ROOFING. 345 FloorLine. GroundLine ROOFING. The Editor of the Mechanics' Magazine will oblige a subscriber and occasional correspondent by eliciting, through the medium of that publication, the efficiency or non-efficiency of the above mode of supporting a roof, similar in its arrangement to that of the Picture Gallery referred to in Nos. 189 and 191 of the Magazine. The author imagines that all partial lateral thrust or strain against the walls, would, by this design of construction, be avoided. The sketch is rough, but will sufficiently explain the intended mode of construction. The only variation in this design from the section given in page 253, No. 191, is the continuation of the arms of the lever A B, and their knee-like terminations on foundation-piers. Perhaps T. G. J. would favour the readers of the Magazine with an analysis of the principle of the roof which is stated to have failed. THE PLAN FOR COMPRESSING EARTH. Sir, The defects of Mr. Barnard's plan for compressing earth are so obvious, that I should not have called your attention to it now had I not seen in your last Number (No. 193) that Mr. Loudon wishes some manufacturer to make a press for him after this model, which, I Ground Line [There can be no question that the "knee-like terminations or foundation-piers" would be useful addition to such a structure; but we are far from being satisfied that "all partial lateral thrust or strain against the walls would, by this design of construction, be avoided." It appears to us, that, at the lower end of the arc, which the upper end of each pillar forms, the thrust would still be nearly the same. We must remark, at the same time, that` neither by this, nor by any of our former observations on the subject, do we wish it to be understood that we question the possibility of effectually supporting a roof in this manner-even without the "knee-like terminations" now proposed. No doubt the iron pillars and the walls by which they are backed may be made thick enough and strong enough to support the weightiest roof. All that we contend for is, that there would, in that case, be nothing geometrical in the construction, but a great waste of iron, brick, and mortar, to make up for a great deficiency of brains.]-Edit. think I may safely say, that no one will ever think of doing. A common screw-press is at once so much more simple, economical, and effective, that I would advise Mr. Loudon to make use of one of them in preference to any thing that I have ever yet seen or heard of for the purpose. May 12, 1827. PERGO. OF OPTICAL GLASSES. Sir,-The writer of the Sketch of the Human Eye (p. 153, vol. vii.) has again taken up the pen further to illustrate its properties and peculiarities-its weakness in some, and eccentricity in others. He here presents cases which have come under his own observation during the last ten years: 1st. A youth, about 14 years of age, by trade a jeweller, could not see his work for five minutes together, from weakness of the iris. By using a 40-inch convex preserver, he obtained the greatest relief, and in less than two months, no longer required the aid of glasses. 2nd. A lady, 27 years of age, with very weak sight, had been recommended to wear plain green glasses, without any optical power, but they afforded no relief whatever. She came to me with eyes inflamed and red as ferrets. A 60-inch preserver gave her speedy and effectual relief. The next are cases of odd sights, requiring concave numbers for distant view; not however from shortness of sight, but from weakness of the iris. 3rd. A young man, about 28 years of age, required a pair of concave glasses (No. 1) for distant view, and for reading writing—a 48-inch convex preserver for one eye, and a 26-inch focus for the other. 4th. A gentleman, about 40 years of age, required a No. 2 concave for distant view; and for reading, writing, &c. a 36-inch convex preserver, which gave the necessary relief and assistance. 5th. An old gentleman, about 70 years of age, required a 6-inch convex for reading, &c., and for walking spectacles, a No. 3 concave. 6th. The writer of this requires, for distant view with one eye (only), a No. 1 for reading, writing, &c., an 18-inch convex for the one eye, and a 12-inch for the other.-Here the writer has the evidence of his own sight to confirm him in what he has stated, that the defect is in the contracting power of the iris alone; for when he looks through a hole in a piece of pasteboard rather larger than a pin's head, the pupil is contracted, and he sees objects in the distance clear and sharp, the same as with No. 1 concave. The following are cases of short sights: 7th. A gentleman, short-sighted, required a No. 18 concave for one eye, and for the other a No. 7. As this is rather an extraordinary case, I have here presented the curves of the different numbers. No 18 Concare. No7 Conoare. 8th. A young lady, about 15 years of age, required a No. 7 concave for walking spectacles, and for looking at her music, a No. 3 ditto. 