CONTENTS — {continued) . 

 April 25, 1872. 



PAGE 



I. Contributions to Formal Logic. By Alexander J. Elt.is, F.R.S., F.C.P.S., 



II. On a supposed Periodicity in the elements of Terrestrial Magnetism, with 



a period of 26$ days. By George Biddell Aiey, Astronomer Royal . 308 



List of Presents 313 



TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 



