《螺旋理论》A_Treatise_on_the_Theory_of_Screws-PREFACE.doc

PREFACE. About thirty years ago I commenced to develop the consequences of certain important geometrical and dynamical discoveries properly associated with the illustrious names of Poinsot and Chasles, Hamilton and Klein. The result of my labours I have ventured to designate as The Theory of Screws. As the theory became unfolded I communicated the results in a long series of memoirs read chiefly before the Royal Irish Academy. To this learned body I tender my grateful thanks for the continual kindness with which they have encouraged this work. I published in 1876 a small volume entitled The Theory of Screws:A Study in the Dynamics of a Rigid Body. This contained an account of the subject so far as it was then known. But in a few years great advances were made, the geometrical theories were much extended, and the Theory of Screw-chains opened up a wide field of exploration. The volume just referred to became quite out of date. A comprehensive account of the subject as it stood in 1886 was given in the German work Theoretische Mechanik starrer Systeme:Auf Grund der Methoden und Arbeiten und mit einem Vorworte von Sir Robert S.Ball, herausgegeben von harry Gravelius,Berlin, 1889. This work was largely a translation of the volume of 1876 supplemented by the subsequent memoirs, and Dr Gravelius made some further additions. The theory was still advancing, so that in a few years this considerable volume ceased to present an adequate view of the subject. For example, the Theory of Permanent Screws which forms perhaps one of the most instructive developments was not communicated to the Royal Irish Academy until 1890. The twelfth and latest memoir of the series containing the solution of an important problem which had been under consideration for twenty-five years did not appear until 1898. It therefore seemed that the time had now come when an attempt should be made to set forth the Theory of screws as it stands at present. The present work is the result. I have