184 
VARIETIES, 
form  a  porridge,  which  is  re-introduced  into  the  boiler,  and  heated  to  a 
temperature  of  201°  Fahr.,  at  which  it  is  maintained  for  one  hour.  The 
mass  is  then  pressed  as  before  in  bags  of  coarse  canvas  ;  as  it  is  rich  in 
nitrogenous  compounds,  which  form  the  base  of  the  yeast.  The  liquor* 
resulting  from  both  operations  are  mixed  together;  and  are  exposed  to  the 
action  of  the  air  in  large  uncovered  vats  during  two,  three,  and  even  for 
ten  days,  according  to  the  external  temperature. 
This  exposure  to  the  air  is  one  of  the  chief  points  in  the  new  method.. 
In  order  to  set  the  liquid  in  fermentation,  it  is  re-warmed  to  a  tempera- 
ture of  89.6°  Fahr.,  and  a  small  quantity  of  fresh  yeast  stirred  up  in  a 
little  warm  water  added.  The  fermentation  sets  in  very  soon,  and  may 
be  conducted  either  in  barrels  or  in  vats,  around  which  a  temperature  of 
59°  Fahr.  should  be  maintained  during  the  whole  operation. 
The  yeast  obtained  by  means  of  this  process  possesses  the  following  pro- 
perties : — 
1.  The  raising  power  is  much  superior  to  that  of  all  other  yeast;  2.  It 
has  no  bitter  or  acid  taste,  and  consequently  is  admirably  adapted  for 
pastry  work  ;  and  3.  It  is  of  an  extreme  whiteness,  and  consequently 
does  not  require  to  be  washed — hence  it  preserves  all  its  force. 
The  residue  remaining  after  the  fermentation  may  be  employed  to  make 
vinegar. — Pharm.  Journ.  from  Le  Genie  Industrial,  June,  1854. 
Influence  of  Elevation  of  Soil  on  the  Mortality  from  Cholera. — In  the  re- 
port on  cholera  in  1849,  by  the  Registrar-General  (see  this  Journal  for 
Nov.  1853,  p.  189,  and  for  June,  1854,  p.  100,)  it  is  stated  that  the  eleva- 
tion of  the  soil  in  London  has  a  more  constant  relation  with  the  mortality 
from  cholera  than  any  other  known  element — the  mortality  being  in  the 
inverse  ratio  of  the  elevation  ;  and  so  exactly  has  this  been  verified  in  the 
present  epidemic,  that  a  scale  of  premium  might  safely  have  been  drawn 
out  in  1849  to  rule  in  1854  to  the  following  effect  :  For  a  person  of  average 
condition  dwelling  under  20  feet  of  elevation,  the  premium  to  insure 
1,000?.  would  be  12?.;  while  for  those  living  at  from  100  to  350  feet  eleva- 
tion, the  Life  Office  would  be  secure  with  21.  premium.  But  the  following 
facia  worked  out  by  the  Registrar-General,  show  distinctly  the  inverse  re- 
lation that  the  mortality  of  cholera  bears  to  the  elevation  of  the  ground: — 
182,560  of  the  people  of  London,  in  1851,  lived  upon  sub-districts  cover- 
ing 2,849  acres  of  the  marsh  ground,  ranging  from  3  feet  below  to  1  foot 
above  the  high-water  mark  ;  2,693  died  there  of  cholera  in  1849,  and  2,227 
in  1854,  or  4,920  in  the  two  epidemics. 
263,914  of  the  population,  in  sub-districts  on  12,146  acres  of  ground  of 
80  feet  of  elevation  and  upwards,  lost  398  persons  by  cholera  in  1849,  and 
272  in  1854,  or  670  in  the  two  epidemics, 
12,824  persons  died  of  cholera  in  the  two  years  1849  and  1854  on  the 
18,429  acres  of  low  ground  under  10  feet  of  elevation,  out  of  a  population 
