A. A. R of Phila.—Bo you mean fire gilding of metals or porcelain, or merely electrotyping? B B., of Pa —The mere application of an alarm to a prison could not be patented ; if you have in-Tented any particular improvement in the alarm, whereby its application is rendered more beneficial, a patent could be secured for it. We should need a sketch to enable us to come to a proper conclusion. B. P., of Winchester—We know'nothing of the establishments to which you refer ; we think the steam hammer engines can be adapted to the pur poses named. A. C, of Canada—We do not know of any one wh.o has such a machine as you want. H U., of Ot —We have never known of a pump constructed as described in your letter ; it is pro bably new and paten table, its advantages over the common pump we do not perceive. H.S.j of N. H.—We cannot discover any thing in your washing machine of a novel character ; it is quite common to employ a fluted " rubber " in com bination with a fluted stationary bed, the rubber be ing held in its proper position by means of spiral springs or their equivalents. R. A, of N Y.—Your observations in regard to how much an object appears magnified contain no-thingnew, the same ideas are laid down by the in genious Dr Jurin, in a work entitled " The Micros cope Made Easy," by Henry Baker, London, 1744, a copy of this old work is in our possession. M. M., of Pa.—We cannot undertake to enumerate the different modifications which have been made in the steam engine ; if yon will send us a sketch we can give you a more satisfactory opinion. A, M. a., of P.—There is nothing patentable in the change whioh you present for the construction of paddle wheels ; if yjjamine page 280, Vol. 5, Soi. Am., you will seejgjsthing on the subject. Oh K. G, of-----.—A steam engine is the only power, we can recommend to elevate your spring water; a good wind-mill might answer; if your creek has but a small quantity of water it would be useless to construct a wheel for it. B. J. 0., of Ind.—Your boiler we believe ould work well, but we have seen one lately, and for which a patent will soon be granted, which meets the same conditions. A. 0. 0., of Tenn —There can be no fears about moring the balloon in a direct course, if enough of power can be obtained to propel it. We have seen no plan that .presents to us any hopes of success. Some one may soon be discovered. We do not know of any cement in use that will suit your purpose, but we believe that hydraulic cement used in the inside, and the seams pointed with cement made of dry air slacked lime, white lead, and clean sand and first allowed to dry, would nswer.' J.A. 8., Pa—We could not furnish you with the first 22 numbers of Vol. 7, unless you take the last part of the volume also : we have less numbers of the first part of the volume than we have of the last. T. J. A , of Ohio—Itmatters not how many saws you use in a gang, your claim will cover twenty as securely as it will two H. L. W , of (Jeo.—The weight of the balls is ex pressed upon the leverage of the arms of the wheel, comparatively, and the same result is produced by the sorew with the balls on it according to its pitch, the same law of mechanics rules in every machine —time, space, and weight are the three elements of calculation. F. P C , of S. 0.—The description you give of the alleged improvement in steam engines is very inde finite, but so far as we comprehend its nature we J. D. W , of N. Y—You would observe that a cor rection was made by us respecting Mr. Hudson's let ter at his own request. think it contains no advantages not embraced in oth er dericeB for the purpose. H. W. 8 , of Ind.—We are unable to find any pa tentable novelty in your press ; it is in substance the same as Brown's Eccentric, but more complica ted and less effective for that reason. J. A , of Boston—We transmitted your papers per Adams Co. E. W., of Ct.—We are having an engraving of your pistol prepared; it will be published when com plete. W. R, of Me.—We think it unnecessary to repeat our opinions respecting the use of hot air as a mo tor. Whatever we state in the Scientific American as our opinion, is not intended to contradict ourpri-vate views—we speak as we think ; if you do not it is no fault of ours. L.S , of Ind.—W e do not know of a more com petent person to undertake your agency than Mr. 8 0. Hills, No. 12 Platt St., he has several agencies and attends to them faithfully. Money received ou account of Patent Office busi ness for the week ending Saturday, April 23 :— W. D. E , of Miss., $30 ; G. N., of N. Y., $30; J, W. H., of R I., $5 ; 0. P., of Mich., $30; P. 8., of N. Y., $20; F. 0. D., of Pa, $10; P. G. G, of N. Y., $150; 8. F. A., of N Y , $30: T. D. A. H., of Pa. $30 ; W. W. of Ot., $175 ; W. W., of Ot., $20; J. B . of Mich., $55 ; C. M , of Mo., $48 ; G. A. B., of 111 , $25 ; H. 0. 8., of Ot, $30; I 0., of N. Y., $30 ; 0. 0 , of Ky., $25; J. B , of N. Y., $30 ; 8. M , of Pa, $30. Specifications and drawings belonging to parties with the following initials have been forwarded to the Patent Office during the week ending Saturday April 23 :— W. W. W , of Ot.; 0. P., of Mich.; J 0., of N. Y.; 0. M,, of Mo., G.A. B., of 111) R. C, W., of Ohio ; | A, H R., of Pa.
This article was originally published with the title "To Correspondents"