S. W., of N. Y.—We think the elastic webbing mentioned by you can be procured of II. H. Day, No. 23 Courtland street, this city. F. P.,ofD. C.—Your suggestion in regard to a price current is a good one, but we have generally considered that ourreaders would prefer the same space to be filled with other matter. E. GK W., of Mass.—You assert that sweetness is a positive indication of sugar in substances. This is not so; for there are various metallic salts which are very aweet to the taste, such as the acetate of lead. RE.C, of Md.—We thank you for your communication, and should be happy to publish diagrams of the plane for grooving circular timber, if the invention was publie property, so that our readers could have the benefit of the invention; but it is nearly the same as one patented by W. A. Cole, in 1848. We shall be happy to receive communications from you again on similar practical subjects. A. "W., of Me.—If you were to force air into the boiler at the pressure you speak of, (100 lbs. per inch), the water would not boil, or steam be generated till it had been heated to a temperature of nearly 330 Fah. It would require more heat to give a corresponding increase of elastic force to air at that pressure than if it were at a lower pressure. R. II. C, of Texas.—The great philosopher and traveler, Baron Humboldt, is still alive, and lives in Berlin; he is now very old, put his memory is perfect, and his habits are quiet, but cheerful. You are right in saying that he is one of the greatest nien the world has ever produced. L. P. S., of Conn.—The magneto-electric machine of Saxton has been so improved as to produce a continuous current, but we do not know whether it has been applied economically to electro-plating, although a patent was taken out for this purpose some years ago, by Mr. Elldngton, of Birmingham, Eng. Calvin Carpenter, of Providence, R. I., lias a patent for economising the power of such machines. We cannot tell you what size of magnet is required to do the work of a four-cell Smees' battery. F. D., of N. Y.—The coloring ingredient of indelible ink is nitrate of silver, To make the ink, dissolve ten grains nitrate of silver in twice that quantity of aqua ammonia, and add to it a weak solution (weighing one ounce) of gum arabic. Keep this bottled for use. Write on the cloth to be marked, and expose it to sunlight until it is dry. C. D,, of Pa.—Taylor's work on coal statistics, published by J. W. Moore, Philadelphia, is the best we can recommend on the subject-; it contains the information you desire. H. P. D., of N. J.—Hollow and solid cast iron shotare now used toobtainballs of different weights from the same material. We therefore cannot see what advantage would be secured by the use of a metal of less specific gravity, even if it were equally hard. E. R. M., of Ala.—The current is Ies3 rapid at the^bot-tom, than at the surface of a river, especially near the middle, owing to the resistance of the bottom. The hy-dnmlic force, therefore, which acts against your paddle, must be greatest at the surface of the water, because the power is in proportion to its velocity and volume. L. A. J., of Me.—You cannot make a good foundation for a road across marshy land without driving piles on either side, and filling in with large boulders, gradually diminishing the size as you ascend. Should no boulder stones be available, a good road for cattle and light weights may be made by digging a deep ditch on both sides, narrower at bottom than at top, and having a slight fall to carry off the water. S. E. D., of Miss.—The architecture of the Anglo-Saxons was of a very rude character, for we find that in the year 627, the church at York, Eng., was built of wood, and covered with reeds, the only parts composed of stone being the altars. The first stone church was built in the latter part of the seventh century. John H. Martenstein, of New Orleans, is desirous of obtaining the address of the person whose idea of perpetual motion we published in No- 9 of the present volume. B. F., of Ind.—The ordinary proto-nitrate of cobalt will make an invisible ink for use. It may be. made by dissolving cobalt in nitric acid. J. K., of Ga.—The present volume of the London Engineer contains much interesting correspondence on the subject of aerial navigation; you had better obtain it. The address is 301 Strand, London. W. J. F., of Del.—The best works on mechanics are Bartlett's Mechanics, published by Barnes &Co., New York, and the Mechanics' Text Book, published by Phillips, Sampson &Co., Boston. Should you wish to learn the first principles, any of the hand-books on the subject would answer your purpose. D. C, of Md.