of teeth, because there are different "pitches" of teeth, but in all calculations of speeds or draughts you may either take the diameters of wheels or the numbers of teeth and they will answer as one. As an instance-a pulley 6in. diameter drives by means of a strap another one 2ft. 6in. diameter; how much oftener in a given time will the driver revolve than the driven? You know 6in. ft., and 2ft. 6in. = 5 halves, so that it must be 5 times oftener. But if the two were wheels, the driver having 12 teeth and the driven 60, then we could divide 60 by the 12, and the quotient would be the same as 5. Or if, instead I am not aware that there is any superiority in the make of the thread when the bobbin leads the flyer. The roving is more compressed, consequently a greater length and weight can be laid on the bobbin, There is also less waste made, as the roving is not thrown off from the bobbin when the end is broken, as is sometimes the case when the flyer leads the bobbin; but these advantages are more than counterbalanced by the extra power required to drive, and the extra wear and tear of machinery. B. W. R. SIR,-Draught of Carding Engine.-Our new correspondent, Harmonious Cotton Spinner," seems to understand his business. He is perfectly right in stating that there is not, or ought not to be, any draught between the lap and feed rollers; it would not only be of no use, but would cause irregular feeding in proportion to the draught or pulling out of the lap. The callender or delivery rollers should be so arranged as to take up from the doffer without being slack or very tight. If slack, the sliver probably enters the funnel lumpy; and if very tight, it would be stretched unevenly. Let the rollers take up properly, and there will not be any material draught between the doffer and rollers. This decides the question of draught to be between feed rollers and callender rollers (not doffer). EMIGRATION.-TO "F.R.G.S." SIR,-In answer to "F.R.G.S.'s" invitation, I will lay my case and wants before him. I am a clerk in a cotton mill, 20 years of age, and receiving 128. a week, and if I get 20s. a week by the time I am 25 years old I may think myself lucky. There is little prospect of getting a better situation, as there are far too many clerks already, and the profits of cotton manufacturers are so small, in consequence of the keen competition which exists at present, that they are unable to pay fair wages. Well, I think it folly to stay in England at my present situation, any longer than I can possibly help, and so I have come to the conclusion that it is not only wise, but necessary, to emigrate, though doing so will be about as painful as cutting off a limb, Draught of Drawing Frame.-There are four refor I am a Sunday-school teacher, and a member of a plies to this question, including one from myself, Christian church, and have kind parents and good page 162. The one from "B. W. R." I think is rather friends. After some consideration, I have decided to too keen in the preparing draughts. With regard to turn farmer when I emigrate, as that trade appears to Mr. Slater, of Burnley, there must be some mistake, be the best and most lasting; and during the next judging from his two lengthy communications. I three years, while saving up enough to enable me must give him credit for knowing better than equalisto emigrate, I shall do my best to acquire some know-ing the three draughts. Surely he is not in earnest in ledge of farming. What I wish "F.R.G.S." to do, is advising people less informed than himself to set this, to inform me in what part of Canada or Aus- rollers as he is represented to have stated. tralia, are lands to be had free, or at least for a nominal price, what sort of lands they are, and how to reach them. I must say that I have a decided preference for Canada at present, though quite open to conviction, should "F.R.G.S." think otherwise. I hope that "F.R.G.S." will also mention which is the most suitable climate, nor should I wish him to confine his information to Canada or Australia, but hope that he will give us the benefit of his wide, accurate knowledge, of other parts of the world, and the means of reaching them, where any working man might, in a few years, by pluck, energy, and self-denial, have a comfortable farm, or other occupation, and be able to I cannot now drop on the question of E. Habergham A voirdupois.