WATSONS NON CHANGEABLE GAP LATHE HAS GREAT FACILITIES FOR LARGE OR MEDIUM SIZE WORK JAMES WATSON MANR 1608 S. FRONT ST. PHILA. PA.] POND'S TOOLS, Engine Lathes, Planers, Drills, &c. DAVID W. POND, Worcester, Mass. * * * * * CAN I OBTAIN A PATENT? This is the first inquiry that naturally occurs to every author or discoverer of a new idea or improvement. The quickest and best way to obtain a satisfactory answer, without expense, is to write to us (Munn & Co.), describing the invention, with a small sketch. All we need is to get the _idea_. Do not use pale ink. Be brief. Send stamps for postage. We will immediately answer and inform you whether or not your improvement is probably patentable; and if so, give you the necessary instructions for further procedure. Our long experience enables us to decide quickly. For this advice we make _no charge_. All persons who desire to consult us in regard to obtaining patents are cordially invited to do so. We shall be happy to see them in person at our office, or to advise them by letter. In all cases, they may expect from us a careful consideration of their plans, an honest opinion, and a prompt reply. _WHAT SECURITY HAVE I_ that my communication to Munn & Co. will be faithfully guarded and remain confidential? _Answer_.--You have none except our well-known integrity in this respect, based upon a most extensive practice of thirty years' standing. Our clients are numbered by hundreds of thousands. They are to be found in every town and city in the Union. Please to make inquiry about us. Such a thing as the betrayal of a client's interests, when committed to our professional care, never has occurred, and is not likely to occur. All business and communications intrusted to us are kept _secret and confidential_. Address MUNN & CO., Publishers of the SCIENTIFIC AMERICAN, 37 Park Row New York. * * * * * THE "Scientific American" is printed with CHAS. ENEU JOHNSON & CO.'S INK. Tenth and Lombard Sts., Philadelphia, and 59 Gold St., New York. * * * * * Transcriber's Note: _x_ indicates italic script; =x= indicates bold script. ^ indicates superscript. Some archaic (Early American) spellings have been retained. Erata: 'irridescent' corrected to 'iridescent'. "Glass, iridescent" (Contents) 'monoply' corrected to 'monopoly'. "The cry of monopoly in this case is altogether unfounded,..." (Article 4: Progress of Petroleum) 'possesing' corrected to 'possessing'. "... possessing in every way the original form of the wood." (Article 42: Reduction of Nitrate of Silver by Means of Charcoal.)