52 
Thermometers. 
f  Am.  Jour.  Pharm. 
I    February.  1904. 
As  such  an  instrument  as  this  could  not  conveniently  be  carried 
from  place  to  place  and  having  no  scale  for  reference  or  comparison, 
it  had  little  practical  value;  its  chief  purpose  being  to  draw  attention 
to  the  subject  and  open  the  way  for  further  discoveries.  Efforts  were 
soon  made  to  construct  something  that  would  be  portable  and  more 
durable,  and  as  a  result,  a  few  years  later,  an  instrument  was  brought 
out  made  somewhat  after  the  manner  of  the  first  one,  but  inverted. 
A  glass  ball  was  blown  having  an  opening  at  the  top  through  which 
a  glass  tube,  open  at  both  ends,  was  inserted  and  passed  down  to 
near  the  bottom  of  the  ball  and  under  the  colored  spirits  that  partly 
filled  the  ball.  When  heat  was  applied  the  air  in  the  ball  began  to 
expand  and  the  spirits  was  forced  up  in  the  tube.  A  scale  for  this 
followed  shortly  after,  not  engraved  or  marked  on  the  tube,  but  a 
few  lines  were  ruled  on  a  piece  of  wood  which  was  held  against  the 
tube  when  it  was  desired  to  read  off  the  height  of  the  column.  The 
top  mark  on  this  scale  was  made  to  indicate  the  hottest  day  in  sum- 
mer and  the  lowest  mark  was  placed  where  the  column  stood  when 
the  ball  was  placed  in  snow.  When  the  space  between  the  two 
points  was  divided  into  sixty  parts,  which  followed  later  on,  it  com- 
pleted the  discovery  of  the  thermometer. 
It  was  only  a  short  time  after,  somewhere  about  the  middle  of 
the  seventeenth  century,  that  thermometers  were  made  having  the 
spirits  introduced  into  a  bulb  from  which  all  the  air  was  expelled 
and  having  the  opposite  end  of  the  tube- sealed  over,  very  much  the 
same  as  those  still  in  use.  The  honor  of  constructing  the  first 
mercurial  thermometer  belongs  to  Romer,  who  about  1709  pro- 
duced an  instrument  of  this  kind,  only  failing  to  add  a  scale  to  make 
it  complete.  It  was  in  1724  that  a  scale  having  fixed  and  definite 
points  for  graduation  was  invented  and  introduced  by  Fahrenheit. 
Taking  boiling  water  to  indicate  one  point  and  melting  ice  the  other 
point,  he  divided  the  space  info  180  equal  parts,  and  this  scale 
applied  brought  the  thermometer  to  full  completion.  The  object 
Fahrenheit  had  in  view  when  he  fixed  the  zero  point  320  below 
freezing  is  quite  unknown  and  has  puzzled  many  inquiring  minds, 
but  when  he  selected  the  two  points  named  for  the  foundation  of  his 
scale,  he  did  a  very  wise  thing,  for  experience  has  proved  them  to 
be  the  very  best  that  could  have  been  chosen  and  it  will  always 
remain  to  his  credit. 
Very  fortunately  for  the  thermometer  maker,  the  situation  of  the 