-27 11-32 grains = 1 drachm; 16 I notice Mr, Slater's remark respecting draw- 30 в 60 12 1 16 of calling the driven pulley 2ft. 6in., we had called it 6 14 8 92 16 that 6 does to 14, or= 1in. There is another thing that I am sure must have occurred to you: it is this, that in a set of rollers it is often the case that both the diameters of the rollers themselves, as well as the diameters of the wheels by which they are geared together, are taken advantage of to produce the draught. If you have thought upon the subject even but so far as to see this fact, you may easily master it entirely; so with a few more examples I will leave the subject with you; I know you will fight it best in your own way. Look at the sketch Fig. 1:-There are 5 10 10 5 140 = ог 4 18 8 4 1- and = 1, or 1. If now you were asked to 10 give a "rule" by which the speed of the driven could be found from that of the driver, you would say, multiply the speed of the driver by its diameter, and diride the product by the diameter of the driven. But just think for a moment how silly the rule sounds-multiply the speed by the diameter! It would be just as easy to multiply a pound of cheese by a cartload of turnips. I have no doubt but that you have sense enough to see that numbers alone are all we can multiply, or multiply by. I have not forgot being bothered with this silly thing myself, and the worst of it was I had no MECHANIC to help me. However, when we say the diameter is 18in. and the speed 50 revolutions, the, 18 is the value of the diameter and the 50 the value of the speed, so that we convert both into the numbers which represent to us their value, and then we can either multiply or divide them. Now to the next pair, driver and driven. We find that the 2nd driver must make 90 revolutions, being fixed to shaft of the 1st driven, then it being 20in. diameter, and the one it drives 8in. diameter, how many revolutions must the latter make? Here, again, 8: 20 :: 90. And 90 x 20 225 20 225 20 = 225, and =-, 38 = 2, and 90 8 8 90 8 object of this example is to show you that it is not ne cessary that we should know the speed of revolution in order to find the draught that any arrangement of wheels and diameters would cause, because we are certain of finding the draught if we divide the value of the driven by that of the driver, the ratio between them being the same whatever be their speed of revolution. What is the draught, then, that such an arrangement as this sketch illustrates would cause? Let us see first what is the ratio between driver and driven; then, 16 x 20 = 320, value of driver, and 60 × 40 = 2400, value of driven; then, 320: 2400: : 1 to 2400 the number we seek, and = 75, or 7%. You 320 must observe that this is only the ratio between the values of the wheels, drivers and driven, no account having been taken of the diameters of the rollers "back" and "front." The diameters have been left out so far in the calculation that you might see clearly to which term or sum their respective values belong, And I think you will be able to discern that the surface of the front roller must be locked upon as a driven surface, and that of the back as a driving one. their diameters had been equal, then, of course they could have been left out altogether, but the "front diameter having a value of 8, or, and the back of 7, 8 or, obviously we must bring them in, and as they affect the amount of the draught in the same proportion as they affect the values of driver and driven, we can either multiply the sum of the draught by the value of the front, or driven roller, and divide the product by that of "back" one, or driver, as draught from value of wheels 75 x 8 value of front roller 7 value of 4 back roller = 8-, or we can bring them in altogether as the value of driver and driven. Thus, the value of driver is 16 x 20 x 7 = 2240, and value of 19200 =8 7 8 = 24. So the 2nd driven makes 225 revolutions. Now, driven is 40 x 60 x 8 = 19200, and then, to find the speed of the last. We have 225 revolutions and 16in. diameter driving 6in. diameter, and 225 x 16 6 again, 6:16:: 225 is to the sum required, and 600 16 600 16 6 = 600, =, or - = 23, and == 23. We have 225 6 225 now found the speed of the last driven pulley to be 600 revolutions to 50 of the first driver, 12 to 1, what then would be the draught between them? The 1st driver is 18in. diameter 56 52in. circumference, and this x 50, the number of revolutions 2826in., the distance it would travel. The last driven is 6in. diameter 1884in. circumference, and this sum × 600 11804in. Now if we divide the two sums, we must, as we already know, obtain the draught there 11304 s between the two speeds of travelling, and 2826 4. With 12 times the speed of revolution only 4 of a draught? How is this? Look at the sketch again and you will remember that the diameter of the 1st driver is 18in., or 3 times greater than that of the last driven, so that if you multiply the draught 4 by 3 it becomes 12, or in proportion to the two speeds. You will see this more distinctly if you observe that the 4 or 8-. 7 SIR.-It is difficult to conceive of any method of making a lock stitch not already tried. The shuttle to pass through the needle loop, the hook to carry the needle thread around the lower thread contained in a spool, the form and working of such hooks, spools, and spool holders, and their influence in determining the character of the stitch, deserve here special attention. Hereafter it will be expedient to give a description of some of the machines invented since 1846. Of principles, and simplicity of construction; others, the these some display great ingenuity, true mechanical have been ruined in mind, body, and estate. While these simplicity of the inventors. Many of the unsuccessful FIC.! may receive our sympathy and the successful our praise, all should consider how insignificant is the work of the best compared with the