9th. An old lady, 54 years of age, required a 18-inch convex for reading (called the ninth sight), and yet she assured me she could do the finest needle-work without glasses; a peculiarity most strange and unaccountable. Note. That when the numbers are given for the convexes, each number gives the radii of the tool they are worked from. 10th. Two ladies, one about 40 years of age, the other 75 years, had each lost an eye, and saved the other by couching. Double convex glasses of the following shape PATENT LAWS. 347 The figure represents the left eye, the right eye being closed. Lay five objects on a table, say five wafers; let the left eye be directed (straight and fixedly) to the wafer in the centre, and wafers 2 and 3 be about five inches apart, with the face about 18 inches from the table, PATENT LAWS. LETTERS VIII. IX. AND X. Sir, I consider it as a very fortunate event for ingenious mechanics and others, that the subject of the Patent Laws has had the good fortune to be discussed in the pages of your Magazine. I felt certain, from the time you first mentioned it, that good would spring from such a discussion, and I have not been disappointed in my expectations. The extensive circulation which your work has, and its being in the hands of all classes of scientific men, rendered it the most eligible vehicle by which to attract the attention of those most interested in these Laws to the consideration of them. The Patent Laws were enacted for the purpose of securing to ingenious men the first fruits of their study and research. In framing these laws, the legislators had very properly to guard against the too free admission to a security of this kind of any trivial or unimportant invention, which though original, may not be of sufficient consequence to entitle it to the dignity of a patent; and the only effectual me No. 2 will not be seen, while 1 and 5 you may extend, right and left, to any distance within the limits of the field of view, and see them in every position equally well. Sir, I remain your's, 27, Little Russel-street. thod for this purpose was that of making the expense so great, that none but those whose discoveries are of sufficient importance would venture to incur it. I am certainly of opinion, that the money required for such a purpose is not to be easily had, and that the charge for a patent is too high; but I would not go to the lengths, which some of your correspondents seem inclined, and make the value of a patent of as little expense as the copyright of a book. This would be endeavouring to correct an evil, by substituting one of a more mischievoustendency in its stead. Patents would then be of no value, and the importance of having an article designated patent would be lost. Of this I am certain, that if any man has a discovery which tends to bestow profit, but which requires a patent to secure it, he will always find men of capital ready to undertake the trial. That some plan to ameliorate the present laws patent inventions can be devised, and of a wise and salutary nature, I have not the least doubt; but it seems to me to be going too far to propose that the expense should on be a mere trifle. The laws at present impose too high a price for the protection they afford; let that expense be diminished, and the principal object for which we contend is gained. Through your medium, allow me to suggest to the gentleman who intends calling a public meeting, the expediency of holding it at the London, Mechanics' Institution, the theatre of which the Committee let out for the purpose of holding meetings of a public nature. It would at any rate ensure the attendance of a full number of mechanics; and as the subject is one of vital importance to mechanics, I do not doubt but that the Committee would lend it gratis for that purpose. At any rate should they refuse to be so generous, the expense would be much less than that of hiring a room at the Crown and Anchor. Let me finally recommend to all the mechanics of all the towns in Great Britain, to follow the example set them in London, by holding meetings for the like purpose, and simultaneously to petition the House of Commons on the subject under discussion. With my best wishes for the success of this cause. I am, Sir, Your obedient servant, Sir, The present system of taking out Patents, has been, and justly too, a source of much complaint, owing to the loose and general manner in which a caveat may be worded, and which allows the party ́thus protected to specify, in the enrolment of the patent six months afterwards, almost any thing that may come within the wide range of the caveat, and may consequently comprise many inventions drawn, subsequently to the caveat, from the minds of others who are not thus protected. At the same time this system is partly necessary, that the patentee may have his share of protection during the time that may be consumed in bringing the invention before the public, and in making such alterations as must necessarily arise between theory and practice. Now, Sir, I beg leave earnestly to submit to the consideration of those who have the power of correcting the abuse alluded to, a plan which will at once protect the inventor and remove the evil complained of;-it is simply this: When a person enters a caveat, let him deposit in the office a sketch (more or less detailed as he wishes for protection) of the principles upon which his invention is founded, and let this be sealed under cover by himself and remain in the office until the enrolment of the Patent, and a short time, say six months, afterwards. The writer of this has just