^""MaTiss?'"  }      The  Microscope— Hints  to  Beginners.  257 
spinning  it  takes  on  a  neat  circle  of  cement.  Should  air-bubbles  be  present 
in  the  medium,  they  can  easily  be  removed  before  mounting  by  heating  a 
needle-point  and  touching  the  bubbles  ;  if  they  are  detected  after  mounting 
they  may  disappear  in  the  drying,  but  it  is  best  to  thoroughly  examine  the 
balsam  before  covering,  and  thus  prevent  the  vexation  caused  by  their 
presence. 
In  the  above  description  it  is  recommended  to  make  a  section  from  the 
dry  wood.  In  some  cases  such  a  section  will  be  found,  after  soaking  in  the 
turpentine,  to  be  slightly  curled ;  it  ought  then  to  be  put  between  two 
glass  slips  held  together  by  a  clip  until  quite  flat,  or  else  before  making 
the  section  let  it  soak  in  water  for  a  day  or  longer,  according  to  the  thick- 
ness of  the  wood,  and  then  slice  it;  but  in  order  to  mount  it  in  balsam  it 
must  be  steeped  in  spirit,  then  in  oil  of  cloves,  then  in  turpentine,  and 
lastly  mounted  in  the  balsam. 
In  mounting  an  object  in  fluid  you  have  to  take  into  consideration  the 
nature  of  the  substance  and  the  suitability  of  the  medium.  The  fluids  used 
are  camphor  water,  glycerin,  and  various  solutions.  Glycerin  is  not  recom- 
mended for  many  vegetable  substances,  as  it  is  liable  to  rupture  the  cell 
wall.  I  have  found  camphor  water  a  very  good  preservative,  having 
mounted  starch  granules  in  it  about  six  years  ago,  and  at  the  present  time 
find  them  as  good  as  when  first  mounted.  To  mount  an  object  by  this 
method,  procure  either  a  slide  with  a  sunk  cell,  that  is,  the  glass  hollowed 
out  in  the  centre  (these  can  be  had  from  any  optician),  or  else  make  a  cell 
with  a  ring  of  gold  size,  not  so  wide  as  a  glass  circle,  on  a  plain  slide.  This 
is  usually  done  by  the  turntable  as  mentioned  above.  After  the  cement  is 
dry,  the  cell  should  be  filled  to  overflowing  with  camphor  water,  and  the 
object,  such  as  a  piece  of  cuticle,  immersed  in  it ;  the  cover  is  then  to  be 
carefully  let  down,  taking  the  precaution  to  see  that  no  air-bubbles  have 
been  imprisoned.  The  next  stage  is  to  remove  the  superfluous  water  from 
the  sides  of  the  cell ;  this  is  done  with  a  little  blotting-paper,  taking  care 
not  to  bring  it  too  near  the  edge  of  the  cell,  otherwise  it  will  draw  out 
.  some  of  the  liquid,  thus  causing  air  to  enter,  and  necessitating  remounting. 
Having  now  removed  the  superfluous  moisture  without  disturbing  the 
cover  take  a  camel-hair  brush  dipped  in  gold  size  or  other  cement,  and 
paint  round  but  not  on  the  circle.  When  dry,  paint  afresh,  gradually 
getting  nearer  the  cover,  but  always  remembering  to  allow  each  coating  of 
cement  to  dry ;  flnally  include  the  edge  of  the  cover  about  the  eighth  of  an 
inch,  or  a  little  less;  and,  in  order  to  give  neatness  to  the  slide,  a  ring  of 
some  cement  should  be  put  on  with  the  turntable. 
Mounting  in  glycerin  jelly  is  much  easier  than  the  above,  more  like 
mounting  in  balsam,  and,  as  it  answers  for  many  objects,  and  is  easily 
worked,  it  is  in  great  favor  among  microscopists.  Make  a  thin  longi- 
tudinal section  of  |5ome  soft  stem,  such  as  chickweed,  wash  it  well,  drain, 
transfer  to  a  slide  gently  warmed,  take, a  glass  rod,  dip  it  into  melted 
glycerin  jelly,  and  allow  a  drop  or  two  to  fall  over  the  object  until  you 
think  there  is  sufficient,  of  course  looking  out  as  before  for  air-bubbles ; 
warm  the  glass  cover  and  let  down  gently  ;  put  aside  for  half  an  hour,  and 
it  will  then  be  ready  to  receive  a  ring  of  cement  or  paper  cover. 
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