182 
VARIETIES. 
means  of  accomplishing  this  result  have  been  devised,  and  the  project  of 
tunnel  is  suspended.  It  is  found  that  an  increase  in  the  length  of  a  tube 
connected  with  a  blowing  machine  diminishes,  at  a  rapid  rate,  the  intensity 
of  the  movement.  This  calls  to  mind  the  experiment  of  Wilkinson,  who 
established  the  fact  of  the  resistance  exerted  by  the  walls  of  a  pipe  on  the 
velocity  of  the  compressed  air.  M.  Daru,  engineer  on  the  Northern  rail- 
road, has  added  the  following  facts  meriting  consideration.  A  wheel  which 
made  thirty  revolutions  a  minute  in  driving  a  blast  through  straight  pipes 
one  metre  long,  made  only  twelve  when  the  pipes  were  four  meters  long 
and  were  bent  twice  at  an  angle,  one  of  them  right  and  the  other  very 
obtuse.  When,  on  taking  the  air  from  close  at  hand,  the  effect  produced 
was  great,  it  was  very  feeble  when  it  came  through  ten  meters  long  with  a 
right  angled  bend. 
In  the  experiments  by  Wilkinson,  the  compressed  air  ceased  to  be  trans- 
mitted at  280  meters  ;  and  it  is  not  280  meters,  but  a  length  of  several  kilo- 
meters, which  must  be  met  at  the  tunnel  of  Mount  Cenis.  The  question 
therefore  is  far  from  being  resolved. — Ibid. 
Soft  sulphur  for  stopping  teeth. — M.  H.  Henriothas  successfully  employed 
soft  sulphur  as  a  substitute  for  the  numerous  cements  used  for  decayed 
teeth.  This  substance,  which  acquires  in  a  little  time  after  its  introduction 
in  the  cavity  a  considerable  degree  of  hardness,  is  insoluble  in  all  bodies 
in  the  cold.  It  is  not  attacked  by  any  of  the  alimentary  substances  or 
dentrifices,  and  is  easily  and  quickly  applied.  All  that  is  necessary  is  to 
put  some  fragments  of  sulphur,  or  better,  some  washed  flowers  of  sulphur, 
in  a  glass  tube,  sealed  at  one  end,  heat  it  over  a  spirit  lamp,  and  pour  into 
cold  water.  The  sulphur  should  be  heated  to  a  temperature  above  390°  F., 
when  we  obtain,  on  pouring  into  cold  water,  a  spongy  mass,  brown,  soft, 
and  elastic,  which  is  called  soft  sulphur.  It  is  known  that  the  melted  sul- 
phur, if  the  temperature  is  sufficiently  high,  becomes  thick  and  viscous, 
which  is  then  again  rendered  fluid.  The  preparation  thus  obtained  is  in- 
troduced in  the  form  of  little  balls,  which  are  pressed  into  the  decayed  tooth. 
The  soft  sulphur  may  be  prepared  in  two  minutes. — London  Pharm.  Journ. 
from  Journ  des  Connais.  Med. 
Cements  for  stopping  the  teeth. — M.  Vagner  recommends  the  following  : 
A  drachm  of  gutta  percha,  softened  by  hot  water,  is  to  be  worked  up  with 
catechu  powder  and  tannic  acid,  of  each  half  a  drachm,  and  with  a  drop  of 
essential  oil.  For  use,  a  morsel  is  to  be  softened  over  the  flame  of  a  spirit 
lamp,  introduced  while  warm  into  the  cavity  of  the  tooth,  and  adapted 
properly.  The  mass  becomes  hardened,  and  even  after  several  months  ex- 
hibits no  traces  of  decomposition.  M.  Poufcon  states  that  we  may  also  ob- 
tain an  excellent  cement  by  dissolving  ono  part  of  mastic  in  two  of  collodion. 
•Having  well  dried  out  the  cavity,  a  small  ball  of  cotton  soaked  in  some 