accumulated I hope now that you will fight your way labour of all. From the weavers' shuttle in the time of Job, to the English lace machine, with its many through the subject. Never mind how the wheels are shuttles and eye-pointed needles (from which Howe made to twist and turn, nor how many of them there may, or may not, have got his idea) and to the latest or may be, the principle that holds good with 5 holds best production, we trace a gradual improvement good with 50, and you may understand it if you will. -a Darwinian development. The best examples will My object in writing is to set you thinking. You will be selected, and predominate from their fitness and see at the end of my last letter I told "Factory Lad" beauty; the inferior will die out. It is well known to to divide a total draught of 7, obtained from 4 lines of the trade that some varieties have already died out, rollers, by 3, and make his draughts equal, as 2 + while others have advanced. In no particular did the 2+2 = 7. I purposely in this case left my meaning Exhibitions of 1851 and 1862 display a greater contrast obscure, because no person ought to act upon a short than in the matter of the sewing machine. In 1851 it isolated answer from any correspondent, especially was scarcely known, and the one in the Exhibition when, as in this case, the subject is a very important appeared a mere novelty. In a few years they were in one; if he does, he has no right to complain, when, general use, and were among the most interesting distoo late, he finds it out that both he and his fellow-plays in the Exhibition of 1862. Machines making the correspondent have misunderstood each other. My lock stitch, the two-threaded chain stitch, and the meaning was (from front to back) between front and single thread chain stitch, were all at work. Anxious 2nd roller, 25; between 2nd and 2rd, 169; between inventors vied with each other to please the public, 3rd and 4th, 167; or, reversing their order, 167 × 169 whose judgment was decidedly in favour of two* 2·5 = 7·05575, or something as near this order as threaded machines, especially the lock stitch. Since he should find convenient. I was once rarely puzzled then, untiring efforts have been put forward to advance by a similar answer given to me by a very intelligent the sale of single thread chain stitch machines; it has old man; however, I learnt something from it, and if been named the best stitch with unwarrantable boldyou think, you will do the same. E. S., Burnley. ness; with surprising impudence its superiority has been asserted over lock-stitch machines. A proof to the contrary is shown by an official return of the American sewing machine makers. The actual business done in the year ending June, 1867, was, for the chain stitch, by Willcox and Gibbs, 14,152; for the lock stitch, by five makers, 106,388. Thus seven and a half times more lock stitch than chain stitch machines were sold according to the American official return, and if proper returns were made for Great Britain there can be no doubt that for every single chain-stitch machine sold there would be twenty lock stitch sold. The chain stitch is easy to learn, and has such merit as to entitle it to notice, but twenty reasons to one claim for the lock stitch the preference. P. S.-If no one else answers "Oldham," 2861, I will do so, though I do not like to recommend books, as I would rather see information given through the pages of our MECHANIC; besides, books seldom answer the particular question a person may wish to ask. You will generally find anything in them but just the one thing you are fast with, and that which is worth putting in a good book is worth the space it will take up in our MECHANIC, for the sake of those who cannot come at the good book. SIR,-I am greatly obliged for the numerous answers to my question respecting the proper method of arranging the draughts in a drawing frame. I find that Mutual Improvement comes the nearest to what I have practically found to be the best arrangement, as I have my draughts at present 341 x 175 × 1·17 7:06 working "fair Dhollera." I am rather surprised at the figures given by E. Slater, for if 1 put 2 draught between each line, the total draught would be 12.64, because 2:33 × 2:33 × 2:33 = 1261; the error appears to have been made, by adding instead of multiplying together the separate draughts. With respect to" B. W. R.'s" remark on scutchers, I prefer the down draught machines, as they do their work better, and are not so clumsy in appearance. I have both sorts working, but am decidedly in favour of the down draught machines. SEWING MACHINES.