requisition upon the department for battery | Gaugain could not discover that it interposed In conclusion, M. Gaugain says that Marie Davy's could be used for the work of one wire, but that its resistance is too great to have more than one line per battery. He did not find this difficulty with the Leclanche. Its internal resistance is least of all, but it polarises rapidly when traversed by currents of much quantity. M. Gaugain believes this could be remedied by increasing the size of the plates; he found the ammonia, generated when the battery is active, disagreeable, and fears that those emanations might prove dangerous, and even poisonous where many couples GLASS CUTTING. much resistance, though he experimented careHERE has, says Morgan's British Trade fully and upon the porous cups for that purpose. T Journal, been a very laudable desire of late, He found that the less permeable or less porous cups answer the best in keeping the liquids sepa- by many glass manufacturers, to make glass so beautiful in its finish when it leaves the hands of the glass-blower as not to require any ornamenBut the great demand is for tation afterwards. This cutting, cut glass, especially for table use. or, if the term may be allowed, sculptured glass, is effected as an after process, and is a separate and distinct business from glass-blowing. In the glass-cutting room there are, in most manufactories, from forty to seventy workmen. Each man has in front of him a revolving wheel, first of iron, then of stone, then of wood. The iron wheel is for the first process, in which the forming of patterns or figures upon the plain surface of the glass is effected. The stone is for cutting off the rough surface left by the iron, and the wood for polishing to a brilliant lustre. Supposing a certain pattern is designed, the workman etches it on the body of the article which is to be cut. He then holds his glass to the edge of the iron wheel, changes his hands to all the positions required for the form he wants, until the whole surface is covered, and the pattern is indented in the article. To prevent fracture from friction, as well as to accelerate the process, sand and water is allowed slowly to drop on the wheel from a Thus is the wooden vessel hanging over it. glass kept at a proper temperature. Sometimes the wheel will of necessity have to be changed to that part by which the cutting is effected, and used for the purpose. The edge of the wheel is different shapes and thicknesses are given to the edges, in order to produce different results. The stone wheel then passes over these indentations, with water dropping upon it, giving it a semi or stone emery continually used on its surface nutil half polish. Run the wooden wheel with pumice the pattern is thoroughly brilliant. The object to be attained in cutting glass is to present such a surface to the rays of light that instead of their passing directly through the glass, they may be broken or refracted, so that there may be a" play of light," as it may be termed, upon its surface. resistance in the different elements themselves. ber of wires which can be worked from or supplied ing the figure or pattern upon the exterior of the There were no researches made with the Grove, by the battery. The resistance of the wires is but we give it here as a unit to show approxi- variable, and results from imperfect insulation. glass be the reverse of the line of the interior, and mately the relative electro-motive forces of the This cause reduces the circuits, often to half, the projections left by them, be such as to form that the indentations upon the surface, as well as would be used. There were two reports made, one by the president, M. Gaugain, and another by M. Guillemin, each equally conclusive as to the results obtained by the commission. The report of M. Gaugain describes the various methods by which the electro-motive force of each element was deter mined, and, making that of a Grove cell 100, to adopt it. It requires the care of supplying suit the character of the work, many sizes being they stand as follows: Grove. Marie Davy Leclanche Daniells 100 76 82 56 56 The Commission found that the elecro-motive force of the Calland's did not decrease more than one-tenth in five months, and they think it would take a much longer period to wear it out. Gangain, therefore, believes that it would be well M. with sulphate of copper, but has the advantage of EXTRACT FROM M. GUILLEMIN'S REPORT. Which means that a Grove cell has the same strength, or will produce on a circuit 100 miles in length, the same deflection as a Daniells would on a circuit 56 miles in length; or, again, that two Daniells would produce, in a circuit 112 miles in length, the same deflection as one Grove would in a circuit of 100 miles, and so forth-of course, leaving out of question the fractions of the wires, exactly in these proportions is the num- To effect this, it is necessary that the lines form With different systems in presence. We now view the sometimes to one-quarter, and even to a smaller purpose. motive force fell from 194 on the 4th of June to 174 on the 3rd of November. It polarises very little when connected up in short circuit, weak resistance; but this feature is not perceptible, when the resistance is of the magnitude of ordinary telegraph lines. In this respect the Callaud's behaves very much like an ordinary Daniells element. presents these qualities. Daniells' battery is irregular. This is due to the rapid incrustation and deterioration of the porous cups. Marie Davy's: This battery is unfit for good service, for two reasons. When the line resistance is weak, and short circuit, its electro-motive force diminishes very rapidly, and its internal resistance increases rapidly, so, on a whole, or taking these INTERNAL RESISTANCE OF THE BATTERIES. two features into account, it loses its energy. It will, however, recover a portion of its initial force M. Gaugain says, that with the Callaud, when when the circuit has been opened for a time. The set in spring or river water, the internal resist-Leclanche polarises less rapidly than the Marie ance is considerable; but as the water becomes saturated with sulphate of zinc, this resistance diminishes. He puts its minimum value at five and a half Siemen's units, which, for all practical purposes, we may call five and a half ohmads. For the Daniells, when first set, he found as high as sixty Siemen's units, but its resistance fell rapidly, the minimum being between ten and seven units. This decrease depends very much upon the condition of the porous cup and the quality of the material. If dry and compact in its body, it is some time in becoming fully saturated. However, after complete saturation, M. Davy. Its energy is well maintained when the The foregoing reports were published about a angles. In the cutting called