Transcriber's Note: Underscores "_" before and after a word or phrase indicate _italics_ in the original text, however, they are also used to designate a subscript. Equal signs "=" before and after a word or phrase indicate =bold= in the original text. Carat characters "^" are used to designate a superscript. Small capitals have been converted to SOLID capitals. Illustrations have been moved so they do not break up paragraphs. Old or antiquated spellings have been preserved. Typographical errors have been silently corrected but other variations in spelling and punctuation remain unaltered. THE GASES OF THE ATMOSPHERE [Illustration] [Illustration: STEPHEN HALES.] THE GASES OF THE ATMOSPHERE THE HISTORY OF THEIR DISCOVERY BY WILLIAM RAMSAY, F.R.S. PROFESSOR OF CHEMISTRY IN UNIVERSITY COLLEGE, LONDON WITH PORTRAITS London MACMILLAN AND CO., LTD. NEW YORK: THE MACMILLAN CO. 1896 _All rights reserved_ “Modern discoveries have not been made by large collections of facts, with subsequent discussion, separation, and resulting deduction of a truth thus rendered perceptible. A few facts have suggested an _hypothesis_, which means a _supposition_ proper to explain them. The necessary results of this supposition are worked out, and then, and not till then, other facts are examined to see if their ulterior results are found in Nature.” --DE MORGAN, _A Budget of Paradoxes_, ed. 1872, p. 55. PREFACE