56 
MR. H. M. TAYLOR ON A SPECIAL FORM OF THE 
Such a combination as 
6 I * * 
a [ * * 
c (I 
where the rows and the columns necessarily represent different lines, implies that the 
lines a, c, h, d, taken in order, form a closed quadrilateral. 
The whole truth with respect to these four lines is contained in this figure : no 
further truth is conveyed by the enlarged figure 
Such a combination as 
cl * * • o 
C * 4f: 0 • 
h 
0 * * 
a 
O’** 
a h (■ (1. 
c * * * 
h * * * 
a 
- * * * 
cl e f 
implies that each of the three lines a, h, c intersects each of the three lines d, e,f. 
It follows that the lines a, h, c are non-intersecting, and also that d, e, f are non¬ 
intersecting. This figure therefore conveys the whole truth with respect to the six 
lines. 
We shall call such a set of six lines a “ grille.” 
They form six of the generators of a hyperboloid of one sheet. 
Such a combination as 
c • * * 
h * • * 
a 
* * 
cl c f 
where the rows and the columns necessarily represent different lines, indicates that 
the six’lines a, d, h,f, c, e, taken in order, form a closed hexagon. 
