A"o4mrbefXm-}       History  of  Argon  and  Helium.  551 
constant  until  all  gas  has  condensed  to  liquid,  strongly  indicates,  if  it 
does  not  prove,  that  argon  is  an  element.  Further  work  alone  can 
prove  which  view  is  correct. 
HELIUM. 
In  April,  1895,  Professor  Ramsay  was  studying  the  nature  of  gases 
obtained  by  heating  minerals,  his  object  no  doubt  being  to  obtain 
argon  in  this  way.    From  some  minerals  he  did  obtain  argon,  but 
from  many  of  them  he  obtained  a  very  light,  colorless  gas,  that  was 
lighter  than  argon  and  gave  a  different  spectrum,  and  in  particular  gave 
a  brilliant  D3  line  in  the  yellow,  which  line  had  been  noticed  in  the  solar 
spectrum,  but  had  never  been  obtained  from  an  element  on  the  earth. 
He  named  this  gas  helium,  from  rj\ios,  the  Greek  name  for  the 
sun.    The  D3  yellow  line  had  been  observed  thirty  years  before  by 
Lockyer  and  Frankland,  who  supposed  it  to  be  that  of  a  hypotheti- 
cal element,  which  they  named  helium.    Signor  Palmieri,  in  Italy, 
some  years  since,  obtained  a  soft  substance  from  some  ejected  lava 
of  Mt.  Vesuvius  that  gave  a  yellow  spectral  line  587  5,  the  same  as 
the  D3  line,  but  he  gives  no  details.  Dr.  Hillebrand,  of  Washington, 
D.  C,  studied  some  years  since,  the  gases  occluded  by  minerals,  in 
particular  uraninites  of  various  localities,1  but  found  only  nitrogen, 
as  the  spectrum  of  the  gas  obtained  was  that  of  nitrogen,  and  he 
obtained  nitric  oxide  on  sparking  it  with  oxygen.    He  sent  some  of 
the  uraninite  to  Professor  Ramsay,  who  found  that  it  did  contain  10 
per  cent,  of  nitrogen,  but  also  helium.    The  nitrogen  masked  the 
helium  spectrum  considerably,  and,  as  Professor  Ramsay  says,  it  is 
likely  that  if  Dr.  Hillebrand  had  been  working  with  cleveite  he 
would  have  discovered  helium.  To  extract  the  helium,  five  grammes 
of  coarsely  powdered  mineral  are  heated  in  a  glass  bulb  (made  of 
hard  glass)  which  has  been  exhausted  by  means  of  a  Topler  pump. 
Thus  are  obtained  C02,  H,  N,  H20,  and  helium.    Many  rare  mine- 
rals were  examined,  and  the  following  yielded  more  or  less  helium 
in  the  order  of  their  mention  :  monazite,  cleveite.  bioggerite,  pitch- 
bende,  xenotrim,  orangeite,   samarskite,   yttrotantalite,  hjelmite, 
fergusonite,  tantalite,  polycrase,  etc.  Professor  Ramsay  used  mainly 
cleveite  and  broggerite,  because  they  were  most  available.  Helium 
must  be  mechanically  held  by  the  minerals,  since  any  of  them,  when 
heated  and  allowed  to  cool  in  helium,  do  not  take  up  any  of  the 
1  Bulletin  U.S.  Geolog.  Survey,  78,  43. 