diamond or prism cutting, this object is at once attained. The same effect is also produced by fluting or flat cutting; because whenever two flat cuttings meet at the edge, they form an angle, forming with the line of the interior an imperfect prism. The broader the flat cuts are, the more acute the angle, and consequently the greater the refraction of light. As these flat cuts are always made with the cutter's wheel upon a circular surface, the broader the flats the more expensive they will be. The same theory holds good of all lapidary or flat cutting upon solid glass; that is, when the cutting is all over the surface. To produce the requisite effect, it is essential that whatever the due attention to this that the refraction so necespatterns, flats must be opposite angles. It is by sary to luster and chandelier work is obtained. When two or more colours are seen in the same article, it is because the glass cutter cuts off the skin of ruby or blue which has been put on by the glass blower; these edges of ruby produce a most beautiful effect by contrast with the flint glass beneath it. In addition to the cut surface of glass vessels, whereby such a lustrous play of colours is produced, there are others engraved, which is a more delicate process of cutting than that we have described. The glass engraver, seated at a bench, has before him a lathe; he has at hand a series of small metallic discs or wheels, generally made of copper, and varying from an eighth of an inch to two inches in diameter. He attaches one of those to his lathe, and keeps it in constant rotation, as in the case of glass cutting, either by steam power or by the action of the foot. He touches the edge of the rotating wheel constantly with a little emery moistened with oil, and then holds the glass against the edge of his wheel, by which the desired effect is produced. By dexterous changes in the position of the glass and in the different forms and sizes of his wheels employed, he combines the delicate indentations so as to produce beautiful intaglios or sunken pictures ; opinion of this delicate process is that it is strictly a branch of the Fine Arts, and places the glass our meu. process. SYSTEMATIC MICROSCOPIC EXAMINA TION. MR. of a drilling machine which is exciting some attention this country. The main elements of the drill are the cage, the cylinder, and the piston. The cage is merely a trough, with ways on either side, in which the cylinder, by means of a feed-screw and an automatic feed-lever, is moved forward as the drill cuts away the rock. The piston moves back and forth in the cylinder, propelled and operated substantially like the piston of an ordinary steam engine. engraver on a different level to the other work-valuable than the settlement of a diatom or Taste, both natural and cultivated, and a podura question. In the food we eat, the clothes knowledge of the external forms of natural ob- we wear, the parasites that plague us, and the On the 19th ult. a large number of engineers, jects, and great delicacy both of eye and hand, are very dust about us, there is a large field for inves- scientific men, and others assembled at Messrs. all required in this operation, and it says much tigation as a necessary preparation for other Freeman and Co.'s stone wharf, Deptford, to for the artisans of this beautiful calling, that studies, which has also an interest of its own, in to witness a series of expe iments with the rockthey were quite equal to all foreign competitors in a time when the President of the Board of Trade drilling machine invented by Mr. Charles the Paris Exhibition. Such operations as glass tells us that adulteration is but a form of trade Burleigh, and in extensive use in the United cutting and engraving afford an ample field for competition. The poor Welsh impostor gave States. The apparatus (an illustration of which the display of art knowledge and design. The evidence of her fatal deception only a short time we give) owes its origin to the gigantic enterprise reader, may, perhaps, form some conception of since, in the starch which the microscope dis- in Massachusetts by which the Hoosac Mountains the high artistic finish of engraving upon glass, covered in her stomach; and many other instances are being tunnelled. This great work, which when we inform him that one shallow dish in the might be adduced to recommend the study of com- may be said to rival the Mont Cenis tunnel, was English department of the Paris Exhibition, mon things. Our principal object, however, should commenced some fifteen years ago, under the only 7in. across, was valued at 300 guineas. be to inquire into the natural history of our own direction of Messrs. Francis and William Shanly, Another kind of ornamental manufacture is locality, the minute fauna of which has been but mining engineers, of Canada, and is expected to what is termed the crystallo-ceramic, or glass in imperfectly examined. Our shore offers every be completed early in 1874. The importance in a crustation. It consists of an opaque substance, inducement to extend research. The smaller labour of such magnitude of obtaining a drill embedded in a mass of colourless glass. A me- Crustaceans are scarcely known amongst us, al- which could be worked rapidly by power, indallion or bas-relief, representing any device though two of the most curious and interesting-duced several ingenious mechanics to direct whatever is modelled in a peculiar kind of clay the Caprella and Ammothea-abound on the weed special attention to the subject, and foremost capable of resisting the heat of melted glass. at Kemp Town, and give promise of allied species among these was Mr. Burleigh. The trials on The medallion is enclosed between the two pieces of greater rarities as a reward for search. Acorn the occasion above referred to were highly of soft glass in their melted state; the main diffi- barnacles and shore crabs are instances of strange satisfactory in every respect, and the way in culty of this process consists in so placing the metamorphosis, as are also the polyps, of which which the apparatus did its work elicited the medallion that all the air bubbles shall be ex- Laomeda obliqua and Geniculata abound. The high approval of the practical men who witnessed cluded. The glass in its molten state is dropped urn-shaped egg-cases of Purpura lapillis and the its performances. Blocks of stone, 3ft. in upon the surface of the medallion with such skill riband-like strap of eggs of Doris tuberculata thickness, were bored through in about four and cleverness, that when annealed and polished can generally be found to illustrate the extra- minutes, two men and a boy being engaged in by the glass cutter, its appearance is singularly ordinary embryonic developement of the mollusca; the work. The hole thus bored, at the average chaste and beautiful, for the white