Transcriber’s notes: The text of this book has been preserved in its original form apart from correction of two typographic errors: embarrasment → embarrassment, Cassegranian → Cassegrainian. Inconsistent hyphenation has not been altered. A lengthy preliminary section concerning the Smithsonian Institution precedes the actual subject matter. SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE. VOL. XIV. [Illustration] EVERY MAN IS A VALUABLE MEMBER OF SOCIETY, WHO, BY HIS OBSERVATIONS, RESEARCHES, AND EXPERIMENTS, PROCURES KNOWLEDGE FOR MEN.--SMITHSON. CITY OF WASHINGTON: PUBLISHED BY THE SMITHSONIAN INSTITUTION. MDCCCLXV. ADVERTISEMENT. This volume forms the fourteenth of a series, composed of original memoirs on different branches of knowledge, published at the expense, and under the direction, of the Smithsonian Institution. The publication of this series forms part of a general plan adopted for carrying into effect the benevolent intentions of JAMES SMITHSON, Esq., of England. This gentleman left his property in trust to the United States of America, to found, at Washington, an institution which should bear his own name, and have for its objects the “_increase_ and _diffusion_ of knowledge among men.” This trust was accepted by the Government of the United States, and an Act of Congress was passed August 10, 1846, constituting the President and the other principal executive officers of the general government, the Chief Justice of the Supreme Court, the Mayor of Washington, and such other persons as they might elect honorary members, an establishment under the name of the “SMITHSONIAN INSTITUTION FOR THE INCREASE AND DIFFUSION OF KNOWLEDGE AMONG MEN.” The members and honorary members of this establishment are to hold stated and special meetings for the supervision of the affairs of the Institution, and for the advice and instruction of a Board of Regents, to whom the financial and other affairs are intrusted. The Board of Regents consists of three members _ex officio_ of the establishment, namely, the Vice-President of the United States, the Chief Justice of the Supreme Court, and the Mayor of Washington, together with twelve other members, three of whom are appointed by the Senate from its own body, three by the House of Representatives from its members, and six persons appointed by a joint resolution of both houses. To this Board is given the power of electing a Secretary and other officers, for conducting the active operations of the Institution.