PHARMACEUTICAL  NOTES  ON  TRAVEL. 
17 
British  gum  is  made  by  pouring  a  very  thin  layer  of  dry  starch 
into  a  highly  heated  iron  cylinder,  twenty  feet  long  by  about 
one  foot  in  diameter,  inclined  downwards  towards  the  lower  ex- 
tremity, and  revolving  rapidly  so  as  to  prevent  charring  ;  the 
product  which  drops  out  at  the  lower  end,  after  traversing  a  sin- 
gle length  of  the  cylinder,  has  acquired  the  properties  of  a  gum, 
and  is  extensively  employed  in  finishing  textile  fabrics.  Great 
quantities  of  flake  white  are  also  produced  in  these  works ;  this 
is  a  mixture  of  alum  and  chalk,  and  when  thrown  down  with  red 
color,  extracted  from  Brazil  wood,  constitutes  rose  pink. 
Large  displacement  cylinders  are  used  for  extracting  oak  bark 
and  dye  woods;  they  are  connected  with  the  boilers  so  as  to  have 
the  advantage  of  steam  pressure,  and  the  decoctions  are  passed 
successively  through  different  cylinders  filled  with  the  ground 
wood.  The  yield  of  extract  by  this  process  was  stated  to  be 
very  large. 
Before  leaving  the  subject  of  the  last  few  pages,  it  becomes 
me  to  acknowledge  my  obligations  to  a  member  of  this  firm,  to 
whom  I  am  indebted  for  much  valuable  information,  and  whose 
high  scientific  attainments  and  practical  skill  are  only  equalled 
by  his  liberality  and  freedom  from  that  niggardly  reserve  so 
often  met  with  among  those  who  avail  themselves  of  the  practi- 
cal uses  of  science. 
Manchester  is  a  great  hive  of  manufacturing  industry  ;  no- 
where have  the  applications  of  science  to  the  wants  of  civilized 
man  been  more  thoroughly  manifested  than  in  her  laboratories 
and  work-shops.  These  contribute  immensely  to  swell  the 
aggregate  of  the  nation's  wealth,  and  through  a  prosperous  com- 
merce, to  link  the  Mother  Country  in  lasting  friendship  with 
her  American  offspring.  Long  may  this  continue,  and  long  may 
the  people  of  both  nations  co-operate  in  the  cause  of  science  and 
humanity. 
We  now  leave  Manchester,  and  having  reached  a  convenient 
stopping-place,  must  reserve  for  a  future  essay,  our  Pharmaceuti- 
cal Notes  of  Liverpool,  Edinburgh,  Glasgow,  and  the  far-famed 
French  Capital. 