—The assignee of a patent holds the right to the portion, so assigned, if only one dollar is specified in the contract, regardless of the great value of the patent, and the verbal understanding that you should be further remunerated. The amount of consideration specified in an instrument of this kind does not affect its validity. W. W. D., of Cal.—Your English and French patents were shipped to you on the 20th inst. by Wells, Fargo &Co.'s Express. The American case is not being neglected ; you will hear from it soon. Rusticus, of Texas—You are entirely wrong, as we are not aware that it ever was " a prevalent notion that sound travels faster in warm than cold air1' so you have been fighting against a fallacy. Your method of measuring vibration is good. The edition of Graham's Chemistry must be old, oryou would find that he doubts his former statement in regard to sulphuric acid, and that if it ever does exist, it immediately combines with water. T. W. B., of Wia.—Your boat hung on journals is an old idea. The umbrella-like construction of the boat was patented two or threeyears ago. J. A., of Conn.—At present there is no law in" Canada by the aid of which patents can be issued to American citizens. W. B. P., of Mass,—Your communication will receive attention next week. C. C. T., of Wis.—We will hold the assignment until the recording fees are paid. The assignee's neglect, in this instance, cannot affect your interests. The patent will issue in your name, if granted. Money received at the Scientific American Office on account of Patent Office business, for the week ending Saturday, November2l, 1857 :— A. S., of N. Y., $30 ; L. T. W., of Ohio, $25 ; R N. W., of Ohio, $25; H. . of Ohio, $70; J. R V.,of Cal., $50; J. H. F., of Cal., $30; J. E. II., of N. Y., $30; J. K. B., of N. Y., $20; J. L., of Mass., $25; I* E. P., of Wis., $55; S. M., of Ohio, $25; J. M. S.,of Conn., $25; V. N. M., of N. C., $30; J. IX, of N. Y., $10; S. P. C, of Ohio, $25; J. E., of 111., $30; J. II. H., of Pa., $25; D. D., ol Pa., $25; II. U., of N. Y., $10; S. O., of Ind., $30; S. C, of S. C, $25; A. M., of N. Y., $25; F. B. 15. of N. Y.. $225; T. &T., of Ohio, $30; H. B., of N. Y., $100; J. L. W., of Pa., $100; J. W. L., oflll., 25; G. W. IL, of Conn., $00; E. II. T., of N. Y., $25; H. W., of Mass., $55; , D., of Ala., $20; G. II. II., of Conn., W. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday, November 21,1857 :— J. M. S., of Conn.; E. M., of N. Y.; S. M., of Ohio ; J. E. V. O., of Cal.; E. N. W., of Ohio; J. L., of Mass.5 A. M., of N. Y. ; N. A., of Conn. ; D. D., of Pa.; E. II. T., of N. Y.; S. P. C, of Ohio; J. II. II., of Pa. ; J. B. E., of Pa. ; J. W. L., of 111. ; H. W., of Mass. ; T. D., of Ala. Literary Notices THE CHAR-LESTON MEDICAL JOTTRNAL AT^D REVIEW— Dr. Huppoldt, editor and publisher. The November number contains much valuable and scientific lnfornyi-tion in the medical sciences, and has an able translation of M. Florena1 lectures on Comparative Physiology, and a few valuable suggestions on 'k Malaria.1' REPORT ON INFANT MORTALITY IN XJARGE CITIES— ByD. Meredith Reese, —1.D.,LL.D. T. 1C &F. G. Collins, Philadelphia. This pamphlet, which ia extracted from the transactions 'of the American Medical Association, is a valuable contribution on tlria subject, and exhibits great research on the part of its author. It is a topic that should be more closely attended to and ntudied, so that many of the causes may be removed. He tells us the astonishing fact that infant mortality is greater in American cities than in Paris, and gives some clue to the causes. HISTORY OF PETER THE GREAT.—By Sarah IT. Bradford. Appleton &Co., publishers, New York. The life of this great man ia well a ad pleasantly told, in a style suitable to children: and perhaps the reading may stimulate boys to follow the energy, perseverance and courage of the hero of this biography. CHILDRENS' HOLIDAYS: A Story Book for the Whole If ear.__Appleton &Co.. New York. This little work is lull of pretty stories, all tending to the moral improvement of little readers. GEOEGE READY, OR. HOW TO LIVE FOR OTHERS—By Robert O' Lincoln. Appleton &—Jo., New York. A Christmas story, with a boy for hero, plenty of pictures, and full of interest. A PLACE FOR EVERYTHING AND EVERYTHING IN ITS PLACE—By Alice 13. Haven. Published by Appleton &Co., New York. Another story for children, inculcating the moral indicated by its title—one that cannot be too early instilled into the minds of the young, that they may be orderly by force of habit in their later years. 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This article was originally published with the title "Correspondents"