88 L. Schwendler—On a new Standard of Light. [No. 2, 
The P. S. L. (B)* with a current = 5.9 webers was used as unit. 
1st Candle, 7 readings in 10 minutes 
mean = 1.08 P. S. L. (B) 
max: _ 1.19 
min: 1.00 
The maximum was obtained directly after having opened the Photo- 
meter when fresh air entered. 
2nd Candle, 10 readings in 14 minutes 
mean = 1.07 P. S. L. (B) 
max : 1.32 
min: 0.69 
The minimum was obtained directly after freshly lighting the candle. 
8rd Candle, 12 readings in 24 minutes 
mean = 1.07 P. S. L. (B) 
max: 1.80 
ine Oe total variation = 46 per cent. 
or total variation = 17.6 per cent. 
or total variation = 59 per cent. 
The lowest reading was obtained shortly after lighting the candle. 
4th Candle, 14 readings in 22 minutes 
mean = 0.94 P. S. L. (B) 
max: 1.26 by A 
=e (ie total variation = 72 per cent. 
The lowest reading cannot be accounted for. 
Two new Platinum Light Standards of the same form and size as the 
P. L. S. (A) described before, were placed in circuit of 8 Grove’s cells 
connected up successively and with a Mercury Rheostat in circuit, to keep 
the needle of the Tangent Galvanometer at a constant deflection. 
These two new P. L. S., called II and III, were placed in the Photo- 
meter to compare their lights and by it test the accuracy of the Photo- 
meter readings, and other influences to be named further on. (see fig. 2, 
Plate VIII.) 
d + d’=D = 250 mm (constant). 
Light ¢ produced by P. L. 8. (III), Light z* produced by P. L. 8. (II). 
The balance between the two lights being obtained by moving the prisms 
within that fixed distance. A piece of red glass was used for taking the 
readings. 
* This Platinum standard (B) was the first made, and has a different form from 
the other (A) described: Dimensions and weight cannot be accurately given now. 