entered a caveat for an invention of much importance, and yet he by no means considers himself secure until the patent is enrolled, because those caveats previously entered, upon the same subject (there are several), are couched in such vague terms, that if any person who has so entered a caveat, should discover and be mean enough to take advantage of the invention of the writer, during the making of the model, &c. he might comprise such invention under his caveat. But if the proposed plan were adopted, such interference could not take place, as the inven tions of all parties would be in existence under their respective dates, and might be immediately referred to; and every person might proceed fearlessly in the practical fulfilment of the object adverted to in his caveat. Hoping, that through the wide circulation of your excellent work, these remarks may reach the proper quarter, and at any rate induce a consideration of the' subject, I am, Sir, Your obedient Servant, Sir, The promptitude which you have evinced by the insertion of my two letters, and the courtesy of your remarks thereon, claim my respect and esteem. As it appears probable that the Meeting at the Crown and Anchor may not take place before the publication of your next number, PATENT LAWS. permit me to trespass once more upon your indulgence, in order that a small error may be rectified as regards the observations of Mr. Mac Carthy on the expense of patents; that gentleman said, it was his custom to sue out, or obtain all his patents himself, without employing a patent agent; by which attention, he saved a certain sum, but the amount of that saving I do not recollect to have heard mentioned. The wording of the specification obscurely, had no reference. whatever to that part of the subject, but solely to prevent piracy. I feel the force and justice of your remark as to such obscurity of description; nevertheless Mr. Mac Carthy's ideas on that head are not singular; for the same sentiments have been expressed to me by three other gentlemen, as applicable to their patents. You are perfectly correct in assuming that foreign manufactures are inferior to English, and that the latter are preferred when prices are nearly the same. How ever, merchants abroad say, that very heavy imports are levied upon various kinds of English goods; and on some articles I know this to be the fact, that from 20 to 25 per cent. duty has been charged; which, in addition to insurance, freight, wharfage, warehousing and factor's commission, place such English manufactures out of the reach of numerous persons who would otherwise become purchasers of them. There remains to make one observation as to foreign manufactures, which is not, perhaps, generally known in this country. I mean the sale of many articles at a less price than they cost the parties interested in the manufacture; and of this fact you may rest assured. I agree with you that foreign competition stimulates our artizans to proceed on more scientific principles, with greater dispatch, and of course to sell as cheaply as possible; but I consider their attention to arrive at perfection, expedition and cheapness, has been one cause of throwing thousands out of employ, and for whose future services as artizans, there does not appear to me to be 349 any prospect of demand; and if I am right in taking such a view of the subject, they injure themselves by their extraordinary exertions to obtain perfection. At home, tens of thousands are incapacitated from becoming purchasers; and abroad tens of thousands are debarred from purchasing by the edicts of those who are anxious that their own subjects should supply the markets of their country, to the exclusion of the British merchant. And while the government of any country chooses to incur a loss, in order to keep out foreigners, the competition must be successful; but many of these establishments have failed, and others may be expected to fail, before they can arrive at that degree of excellence and expedition as will ensure to them a remunerating profit for the capital invested. Ĭ consider every pound sterling received abroad, as excessive impost upon British goods, is absorbed in the attempts of the government receiving such impost, to manufacture in opposition to Englishmen ; and I possess pretty good data for saying this much. Now I beg to suggest the propriety of the Meeting about to be held, turning their attention to the expense of procuring patents in foreign countries; and I think among your numerous readers that point might be easily ascertained, by means of your valuable journal, or by their coming with or sending to the meeting, such information. The expense is less than in England, certainly; consequently, if patents were to be reduced to one general standard, they would not appear to lose so much; but I conceive there would not be any loss ultimately, for every person would then be anxious to procure a patent, who now either goes about boasting of having made a valuable discovery, but wants money to procure a patent, or else vituperates public bodies or private individuals, who have adopted a similar proceeding, or procured a patent for a similar invention, without perhaps knowing of the existence of the party who vituperates them, or of any invention of a nature likely |