208 Dr. A. A. Pobb : Graphical Solution of Differential 

 Let DE be the curve thus drawn. 



Now take a plain sheet of paper fastened to a drawing- 

 board and let a point P be marked on it with a dot. 



Let the transparent squared paper be placed on the top 

 of this, so that one of the lines on the squared paper parallel 

 to OX passes through the point P, and let this line intersect 

 the curve DE in the point P . 



Let the perpendicular through P on OX meet OX in the 

 point N , and let the perpendicular through R on OX meet 

 OX in the point A . Now let a pin-prick be made through N 

 into the lower paper, and let the point thus marked on the 

 lower paper be denoted by N . 



Further, let a pin be stuck through A into the drawing- 

 board and let the point thus marked on the lower paper be 

 denoted by A . 



Next let the squared paper be turned through a very small 

 angle about the pin through A , so that another of the liues 

 on it parallel to OX passes through the point P. 



Let this line intersect the curve DE in the point R u which 

 will be very near to P . 



Let the perpendicular through P on OX in its new position 



