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The Editors are not responsible for the Opinions expressed by their Correwondentt Printers' Ink in the Sale of Patented Articles An Important Suggestion MESSRS EDITORS :I want to make some complaint about the manner in which patented articles are introduced to the public, and to point out a remedy In the first place, nine tenths of all " the people " are totally incapable of understanding the principle of a machine, more complicated than a crow bar That we cannot help Our only remedy lies in presenting an article with a full explanation, and explicit directions for using, applying, etc Retail hardware merchants sell a great many patented articles intended for domestic use Now a hardware merchant is liable to be a natural mechanic and to be able to explain the uses of his goods, but he is a good deal more likely to be utterly wanting in these qualities and is usually content to sell a machine with as little comment and instruction as he would a nail rod He tells the purchaser " They say' it's a tiptop thing and works nice I don't exactly understand how it works, but I guess you'll have no trouble ; any way if it don't work well, you can bring it back" So the customer takes it,and just for the want of a little printers' ink (which should always accompany an article of this kind, in the form of explicit directions) lie fails to make it work, concludes it is a humbug, tells all his neighbors so, and takes it back to the merchant (who is selling on commission), and the fate of that invention is decidedin that community at least It has been my good fortune to save from disgrace many a really good article by explaining to its possessor its principle I was visiting a friend in the country a short time ago He had j ust brought home a patent arrangement for holding the sickles of reapers and mowers while grinding theman arrangement with four distinct motions to adjust the two bevels to the stone We tried to apply it properly to the grindstone frame We worked at it without the Iea3t real success for a long time and then searched through a file of agricultural papers to find the advertisement and get some instructions from that Now I will tell you in the strictest confidence what I found, and you can imagine how I felt In plain type and good English, this was the explanation: " It is so simple that a child can understand it" In one sense that was true, but there should have been added"after it has been explained to him" I also found in the agricultural paper one of those abominations by courtesy styled engravings It represented the grindstone, complacently but evidently grinding off the point of the " section" I remarked to my friend " If this was a SCIENTIFIC AMERICAN engraving I could set your " grinder" without a word of explanation He thought we had better let it go, and he would carry it back ; but I was spunky and saw some good points about it The result was that we conquered it,and he was delighted with its working Now I could tell anyone in a few words how to set that kind of a grinder ; but bettor than that I could write it, and any printer could print it, and then if a copy was furnished with each grinder everyone would know how to use it Wouldn't that be better than to send the machine out as a sort of Chinese puzzle ? Wouldn't the inventor or manufacturer make more money, and wouldn't the public be benefited ? Of course we who read the SCIENTIFIC AMERICAN, know that an inventor cannot make half as good use of his money as to have his invention engraved and explained in your paper simply on account of the widespread advertisement which it gives his invention ; but when we consider that he can have the engraving electrotyped, and can copy your explanation into his circulars, the benefits become immense, and I do not doubt but it would in thousands of instances quadruple the profits, to say nothing of the benefit which would accrue to users and consumers by thus having a good article presented in a good manner M S BAXTER Aurora, 111 Variations oV Chronometers MESSRS EDITORS:Traders on the west coast of Africa, and perhaps on the east coast, sometimes experience inconvenience, and sometimes loss, from the " loss of rate" of their chronometers in the tropics of that region Occasionally good instruments that are perfectly reliable on other voyages, on approaching these tropics exhibit signs of perturbation, very marked, and hitherto unaccounted for so far as the writer knows These variations cease altogether when that locality is left behind, and cases are known of variation of rate on that coast, with a precise resumption of the true one on approaching our own Marine chronometers sometimes, and perhaps generally, have steel balance wheels, and the presence of these may account for the troubleof at least some of the employes of the writerin the temporary loss and often resumption of the " rate " of their instruments The magnetic, status of central Africa is believed to differ from ours, and a magnetic power in the balance wheel would ' at once produce there a marked variation of " rate," and account for the occasional embarrassments hinted at The proofs that this is soassuming only a difference in