This unrivaled publication is now in its fifty-fourth year, and is acknowledged to be the foremost and most popular scientific journal published. The excellence and variety of the reading matter render it one of the most interesting and widely read journals in the world. Each issue is fully illustrated and no topic of popular interest germane to science or industry is neglected. The latest tricks of the greatest modern conjurers are published from time to time. Those who are not familiar with the Scientific American may send for a free sample copy. Subscription price, $3.00 per annum. MUNN & CO., Publishers, Scientific American Office, 361 Broadway, New York City. [Illustration: (the magazine cover) THE EDISON MAGNETIC CONCENTRATING WORKS. THE GIANT ROLLS.] MUNN & CO., Publishers, 361 BROADWAY, NEW YORK. 1898 EDITION --OF-- Experimental Science BY GEO. M. HOPKINS. 20th Edition Revised and Enlarged. 914 Pages, 820 Illustrations. Price $4.00 in cloth; $5.00 in half morocco, postpaid THE MOST POPULAR SCIENTIFIC BOOK OF THE DAY [Illustration: (the book cover)] This is a book full of interest and value for Teachers, Students, and others who desire to impart or obtain a practical knowledge of Physics. This splendid work gives young and old something worthy of thought. It has influenced thousands of men in the choice of a career. It will give anyone, young or old, information that will enable him to comprehend the great improvements of the day. It furnishes suggestions for hours of instructive recreation. This new edition is now ready. It contains a large amount of new matter, bringing it up to date. Such subjects as the X-rays and liquefied air being fully treated. Send for large Illustrated Circular and complete Table of Contents. MUNN & CO., Publishers, OFFICE OF THE SCIENTIFIC AMERICAN, 361 BROADWAY, NEW YORK. TRANSCRIBER’S NOTE Obvious typographical errors and punctuation errors have been corrected after careful comparison with other occurrences within the text and consultation of external sources. Except for those changes noted below, all misspellings in the text, and inconsistent or archaic usage, have been retained. Pg 61: ‘are nable to see’ replaced by ‘are unable to see’. Pg 82: ‘great standbies’ replaced by ‘great standbys’. Pg 129: ‘handerchief, and’ replaced by ‘handkerchief, and’. Pg 147; Index entry ‘Post tests’: ‘93-1 0’ replaced by ‘93-100’. Pg 147; Index entry ‘Slates, padlocked’: ‘3’ replaced by ‘32’. End of the Project Gutenberg EBook of Spirit Slate Writing and Kindred Phenomena, by William E. Robinson