1909-10.] Illuminating Power of Groups of Pin-hole Burners. 57 
Table IV. — Continued. 
Distance between 
Adjacent Burners 
(4 
Illuminating Power. 
Observed. 
Calculated (P,). 
Calculated (P 2 ). 
-5‘15(a:-l-19)2 
j P^l + ’32e‘ 
Series B, 4 burners. ] _ j e 11 * ( 
( 2 ^ i P5xl0 9 j 
•78 cm. 
1*00 „ 
1-25 „ 
1- 49 „ 
2 - 00 „ 
7T0 „ 
1T3 
1T3 
1 27 
1-27 
1-31 
1-31 
1-20 
1-20 
1*04 
1-01 
1-00 
POO 
1T3 
1-27 
1*31 
1-20 
1*04 
1*00 
j Pj = 1 + *45e -5 s(x_1 1)2 - 
Series C, 4 burners. .{ - 5 -sf*-i-i)» { 
j P 2 =l + ’45e < 
•79 cm. 
*98 „ 
1 + 
2 x 10 6 
1*19 
1- 52 
2- 06 
3* 10 
6T1 
1-27 
1-27 
1*41 
1-41 
1-43 
P43 
P21 
1T8 
P06 
1-00 
P01 
1-00 
POO 
1-00 
Series D, 4 burners 
/ p _ i .g4g-5-62(x-l-13) 2 
• < . —5‘62(a;— 1*13)2 
P 9 =l + -34e 
1 + 
1-2 x 10 7 
1-27 
1*41 
1-43 
1-21 
1-06 
POO 
1 00 
}■ 
•78 cm. 
•90 
1-00 
P25 
2-00 
6*00 
1T7 
P17 
P17 
1-25 
1-25 
P25 
1-31 
1*31 
P31 
1*31 
1-31 
1-315 
1-03 
P005 
P03 
100 
POO 
POO 
Although the four-burner curves agree with each other in general features, 
the value of P corresponding to the lowest value of oc is much greater in 
the case of series C than in the other cases. This is probably due to the 
large experimental errors that are introduced when small distances are 
worked with. When the distance between the burners was very small, it 
was extremely difficult to get the four flames exactly symmetrical, for the 
least inclination of the flames to the vertical made two or more flames 
coalesce while the remainder were separate. Errors in the vertical, being 