clay seen there is, in fact, scarcely a limit to the list of sub-rate of 9in. per minute, was 24in. in diameter, and within the clean and highly-refractive glass pre-jects waiting for examination. For full apprecia- the motive power was derived from a 4-horse sents an appearance nearly resembling that of tion of minute structure, comparison with per- engine, with a pressure of steam of 25lb. to the unburnished silver. This process of art-i.e., in- manent specimens is both necessary and interesting. square inch. There are five sizes, drilling from crustation of clay devices, was invented about 73 They cannot, however, be seen under sufficiently-in. to 5in. holes, and feeding from 30in. to years ago by a Bohemian. At a later period varied condition; and we may as well take an 8tin. without change of drill points. The size some French manufacturers invented medallions ancient Egyptian as a specimen man, and trust recommended for general mining is the tunnel of Napoleon in this way, which sold at enormous exclusively to the mummies in balsam which fill size, its weight being about 400lb. prices; but since the introduction into England, our cabinets; we must, instead,-as students of under an improved form, a wide extension has Nature,-follow her home, and watch her ways been given to its applicability. This incrustation patiently, as far as we can. Nothing can be known may be painted in metallic colours which will re- of the protozoa, or rotatoria, unless we examine main uninjured by the heat required in the them in life. Cyclosis in vegetable cells must in like manner be seen in life to be seen at all. The generation of the cryptogams would be really hidden if the germination of their spores had not been a subject of unwearied attention. The The drill point is attached to the by Carpenter without systematic work. The dis- The piston is rotated as it moves back and forth, structure of the Foraminifera was not demonstrated end of the piston, which is a solid bar of steel. covery of the alternation of generations was due by ingenious and simple mechanism. The forto careful study, and the knowledge of the fact ward motion of the cylinder in the trough is of the Polyps of our shores having other existences regulated by an automatic feed as the rock is "I wish simply to enter a protest against the as free swimming Medusa considerably modified cut away; the advance being more or less rapid, loss of time involved in the employment of un-known sections of insects, by Dr. Hallifax, show cutting is fast or slow. our previous ideas respecting them. The well-as, by the variation in the nature of the rock, the suitable means. Whether we use high or low It will thus be seen that powers, we should-in original investigationsthe viscera and nervous system undistubed, and-the drill point and solid steel piston alone receive be on our guard against the unconscious tendency ourselves, of well-directed work. As a concluding been fed forward the entire length of the feedbetter still-the advantage to others, as well as the shock of the blow. When the cylinder has of the mind to make the wish father to the illustration, I may mention that the stupendous screw it may be run back, and a longer drill thought;" and although we cannot be altogether free from preconceived ideas, their influence chalk cliffs, would have been incomplete without ingenious peculiarity in the form of the cuttingtale of past life, read by the microscope in our point inserted in the end of the piston. By an should be limited to the suggestion of inquiry. that systematic comparison with the bottom of edge of the drill-point, perfectly round holes are It is necessary for a just appreciation of our own the present ocean which has proved the persistence insured; thus giving a greater area to the hole, work (and that of others) that we should be well through ages not only of the laws of nature, but and a larger percentage of the powder near its acquainted with the literature of the microscope. of the forms of life. I have not chosen Patho- bottom. The regular rotation of the drill inIt is, however, already so much scattered that it logical examples, notwithstanding the pre-eminent sures the delivery of each blow at the pint of is difficult to ascertain the actual amount of know- importance of microscopic examination in Patho- greatest efficiency; each wing of the drill point ledge on any given subject, and much time is logy, as its study is scarcely within our province. striking the rock at a point just far enough in wasted in investigations which should be but past hope, however, that I have sufficiently supported advance of the cut of the preceding blow to steps in our progress. At the same time, we should not too readily accept authority on matters tie work in place of such desultory observations of the chip saves the edge of the drill point, and my opening statement of the advantage of systema- chip away the rock lying between. The yielding difficult of proof, as a false idea of the state of microscopical knowledge is frequently given, and must increase with well-directed study; and num- without sharpening, is ten times greater than is as are comparatively worthless. Our interest thus the advance of the drill point in the rock, doubt arises as to our powers of observation or berless facts which we at first pass by, unnoticed, possible in hand-drilling, where the hole is formed the instruments we are using. I may instance the structure of some of the diatom valves, may eventually teach lessons of lasting use. The by the crushing and pulverising of the rock. which, although demonstrated nearly fifteen fore Newton's intellect gave its interpretation; prism had shown the spectrum to thousands beyears ago, was, in consequence of the erroneous and, although the comparison may seem farviews of Griffiths, Wallich, and others, held still fetched, there are subjects within range of the to be an open question until only last year, the microscope which, by the exercise of thought and President of the Royal Microscopical Society reason, may still further demonstrate tho connecannouncing his demonstration of their structure tion of the infinitely great and the infinitely little, as a "new birth to the microscope." In making and assist us to know more of the life which it these remarks, I wish to acknowledge fully the has already taught begins in a germ-apparently obligations we are under to men who have the same, whether it results in the highest or laboured so earnestly to our advantage, and in lowest of organised beings. We can all make calling attention to exceptional error, I am but some advance to such knowledge by the systemaendeavouring to provoke careful, original investi- tic study of recent things, which I have engation amongst us in place of idle reliance on any authority. In the frequent intercourse of to recommend, even