Am'jJiy r'ioih8.rm' )    Romance  of  Chemical  Elements.  485 
Table  3. — Continued. 
Name. 
Sym- 
bol. 
Num- 
ber. 
Etymology. 
In  Allusion,  in 
Honor  of 
Tin 
Sn 
50 
T  z\t    Qt^nnnm  =  fin 
J — t  a  L-  •   O  LCUX1X  U  111  —  U1JL1 
T'tanium 
Ti 
22 
Gr.  Titanes  —  half  gods 
Tim  aofpn 
W 
74 
Swedish  tung-sten  heavy  stone 
Occurrence 
Uranium  
U 
92 
Planet  Uranus 
V 
23 
Northern  mythology  Vanades  —  Frigg 
Wolfram  
w 
74 
Old  Germ,  wolfram 
Occurrence 
Xenon  
Xe 
54 
Gr.  xenon  =  strange,  foreign 
"  The  strange 
element " 
Yb 
7i 
Swedish  town  Ytterby 
Occurrence 
Yttrium  
Y 
39 
Swedish  town  Ytterby 
Occurrence 
Zinc  
Zn 
30 
Germ,  zinke  =  prong,  tine 
Crystalline 
structure 
Zirconium  
Zr 
40 
Arab,  zargun  =  a  gem  stone,  zircon 
Occurrence 
contraction  of  the  respective  end  products  with  the  Greek  gennao — I 
produce,  thus  water-producing,  niter-producing  and  acid-producing 
element.  Again  many  of  the  rare  earth  metals  have  been  named 
after  asteroids  or  other  stars,  thus  cerium,  aldebaranium  (or  ytter- 
bium), cassiopeium  (or  lutecium),  dubhium  (or  thulium  1),  dene- 
bium  (or  thulium  2).  Uniform  is  also  the  ending  for  the  halogens 
— chlorine,  bromine,  iodine ;  while  the  metals  end  generally  in  -ium, 
and  the  metaloxides  of  the  basic  metals  in  -ia. 
Rare  Earth  Metals. 
The  rare  earth  metals  have  a  very  complex  and  confusing  his- 
tory, which  is  illustrated  in  their  "  family  tree  "  in  Tables  IV  and  V. 
The  first  column  gives  the  year,  the  last  column  the  name  of  the 
discoverer  or  rather  separator,  for  their  properties  are  so  alike  that 
their  separation  is  extremely  difficult.  Nevertheless  there  is  a  limit 
of  their  "separability,"  though  some  chemists  proposed  theories 
that  there  were  no  limit.  The  reason  for  their  great  similarity  must 
be  found  in  their  atomic  structure  and  the  periodic  system,  for  they 
form  a  very  slow  and  gradual  transition  from  electro-negative  to 
electro-positive  elements,  and  thus  their  difference  in  electropotential 
is  very  small.  This  is  just  as  bridging  two  rivers  of  equal  width  in 
one  case  with  seven,  in  the  other  case  with  thirty-six  pillars.  It  is 
clear  how  the  distance  of  the  pillars  in  these  two  cases  would  com- 
pare to  each  other.  So  we  have  in  the  periodic  system  in  one  in- 
stance between  two  inert  gases  seven  elements,  which  differ  natu- 
