482        New  Application  of  Tube  Hydrometers.  {A\Jo™iim™' 
Having  immersed  a  tube,  closed  at  the  lower  end  as  before,  in 
water,  we  pour  water  into  the  tube  until  it  sinks  about  §  of  its  length. 
It  should  float  upright.  We  are  now  to  mark  the  surface  of  the 
water  in  which  the  tube  floats,  and  also  the  surface  of  the  water  within 
the  tube.  The  tube  below  this  latter  mark  must  then  be  divided  into 
145  parts,  either  by  etching  on  the  glass  or,  what  is  more  practical,  by 
drawing  a  scale  on  paper,  numbering  the  degrees  from  the  top  (0°) 
downwards.  In  ascertaining  the  density  of  any  liquid  heavier  than 
water  the  tube  must  be  emptied  and  dried  by  rinsing  with  alcohol  and 
drawing  air  through  it  by  means  of  a  long  tube,  then  immersed  in 
water  of  60°  F.,  and  the  liquid  to  be  tried  poured  in  until  the  tube 
sinks  to  the  upper  mark.  It  can  then  be  taken  out,  and  the  degree 
of  density  shown  on  the  tube,  if  it  be  etched,  or  else  by  holding  it  on 
the  paper  scale  in  its  proper  position. 
Our  illustrations  have  been  thus  far  for  liquids  heavier  than  water ; 
for  those  lighter  than  water  the  tubes  or  scales  require  a  different 
division.  Unfortunately,  Beaume°s  method  of  dividing  his  hydrome- 
ters rendered  the  degrees  for  those  of  light  liquids  larger  than  those 
for  heavy  liquids,  and  by  comparison  we  find  they  ars  in  the  ratio  of 
145  to  140.  In  order,  therefore,  to  make  a  scale  for  light  liquids, 
we  divide  the  space  below  the  surface  of  the  water  within  the  tube 
into  140  parts  instead  of  145  parts,  as  at  first ;  the  degrees  are  then 
continued  upwards  70  or  more  parts.  These  divisions  are  numbered 
at  the  water  point  10°  (another  peculiarity  of  Beaume"s  scale),  and 
running  upwards  so  high  as  desired.  The  scale  below  the  water  point 
need  not  be  marked,  as  it  can  be  only  used  for  liquids  lighter  than 
water. 
The  tube  is  used  for  all  liquids  in  the  same  manner,  namely,  by 
pouring  into  it  the  liquid  to  be  tried  until  it  sinks  in  water  down  to 
the  mark  made  at  first  on  the  tube ;  then  by  holding  it  against  the 
paper  scale  marked  as  just  described.  The  surface  of  the  liquid  will 
indicate  its  proper  degree  of  density. 
An  advantage  which  the  tube  when  used  in  this  manner  possesses, 
is  the  small  quantity  of  liquid  necessary,  as  the  tube  can  be  made 
quite  small  in  diameter,  and  by  increasing  its  length  the  degrees  are 
rendered  larger,  and  thus  greater  accuracy  is  obtained.  It  may  also 
be  employed  in  ascertaining  the  density  of  extremely  heavy  liquids, 
where  no  hydrometer  could  be  found  of  service. 
