SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE. 



239 



OBSERVATIONS 



TERRESTRIAL MAGNETISM 



AND ON THE 



DEVIATIONS OF THE COMPASSES 



OF THE UNITED STATES IRON CLAD MONADNOCK DURING HER CRUISE FROM PHILADELPHIA 

 TO SAN FRANCISCO, IN 1865 AND 1866. 



BY 



WM. HARKNESS, M.D., 



PROFESSOR OP MATHEMATICS, DN1TED STATES NAVY. 



[ACCEPTED FOR PUBLICATION, SEPTEMBER, 1871.] 



