VARIETIES. 
181 
1  beg  your  Excellency  to  receive,  with  the  reiterated  assurance  of  my 
lively  regrets  at  my  inability  to  except  the  chair  that  you  offer  me,  the  as- 
surance of  my  high  consideration.  Louis  Agassiz, 
Professor  in  the  University  of  Cambridge,  United  States  of  America. 
Cambridge,  Sept.  25,  1857.      [Boston  Daily  Adv.  and  Eclec.  Med.  Jour. 
Aquarium. — The  aquarium  has  already  become  a  common  source  of 
amusement  and  instruction.  The  cultivation  of  water  plants,  as  the  Victoria 
regia,  and  experiments  in  pisciculture  have  contributed  to  this  result;  and 
also,  the  researches  of  Mr.  Warrington,  on  what  is  called  the  organic  equili« 
brium  for  waters,  so  that  the  water  in  a  globe,  by  a  proper  selection  of 
kinds  of  animals  and  plants,  may  be  kept  pure  and  wholesome  for  the 
species  without  changing  it. 
The  first  idea  of  such  aquatic  reservoirs  is  attributed  in  the  Cosmos  to 
Mrs.  Power,  a  lady  of  French  descent,  but  English  by  marriage,  known  to 
naturalists  for  her  important  researches  on  molluscs. 
In  1832,  Mrs.  Power  took  up  her  residence  on  the  coast  of  Sicily  in  order 
to  study  the  molluscs  and  other  marine  animals.  She  remained  there  ten 
years,  and  made  two  aquaria,  one  for  molluscs  without  shells  and  the  other 
for  those  with  shells.  The  bottom  of  the  aquaria  was  covered  with  sand, 
stones  with  sea-weeds  attached,  branches  of  corals,  star  fish,  different  crus- 
taceans and  some  small  fishes,  while  her  principal  object  of  study  was  the 
Argonauta  Argo.  Situated  on  the  coast  she  could  readily  change  the  water 
of  the  aquaria ;  the  plan  since  developed  by  Mr.  Warrington  was  not  then 
understood. 
Mrs.  Power  also  used  marine  cages,  called  in  Italy  "  Gabiole  alia  Power/7 
in  England  "Power  Gages,"  which  she  had  constructed  in  the  lazaretto  of 
Messina.  Stones  with  algse,  and  corals  with  adhering  shells,  were  intro- 
duced, and  then,  the  Argonauta,  Echini,  fishes,  etc.  The  feeding  of  the 
animals  was  attended  to  twice  a  day.  A  staging  was  erected  just  above  the 
water's  surface,  where  the  cage  could  be  raised  near  the  surface;  and  the 
animals  conveniently  examined ;  and  there  Mrs.  Power  sat  during  the  long 
hours  carrying  on  her  observations,  witnessing  the  Polypus  or  Cephalopod 
>f  the  Argonaut  mending  its  shell,  and  studying  the  habits  of  many  other 
species. 
Mrs.  Power  also  constructed  a  portable  aquarium  for  studying  small 
molluscs.  Her  researches  were  continued  through  fifteen  years,  and  many 
important  results  were  contributed  by  her  to  the  progress  of  science. — 
American  Journal  of  Science  and  Arts. 
Compressed  air. —It  is  well  known  that  in  the  construction  of  the  Franco* 
Italian  railroad  it  is  necessary  to  tunnel  Mount  Cenis  through  a  distance  of 
several  kilometers  in  length.  To  supply  the  air  needed  for  the  workmen 
for  respiration,  it  has  been  proposed  to  use  powerful  pressure.    But  no 
