SMITHSONIAN CONTEIBUTIONS TO KNOWLEDGE. 



186 



DISCUSSION 



OF THE 



MAGNETIC AND METEOROLOGICAL OBSERVATIONS 



MADE AT THE GIEABD COLLEGE OBSERVATORY, PHILADELPHIA, 

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



FOURTH SECTION, 



COMPRISING PARTS X, XI, AND XII. DIP AND TOTAL FORCE. 



ANALYSIS OF THE DISTURBANCES OF THE DIP AND TOTAL FORCE ; DISCUSSION OF THE SOLAR 



DIURNAL VARIATION AND ANNUAL INEQUALITY OF THE DIP AND TOTAL FORCE ; 



AND DISCUSSION OF THE ABSOLUTE DIP, WITH THE FINAL VALUES FOB 



DECLINATION, DIP AND FORCE BETWEEN 1841 AND 1845. 



BY 



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



MEM. CORR. ACAD. BC. PARIS ; PKEST. If AT. ACAD. SCIENCES; StTPEBlHTEHDENT IT. 8. COAST SCBVET. 



[ACCEPTED FOR PUBLICATION, MAT, 1864.] 