by tedious men engaged in a common pursuit-such as it is repetition; and I trust that by our work we may the intention of this Section to promote-lies the justify the formation of this Section of our best substitute for individual experience; the knowledge acquired by any should be available for all, and errors of solitary observation are soon THE BURLEIGH DRILLING MACHINE. corrected when brought to the test of criticism (Illustrated on next page.) and comparison. Most conducive to a true LAST week we gave an illustrated description knowledge of objects is their examination in a of diamond-pointed steam drills used for borrecent state, and an acquaintance with the appear-ing rocks, and which are exciting some attention ance of ordinary things will be found much more' in the United States. We now give a description I deavoured Society, drill strikes the rock from 250 to 300 blows per the compressed air is carried upwards of one and ENGLISH MECHANIC SOCIETY OF ARTS. EDINBURGH BRANCH. THE second monthly meeting of the ENGLISH MECHANIC Society of Arts, Edinburgh Branch, was held on Thursday evening, the 2nd of June, in the New Waverley Hotel, Waterloo-place, Mr. W. T. Williams, President, in the chair, who delivered an inaugural address, bearing chiefly on the important points to be gained by the proper carrying out of the objects contemplated in the formation of the society, and also on the amount of good its members would reap for themselves, and the benefit to the nation at large, by the careful study of those subjects brought under notice in the MECHANIC, which paper he characterised as a complete self-instructor on every point requiring technical education. After pointing out its numerous features and characteristics, and eulogising some of its contributors, he gave a number of useful hints on the working out of the various experiments and examples given weekly in its pages, remarking on the great advantage of being able to perform them, as well as understanding their theory; he himself had found much, besides saving some pounds, by trying, and ultimately succeeding in making several of the instruments, and perform the experiments given-for instance, in the series of articles on Electricity, by Mr. Sprague. He concluded by urging on all to study well, and closely aim at perfection, having no doubt but that, ere long, fruit would come forth. Esq., thanking the society, through him its founder, for the FOR NOTICE. OR years past the ENGLISH MECHANIC, though professing to be published on each Friday morning, has in reality been published on the preceding Monday. We have, therefore, been obliged to go to press on Friday evenings, or a week before the nominal day of publication. As this arrangement has occasioned no end of inconvenience to LETTERS TO THE EDITOR. [We do not hold ourselves responsible for the opinions of our correspondents. The EDITOR respectfully requests that all communications should be drawn up as briefly as possible.] EDITOR of the ENGLISH MECHANIC, 31, Tavistockstreet, Covent Garden, W.C. .*All communications should be addressed to the All eheques and Post Office Orders to be made payable to J. PASSMORE EDWARDS. I would have every one write what he knows, and as much as he knows, but no more; and that not in this only, but in all other subjects: For such a person may have some particular knowledge and experience of the nature of such a person or such a fountain, that, as to other things, knows no more than what everybody does, and yet to keep a clutter with whole body of physicks: a vice from whence great inthis little pittance of his, will undertake to write the conveniences derive their original. -Montaigne's Essays. TO SQUARE THE CIRCLE BY PRACTICAL GEOMETRY. SIR, I beg to send the enclosed original diagram, the area of a perfect circle to the area of a square. intended to represent a possible method of reducing and which will admit of the proof by means of ocular without any loss of material, all the parts of the same demonstration as a geometrical problem, and thus size, number, and shape can be identified in each. the circle can be squared, and proof of its relative The possible geometrical method by means of which After some remarks by Mr. Gordon, Mr. D. W. Kemp read a paper on Boomerangs, or Bommerengs, illustrated with diagrams and specimens. He stated that there were several varieties of this weapon, and that it was not confined to Australia, but had its representatives in various countries, under characteristic names and slightly varying forms, but all correspondents and advertisers, it has been deter possessing, in a greater or less degree, the singular property of returning within a few yards of the thrower. In Africa, mined in future to go to press on Tuesday evenings, the southern tribes have the Hunga Munga, which is a double and publish early on Friday mornings; in other curved instrument, and made of iron. The Central African tribes have the Trombash, with a curvature of double the words, on and after the 8th of July next, the Australian weapon, and also made of iron. The tribes of the ENGLISH MECHANIC AND MIRROR OF SCIENCE Desert have the Sellem, or Es-Sellem, which is made of the root of the gum arabic tree, and is straight for four-fifths of will be published at the same time as the widely-accuracy tested by ocular demonstration, is shown in its length, the point only being curved; and, unlike the preceding ones, which are all flat missiles, this one is perfectly circulated London weekly papers. In order that round. But apart from the remarkable property which this no inconvenience or disappointment may arise, weapon possesses, owing doubtless to its partaking more or less of the curve of a parabola, the great antiquity of it gives our readers will oblige us by informing their additional interest to the subject. In a mummy's hand, in the British Museum, is an ebony specimen of the Es-Sellem; and on an ancient basso relievo at Thebes, and an Egyptian slab in London, are represented buntsmen who are about to We beg also to inform our Subscribers that we throw a species of boomerang at some birds. But the most curious of all, are the sculptured slabs from the excavations have purchased the copyright of Scientific Opiof Nineveh, one being supposed to represent Nimrod, the nion, and that on the day mentioned-the 8th "mighty hunter," he holds a weapon in his hand which is proximo, that well known and high-class scientific analogous to the Australian boomerang. It is therefore singular that a weapon which was in use so many thousand publication will be incorporated with the ENGLISH years ago, should still be found in use with the aborigines of MECHANIC. Scientific Opinion has a good staff Australia and Africa. of contributors and correspondents; these, added a large number of the members took part. The secretary to