J. 0., of Phila.—You can introduce your inven- tt°n as early as you please; we shall have the papers prepared for you to execute very .oon. W. F. 0., of Texas-Gum shellac dissolved in spi • rits of turpentine, in a close bottle, will make a ce ment admirably adapted to the purpose for which you require it. $10 received, which is correct for the number of subscribers you sent. ' E. G of .ohio-We have received the pamphlet, and will give the substance about the tunnel inour next. T. H., ofPa.—Inthe hot-blast the oxygen does not combine with the hot iron of the pipes; if it did, how long would the pipes stand ? There is a gene - ral mistaken idea that the oxygen of the atmosphere io continually combining with the iron of an expo sed red-hot plate, if such were the case, how long w°uld a plq,te stand before it was oxydized ? E. of Mass.—There is a work named .” Hum - phrey's Photography;” also Hunt's, which latter contains full instructions. There is no way to ob tain a good and complete knowledge of making phi losophical instruments, except by model and read ing the works that have been published on the same, which are very extensive in their range. We like your ideas, they are just and sound. J. C. S.j of N. Y. —We have been aware, for a long time, of a mill, driven by water, doing more work by night, in a given time, than during the day, and this information we have published before. Fires burn better during night than day. The article would be acceptable, you know the rule—short, clear, crisp, and stickingfull of facts. A. F., of Mass.—There is nothing new in the spiral bucket wheel you have described; they are old and well known. W.S. T , ofN. Y.—Neither of your plans ar®, in our judgment, practicable; aerial navigation is an airy scheme and requires a great stretch of theima- gination to bring the mind up to even a reasonable hope of success ; this has resulted from the failure of every plan to accomplish useful results; at pre sent the system is fraught with much more pleasure than profit ; we have no faith whatever in any plan yet proposed. The paddle wheels are old and well known. W. J., of Ala.—We would allow 16 cubic feet per second for the 45 feet fall, and 15 cubic feet for the 50 feet fall; this is a little more (not quite a cubic foot) than by actual rule is allowed, and it makes al lowance for the common deduction of one> third for loss; the rule for exact calculation is to multiply the power of wheel wanted, say 60 horse-power, by 33,000 (a horse-power), and divide this by your fall, fifty feet high, then divide by 62 1-2, to bring the pound to cubic feet in one minute, and bf\60 for the cubic feet per second, and add one-third forthe usual loss. ' J. R. B., of N. Y.—The quantity or water being the same, we can see no difference in the two wheels (8 and 14 feet) except in the height of the fall—the ratio then ill< in proportion to this. The ratio of pow er, by this mode IIf estimating effect, will be the same by doubling the diameter of each wheel, but recollect that the power of the wafer is &s the quan- ty and the fall; we cannot view the question in any other light. A. N. Piper, of Athens. Geo., wants information about the price of a lathe for turning bobbins - Some of our readers may be able to inform him. J. O.,ofN. Y —Will you be pleased.tosend us afew more articles before we commencetheir publication , This will be the best way for us both. J. K. L., of D. C.—We see nothing patentable in the sketches you have sent us. Whenever you cor respond with this office again you must sign your name in full or no attention will be paid to your J. B. B” of Ark.—It is quit e difficult to obtain in a single book a general knowledge of mechanism . We have sent you the “Hand Book of the Useful Arts,” which we hope will please you. R. G., of N. Y.—You are right about the steam engine; no person that we are aware of entertains a different opinion. The valves of steamboat en gines are worked by inclined planes and by cams, so as to cut off suddenly. We caQaotgive you any in formation about those who are now applicants' for patents. If you look on page 296, Vol. 4, Scientific American you will find a water-wheel that acts upon the same principle as yours, but not in the same manner. W. J.I McA.,?of N. Y.-We have not received the number,but haveread it in another. We are aware of the truth of the critcism, and when you werere- moved we stigmatized the acceptance ofthe office as a mere trick. G. W. B., of 0.; W. H B.,of N. Y.; E. B., ofMiss.; G. H., of Texas, and N. B. D., of S. C.—We have obeyed your instructions in forwarding a stereotype plate of the Crystal Palace by the different routes designated by each. Money received on account of Patent Office busi ness tor the week ending Saturday, Dec. 11:— A. L., of N. J , $30; J. 0, of Pa., $40 ; G L, W, of Md., $30; N. C. T., of II. Y., $30; W. R. G., of N. Y., $30 ; C.&R., of N. Y., $40 ; G. N. L. D., of N. Y., $30; G. B. D., of Mass., $25 ; D. B., of N. 'Y., $100, J. S. Van G., of Tenn., $30; J. C., of N. Y., $20. Specifications and drawing'l belonging to parties with the following initials have been forwarded to the Patent Office daring the week ending Saturday, Dec. 11: T, A.,of N. Y.; H.&McL., of Gil.; M.&E., of N Y ; C. &R.,ofN.Y.