SMITHSONIAN CONTKIBUTIONS TO KNOWLEDGE. 



175 



DISCUSSION 



OF THE 



MAGNETIC AND METEOROLOGICAL OBSERVATIONS 



MADE AT THE GIRARD COLLEGE OBSERVATORY, PHILADELPHIA, 

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



THIRD SECTION, 



COMPRISING PARTS VII, VIII, AND IX. VERTICAL FORCE. 



INVESTIGATION OF THE ELEVEN (OE TEN) TEAR PERIOD AND OF THE DISTURBANCES OP THE 

 VERTICAL COMPONENT OF THE MAGNETIC FORCE, AND APPENDIX ON THE MAGNETIC 

 EFFECT OF THE AURORA BOREALIS; WITH AN INVESTIGATION OF THE SOLAR 

 DIURNAL VARIATION, AND OF THE ANNUAL INEQUALITY OF THE VER- 

 TICAL FORCE ; AND OF THE LUNAR EFFECT ON THE VERTICAL 

 FORCE, THE INCLINATION, AND TOTAL FORCE. 



BY 



A. D. BACHE, LI.D., F.R.S., 



HEX. CORE. ACAf). SC. PARIS ; PBBST. NAT. ACAD. SCIENCES; SUPERINTENDENT U. S. COAST SURVEY. 



[ACCRPTED FOR PUBLICATION, AUGUST, 1863.] 