our own, will no doubt materially enhance the then read a letter to Mr. Kemp, from J. Passmore Edwards, value of the ENGLISH MECHANIC. This paper led to a very interesting conversation, in which the accompanying diagram. It may be so constructed that in each different figure may be found exactly the and size-a proof that no loss of materials is involved same number of pieces, of the same identical shape in substituting one figure for the other of equal area. Divide the circle into any number of equal parts; draw reference number them; make every alternate wedge a shade darker for distinction. respective booksellers or newsagents of the con-lines from the centre to the circumference, and for templated alteration in the day of publication. Then make a parallelogram, with exactly the same number of wedges, dark and light alternately, of exactly the same size as those used in the subdivision of the circle, and transfer the same numbers used to the so-called wedges for references. The proportions of the parallelogram are made by taking half the circumference for the length, and half the diameter of the circle for the breadth, exactly. The parallelogram is then converted into the square by means of a mean proportional, and the identical parts A B C cut out and inserted in the square, which is exactly equal to the area of the circle (by Prop. XIV., Euclid, Book | II. In actual experimental trials, to make the divisions of the circle too small, and, consequently, too numerous, involves the risk of failure, and would be very tedious in the transposition of the different wedges from the circle to the square to prove the correctness of the principle by actual test, and by ocular demonstration; but, abstractly, on paper, the more numerous the divisions, the nearer the critical exactness, and a perfect identification as a curious geometrical coincidence is insured, and without loss of material. All the regular polygons have been reduced by the method indicated into perfect squares, and admit of the means of teaching by occular demonstration, geometrical propositions, and performed with great facility. To give an interest in the study of practical geometry by the mere exercise of ingenuity, may, it is presumed, exert an influence upon popular scientific education, and tend to cultivate the powers of observation by pleasing the taste. ARTHUR GEARING, Great Paris-street, London, S. FLY WHEELS OF STEAM ENGINES-ANSWER TO" STEAM SPIRIT."-OBSERVATIONS ON J. HARRISON'S DICTUM ON THE "LINK MOTION" AND "LLAH'S " ECONOMISER OR FEED WATER HEATER. SIR,-The weight and diameter of the steam engine fly wheel depend upon several considerations, of which the following are the most important-viz., the nature of the work to be done, whether it is of a regular steady character like driving a corn mill, where no sudden and violent fluctuations occur in the work, in which case a moderate-sized fly wheel will suffice, or whether it is of a variable and unsteady nature, and subject to violent and frequent alternations, like that of a rolling mill, in which case a very heavy fly wheel is indispensable. If the engine works very expansively it will need a much heavier wheel than would suffice if it is worked with little or no expansion. If it is a double cylinder engine with the cranks set at right angles to each other, and working with short expansion, a much smaller fly wheel will do than would be required by a single cylinder engine of equal power, and equal length and number of strokes. A compound engine will do with a much less fly fly wheel; in this case, as the piston approaches the end of each stroke, its power falls below the mean necessary for driving the mill, and the millstones become the drivers of the engine till the crank passes the dead centre, when the piston again becomes the driver; thus twice in every revolution of the fly wheel is the order of driving and driven reversed, causing a terrible racket in the gearing, and great wear and tear in all the parts concerned. The obvious cure for this state of things is not a fly wheel of a certain diameter, but one of sufficient weight to cause the engine to continue in motion for a few seconds after the millstones would have ceased moving by their momentum. The order of driver and driven would then never be reversed, and back lash could not exist. FIC.I wheel than a single cylinder engine, of equal power and equal ratio of expansion, on account of the pressure exerted on the crank-pin being in the former case more uniform than in the latter, and therein consists the only advantage possessed by the compound engine over the single cylinder engine; in every other circumstance and aspect of the comparison of the two systems, the single cylinder engine has a decided superiority over its rival, and the delusion that has sprung up within the last few years in their favour, and the revival of a system which was tried and exploded 60 years ago, is most extraordinary and unaccountable; the only case in which it has a shadow of advantage is in screw boat engines, where a fly wheel is inadmissible or impossible from want of room, but in every other situation where a sufficiently heavy fly wheel can be adopted with the single cylinder expansive engine, it is beyond all comparison the bèst and most economical in first cost, in fuel, in lubrication, in friction, in wear and tear, and in repairs. No rule can be given for fly wheeis which can take in all the above circumstances, and practical men are seldom guided by mere" book rules" in this matter, but rather consider, and very properly so, the circumstauces of each case in themselves. A very absurd idea with regard to fly wheels for should move faster than the periphery of the mill corn mill engines is that the rim of the fly wheel stones to prevent "back lash"; this old tradition, which has been handed down from generation to generation of millwrights, and accepted without question as an "infallible dogma," is like many other traditions we know of, "false and absurd" and without foundation in fact or theory. What is back lash? It is the tendency of the driven parts of machinery to over-run the driving power, and thus cause a nasty rattle and jar among the teeth of the wheels concerned, and the mere diameter of the engine fly wheel in a corn mill has nothing to do in causing or curing that. When the steam is shut off in order to stop the mill, if the engine, owing to the want of sufficient weight and momentum in the fly wheel, has a tendency to come to rest before the millstones, then the latter become the drivers of the former for several revolutions, and" back lash" or back action of the teeth of the wheel ensues. The same thing occurs if the engine is working very expansively and has but a light There is no rule that I ever heard of which will give the proper dimensions of the fly wheel for