189 
Parr .— The Response of Pilobolns to Light. 
Light 
source. 
Standard of 
« comparison . 
Spectral 
region. 
Galvanometer deflexions 
in mm. 
Average 
deflexion 
in mm. 
Ergs per 
sec. per 
cm . 2 
Nernst 
lamp 
Hefner 
value 
±631 
(Orange) 
245-140 = 105 
230-125 = 105 
235 — 120 = 115 
215-115 = 100 
106 
0-647 
± 5 8 9 
(Yellow) 
235-190= 45 
240-185= 55 
165-115= 50 
175-525= 50 
50 
0*305 
» 
±523 
(Green) 
242 — 220 22 
270—249 = 21 
282 — 261 = 21 
21 
0*128 
>> 
±437 
(Indigo) 
310-302 = S 
240-231 = 9 
200—191 = 9 
187-178= 9 
9 
0*055 
± 5 2 3 
± 5 2 3 
(Green) 
255 - 195 = 60 
260-175= 85 
23 0 -i 55 = 75 
300-235 = 65 
7 i 
0-128 
if 
± 4 6 4 
(Indigo) 
375-345 = 30 
340-310= 30 
330-285 = 40 
330-290= 40 
35 
0*063 
Table V gives the galvanometer deflexions in the spectral regions of 
a 200-watt nitrogen-filled tungsten Mazda lamp as compared with those of 
the Hefner—the values being expressed in ergs. Since the spectrum of 
the tungsten lamp was but 8 mm. in width and the slit of the thermopile 
18 mm., a correction was necessary in order to make the readings com¬ 
parable with those of the wider spectral regions of the Nernst lamp. The 
calculations for the energy values in red (+ 708) and yellow (+ 589) are 
made directly from comparison with the energy from the Hefner lamp. 
Other determinations were made and compared with the energy of the 
yellow region. These values are later summarized in Table IX. 
Table V. 
Light 
Standard of 
Spectral 
Galvanometer deflex¬ 
Corrected deflex¬ 
Ergs per sec. 
source. 
comparison. 
region. 
ions in mm. 
ion in mm. 
per cm? 
Hefner 
Angstrom 
Total 
480—370= 110 
lamp 
value 
radiation 
485-360=125 
at 2 m. 
490 - 370 = 1 20 
500-385 = 115 
Average =117 
1 17 
2*075 
Tungsten 
Hefner 
+ 708 
550-350 = 200 
lamp 
value 
(Ked> 
545-345 = 200 
540 —340= 200 
540-340 = 200 
Average = 200 
450 
7*980 
a 
± 589 
504 — 440= 64 
(.Yellow) 
512 — 450= 62 
522 — 460= 62 
522—462= 60 
Average = 62 
140 
2*480 
