SMITHSONIAN CONTRIBUTIONS TO KNOWLEDGE. 



186 — 



DISCUSSION 



MAGNETIC AND METEOROLOGICAL OBSEEVATIONS 



MADE AT THE GIRAED COLLEGE OBSERVATORY, PHILADELPHIA, 



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



FOURTH SECTION, 



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



ANALYBIS OB THE DISTURBANCES OF THE DIP AND TOTAL FORCE ; DISCUSSION OP THE SOLAR 



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



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



DECLINATION, DIP AND FORCE BETWEEN 1841 AND 1845. 



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



JIEM. COKK. ACAD. SO. PAEIS ; PBEST. NAT. ACAD. SCIENCES ; SOPEEINTENDENT U, S. COAST STIEVET. 



[accepted foe publication, mat, 1864.] 



