SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE. 



DISCUSSION 



MAGNETIC AND METEOROLOGICAL OBSERVATIONS 



MADE AT THE GIRARD COLLEGE OBSERVATORY, PHILADELPHIA, 



IN 1840, 1841, 1842, 1843, 1844, AND 1845. 



PART I. 



INVESTIGATION OF THE ELEVEN YEAR PERIOD IN THE AMPLITUDE OF THE SOLAR-DIURNAL 

 VARIATION AND OF THE DISTURBANCES OF THE MAGNETIC DECLINATION. 



BY 



A. T). BACHE, LL.D. 



[ACCEPTED FOII PUBLIC ATION, JUNE, 1859.] 



