370      SOME  REMARKS  ON  CRYSTALS  CONTAINING  FLUID. 
SOME  REMARKS  ON  CRYSTALS  CONTAINING  FLUID. 
By  J.  B.  Dancer,  F.R.A.S. 
The  author  gave  a  brief  history  of  the  discovery  of  fluids  in 
crystals,  including  Sir  H.  Davy's  chemical  experiments  on  the 
fluids  and  gasses  obtained  from  the  cavities  in  quartz  crystals  ; 
Sir  David  Brewster's  discovery  of  the  pressure  cavities  in  the 
diamond,  ruby,  emerald,  amethyst,  chrysoberyl,  &c.  ;  the  exis- 
tence of  minute  crystals  in  these  cavities  and  the  two  new  and 
remarkable  fluids,  which  are  immiscible,  but  sometimes  found 
together  in  the  same  cavity — one  a  liquid  hydrocarbon,  named 
Brewstoline,  the  other  Cryptoline  ;  his  experiments  and  exami- 
nation of  artificial  crystals  deposited  from  aqueous  solutions  ; 
his  examination  of  the  Koh-i-noor  diamond  and  others  in  the 
East  India  Company's  museum  ;  and  the  geological  speculations 
to  which  these  discoveries  gave  rise.  Mr.  Dancer  mentioned 
the  experiments  of  his  late  father  and  others  in  producing  artifi- 
cial gems  by  intense  heat,  and  stated  that  his  own  attention  was 
drawn  to  this  subject  some  twenty-four  years  since,  by  Sir 
David  Brewster  presenting  him  with  a  specimen  of  topaz  containing 
fluid.  Since  that  time  he  had  examined  a  large  number  of  crys- 
tals, of  various  kinds,  from  the  collections  of  friends  ;  and  had 
found  fluid  in  quartz  from  South  America,  Norway,  the  Alps, 
Ireland,  Snowdon,  and  the  Isle  of  Man  ;  and  in  fluor  spar  from 
Derbyshire ;  this  latter  specimen  contained  a  considerable 
quantity  of  fluid,  which  burst  the  crystal  at  180°  temperature.* 
He  suggested  the  employment  of  the  microscope  as  a  valuable 
assistance  in  detecting  spurious  from  real  gems  ;  very  few  of 
the  latter  are  perfect,  and  the  flaws  and  cavities  are  so  distinct 
in  character  from  those  which  are  so  abundant  generally  in  arti- 
ficial gems  that  very  little  experience  is  sufficient  for  the  purpose. 
This  mode  of  testing  of  course  is  limited  to  transparent  crystals, 
but  might  be  employed  when  the  usual  methods  are  not  practi- 
cable. He  also  mentioned  Mr.  Sorby's  (F.R.S.)  discovery  of 
fluid  cavities  in  the  quartz  of  granite,  in  the  quartz  of  volcanic 
rocks,  and  also  in  the  feldspar  ejected  from  the  crater  of  Vesu- 
*After  this  paper  was  written,  Sir  David  Brewster  informed  the  author 
that  the  fluid  contained  in  crystals  of  fluor  spar  was  water,  and  that  the 
cavities  burst  at  a  temperature  of  150°. 
