In a letter accompanying the above communication, the writer informs us that if we should refuse it a place in our columns, he would procure it an insertion elsewhere. If we had treated it as it justly deserves, we should have declined its publication; and no doubt its appearance elsewhere would have subjected its author to the mortification of seeing the word advertisement standing at its head. There is a certain amount of smartness in the communication not unlike that of some rattle-brained attorney who rushes to the rescue of his cause, without regard to truth or candor. The position assumed by the writer is manifestly so one-sided and unjust that we might have been excused if we had taken the liberty of substituting "Foul Play " as a proper signature for his communication. In the first place, it is a gross libel on inventors generally ; and, in the next place, if allowed to pass unrebuked, it would tend to injure the value of useful patented inventions in public estimation: hence our willingness to give "Fair Play" a chance to be heard. The autkor of this libel on the rights of inventors and their property purports to reside in this great city, where evidences are presented on every hand of the great value of patented inventions; and yet we feel bound to say that he is either the mere echo of some one who has felt the force of our criticisms, or whose mind has become so perverted that an invention seems of not much more importance than a bundle of straw. If the ideas of "Fair Play" are sound, it would be better for the interests of the people that the Patent Office be abolished at once, as, on his theory, it is simply putting an instrument into the hands of a few for no other purpose than to cheat the multitudea business which the government, at least, would not sanction. Fortunately, we are enabled to put forth with our own views in contradiction to the abo-ve, those of both the Secretary of the Army and the Secretary of the Navy, who, in their late reports, stamp the leading sentiments in the letter as false, and pernicious to the interests of tho government and people. Imbued with the very sentiments set forth in the above communication, a United States Senator prepared a hill, and cb-tained its passage nt tho last session of Congress ; but what has been its effects? NAVY PATENTS.The following extract, from the report of Secretary Toucey on the state of the navy, affords a most practical answer:"The provision in the act of Congress of June 23, 18C0, which prohibits the purchase of patented articles for the use of the army and navy, will be found injuriou to the latter service. Since the introduction of steam to propel ships of war, a great variety of patented articles have, in the construction and repair of a steamship, become of daily use, and, in many case, of indispensable necessity. Patented boilers, surface condensers, friction thrusts, governors or speed regulators, steam pumps, capstans, air ports, boat detachers, galleys or cooking stoves, ventilators, steering apparatuses, lanterna, logs and leads, vulcanized rubber, barometers, counters, hydraulic jacks, water gages, and-msny tools for manufacturing machinery and driving and drawing bolts, are of this description. And what is true of the steam machinery is also, in some measure, true of the armament. A war steamer built now according to the fashion of the past, excluding all modern patented improvements, would be an antiquated object, far behind the present age, and as inefficient as it would be antiquated. The best modern patented improved boiler will make a saving of 18 per cent of steam. To dispense with all patented surface conden-ers would be wanton extravagance. To arm a ship of war without a modern patented invention would give great advantage to the enemy. To prohibit the sailor the use of his seamless pea jacket and cap would be to deprive him of tha comfort of some of his light, warm, most darablo and cheap, and nearly waterproof clothing. To withhold from him the use of American patent desiccated vegetables would take from him a portion of his most nutritious and acceptable food. It is impossible to build, equip, arm and provide a steam ship ef war, having anything like usual modern efficiency, without ti-epassing on all sides upon modern patented improvements. Something, also, is due to the inventive genius of our countrymen. It is within the memory of the living when the great inventions and discoveries which have almost revolutionized the world wera unknown." ARMY PATENTS. The following extract from the report of the Secretary of War is equally pertinent as an answer to the above:"The law which prohibits the purchase of any arms or military supplies whatever which are of a patented invention, i too general and comprehensive in its terms, embarrasses the operations of the War Department, and is, in some respects, injurious to the military service, both as regards the army and the militia. There are certain arms and military supplies of patented inventions, the merits of which have been so well established as to have caused their introduction regularly into the service. These are frequently embraced in requisitions for supplies coming from the army and from the States ; but the few left on hand of those whicli were purchased before the passage of the prohibitory law constitute the only source from which those requisitions can be mot, and that source is now either entirely or very nearly exhausted. It is therefore recommended that the law be so amended as to except from the prohibition such arms or other military supplies as constitute a regular part of the armament or equipment of troops, and also the improved patented mode of casting and cooling for iron cannon. It should be repealad as to all articles used in the Quartermaster's Department." If the spirit of the author of the above communication were to prevail in administering the affairs of the Patent Office, we have no doubt but that our whole country would soon become as embarrassed in its manufacturing and agricultural improvements as our army and navy have been in theirs. Very few, if any, inventions are useful but those which are patented. It is, indeed, trne that all improvements are not of equal value and utility ; it is not every day that we can have such a great invention as the steam engine, cotton gin, telegraph, printing press, reaping machine orpower loom ;but every improvement, however small, deserves a patent, because it is a drop added to the tida of invention, progress and cirilization. The author of the letter is entirely wrong in his statements respecting the difficulty of obtaining patents prior to 1853, and the validity of those issued of recent years. Previous to that year, the decisions or the Patent Office were more proverbial for the rejection of good improvements and the granting of patents for trifling discoveries. Every person who has been long acquainted with the business of the Patent Office knows that vast improvements have been made in the drawings, specifications and models furnished to the Office. Very few of the patents issued prior to 1850 could bear a critical examination in a court of law, because they were prepared by very incompetent persons. Those which are now prepared for the Patent Office are far more accurate and complete in every respect, and are therefore better able " to stand tlie test of a court." This is a well known fact to us, if it is not to "Fair Play." We object to the Revisory Board in the Patent Office, because, unless it embodies more wisdom and more knowledge of science and inventions than all the Examiners combined, it must do evil, and not good, to inventors and the public. This requires no argument; it is a self-evident fact. According to law and custom, a patent must issue for every invention that contains any degreeof originality and utility. Our correspondent seems to be either ignorant or oblivious to numerous legal decisions on this point. His egotism respecting his judgment of what are worthless and what are valid patents, approaches to the ludicrous. The low prices for which patents can sometimes be purchased is not a true test of their inherent merits. We could name a number of patents, which were sold for quite small sums, that afterward became of immense value, and yielded large profits to purchasers ; and we have no doubt but that such will be the case in many instances again. The majority of our inventors are mechanics of limited means, who are frequently compelled to sell good patents for small sums, but probably there is not another man in the country, except our correspondent, who would have the audacity to fling their poverty in their teeth, and denounce their patents as useful only for gambling purpose. It is a libel upon our inventors and a stigma upon the benefits which they have conferred upon the public.