Remit by postal order. Address MUNN & CO., 37 Park Row, New York. -->To Advertisers.--The regular circulation of the SCIENTIFIC AMERICAN is now FIFTY THOUSAND COPIES weekly. For 1880 the publishers anticipate a still larger circulation. THE SCIENTIFIC AMERICAN SUPPLEMENT Is a distinct paper from the SCIENTIFIC AMERICAN. THE SUPPLEMENT is issued weekly. Every number contains 16 octavo pages, uniform in size with SCIENTIFIC AMERICAN. Terms of subscription for SUPPLEMENT, $5.00 a year, postage paid, to subscribers. Single copies, 10 cents. Sold by all news dealers throughout the country. COMBINED RATES.--The SCIENTIFIC AMERICAN and SUPPLEMENT will be sent for one year, postage free, on receipt of _seven dollars_. Both papers to one address or different addresses, as desired. The safest way to remit is by draft, postal order, or registered letter. Address MUNN & CO., 37 Park Row, N. Y. SCIENTIFIC AMERICAN EXPORT EDITION. The SCIENTIFIC AMERICAN Export Edition is a large and splendid periodical, issued once a month. Each number contains about one hundred large quarto pages, profusely illustrated, embracing: (1.) Most of the plates and pages of the four preceding weekly issues of the SCIENTIFIC AMERICAN, with its splendid engravings and valuable information; (2.) Commercial, trade, and manufacturing announcements of leading houses. Terms for Export Edition, $5.00 a year, sent prepaid to any part of the world. Single copies 50 cents. -->Manufacturers and others who desire to secure foreign trade may have large, and handsomely displayed announcements published in this edition at a very moderate cost. The SCIENTIFIC AMERICAN Export Edition has a large guaranteed circulation in all commercial places throughout the world. Address MUNN & CO., 37 Park Row, New York. * * * * * NEW YORK, SATURDAY, JULY 3, 1880. * * * * * TABLE OF CONTENTS OF THE SCIENTIFIC AMERICAN SUPPLEMENT No. 235, For the Week ending July 3, 1880. Price 10 cents. For sale by all newsdealers.