such cases; experience alone, and a judicious use of the "good old rule of thumb" are the only guides the practical man has to fall back upon. Nevertheless, some sort of rule is useful as a starting point, or, for what we may call normal cases, such as where the work to be done is regular and uniform, and the engine not working with much expansion, as is the case with the majority of low priced non-condensing engines "Steam Every book on the steam engine contains a rule for the fly wheel, but I shall not trouble you or Spirit" with the repetition of any of them here, as no two of them agree, and all lead to different results, and, as I presume, what he wants is a verbal "rough and ready" approximate rule, easily remembered. I therefore give him the following rule,which he will find useful in a majority of ordinary cases. Let the diameter of the rim be equal to eight times the length of the crank; let its breadth be equal to one-twelfth of its diameter, and its thickness equal to two-thirds of its breadth. This rule pre-supposes the usual proportion of stroke of piston to its diameter-viz., 2 to 1. Mr. J. Harrison (in No. 268, reply to query 2639), in laying down the law for J. W. Bedford's information, about the link motion, says, "When they are properly set the links ought to vibrate on the valve spindle or stud without imparting any motion to either spindle or stud, when his lever is in the centre notch." This condition is impossible of attainment, and if it could be attained would be utterly useless as a valve motion, instead of being the "perfect curve" Mr. Harrison supposes. The function of the link motion is two-fold viz., that of reversing the engine, and that of cutting off the steam at any required part of the stroke within certain limits for expansive working; for this latter purpose the slide valve must always have some lap, and it is the custom with all engineers to give it some lead also; now if the lap and lead be added together and multiplied by 2, the product is the amount of vibration that the middle of the link should have, and it must have that amount and impart it to the valve spindle too, and if it does not do so it is all wrong. Suppose the valve has 14in. of lap, and in. of lead, these together make 14in, which, multiplied by 2, gives 3in. as the proper amount of vibration, for the middle of the link for such a valve. The impossibility of constructing an ordinary link motion which shall give no vibration to the middle of the link is illustrated in the annexed diagram (Fig. 1). The circle is the path described by the centres of the is only necessary to consider their centres); these are eccentrics (the eccentrics themselves are omitted, as it set diametrically opposite each other, and at right angles to the crank C, that being the position in which they will impart the least possible vibration to the centre of the link. The eccentric rods are 3ft. long, the diameter of the circle described by the centres of the eccentrics is 8in. and the length of the link is 16in. from centre to centre of eccentric rod ends. The full dark lines show the position of the rods and link when the crank is on the back centre at C, and the dotted lines show their position when the crank has made half a revolution and arrived at C'. The whole body of the link is now in a position exactly parallel to its first position, but there is a distance of 2in. between the two positions; this is owing to the crossing of the eccentric rods in the latter position, which shorten the distance between the shaft and the link; this crossing of the rods is an unavoidable necessity of the case and involves the condition of motion at the middle of the link, in the present case as a minimum. If this link motion be employed to drive a valve Ws ap is in, and lead in., which together make bed by 2 give 4in. as the least disarc w uch shout intervene between the two posiLavas of the liak, and this in. is the minimum amenat of vibration which the centre of the link shald have when working, and to obtain that the centres of the eccentrics must be shifted round towards each other to a position lin. in advance of the diameter line they at present stand upon. The belief that the middle of the link has no motion sad should, if properly constructed, have no motion, as Mr. Harrison says, is not peculiar to that gentleman, for strange to say, it is very common amongst work. ing engine fitters and erectors, and I have even met with several foremen who, from their position, one should think ought to know better, who were firmly grounded in the same faith, although a single glauce at any link motion when working should be sufficient to disabuse their minds of such a very palpable error. On page 181, No. 268, May 20, a feed water heater is described and illustrated, "for general information to Manchestrian' and others," by "Llah" (this word when transposed will spell "Hall," probably the gentleman's name). He says that "This very effective appliance or economiser will heat the feed water to within 10 degrees of the steam in the boiler." The fallacy of such an assertion cannot be too widely or too promptly exposed, as from the very tempting promise held forth others might be induced to construct similar economisers," with the certainty of being disappointed by their performance, for it is physically impossible that any water heater, deriving its heat from the exhaust steam, can raise the temperature of the water passing through it to within 10 degrees of the steam in the boiler. I mean the boiler of a noncondensing engine, which" Llah's "is, or it would have no waste steam pipe. The temperature of the waste steam escaping from a non-condensing engine is 212 degrees or so, and that is the maximum of heat which it can impart to the feed water passing through it, but as a matter of fact it never does do so by many degrees; however we will give Llah's' effective appliance" the benefit of the doubt, and admit that it does heat the feed water to 212 degrees, then if to that we add 10, the number of degrees which "Llah says it is short of the heat of the boiler, we have 222 degrees for the heat of the steam in that vessel. Now what is the pressure of steam whose temperature is 222 degrees? Why just 186. per square inch abore a perfect vacuum, or 3lb. above the atmosphere. Will "Llah kindly tell us if his engine works with steam no higher than 3lb. per square inch ? But as yet I have said nothing about the "latent" heat of the steam, and have only spoken of the "sensible" or thermometric" heat, for as I infer from "Llah's letter, it is very likely that it is the only heat recognised or understood by him. I have, there fore, in the first instance, taken it by itself, to show that steam in the boiler only 10 degrees (sensible heat) hotter than the waste steam escaping from the engine can have no efficiency