magnetic conditions of the two coastsare not wanting A fine old English watch with a steel balance recently dis j covered to be magnetic (a magnet) is in possession of the ! writer of this article, to the beats of which a delicate needle I responds, when properly placed, with certainty and precision, swinging1 around half the circle and returning with the movement of the wheel A chronometer circumstanced like this watch would probably lose its " rate "however good it might, otherwise b on any other magnetic meridian than that of its rating, and perhaps would do so in simply a change of position The variation, however, would doubtless be influenced ^y the length and rapidity of the swing It will be seen that if the north pole of this " swinging magnet " should be placed north, the vibrations would be shortened, and the instrument would gain time; if south, they would be prolonged, and time would be lost Thus no true rating could exist A ^ A Simple Pendulum MESSRS EDITORS :The compensation pendulum rod you give in your issue of August 7th, is not new I have had different arrangements of the lever to accomplish the end ; one of which you give I have an arrangement of a single lever at the top of the rod, but it also requires three rods, which are unnecessary Inclosed I send you a diagram of a plan I prefer to all others It is decidedly the most simple in appearance, if not in construction The rod is composed of a steel rod in a brass tube At the top a thin washer is put between the rod and the tube; the steel rod, the washer, and the brass tube are then firmly soldered together, a a are continuations of the steel rod ; cb d are levers pivoted to a at b ; the brass tube is pivoted to levers at c The length of levers from b to d, and from b to c, are as the expansion of brass to steel The bob rests on points, d Fig 2 shows a plan by which a clock can be regulated in the face and without stopping, a is a screw with a square head to which the rod is attached, and slides between the sides, b At c is a nut resting on b, which projects a trifle through the dial to allow turning Philadelphia, Pa DAVID SniVE 0 im m Treatment of Corns MESSRS EDITORS:The treatment you indorse for corns, perhaps, is well enough if you decide to retain them and nurse them I cultivated them some twentyfive years, but came to the conclusion that they were neither profitable nor comfortable, and resolved to abandon them The way I did was to have a pair of lasts made which were the shape of my feet; thus instead of fitting my feet to the boots or shoes, the boots or shoes were made to fit my feet, thereby saving the misery of " breakingin " a new pair The result has been, that for the last three years I have not found the least inconvenience from corns ; in fact they have abandoned me with apparent disgust No traces of them are left F W B [Our correspondent is perfectly right If people would begin sensibly, and wear only such shoes as fitted their feet, they would never be troubled with corns Neglecting to do this, the disease penetrates so deeply that the slightest pressure brings on irritation and pain The writer of this has suffered very much from corns, and has patronized all sorts of remedies, even resorting to the professional quackery of a corn doctorbut all to no purpose, until he found a shoemaker who was not only willing but competent to fit the shoe to the foot The shoe is now made wide enough to allow abundant room for the toes and toe joints ; all the annoyance of corns, quackery, and specifics is done away with Such is the writer's experience But for nursing purposes, the lemon application is goodEDS Wanted a Substitute for the Present Method of Branding Cattle MESSRS EDITORS :I will venture to ask that you or some of your able contributors, through the medium of your columns, recommend (if there be such) some chemical agent (safe pnd convenient for usu by all classes) with which horses or cattle may be permanently and legibly " lettered," " numbered," or ' branded," and whereby the barbarous style of burning the legal marks of ownership on or into them with red hot irons may be superseded Our grazing grounds extending from the Sabine to the Rio Grande, and from the Gulf of Mexico to Elpasso, are in common" The cattle of a thousand Mils," roam without restraint Hence the application of some indelible mark of recognition by which the property of different individuals may be distinguished is indispensable Yet it is a matter of great doubt whether the geographical munificence of our range nr the " abundance " oi our flocks, or herds warrants the maintenance of a system at once prodigal and inhuman The suffering of animals directly induced by this process of fire branding is often but a tithe of its future results For the sore left by the burning iron serves both as an irritation and an initial point of opeiations for the murderous " screw horn "the peculiar pest of our latitudefrom the ravages of which thousands of stock of all classes die here annually In the hope that some means may be devised, or suggested, whereby the severities of the merciless necessity for branding can be mitigated, and its purposes as well otherwise subserved, I have written N L NORTON Clinton, Texas