ELECTRIC CHARGE. THE CONDENSER. 193 



charged plate as the region of zero potential and plot a curve of 

 which the abscissas are distances measured along the line X and 

 of which the ordinates represent the values of the potential at 

 points along this line. 



141. An inclined plane is viewed from above. A series of 

 contour lines and of slope lines are drawn upon the plane. Make 

 a diagram showing the appearance of these lines as projected 

 upon the base plane. 



142. A circular cone is viewed from above and a series of con- 

 tour lines and slope lines are seen projected upon the base plane 

 of the cone. Draw a diagram showing the appearance of these 

 lines on the base plane. 



