428 
WATER  OF  THE  DELAWARE  RIVER. 
For  convenience  of  comparison,  I  will  here  quote  the  results 
of  Professor  B,  Silliman,  Jr.,  obtained  some  years  ago  with  the 
Croton  and  Schuylkill  waters. 
Solid  matter  found  by  Prcf.  Silliman  : 
Grains. 
In  one  gallon  of  Croton  water,  .....  10.93 
In  one  gallon  of  Schuylkill  water,      .       .       .       .       .  5.50 
The  most  remarkable  thing  about  these  results  is  that  notwith- 
standing the  quantity  of  sand,  mud,  and  other  sediment  which 
is  suspended  in  the  river  water,  so  much  as  to  injure  the  pumps, 
and  which  must  be  in  great  measure  deposited  and  separated 
from  the  water  in  the  reservoir,  the  latter,  nevertheless,  actually 
contains  more  solid  matter  than  the  river  water  itself.  This  can 
only  be  accounted  for  by  the  favorable  conditions  presented  in 
the  reservoir  for  the  growth  of  minute  animals  and  plants,  whose 
remains  add  of  course  to  the  weight  of  the  solid  residue  obtained 
on  evaporation.  My  pupil,  Mr.  Holland  Bill,  has  at  my  request 
submitted  the  water  in  the  reservoir,  and  the  deposit  formed  at 
the  bottom,  to  a  microscopic  examination,  and  reports  to  me  that 
he  finds  in  the  water  several  varieties  of  animalcules  and  lichens 
or  minute  plants,  and  that  the  sediment  especially  is  almost 
wholly  composed  of  forests  of  minute  plants  through  which  roam 
herds  of  such  animals  as  Volvox  globator,  or  "  globejelly," 
Vibrio  anser,  or  "  goose  animalcule,"  and  several  species  of 
Baccillaria  and  Navicula.  On  the  surface  of  the  water  he  found 
a  slight  green  scum,  which  when  magnified  resolved  itself  into 
collections  of  the  Cercaria  mutabilis,  an  animal  production  char- 
acteristic of  stagnant  water.  Numerous  large  green  water  weeds 
may  also  be  seen  floating  in  the  reservoir. 
Recurring  to  the  results  given  above,  it  may  also  be  remarked 
that  the  river  water  is  really  somewhat  less  charged  with  foreign 
ingredients  than  that  of  the  springs,  although  the  latter  is  so 
much  more  pleasant  to  persons  possessing  delicate  organs  of 
taste.  This  probably  arises  from  the  fact  that  the  principal 
mineral  ingredient  in  spring  water,  as  shown  by  analysis,  is 
clilorid  of  sodium  or  common  salt,  while  the  river  water  is  prin- 
cipally contaminated  with  carbonates  of  lime,  magnesia,  potash, 
etc.,  which  give  water  a  bitter  taste. 
The  analysis  will  be  found  below  in  a  complete  form  and  ar- 