On the Flow of Elastic Fluids through Orifices or Pipes MESSRS EDITORS :In the article under this head appearing on page 50, current volume, and taken from the London paper Engineer, appears a serious mistake in the reasonings and conclusions, and consequently in the result of the calculation, which it will be necessary to correct, as those investigating this subject may be led astray by the erroneous rule prescribed there The rule I refer to is, that in order to find the velocity with which gas or steam will flow from a vessel in which it is confined under higher pressure, into a vessel in which there is a lower pressure, we must calculate just the velocity with which it will escape from each vessel into a vacuum, subtract these velocities, and the difference between them will be " the velocity with which steam will flow into the lower pressure" This rule is entirely wrong, as I will demonstrate In the article referred to, is the following pneumatical standard law, nearly correctly stated, in italics: Gases and vapors will flow into a vacuum with the same velocity that a body would acquire in freely falling through a space equal to the hight of a homogeneous volume of gas or vapor of the given pressure and density When calculating this hight it is found that it is the same, whatever be the pressure and density of the gas we are dealing with, if only the temperature be the same Let me illustrate this by an example: Suppose we have common air, which, at the pressure of 14 lbs per square in weighs 0*08 lbs per cubic foot, its pressure on a square foot must then be 14^ X 144, or 2,088 lbs; the hight of a uniform volume of air of this weight and of one square foot section would be equal to 2,088 lbs, divided by 0'08, or 26,100 ieet Suppose now again we have air at four times this pressure, therefore 58 lbs per square in, which, at the same temperature, according to Mariotte's law, will weigh 4x0 08, or 0*32 lbs; its pressure on a square foot will be 58 X 144, or 8,352 lbs; and to find the hight of the uniform volume of air of this weight we have this time to divide the 8,352 lbs by 0'32, which also gives 26,100 feet The hights being the same, bodies falling from these hights will acquire equal velocities, and we see then that it is a necessary consequence of the standard rule and of Mariotte's law, that the same gas will flow into a vacuum with the same velocity whatever be the pressure and density under which it is confined, other circumstances being equal The simple cause being, that the increase in pressure is compensated by the exactly corresponding increase in density, which practically retards the flow It is therefore clear that a substraction of the two velocities, first calculated separately, cannot be the correct rule, as it would lead to the absurd conclusion that there being in the above case no difference in the velocities it would not flow at all from a vessel in which it was confined under four 'atmospheres pressure (or any other pressure which we may suppose) into the atmosphere The true way of calculating is to substract first the two pressures before calculating anything else, and then find the hight of a volume of homogeneous vapor or gas, exerting by its weight the same pressure on its base Applying this rule to the case referred to (page 50) of a steam cylinder with a pressure of 20 lbs and a condenser of 5 lbs, we find the difference 15 lbs, and a homogeneous volume of steam of this pressure would be equal to very near 43,264 feet, and a body falling from this hight would acquire a final velocity of nearly 1,679 feet per second ; therefore the true velocity with which steam of 20lb pressure will flow from a cylinder into a condenser where there is only 5 lb pressure, is 1,679 feet per second in place of only 367 as calculated by the London Engineer, and reprinted on page 50 of this volume of the SCIENTIFIC AMERICAN P H VANDER WEYDE, M D New York city The Lowell WaterWheel Test MESSRS EDITORS :Inclosed you will find a sample of the numerous letters that I daily receive in regard to the test of turbine waterwheels at this place The test is creating much interest from one end of the country to the other I can not give the information required, because, at the beginning of the test, it was agreed not to publish or make public the results until all had been tested, as it might deter some from testing their wheels if the first gave good results Only the Swain wheel has been tested, the others had to prepare alter that was tested, as that was the opening of the test, and the conditions were not settled until that time When the others commence all will probably be ready to take their turn The Bodine Jonval will probably be the first and very soon When the test is completed a full report will be made up for the SCIENTIFIC AMERICAN, and published free to all, so far as I am concerned, I have no knowledge that the report will be published in 119 pamphlet form I require no money for information that I I can give ; correspondents will govern themselves accordingly JAMBS EMEESON Lowell, Mass When Doctors Disagree Wlio Shall Decide 1 MESSK 8 EDITORS :I have read your article headed " When Doctors Disagree Who shall Decide 1" in the issue of