20G 
TROWBRIDGE. 
HIGH ELECTROMOTIVE FORCE. 
occurrence of 
ordinarily called 
fou 
an exhausted tube is filled 
spectrum of h\ 
apor 
The readiness with which 
when 
f o u r- 
line spectrum can be obtained in water vapor, and the comparative difficulty of obtain 
ing it in dry rarefied hydrogen with powerful discharges, leads to much reflection 
Is it not possible that the common occurrence of this spectrum of hydrogen amom 
the stars, and especially in the atmosphere of the sun, is an evidence of the prevalence 
of water vapor and consequently of oxygen ? 
The following experiment is of interest in this connection 
expe 
to a 
determine wheth 
the 
f hyd 
and 
of physical 
The object of the 
chemistry applies 
x } 
An end-on Geissler tube T was connected to a mercury pump which was provided 
McCleod araiiffe, and 
tube of ignition tubing in which oxv<?en could 
8 
be generated by 
the 
d 
per 
d 
Close to the G 
bulb filled with distilled water. 
tube was a 
By open- 
ing a v 
Geissler tube could be filled 
i the heated bulb, or with 
with steam from 
water vapor at a lower temperat 
x 
steam. An 
d 
Figure B. 
hyd 
at a defi 
fited from the p 
than 
i tube filled with 
pressure was sepa- 
served 
panaon tube. Tho same current from the storage battery was fed through both 
tube 
d to the 
th 
ed 
mm 
pump and this comparison tube 
A 
on its sides received the 
P 
pectroscope gave 
a 
cted the red line of hyd 
pect 
ght from the 
i line from e 
P 
ided 
with 
d 
tub 
d 
nected to 
o 
for 
tube 
de by sid 
I 
ed 
appeared 
tly exac tfor 
be of equal brilliancy 
p to and 
d 
tube wh 
fro until the lines seen- in the spectroscope 
consisting 
purpose of 
This method of observation seemed to b 
su 
ffi 
™ -« purpose ot the experiment. Atone 
the well-known arrangement of two nicol p 
pectrophotometer 
connection with a 
n, . , uuerea oy such an instrument. 
The tube containing water vapor was exhausted 
separated tube was adjusted 
appeared to be equal under th 
to a certain pressure, and the 
brilliancy of the red lines in the two 
then varying amounts of 
tub 
dmitted to the tube connected to tl T ^'^ am ° UntS ° f ° X ^ en were 
ected to the pump, and the brilliancy again compared after 