-REPLY TO "S "STUDY." SIR, I am thankful for the good intention of Study" to point out one or two slight errors in my letter at page 158, but the errors, such as they are, only amount to a difference of opinion. I must acknowledge myself wrong if a-in. shuttle will make as good a stitch on boot-work as a smaller one. Finding the majority of workers on boot-work do not approve a -in. shuttle in a No. 2 Thomas, a smaller size was taken fairly for comparison. If "Study" has compared things unlike, his conclusion may be wrong, and my statement that Singer's shuttle holds most, Howe's next, and Thomas's least, is not a slight error. I quite agree with "Study" that Thomas's cam is defective. By the way, if through the ENGLISH MECHANIC the makers and blind imitators could have been convinced of this years ago, boot makers, tailors, &c., would have experienced much less trouble in their work. The question of the pause, and other matters, will be considered in due cause. Having laid down a plan for the treatment of the subject, including descriptions of a variety of machines, and comparing them fairly, so as to be interesting to the general reader, I In the development of the lock stitch sewing machine, one of the earliest attempts to improve it was to substitute a carrying for a sliding motion of the shuttle. The shuttle was placed on a horizontal working disc and revolved with it, the rounded part being supported on the disc, the face of the shuttle being curved to correspond to the perpendicular face of the frame against which it worked. In another machine the disc revolved vertically, the shuttle face being flat, and worked against, a perpendicular ring surface. This circular motion of the shuttle had two serious defects-first, it must either twist or untwist the shuttle thread; and, secondly, it nearly doubled the travel of the shuttle, whereby a grinding tendency was produced, so that the shuttle would oftener want repairing or renewing. This arrangement was a step made towards a machine displaying the very highest class of design and practical ability, known as the Wheeler and Wilson machine. This revolving shuttle arrangement has been followed by other modifications. The shuttle has been made to travel in a nearly circular form, in a recently invented machine, but with an important improvement to prevent the twisting or untwisting of the thread, by causing the shuttle to be carried around without somersaulting, by placing it on a shuttle frame worked from a supporting guide by a crank motion. The rounded part of the shuttle is supported on this shuttle frame, the shuttle face being thus kept against the perpendicular face of the machine. Instead of the shuttle reciprocating, with the least waste of movement, this plan makes it travel over a largely extended surface, which is a mechanical defect in itself, and has no advantage in working the needle thread. If a motion could be contrived for passing the lower thread through the needle thread loop without touching it, it would be perfection. The Howe system is the nearest to it, and the plan last described the most remote from it. An ascending and descending motion of the shuttle serves no useful purpose, it wears the shuttle faster, strains the needle thread, and thus limits the speed of the machine. Other machines of recent production resemble an older patent which provides for the carrying the shuttlo on the top end of a vibrating lever. This arrangement imparts a curved motion to the shuttle vertically; it rises and falls less than in the case last noticed, and is consequently to be preferred, the defects being so much reduced. An example of this class may be seen in the Little Wanzer hand sewing machine. All the machines under the class here referred to have failed to come into manufacturing or trade use-it would not pay for rich or poor to use them in trade. It may be taken as a rule that a shuttle should travel horizontally, and no more than the actual distance required for the formation of the stitch; travelling beyond it wears out the shuttle faster, as may be observed in the Singer class of machines driving the shuttle by a crank motion or its equivalent, instead of a cam. The cam movement has a special advantage over any other known plan for driving the shuttle, although in many cam machines it is not made available. When the shuttle has passed the needle loop, the shuttle carrier should recede a distance sufficient for the needle thread to pass between the shuttle and carrier without touching the carrier. Many cam machines work on this plan, and it is a decided improvement. Other minute defects or improvements will come under notice when a machine is illustrated completely. The present plan of collection, classification, and comparison of instruments for the formation of the stitch is chosen as the best method to convey the information desired. A more correct motion for working the shuttle than the class of circular moving shuttles, will now be considered. The shuttle slides with a movement reciprocating, as in the Howe machine, horizontally, but in a curved instead of a straight direction. The advantage bere gained is reduction of the wearing joints and parts for driving the shuttle. The same system has been successfully applied to work a shuttle in the end of an arm machine; the arm being specially arranged for stitching side springs into old boots, or any work that can only be stitched on the extreme end of the arm. The arm is so narrow as to admit the boot over it, with freedom to turn the work in all directions. A circular recess is formed in the end of the arm, and in it works the shuttle horizontally; on the axis of the