DISCUSSION OF THE MAGNETIC 
IN 1840, 41,42, 43,44,& 45 
Lunar-diurnal Variation of the Magnetic Declination 
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AND METEOROLOGICAL OBSERVATIONS MADE AT THE GIRARD COLLEGE PHILADELPHIA 
DIAGRAMS TO PART 3.1860 A.D. BACHE L.L.D. SUPERINTENDENT 
Lunar-diurnal Variation 
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