Produced by Juliet Sutherland and the Online Distributed Proofreading Team at www.pgdp.net [Illustration] SCIENTIFIC AMERICAN A WEEKLY JOURNAL OF PRACTICAL INFORMATION, ART, SCIENCE, MECHANICS, CHEMISTRY, AND MANUFACTURES. NEW YORK, FEBRUARY 24, 1877. Vol. XXXVI.--No. 8. [NEW SERIES.] $3.20 per Annum [POSTAGE PREPAID.] * * * * * SCIENTIFIC AMERICAN ESTABLISHED 1845 MUNN & CO., Editors and Proprietors. PUBLISHED WEEKLY AT NO. 37 PARK ROW, NEW YORK. O.D. MUNN. A.E. BEACH. * * * * * TERMS FOR THE SCIENTIFIC AMERICAN. One copy, one year, postage included. $3.20 One copy, six months, postage included. 1.60 Clubs.--One extra copy of THE SCIENTIFIC AMERICAN will be supplied gratis for every club of five subscribers at $3.20 each; additional copies at same proportionate rate. Postage prepaid. THE SCIENTIFIC AMERICAN SUPPLEMENT is a distinct paper from the SCIENTIFIC AMERICAN. THE SUPPLEMENT is issued weekly; every number contains 16 octavo pages, with handsome cover, 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. Subscriptions received and single copies of either paper sold by all the news agents. * * * * * VOL. XXXVI., No. 8. [NEW SERIES.] _Thirty-second Year_. NEW YORK, SATURDAY, FEBRUARY 24, 1877. * * * * * CONTENTS. (Illustrated articles are marked with an asterisk.)