PREPARED BY C. A. The Isogonic Curves or Lines of Equal Magnetic Declination, are drawn for each de number and East Declination by a Minus sign. To he right of the Agonic or Zero Curve the north end o The Isoclinic Lines or Lines of Equal Magnetic Dip are drawn for intervals of tyvo deg The Isodynamic Lines or Lines of Equal Horizontal Component of Magnetic Intensity |