SMITHSONIAN CONTRIBUTIONS TO KNOWLKDGK. 



DISCUSSION 



MAGNETIC AND METEOROLOGICAL OBSERVATIONS 



MADE AT THE GIRARD COLLEGE OBSERVATORY, PHILADELPHIA, 



IN 1840, 1841, 184l>, Ie4^, 1844, AND 1845. 



SECOND SECTION, 



COMPRISING PARTS IT, Y, AXD YI. HORIZONTAL FORCE. 



INVESTIGATION OF THE ELEVEN (OR TEN) YEAR PERIOD AND OF THE DISTURBANCES OF THE 

 HORIZONTAL COMPONENT OF THE MAGNETIC FORCE, WITH AN INVESTIGATION OF THE 

 SOLAR DIURNAL VARIATION, AND OF THE ANNUAL INEQUALITY OF THE HORI- 

 ZONTAL FORCE; AND OF THE LUNAR EFFECT ON THE SAME. 



BY 



A. I). BACHE, LLD,, F.R.S., 



MEM. CORK. ACAD. BC. PARIS ; SUPERINTENDENT U. S. COAST Sl'RVET. 



[ACCEPTED FOR PUBLICATION, JUNE, 18C2.] 



