i8 73 ] STREAM LINES 63 



ties of a diameter. For brevity, we shall speak only 

 of the source, assuming the existence of a corresponding 

 sink. 



When there is one source, the stream lines are mani- 



Lines of flow when the sources form a rectangular parallelogram, 

 whose diagonals make an angle of -. The unbroken lines are lines of 

 flow when sources of the same sign are diagonally opposite. One line 

 sinks to a circle, another to a rectangular hyperbola, the rest are 

 lemniscates. When a source and sink are transposed, the circle is still 

 part of a stream whose other branch is a straight line, but the lemnis 

 cates pass over into the dotted curves. 



