magnesium:  its  preparation  and  properties.  281 
If  this  view  is  adopted,  emery  must  be  ranked  as  a  distinct 
species,  and  not  as  a  mere  granular  form  of  corundum  or  sap- 
phire. 
In  conclusion,  I  would  state  that  practical  trials  of  the  Ches- 
ter emery,  in  several  of  the  large  armories  and  machine  shop3 
of  this  and  the  adjoinining  States,  have  proved  it  to  be  fully 
equal  in  value  to  the  well  known  emery  of  Naxos,  which  I  have 
no  doubt  it  will  wholly  supplant  in  this  country,  and  that  it 
will  ere  long  become  an  article  of  export  to  Europe,  either  in 
its  native  form,  or  in  a  manufactured  state. 
It  may  be  proper  to  add,  that  John  B.  Taft,  Esq.,  of  Boston, 
in  behalf  of  his  associates,  owners  of  the  emery  mine,  has  the 
sole  management  of  the  business  connected  with  the  mine. 
I  would  express  my  obligations  to  Mr.  J.  L.  Smith  for  the 
valuable  information  contained  in  his  articles  on  the  emery  of 
Asia  Minor  and  on  the  associated  minerals  of  the  emery  locali- 
ties, published  in  vols.  x.  and  xi.  of  this  Journal.  Also  to  Dr. 
H.  S.  Lucas,  of  Chester,  for  kind  assistance  in  the  field. 
32  Somerset  St.,  Boston,  Dec.  12th,  1864. 
Amer.  Journ.  Science  and  Arts,  Jan.,  1865. 
MAGNESIUM :  ITS  PREPARATION  AND  PROPERTIES. 
By  Emerson  J.  Reynolds,  F.R.G.S. 
Lecturer  on  Practical  Chemistry,  Ledwich  School  of  Medicine  and 
Surgery,  Dublin. 
Little  more  than  five  years  have  now  elapsed  since  two  dis- 
tinguished chemists  and  physicists,  Professors  Bunsen  and 
Roscoe,  while  engaged  in  some  photo-chemical  researches,  ob- 
served the  high  refrangibility  of  the  light  emitted  by  burning 
magnesium-wire,  and  also  its  great  "actinic  "  power  ;  these  ob- 
servations led  them  to  propose  it  as  a  convenient  source  of  light 
for  photographic  purposes.  It  is  but  recently  that  any  attempt 
has  been  made  to  utilize  the  valuable  hint  thus  thrown  out ;  this 
has  not  been  due  to  apathy  or  neglect,  but  principally  in  con- 
sequence of  the  difficulties  in  the  way  of  obtaining  the  metal  in 
sufficient  quantities  for  commercial  purposes.  The  first  steps 
toward  the  simplification  of  the  manufacture  of  this  metal  we 
owe  to  the  researches  of  Bunsen  and  Matthiessen  ;  but  to  St. 
