PREFACE. We have now concluded the third volume of the PENNY MECHANIC, and dismiss it, not "with frigid indifference," but with our warmest thanks to the numerous contributors and subscribers who have promoted and secured the extensive circulation which this publication has now attained. A great number of curious and useful inventions are recorded in this volume; and writers of distinguished talent have testified their approval of its plan and management, by contributing original papers, which will be found interesting and profitable to all classes of readers. Its usefulness is no longer questionable; the flattering and spontaneous notices which frequently appear in contemporary publications, and above all, the increased and still increasing circulation which it has obtained, are unequivocal marks of public favour. This favour we are solicitous to acknowledge in the manner which will be most agreeable and satisfactory to our friends. The best, indeed the only means we possess of doing so, is to increase our exertions to merit their patronage. The propagation of practical and useful science, is our chief and best object; for, in the words of Lord Bacon," The true end of all science, is to enrich human nature with useful arts and inventions." To promote this object, we have made arrangements which will enable us to give our readers the earliest account of foreign inventions, and the proceedings of learned bodies, when their researches lead to any useful or interesting result. "THE CHEMIST" will contain, every week, an original article, or the description of some new discoveries, which, being derived from various distant sources, will rarely be found in any other English publication. This department has now become valuable to every one interested in chemical science. Considerable latitude will be given to the publication of original papers; and we invite our ingenious readers to publish their inventions before they expend their time and money in experiments, unless they are prepared to sacrifice two or three hundred pounds for the precarious guarantee of a patent. Without this, secrecy is utterly useless; and publicity will at least secure them the credit of their discoveries, and, which is, perhaps, still more important, they will thereby be enabled to appreciate their projects according to their real value. Theourth Volume will commence with an alteration in the Title; the word "Penny" will be suppressed, but the price will remain the same. In conclusion, we respectfully solicit a continuation of the patronage which encourages and obliges us to redouble our efforts to make "THE MECHANIC AND CHEMIST" a source of useful instruction, and agreeable amusement. THE GRINDER'S ASTHMA, AND ITS PREVENTION. To the Editor of the Penny Mechanic. SIR, AS I happened to be in Sheffield a little time since on business, I took the trouble whilst there to make a few enquiries, that I might be able, on my return, to answer the queries of one of your correspondents "B. G.," in No. 49. I trust, therefore, that the following remarks on this subject, which I have hastily committed to paper, will prove interesting to others of your readers as well as to him. Though the operatives of Sheffield are not in general shorter lived than those of other populous towns, a sad exception must be made with respect to the grinders. Dr. Knight, in a paper read a few months since before the Medical and Surgical Society, said, "the grinders' asthma had become so prevalent, that out of 2,500 grinders, there are not thirty-five who have arrived at the age of fifty years, and perhaps not double that number who have reached the age of forty-five. There are above 800 fork-grinders (dry-grinders,) exclusive of boys, and there is not a single individual amongst them thirty-six years old!" Until the beginning of the last century, grinding was not a distinct business, but was performed by the cutlers who finished the goods. The grinders' asthma was then unknown, and it did not become very prevalent until the erection of large steam grinding-wheels, in which the grinders are crowded together in low rooms, with scarcely any circulation of air to carry away the clouds of dust evolved from so many stones. In addition to this evil, the steam-engine, unlike the stream which formerly supplied the grinder's wheel, allows him no season of relaxation for the recovery of his health, for he now works ten or twelve hours a day on an average, whilst formerly, for several months in each summer, he could not work more than four or five hours a day, owing to a scarcity of water. There are, however, still several of the old water-grinding wheels on the various streams in the neighbourhood; but more than threefourths of the grinders are employed in the large steam-wheels in the town. To discover a remedy for the destructive asthma which commits such ravages among the grinders, has, I am happy to say, successfully excited the attention of philanthropists. A magnetized steel mask or visor was proposed by Mr. J. H. Abraham, of Sheffield, in 1822, for which he obtained a superb service of plate from his townsmen, and a gold medal from the Society of Arts. It has since come partially into use, but the workmen object to it on account of the trouble and inconvenience it occasions them by its frequent want of cleaning. This is caused by its attracting the particles of steel floating in the atmosphere of the room in such quantities as to impede their breathing, &c. (How "B.G." would apply a "galvanic magnet" to this purpose I know not, but he is perhaps better acquainted with the sciences of galvanism and magnetism than your correspondent "J. G.") The late Mr. John Elliott's invention is much more simple and effective, and where it is brought into general use, it may be reasonably hoped that the grinders' asthma will cease to exist, or at least be greatly mitigated. It consists of a plain wood box, placed over the stone, with a wooden chimney, through which the metal and stone dust evolve, and are carried to the outside of the building by the current of air pro| duced by the revolution of the stone. For this invention Mr. Elliott was presented by the Society of Arts, with their Vulcan gold medal, and a handsome subscription was raised for him in Sheffield, to which the Cutler's Company contributed £20; but the idea of this simple apparatus is said to have been first con| ceived by one Colton, a grinder. If this be the "machine" referred to by "B. G.," I have never heard any objec tion to it, for in the manufactories where it has been introduced, I am told it has given great satisfaction. By an ingenious application of the principle of a forced ventilation, Mr. Prior has been able to prevent, or very materially diminish, the danger attendant on the dry-grinding of needles, and other articles manufactured in steel. His apparatus consists of a conical box, or case, enclosing nearly one-half of the grindstone, to receive the dust of steel and stone made in the operation of grinding, which is caused to enter the box by a current of air produced by a pair of bellows. The needle-grinding-mills are generally very extensive buildings, with numerous apartments, each containing numerous grindstones for pointing needles, all of which are driven by one powerful water-wheel or other first mover. bellows which are employed in Mr. Prior's plan to carry off the dust, might be made large enough to supply all the grindstones contained in one room or even one wing of the mill, The |