S. W. B. of N. Y.—It will be somewhat troaMesomo for you to zinc tlie inside of your air dmmlieK Seoul it bright with sand and a little sulphuric acid, then wash its surface with a soluficn of eal ammoniac, and plunge the air c!iamber"intb a b'uth of molten zinc, for ten minutes ; this willicoat if. J. W. L., of Pa.—As we haa nothing whatever to do with the cases to which you refer, ire cannot answer your inquiry. K. M., oi S. C__The best work on the construction of steam engines is Tredgold's, which is very expensive. "Hodge on the Steam Engine," published by Appleton &Co.,thia city, we think, will answer your purpose. We have volumes 6 and 7, bound, for $1 26 each, and volume 12, bound, $2 75. There are various steel squares now used by carpenters : ask some one of them to explain the scales on the blades, as it would require alai'gcspaceforustodo so. We cannot give you the pries of the stones employed in grinding corn. C. E. H., of N. Y.—We cannot say that there ia any absolute rule for the direction of the shadows on mechanical drawings. The most common method is to suppose the light tocomefrom the upper lefthand corner of the sheet; and this ia the method we use in all drawings prepared at our office, for the reason tliat it is more convenient. In drawing with squares and straightedges it is impossible, unless a person U left-handed, to draw with the light at the right side of the sheet. French draftsmen represent the light to come from the upper left hand corner isi elevations, and the lower left hand corner in plans. Tho reason tor making the variation in the plans is to make the light appear to fall on the object, (not on the paper,) always in the same direction. There is some reason in this, though we do not adopt it. P. H. S., of N. Y.—As you state, we know that lead becomes brittle after several meltings and coolings ; we have never made any experiments to restore it to its previous softness and ductility. We have been assured, however, that if it is heated up to a point very near, but not qaite high enough to melt it, and then plunge it in cold water, it -will be restored to its former softness. It will not be very troublesome for you to try the experiment. S. W. D., of Ha.—Wo are not acquainted with any instrument for finding gold and silver. No such instrument exists, so far as we know. H. K., of Ind__We cannot give you a rule to shape a piece of metal or timber that will bend and for r. part of a perfect circle, by holding it fast at one end, and applying a deflecting weight at the [other. To make a piece of metal or timber assume such a. form by such means it should bo perfectly homogeneous. D. D., ofN. Y.—We are of opinion that your room for drying luiftber could bo fitted up with a sufficient number of steam pipes at a less co3t than to put up a large lieaterandfoTceairthronghit withabloirer driven by a steam engine. By running large flues through your drying rooms, and heating with common furnaces, you can dry the lumber more economically than by steam, but not so safely. The " Smikes," and all others whom it may concern, are respectfully advised that letters sent to us, without proper signatures cannot receive any attention whatever. We can neither answer nor preserve anonymous letters. Our practice is to throw them into the waste basket sans ceremonic. M. S. F., of W.—The chimera of perpetual motion has, ever since men began to study natural laws, been a phantom whiclihas haunted the brains of the ivisest philosophers ; and we published the engraving and description of a supposed machins that would move for ever, on page 132 of the present volume of theSci. AM.. simply to shoiv how a parson becmsang possessed of a fixed idea could indulge in the wildest dreama Your experiment tried twenty-five years ago* with nearly the same appliance as that above referred to, convinces you of its utter nonsense, and we only wish that all the dreamers on this subject would follow- your example and give it up, employing their talen&0 and ingenuity on something that would bs of practical benefit. W. S., of N. Y.—Lard oil is obtained by submitting granulated lard placed ia bags to severs pressure. The oil is the fluid wbich is squeezed out; stearine ia left behind. Lucifer matches are tipped with the chloride of potash and phosphorus in a solution of gum arabic. A good paste blacking is made of 4 lbs. of ivory black, S lbs. of molasses, 0 oz. of hot sperm oil, 1 oz. of gum arabic, and 12 oz. of vinegar, mixed together and stirred frequently for six days. It is then fit for use. E. P., of Iowa.—Voltaic electricity can produce rotary motion by many other means than the one you describe, and there is nothing really novel in your combination, although it may ba original with yourself. Until the action of the battery itself can be made cheaper, voltaic electricity is of no practical use as a motive power. H. B., of 111.—There is no periodical published, so far as we know, specially devoted to " milling." C. T., of Conn.—A preparation of gastric juice for curing dyspepsia caBnot bo patented. We have heard of the gastric juice of animals being used for this purpose, but have never known a single case ourselves. S. R., and others, f 111.—You will find all the inf orm-ation requested obout floating heavy logs on page 08, Vol. XI, Soi. AM. J. C of N. J.—You can purchase "Chevreul's Harmony of Colora" from C. E. Bailliere, No, 280 Broadway, this city. W. B. G,, of N. Y—Write to S. D. Humphrey, 287 Broadway, this city, regarding periodicals ana works on photography. John Wiley & Co., this city, are the publishers of "Smee's Electro-Metallurgy," the kind of work you want. E J. S., of C. E.—No number of our paper contains the information which you want in regard to specifications and contracts for building purposes. C. D., of Pa.