1909-10.] Illuminating Power of Groups of Pin-hole Burners. 59 
The inflexion point further to the right of the origin is given by 
n 
x = c+ . / — . 
V 2 b 
These values are tabulated below 
Table VI. 
Values of x at Inflexion Points. 
3 Burners. 
4 Burners. 
Series A, 1*42 cm. 
„ B, 1-37 „ 
Series A, 1*35 cm. 
„ B, 1-50 „ 
„ C, 1-41 „ 
„ D, 1-47 „ 
Average = 1 ’40 cm. 
1*43 cm. 
General Discussion. 
Although the graphs for the two, three, and four burners are alike in 
form, there are considerable numerical differences. This is brought out in 
the data for turning points and inflexion points. The following table of 
turning values is collected from page 53 and Table V., and shows that the 
maximum increase for the two burners is decidedly greater than for three 
or four. 
Table VII. 
No. of Burners 
Max. Increase in 
Corresponding Distance of 
in Group. 
Illuminating Power. 
Adjacent Burners. 
2 
Say 40 per cent. 
Say *4 or *5 cm. 
3 
37 „ 
1T0 cm. 
4 
35 „ 
1T4 cm. 
Thus the maximum value of P, and the corresponding distance of adjacent 
burners, are nearly the same for the three and four burners. Also, the more 
burners the smaller is the maximum increase in P, and the greater is the 
distance required to give the maximum. 
Comparing the inflexion values on page 53 with those in Table VI., 
we see that the greater the number of burners the greater is the 
value of the cc-co-ordinate of the inflexion point. Thus in all these 