or moving force in the non-condensing engine, and it is only equal to 3lb. per square inch above the atmosphere. But I must now add to the 222 degrees of "sensible heat of such steam, its 958 degrees of "latent heat,' making in all 1180 degrees as the "total heat," and the heat of the feed water being at most only 212, we see that it is 968 degrees short of the heat of the steam in the boiler instead of 10 only, as imagined by "Llah." I have hitherto taken it for granted that the "economiser" in question raises the feed water passing through it to the boiling point 212 degrees, in order to try it under the most favourable aspect, but I am very far from believing that it will do any such thing, and I will give you my reasons for the faith that is not in me respecting it, The engine is a 14-horse power noncondenser, and if it works without much expansion it will require about 14 cubic feet of water per hour for steam, or 24192 cubic inches. The heating pipe is 14in. in diameter, or 176 square inches area, and if we divide 24192 by 176, we get 13745 lineal inches per hour, or 229 per ininute, as the rate at which the water passes through the heating pipe, which is 18ft. long, or 216 inches; this gives 56 seconds as the time that the water is in contact with the heating pipe, a time totally insufficient in my opinion to raise it to the tem perature of the waste steam surrounding it. The above calculation is founded upon the supposition that the water travels regularly and continuously through the pipe to the boiler, and is the most favourable view of the case, but if the boiler is fed intermittently, off and on, as is often the case, the water must be driven more rapidly through the pipe, and will consequently be a shorter time in contact with it, and of course pick up less heat with it. There is no appendage of the steam engine which is, in general, less understood than the feed water heater, and the benefit to be derived from it is always over-rated, "the inevitable 25 per cent" is the least saving ever promised by the patentees and inventors of these contrivances, and many of them in their utter ignorance of the scientific principles of the matter go in boldly for a saving of half the fuel. The utterly delusive nature of these promises become apparent when we know that from the very nature of the case, a saving of less than one-fifth of the fuel is the greatest that can possibly be obtained, for if the original temperature of the water be 329, and it is raised to 212 by the "Economiser," we have 180° saved, but to raise this water into steam of only atmospheric pressure, requires an addition of 966 degrees more, or 53 times the amount saved, and that is all that can be done by heating the feed water before entering the pump; thus it appears that — heat escaping from the waste steam pipe is all that can be utilised, and the generality of "economisers" do not even do half that, and their efficiency may be taken at 1-8th or 1-10th of fuel saved. 1 5:3 of the The most efficient" economiser" I know of also fortunately happens to be the most simple and cheapest it is illustrated in (Fig. 2). It consists of a small cistern A set up in close proximity to the waste team pipe B, and elevated a few feet above the pump, a small pipe C is introduced into B in the manner shown, its outer end turns downward and dips 5 or 6 "T. A." his own account, but I wish he would not put non- RICHARD A. PROCTOR. I do find that, right away from the first emigration movement at Babel, that emigration and agriculture have been the means of placing food in the mouths of the hungry, and prosperity and independence in the possession of all who would or could go where land was to be had for little or nothing. With these thoughts I have recently reviewed the various emigration fields presented to our notice. I look upon the Australias as too distant, Canada as atlicted with a severe winter, and the South American States, though possessing a flue soil and climate, yet with another language, and the governing powers being in the hands of a foreign race, where Englishmen would not feel so much at home as elsewhere. Then we have the United States to consider. There we have our own language, and laws equal and in some respects superior to those of England, with an extent of climate from a Canadian winter to a tropical summer, and midway between these are a few states destined at no distant day to be in the line of the overland route to Australia. The states I allude to are Nebraska, Colorado, and Kansas, the latter of which I think to be the best. Kansas is somewhat larger than the whole of England. It contains 81,318 square miles, but at present only 48,318 have been surveyed. The educational machinery of the United States is, I think superior to that which we are discussing at the present time, and Kansas, though a young State, has taken advantage of its benefits, for there are now 953 schools, with 45,150 pupils; besides these schools there are eleven or twelve universities, colleges, and institutes. In this State alone there are 14 dol. to 4 or 5 dols., and land not like Canadian land, but principally prairie land, where its first year's crop which costs more to clear it than its original price, will frequently pay all its cost. It is indeed so prolific that at one of the agricultural fairs there were exhibited potatoes of five and six pounds' weight, turnips of nine pounds' weight, and cabbages of thirty and forty pounds' and a gentleman who lived at Kansas I happened :o see in England a short time since said out first; he sowed it and found radishes nearly as he took some radish seed with him when he went large quantities of apples, peaches, and grapes are thick as his arm. Fruits also thrive abundantly; produced. Then, with regard to minerals, iron has marble has been met with, and limestone of various been found, coal is being mined in several places, and colours, from a red tint to a fine cream colour, is abundant. And we must bear in mind that all the minerals belong to the freeholders, and almost every person can become such under the Homestead or Preemption laws, and I believe one-eighth of the population are freeholders. These laws contrast so favourably with our own that in them I think I see one cause of the rapid prosperity of the United States. Then with regard to labour, I had before me a week or two since the Missouri Democrat, published at St. Louis,date April 6, 1870, when amongst others I saw an advertisement for a timekeeper for a mill, wage 90 dollars per month; same paper, boarding-house list, board 44 saving than most timekeepers have here. to 5 dols. weekly, leaving rather more margin for EMIGRATION.-TO "COTTON CLERK." SIR.