234 
Editorial. 
( Am.  Jour.  Pharm. 
I       May,  1899. 
EDITORIAL. 
URANIC,  THORIC  AND  POI,ONIC  RAYS. 
It  is  now  twenty-five  years  since  Balfour  Stewart  wrote  his  remarkable  treatise 
on  "The  Conservation  of  Energy."  In  it  was  shown,  among  other  things, 
that  the  ancients  even  as  far  back  as  Heraclitus,  who  lived  at  Ephesus  B.C. 
500,  conceived  the  idea  of  the  essential  unrest  and  energy  of  things.  He  gives 
us,  it  will  be  recalled,  at  one  place,  a  classification  of  energies,  and  in  doing  so 
proceeds  with  the  following  words  of  caution  :  "We  must  warn  our  readers 
that  this  enumeration  has  nothing  absolute  or  complete  about  it,  representing  as 
it  does,  not  so  much  the  present  state  of  our  knowledge  as  of  our  want  of  knowl. 
edge,  or  rather  of  profound  ignorance  of  the  ultimate  constitution  of  matter." 
Since  the  publication  of  this  book  the  law  of  the  conservation  of  energy  has 
come  to  be  regarded  as  one  of  the  most  essential  conditions  in  nature. 
A  few  years  ago  the  world  was  startled  by  the  discovery  by  Professor  Roentgen 
of  certain  rays  from  a  Crookes'  vacuum  tube.  These  rays  are  not  refracted, 
develop  no  heat,  the  retina  of  the  eye  is  not  sensitive  to  them,  and  they  are 
without  influence  upon  the  most  sensitive  magnetic  instruments.  These  rays 
have  been  called  Roentgen  X-Rays,  and  are  supposed  to  be  due  to  longitudinal 
vibrations  of  ether.  In  this  respect  they  agree  with  Hittorfs  Kathode  Rays, 
but  in  the  latter  the  waves  are  of  extremely  short  wave  lengths.  "Hertz's 
electric  light  waves,'"  on  the  other  hand,  differ  from  those  of  either  Roentgen 
or  Hittorf  in  that  they  are  transversal  and  of  greater  wave  length  than  either 
of  them.  More  recently,  since  the  well-known  discovery  by  Roentgen,  Bec- 
querel  has  undertaken  to  determine  the  photographic  effects  of  certain  phos- 
phorescent and  fluorescent  substances,  and  we  have  as  a  result  of  the  author's 
experiments  what  are  known  as  BecquereVs  Rays. 
In  January,  1896,  Poincare  inquired,  after  certain  experiments  had  been 
made  by  him,  if  in  all  bodies  in  which  the  fluorescence  is  sufficiently  intense 
there  is  not  an  emission  of  Roentgen,  as  well  as  luminous  rays,  no  matter  what 
may  be  the  cause  of  the  fluorescence.  M.  Henry  has  shown  that  "phosphor- 
escent sulphide  of  zinc  could  produce  photographic  impressions  through  a  sheet 
of  black  paper  which  was  quite  impervious  to  light."  Niewenglowski  observed 
the  same  phenomenon  with  sulphide  of  calcium  which  has  been  exposed  to 
light.  Later  on,  Troost  obtained  strong  photographic  impressions  with  an  arti- 
ficial phosphorescent  hexagonal  blende  through  black  paper  and  thick  card- 
board. Becquerel  made  similar  experiments  with  uranium  salts,  some  of  which 
are  fluorescent.  He  obtained  photographic  impressions  through  black  paper 
with  the  double  sulphate  of  uranium  and  potassium.  Becquerel  found  that 
uranium  and  all  of  its  compounds,  whether  fluorescent  or  not,  act  in  the  same 
manner,  and  metallic  uranium  is  the  most  active  of  them  all.  He  also  noticed 
that  light  is  not  necessary,  but  that  uranium  compounds  kept  in  the  dark  for 
years  continued  to  act  on  photographic  plates.  This  was  an  entirely  new  phe- 
nomenon. He  also  showed  that  uranic  rays  were  possessed  of  the  following 
properties  :  They  traverse  opaque  bodies,  but  are  absorbed  more  easily  and  are, 
therefore,  less  penetrating  than  Roentgen  rays.  They  make  the  air  through 
which  they  pass  a  conductor  of  electricity,  as  do  Roentgen  rays  ;  this  is  an  im- 
portant property  of  both  kinds  of  rays.  Following  these  results  it  was  only 
natural  to  ask  if  uranium  were  the  only  metal  possessed  of  this  property,  and 
