86 
VARIETIES. 
num  in  aqua  regia,  a  precipitate  consisting  of  the  double  chloride  of  pla- 
tinum and  ammonium  is  formed.  If  this  double  salt  be  heated  to  redness, 
its  volatile  constituents  escape  into  the  atmosphere  and  leave  the  platinum 
behind  in  porous  and  slightly  adherent  masses — as  spongy  platinum,  in 
fact. — Journal  of  Applied  Chemistry. 
Porosity  of  Caoutchouc. — M.  Payen  states  in  Comptes  Rendus  that  a 
microscopic  examination  of  thin  sheets  of  caoutchouc  discloses  minute 
holes  or  pores,  which  are  rounded,  and  communicate  with  each  other. 
Contact  with  liquid  makes  these  pores  more  distinct.  Vulcanized  India- 
rubber  exhibits  narrower  cavities  and  concentric  circles  spreading  from 
one  pore  to  another,  showing  successive  zones  of  diminishing  action  of  the 
sulphur.  By  exposure  to  water  the  caoutchouc  becomes  whiter  and  opaque 
through  absorbing  the  fluid.  M.  Payen  considers  this  porosity  to  be  con- 
cerned in  the  dialytic  action  of  India-rubber  on  gases  discovered  by  Pro- 
fessor Graham. — Intellectual  Observer. 
Science  in  the  Dairy. — There  are  many  dairymen  who  persist  in  thinking 
it  a  foolish  whim,  that  the  milk  last  drawn  from  the  udder  of  a  cow  con- 
tains more  cream  than  the  first  obtained.  Yet  careful  analyses  have  fully 
proven  the  correctness  of  the  assumption.  Schubler  says  the  milk  .last 
drawn  contains  three  times  as  much  cream  as  that  first  procured.  Dr. 
Anderson,  in  "  Dickerson's  Practical  Agriculture,"  asserts  that  he  found, 
by  actual  analysis,  in  one  instance,  that  the  last  cup  of  milk  drawn  from 
the  udder  contained  sixteen  times  as  much  cream  as  the  first  cup.  The 
separation  of  cream  from  the  milk  takes  place,  in  part,  in  the  udder  of  the 
cow,  particularly  if  the  cow  is  suffered  to  stand  at  rest  for  some  time  pre- 
vious k>  milking. 
The  exercise  required  of  a  cow  that  is  driven  a  considerable  distance, 
just  before  being  milked,  causes  an  increased  play  of  her  respiratory  or- 
gans. The  excess  of  oxygen  thus  respired  unites  with  a  portion  of  the 
butter,  of  which  the  cream  is  largely  composed,  and  consumes  it.  The 
same  is  the  case  when  a  cow  is  harassed,  or  in  any  way  seriously  annoyed, 
just  previous  to  being  milked.  It  should  be  a  great  care  of  all  dairy 
farmers,  to  keep  their  cows  as  free  as  possible  from  every  kind  of  annoy- 
ance, and  thus  prevent  them  from  inhaling  an  excess  of  oxygen. 
The  animal  heat  evolved  in  the  consumption  of  an  excess  of  oxygen, 
more  than  is  sufficient  to  act  properly  on  the  blood,  besides  destroying  the 
cream,  also  decreases  the  volume  of  milk,  and  elevates  the  temperature  of 
the  same  to  such  an  extent  that  acetous  fermentation  is  induced,  which  can- 
not be  arrested  even  after  the  milk  is  taken  from  the  cow  ;  hence  the  milk 
is  diminished  in  richness,  and  speedily  becomes  sour.  For  the  above  rea- 
sons stall-fed  cows,  as  a  general  thing,  give  richer  milk  than  those  suffered 
to  run  in  the  fields.  For  the  same  reason  morning's  milk  is  richer  than 
night's  milk.    The  quietness  of  night  is  favorable  to  the  formation  and 