shuttle driver is fixed a pinion, which is actuated by a rack working lengthways in the arm from a cam on the main shaft, similar to Thomas's machine. Fig. 1 represents a plan view of the end of the arm containing the shuttle. The shuttle A is shown ready to enter the loop of the Deedle thread. B is the slot in which the needle rests while the shuttle is passing through the loop. To complete the stitch the shuttle travels as far as represented by the dotted lines, and then back again for the next stitch. For the purpose intended a better arrangement cannot be conceived, but for general work it is defective as regards wear, owing to the circular surface C being so small. The part around which the shuttle travels soon wears, and then the curved face of the shuttle is not kept to frame, whereby the shuttle falls backward from the needle, and slips or misses stitcn. It also requires too long a needle thread loop to pass around its bedy, the defect of which has been already explained. It may be interesting now to notice how few of thoseimproved (?) shuttles and drivers have come into use; yet they afford a rich store of experience for experimentors. Passing from the circular movement shuttle to a better centrivance, yet still working on the same idea of a direct circular movement, a wonderful success has been achieved by the production of a machine substituting for the shuttle a metallic bobbin or spool to contain the lower thread, and carrying the needle thread around it by a rotating hook, as in the Wheeler and Wilson Machine, or by an elliptic moving hook, forming the stitch in a somewhat similar manner. Fig. 2 represents a front view, and 3 a section of the metallic bobbin or spool. It is formed of two thin metallic discs ab fixed on a brass axis c, with a hole through it which fits on the shaft of the machine to receive a rotary motion for winding on the thread, and in the space between the double convex spool. It holds 18 yards in the Wheeler and Wilson, and in the Elliptic spool 14 yards, of No. 24 cotton. Unlike the shuttle, there are neither holes nor springs to regulate the tension of the lower thread. The formation of the stitch in its pulling and straining on the needle thread is less perfect than a shuttle stitch. The needle thread is sunk well in the upper surface of the fabric and pulled below too much, where it forms a ridge. The two sides are not alike, but, while inferior to a good shuttle stitch, it is immensely superior to a chain stitch, either single or double thread, in appearance, strength, and economy of thread. The spool is held to its work and rests between a spool-ring or holder and the revolving hook which carries the needle thread around the spool. In due course the machine will be illustrated, and no doubt will amply repay a careful study of its working. A PRACTICAL MAN. NEEDHAM'S PATENT "STARTER" FOR SIR,-A description of an American invention, patented by Mr. O. H. Needham, of New York, which has for its object the removal of a difficulty wel known to workers of sewing machines, may be of interest. Although it is claimed by some machine operators that they know by the pitch or inclination of the treadle whether its movement should be up or down in setting the machine in motion, the difficulty of so doing is evident on reflection that there are four positions of the crank near the upper and lower dead centres, in which the pitch of the treadle is the same, but requires different motions of the foot to produce the movement of the shaft in the requisite direction. Consequently, after stopping, the operator, not seeing the crank, cannot be positive that it will turn the right way in starting without using the hand, or in its stead some automatic device like that under consideration. Fig. 1 shows a sewing machine fitted with the appliance, and Figs. 2 and 3 exhibit, on an enlarged scale, the appliance itself, in different positions, detached from the machine. A collar A is secured upon the rock-shaft carrying the treadles, and is furnished at one end with an enlargement or disc. Upon the face of this last, next to the treadles, is to the crank-shaft as previously explained, and of course starts the rotation of the latter before any movement has been communicated to the treadles, or through them and the pitman to the crank. As soon as the crank-shaft has thus received an initial impulse, the treadles are worked to continue the motion in the ordinary way. The movement of the slide, moreover, is sufficient not only to thus impart motion to the crank-shaft, but also to bring the pawl b into such position that by its own weight it will drop out of gear with the ratchet-wheel, to permit, without interference, the rotation of the crank-shaft. When the machine is stopped and the foot raised from the treadle, the spring draws back the arm of the sleeve D to bring the pawl in suitable relation with the ratchet-wheel to repeat its action thereon when the machine is again started, the movement of the leverarm operating of course through the connecting parts, lifting the slide B, to its original position. KAPPA. COLOUR-BLINDNESS. SIR,-As I perceive that