August 14th, respecting Prof Horsford's method of manufacturing acid phosphates so as to render them useful in the making of bread At the close of this article you say : " The celebrated Liebig has stated that the nutritive value of ordinary flour is increased ten per cent by the use of Prof Horsford's phosphatic bread preparations" We can truly say " when doctor's disagree who shall decide," for Prof A J Bellows, late Professor of Chemistry at Harvard, in his book recently published in this city, entitled " How not to be Sick," and in the " Philosophy of Living," distinctly asserts that this same preparation of Prof Horsford's is " poison !" that it is simply phosphorus disorganized, made from calcined bones, and, as such, as dangerous to use as any other poison, and should, of course, never be used On the, contrary, phosphorus as organised in our food as it grows (wheat unbolted, etc), is the only form in which it can be taken with safety " Who shall decide V B H J Boston, Mass Another Invention Wanted MKSSBS EDITORS:Often during dry hot summers we have to witness the destruction of our corn by drought on the banks of streams, with water flowing by in waste, sufficient to Biake corn in abundance We need machinery to raise the water out of the streams and apply it on the adjacent fields of corn There are generally no falls in the streams to raise water by dams for irrigation Here is a fine field for inventors to benefit a large farming interest and themselves also The machinery must be light and of easy transportation, adapted to horse uovver for small farmers, and not too costly, as it may not be necessary to use it every year On many of our rivers the lands are highest at the banks, with a gentle slope across the bottoms to the foot of the highlands, and water raised to the top of the banks would flow across the fields We hope inventors will take this subject into consideration and help us MAKY FABMEBS Indian Springs, Ga Importance ol' Smooth Edges on Cutting Tools MESSES EDITOBS :Allow me to say a few words more an regard to serrated, or roughedged instruments, intended as cutting instruments I am fully aware that some hold the idea that an absolutely smooth edge cannot be attained It was not the intent of my former article, neither is it now my intent to discuss imaginary, or theoretical cutting edges ; but will state that if an edge cannot be attained smooth enough so that a saw edge will not appear, nven under the most powerful microscope, then the theory that an absolute smooth edge cannot be attained is established It is also established that the first series of notches has notches also, and so on infinitely The object of my former article was to do away with something that has become a public nuisance The teeth of a saw are the same as the sections of a sickle ; not as the serrated teeth of the sickle edge I never heard any one argue that the edge of saw teeth ought to be serrated The teeth of saws are a series of cutting edges, not the whole saw one continuous cutting edge Now 1 wish to state one uncentrovertible fact; all cutting edges should be made just as smooth as they can be, and have them practically profitable A K SMITH Nebraska, Ohio The Oxyhydrogen Light, The oxyhydrogen light scheme has now taken a definite shape in Paris A company has been formed, the capital necessary has been raised, and application has been made for permission to lay down pipes to carry oxygen and hydrogen over about a fourth of the city It is not very likely the permission will be granted, and the promoters will have to confine themselves to supplying individuals with compressed gases, as was originally proposed We have published the patented processes by which M Tessie du Motay obtains the oxygen and hydrogen which he proposes to distribute over Paris, at a cost so low that the oxyhydrogen light is promised much cheaper than common gaslight; but ingenious and relatively cheap as they undoubtedly are, it is impossible to believe that the service can be made so inexpensive as to supersede coal gas The prospectus of the company enlarges upon the cheapness and purity of the light, the complete combustion, and the absence of all deleterious matters in the products of combustion ; but is quite silent as to vlie danger of introducing into a house two gases not possessing any smell, and which, consequently, may escape without observation, and the mixture of which forms an explosive compound of far greater power than any mixture of coal gas and air To any danger of this kind, continental engineers appear to shut their eyes We saw, a short time ago, a patent taken out in Belgium for making a mixture of coal gas and air, storing it in gasholders, and distributing it over the city of Brussels for heating purposes, 'l'he engineering details given showed a complete knowledge of the manufacture and distribution of gas, but there seemed to be no recognition of the risk, imminent enough, of blowing up the whole concern A consideration of this kind, some years ago, stood in the way of a scheme of the kind projected for Birmingham, and will, no doubt, now prevent the Oxyhydrogen Light Company from getting permission to lay down their pipes over ParisMechanics' Magazine