SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE. 



DISCUSSION 



MAGNETIC AND METEOROLOGICAL OBSERVATIONS 



MADE AT THE GIRARD COLLEGE OBSERVATORY, PHILADELPHIA. 

 IX 1840, 1841, 1842, L843, 1844, AXD 1845. 



SECOND SECTION, 



COMPRISING PARTS IT, V, AND VI. HORIZONTAL FORCE. 



INVESTIGATION OF THE ELEVEN (OR TEN) YEAR PERIOD AND OP 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, LL.D., F.R.S., 



■EH. COBB. ACAD. SC. PARIS; SUPERINTENDENT I'. S. COAST SIRVEY. 



(ACCEPTED FOR PUBLICATION, JUNK, 1 8 6 '.! . j 