the subject of colour blindness is one to which you have devoted considerable space, I wish to ask permission to describe my own case, which I think involves a peculiar form of the evil that has not been dwelt upon by "Omicron," in his interesting, and probably exhaustive, memoir. The peculiarity to which I allude is a tendency in my eye to see red as black, not as any intermediate shade between black and white, but as a decided black. It is not a little singular that, notwithstanding the great difference there is usually admitted to be between black and red, it was not till I was more than twenty years of age that I discovered that I had never seeu red as a distinct impression, and considering the remarks that "Omicron " has made on congenital colour-blindness, I believe I never have, and never shall see it. The way in which I discovered my defect was singular enough, and as it evidences my complete disability to distinguish red from black, I make bold to tell the "little circumstance," though it may not be thought to be of sufficient value for the pages of your magazine that are devoted to correspondents' letters. On one occasion I splashed some white material, I believe white paint, over a nearly new black vest, and as the effect was rather a disfigurement, I thought I I did so, and produced, to my eye a result that I would remedy it by covering the spots with black ink. thought infinitely superior to the speckled aspect it had before presented; but I noticed that my friends did not at all appreciate the improvement that I flatthan the rest explained to me that, in point of fact, to tered myself I had effected, and one more intimate red ink-imagine my disappointment. Since that end quickly an unimportant matter, I had employed time, I have made many unfortunate and ridiculous mistakes, and my own impression is, whatever ingenious theory may account for it, that the defect is incurable, and I have not much faith in the use of coloured glasses, or other ingenious apparatus, to cure, or at least to mitigate, the inconveniences of colourblindness. I may mention that I recognize other colours as a normal eye. I express my thanks to Omicron" for his entertaining memoir, STEAM LIFE BOAT. AN IDIPOT. SIR,-Concerning the steam life (boat to which you refer, my sentiments on the subject are embodied in the enclosed copy of a letter I had the pleasure to address to Mr. Luff on the 14th ult. I feel assured that nothing like a steam life boat has so far been invented; most of the plans merely aim at putting an engine in one of our life-boats, which is absolutely impracticable. RICHARD LEWIS, Royal National Life-boat Institution, 14, John-street, Adelphi. [COPY.] DEAR SIR,-I have your note of the 12th inst. It is most kind of you to take such a warm interest in the life-boat cause. I trust, however, that the ENGLISH MECHANIC will not, on any account, solicit contributions for a life-boat to be propelled by a screw. After mature consideration, I assure you we are of opinion that such a boat is impracticable in the present state of things, and perhaps you will also be of the same opinion if you will kindly give your attention to the following reasons, which, in my opinion, militate against the adoption of steam life-boats. 1st. That owing to the large quantity of water which must break over life-boats in heavy surfs, amounting often to three or four tons, it would be very difficult to keep the fires from being put out, and at the same time provide sufficient ventilation. 2nd. That the motion of boats, under such circumstances, is so great and violent they sometimes standing almost perpendicular, with either the bow or stern uppermost, that the propeller would work at great disadvantage, and the machinery be perhaps liable to disarrangement. 3rd. That since the space occupied by the engine, &c., would make it impossible to use oars if the former should become disabled whilst afloat, the boat would be at the mercy of the sea, and her own destruction, and that of the crew, might follow. 4th. That wherever such boats were placed, this institution would require to have a qualified engineer to keep the machinery in order and work it when afloat, with a salary sufficient to maintain him, since the fishermen and other local boatmen who now, as coxswains, for a small salary devote only a trifling portion of their spare time to keep the boats in order and ready for service, would neither have the time at disposal nor the skill to keep machinery in order and to work it when afloat. 5th. That some time would be lost in lighting the fires and getting up steam. 6th. That it would be difficult to apply the self-righting property to such boats, and if they were to remain more than momentarily keel up, the fires would be put out, or they might set the boat on fire. 7th. That the cases of failure of the present life-boats are so rare that the committee of the institution have not felt called on to expend large sums of money on experiments, which might not afterwards be attended with any beneficial results. 8th. That wherever steam tugs are available, I think it probable that steam power can be more |