-Under the above I have read several replies to queries respecting emigration; some are extol-millions of acres to be disposed of, at prices from ling the colonies or the continent of South America. more than anyone having South American experience With your permission I will endeavour not to state can endorse; mine is based upon some ten years exresidence in various parts, from Buenos Ayres to Pernambuco, which is in and out of the Tropics. Although it is some years since I returned from the River Plato, and from all accounts I glean up to the present, it is making rapid progress in colonisation, the River Plate than in Brazil, since the Argentine there are, in my opinion, greater facilities offered in Government has for years encouraged such, and now there are to be formed settlements apon its plains of nearly every European nation's children, but at the its lack of wood and stone, and together with the same time, this republic has serious drawbacks, from droughts, which are periodical, also the utter want of hill and dale, which in Brazil are perhaps too frequent; yet the great objections of the absence of timber and stone are over-supplied in the adjacent empire. I can speak with a greater degree of confidence of the latter since I returned from there since last Autum n. South of the City of Bahia is a rich fertile country, all along the coast, well watered by endless rivers, and and fresh, to say nothing of wild game and fowl. an abundent supply of wood, stone and fish, both sea Grants of land are easily obtained from the provincial governments, either given or purchased, but in either case there are difficulties to encounter, since the exact spot is not given, and also the district may not be tending to make this country his future abode should suitable as regards soil or locality. Everyone inchose a spot where there is a river (navigable for canoes the whole year round) close at hand, or he by having to make a road through a dense wood, may find his means of arriving there greatly increased streams are to be met with in most localities, which are preferable to the main river. Anyone going out should first remain a short time at one of the small he can about the various localities in the neighbourtowns on the coast and gather there what information formation cannot with any degree of correctness be hood, by going to one of the large seaports such inobtained, besides the expenses of living are much increased by living cities, even for only a week. I know most of the small coast towns from Bahia to Rio Janerio, some 750 miles, having visited them. understands Portuguese how can he get along? I was But again, unless the intended emigrant speaks and of my own language, nor had I an opportunity: my some three years in Brazil and never spoke one word Indians and slaves. There is one great trait in all the companions were for the greater part of that time natives' characters, they are hospitable to one and all. It is true that food, such as they are accustomed to command, is plentiful, and costs next to nothing, but such is very unsuitable to our European palates. I and farinha," such as forms the staple of their living. was six weeks before I could eat the "jerked meat There is plenty of wild game, fowl, and fresh fish, such. There are thousands of difficulties to be met but Europeans have not the experience of catching with that none but those that have been among these people would ever dream of. All our everyday conbread, butter, potatoes, nor beer; there are thousands diments of food are not to be met with, there is no the commonest bread or even have the most remote in Brazil that live and die, and never see a piece of idea of how such is made. comer has to put up with are such as to make all who eighteen months since I sat down to a dinner where a J, G. best my views on emigration with regard to the The authority I have for these facts is not obtained from any railway agency or land jobbing company, but I have lying before me the report of the General Land Office for 1869, published at Washington under the authority of Joseph S. Wilson, Chief Commissioner, who, I may say, has written a letter to a friend of mine, in reply to a few questions, wherein he says the size of the country is so vast, and its domestic that Englishinen will be heartily welcomed, and that exercise of the most diversified labour and skill. wants so numerous, that there is ample room for the Now, with these facts before us, a few working men at Mile End have united together, aud done what the Rochdale men did long ago, put their pence and shillings together, only we do it for the purpose of forming a Co-operative Emigration Society. We have at present no capitalist amongst us, only bona fide surely. If any brother mechanic wishes any further working men, and we are progressing slowly but information I will reply to the best of my ability. J. D. ROGERS, Bruce-road, Devons-road, Bromley, E. COTTON SPINNING. draughts in a drawing frame, when taken in connection SIR,- The question raised by "Factory Lad" on with the doubling, is about one of the most important a good or bad arrangement of the draughts and that occurs in the whole range of cotton spinning. On doublings depends in a great measure the goodness or badness of the yarn when finished; any defect here affects the whole of the subsequent processes through which the cotton passes, and is very materially felt in the spinning frames, where the attenuation of the thread is carried out to a great degree: so that at this stage of the work it is of the highest importance that the setting out the different draughts so as to obtain the best judgment and the greatest care should be used in best results. For ordinary work there are generally three heads of drawing to what is called a drawing frame, each of number of ends or slivers-say 6-from the carding which is furuished with 4 lines of rollers; a certain engines are put up side by side at the back roller of the first head; in passing through the 4 lines of rollers, these slivers are drawn out or lengthened, so that the 6 slivers are reduced in thickness, aud form jointly a sliver of about the same thickness as one of those put up at the back; 6 from the first head are then put up at the back of the second head, and reduced by drawing as before to 1 silver; 6 from the second head are put up at the third or last head, and reduced to 1 as before. From a consideration of these processes it will be evident that the sliver from the last head is doubling of 216 of the slivers from the engines. made up from 216 slivers, or, as we say, there is a assuming, for the sake of illustration, that the sliver delivered at the last head is the same weight, for an equal length, as the engine sliver (although in practice in the operation, it will also be evident that each this is seldom the case), and that there has been no loss sliver from the engine has been drawn out or elongated to 216 times that of its original length at the engine; Now |