—The ore you have sent us is iron pyrites containing perhaps a little copper. It is almost valueless. H. W., of Mass—Iron is annealed by cooling it from a high to a low heat very slowly. The result is not due, as you suppose, to cast or wrought iron turnings. C. S. H., of N. Y.—Your method of producing ornamental slabs for tables and other articles of furniture, seemfl to consist of a mixture of mosaic and buhl work, aad to resemble, in a great degree, what is known as marquetry in woodwork. There have been so many varieties -of inlaid work in marble, wood, shells, metal, ivory,, mother-of-pearl, and other substances, that it •would be impossible for you to obtain a patent. We have seen table-tops made as you propose, of different colored marbles. K. A. M., of Conn__Eye flour bolted but once, merely to remove the bran, is the sweetest—it is the same ?with buckwheat; but the flour sent to market, goes through two boltings at least. The number of bolting ' cloths used entirely depends on the kind of flour desired to be made. Ralph Grow, of Aledo, Mercer co., 111., Irishes to correspond with some one who can furnish the bc3t plans for a court-house and jail combined, the cost not to exceed $20,000. Money received at the Scientific American Oflice on account of Patent Oflice business, for the week ending Saturday, January 23,1858 :— S. B. & S., of Pa, $28 ; F. C. W., of Conn., $60 ; C. F. A.,ofN. H.,$30; F. P. A. Jr., of Conn., $30 ; J. H. of N. V.,$30; S. E. T., of Conn., $10; C.F.,ofN.Y., SM ; C. B C, of N. Y., $30; C. R, of Mass., $35 ; J. B., of Pa., $30 ; T. S., of Conn., $30 ; S. W., of Mass., $35 ; J. A. & A. D., of N. Y., $25 ; J. J., of S. C., $40 ; P. D., ofN. Y., $30 ; E. K. & Bro., of Vt, $35 ; W. O. H., of Pa., $85; P. A. G., of Mass., $27 ; A. E. L., of Pa., $10 ; H. B., of N. Y., $30 ; H. & G., of Ohio, $17 ; C. M., of N. Y., $25; T. S.. of N. Y, $15 ; II. A. L., of N. Y., $25 ; J. B. A., of N. Y, $25 ; V. & H., ofN. Y., $25. Specifications and drawings belonging to parties with the following initials have been f orwarded to the Patent Office during the week ending Saturday, January 23,1858 :— C. M., ofN. Y. ; W. & S., of Mass. ; S. B. & S., of Pa. ; S. E. T., of Conn. ; T. S., of N. Y.: S. W., of Mass. ; H. A. L., of N. Y. ; J. B. A, of N. Y. ; C. B., of Maes. ; H. & G., of Ohio ; P. A. G, of Mass. ; J. A &F. D., ofN. Y. ; G. I. L., of N. Y. ; E. L. E., of K. I.; V. & H, of N. Y. TEEMS OF ADVERTISING. Twenty-five cents per line each insertion. We re-pectfully request that our patrons will make their advertisements as short as possible. Engravings cannot be admitted into the advertising columns. \* All advertisements must be paid for before inserting. Three hundred and thirty-six pages, and four hundred and forty engravings. A COMPLETE ENCYCLOPEDIA IN MINIA- -iX ture for every man with a farm, a garden, or a domestic animal—for every place which will grow a flower or a fruit tree—for every purchaser or builder in the country, and for every household in the city, delighting in representations, or looking forward with hopes of rural life. Embracing :— Eural Architecture, Implements & Machinery, Landscape Gardening, Farm Economy, Fruit Culture, Domestic Animals, Ornamental Planting, Farm Buildings, Best Fruits and Flowers, Hints for Cultivators. Beautifully illustrated with 440 engravings. By John J. Thomas, author of the " American Fruit Culturist." &c., &c. Sent post-paid on receipt of $1 in gold, or postage stamps, or bank-note, by the publishers. This, we think, is the best book yet published for school, district and town libraries, as well as for premiums to be awarded by agricultural and horticnltural societies. LUTHEE TUCKER & SON, Albany, N. Y. %* For sale in New York (wholesale and retail) by A. O. Moore, 140 Fulton street, Wiley & Halsted, and Fowler & Wells, Broadway. Agents 'wanted, on liberal terms, in all parts of the country. READ—NEW CATALOGUE, (FOURTH EDITION), with twohundrert and fifty illustrations of Mathematical, Optical and Philosophical Instruments, and attachment of a large illustrated sheet, representing the Swiss instruments in their actual size and shape, will be delivered, on application, to all parts of the I United States, by sending 12 cents in postage stamps or j money, which amount will be deducted from the bill, if an order is sent. C. T. AMSLEE, No. 635 Chestnut st., Philadelphia, Pa. HARRISON'S OKIST MII/LS—30, 30,36 AND 48 inches diameter, at $100, $200, $300 and $400, with all the modern improvements. Also, Portable and Stationary Steam Engines of all sizes, suitable for said Mills. Also, Bolters, Elevators, Belting, &c., &c. Apply to ' S. C. HILLS, 12 Platt St., New York. CORN STALK CUTTER —THE UNDEE-signed can produce a machine, that, with one horse and boy, will cut down standing corn at the rate of two acres an hour; but, before incurring further expense, he wishes information relative to the need of such an implement1 at the West. Farmers and others interested will please address WILLIAM S. TILTON, Boston, Mass. "C'GGLESTON'S IMPROVED DOUBLE -Ei CIRCULAR SAWMILL—Cuts two planks at the same time, one from each side, until the log is finished, leaving one plank in the center. This mode oi taking lumber from each side at the same time, prevents the log from springing, therefore the timber is of uniform thickness. This mill cuts more than two single circular sawmills, with half the number of hands. It took the first premium at the State Fair of Alabama, in November, 1867 ; and numerous certificates can be produced to prove the superiority of this mill over all others now in use. A portion of the patent right, embracing some of the best States, is still unsold, and can be obtained on reasonable terms, by addressing M. D. HARMON or P. EGGLESTON, Mobile, Ala. TfOR SALE—SIX OP WOODWQETH'S PLAN-F ing Machines. Plane 24 inches wide, and 5 inches thick. Iron frame; weight, 1,800 lbs. Price, delivered in New York, $180, Address HARRISON FLINT, Danbury, Conn.