6i6 
Applied  Crystallography 
f  Am.  Jour.  Pharm. 
<-        Sept.  19 19. 
lid"'  forms  of  ammonium  magnesium  phosphate.  The  different 
attitude  toward  mathematical  crystallography  on  the  part  of  chem- 
ists as  compared  with  mineralogists  is  due  to  the  fact,  indirectly 
mentioned  above,  that  the  chemist  deals  with  minute  forms,  with 
which  our  sense  of  touch  is  not  available.  The  field  of  the  micro- 
scope is  practically  a  two-dimensional  space,  the  full  appreciation  of 
a  crystal  requires  its  measurement  in  three  directions. 
Of  late,  however,  a  much  more  extended  application  of  the  micro- 
scope to  the  solution  of  analytic  problems  has  been  inaugurated, 
and  in  the  course  of  a  few  years  a  vast  amount  of  data  of  the 
most  valuable  type  will  be  obtained.  For  this  special  training  and 
highly  specialized  apparatus  is  required.  Thorough  knowledge  of 
the  mathematics  of  crystallography,  in  the  phenomena  of  polarized 
light  and  good  technical  skill  are  required.  Elaborate  equipment 
of  the  microscope  is  needed,  polarizing  apparatus,  selenites  and 
similar  accessories,  practically  unknown  to  the  general  analyst  and 
works  chemist. 
The  United  States  Bureau  of  Chemistry  has  been  for  some  time 
carrying  out  researches  along  these  lines,  and  has  a  special  worker, 
Dr.  Edgar  T.  Wherry,  to  whom  the  title  of  "  Crystallographer  "  has 
been  given.  As  he  was  a  pupil  of  mine  in  his  elementary  studies  in 
chemistry,  and  as  I  have  been  associated  with  him  in  work  at  the 
Wagner  Free  Institute  of  Science.  I  have  had  special  interest  in 
his  researches.  At  the  meeting  of  the  Philadelphia  Mineralogic 
Society  in  March  last,  Dr.  Wherry  presented  some  of  the  results 
of  his  investigations.  Among  these  was  an  ingenious  detection  of 
an  unusual  sugar  that  had  been  obtained  by  the  bees  of  a  certain 
area  in  the  United  States  through  feeding  on  the  honey-dew  pro- 
duced by  an  immigrant  aphis.  This  sugar  was  not  digestible  by 
the  bees  and  they  starved  to  death  in  great  numbers.  Another  in- 
stance of  the  use  of  the  methods  was  in  determining  the  reason  for 
the  differences  in  color  in  a  new  high  explosive  which  the  United 
States  authorities  were  making.  It  was  found  that  the  differences 
were  due  to  inclusions  in  the  crystals. 
A  remarkable  application  of  x-rays  to  the  study  of  molecular 
structure  has  been  discovered  and  some  extremely  interesting  results 
are  already  at  hand.  So  far  they  have  a  bearing  on  theoretical 
questions  only,  but  chemists  know  very  well  how  soon  pure  science 
may  be  translated  into  a  practical  form.  Space  does  not  permit 
of  discussion  of  these  x-ray  studies. 
