ws] 



Henderson — A Memoir. 



127 



x y z w 



a y 8 



x y z w 



a' & y' 8' " 



and we see by inspection that this line meets the line 3' when 

 we write its equations in the form 



/ y z w\l / y z w\\ 



\ 0' y " 8' /PB \ j8 y 8 //3'8' 



= 0, 



x = 0. 



Line 5, since it meets the lines 4' and 6', has equations Of 

 the form 



z — \w = 



Meeting - line 3' (see form last written), it is necessary to 

 identify the equations 



y H z 



P y 



== o 



s 



1 /8' — £8\ 



(yjS'8' — ky'138) w 



y + - ^ = 



wherefore 



giving 



yy'8(,3' - #) 8 



5\ 1 {yPV — k/ffl 



&/h' — kh\ 1 



8 \0' — W y'8 0' — £0 



