42 Silliman and Wurtz on Air and Gas. 
weights to the counterpoise, measuring the influx by a cen- 
tissimal scale of equal parts attached to the drum of each 
holder. Thisrude admeasurement was controlled by an analysis 
of each mixture. This required also the prior analysis of the 
street gas on each occasion, columns 3, 4, and 5 of the accom- 
panying Table I, show the results of these mixtures as made 
known by the eudiometer. The illu minating power of each 
sample was determined by the Bunsen photometer on the av- 
ss e of fifteen successive observations of one — each 
the usual i te olumns 6 and 7 give these re- 
ae and in columns 1 and 2 _ be found the pteapanding 
densities ‘Ggieet by diffusio 
ince the air added in each case is rendered as gas by the 
meter during the photometric measurement, it is important to 
determine the illuminating power of the gas alone after deduct- 
ing the known volume of air present. The results of these 
calculations are givenin column 8. In columns 9 and 10 the loss 
of illuminating power is given: in 8 in terms of the candle power 
lost for each admixture, and in 9 this loss is stated as a per- 
centage, The ratio of loss of illuminating power in percent- 
age volumes of gas and air is given in column 11, and in col- 
umn 12 is the loss of power corresponding to each one per 
cent of air-a 
The results of the analyses and ‘photometric measurements 
are more conspicuously seen in the curve projected from col- 
umns 5 and 10 of the table upon the annexed diagram, on 
which the vertical and horizontal scales are as 1:3 
The following inferences depend upon the data herein given, 
iz i— 
Ist. For any quantity of air, less than five per cent, 
mixed with gas, the loss in candle power due to the addition 
of each one per cent isa little over #; of a candle (‘611 ex- 
actly) ; above that quantity the ratio of loss falls to 4 a candle 
power for each additional one per cent up to about 12 per 
cent of air; above which, up to twenty-five per cent, the loss 
in illuminating power is as shown by column 12 of the table, 
nearly ,,ths of a candle for each one per cent of air added to 
the In column 11 of Table I, the ratio of loss in candle 
power is given in percentages for ‘the several volumes, while 
in column 10 the destructive effect of air upon the illuminating 
power of gas is most conspicuously exhibited, twelve per cent of 
estroying over 40 per cent of the illuminating power. 
In the diagram this loss of power is represented by the nume- 
rals in the right hand column, which are inverse to those in 
— 10, and stand with the maximum intensity =100. 
d. With less than one-fourth of atmospheric air, not quite 
