74 Mr. six's Account of 
fide, beginning with o at the bottom, afcencls. The divifions 
are afcertained by placing this thermometer with a good flan- 
hard mercurial one in water gradually heating or cooling, and 
marking the divifions- of the new fcale at every 5 0 L Thus 
far our thermometer refembles in fome re ip eels- thofe of Mr. 
Bernoulli and Lord Charles cavendish ; but the method 
■of fhewing how high the mercury had rifen- in the obferver’s- 
ah fence, the eflential property of an inftrument of this kind r 
is wholly different from theirs, and' effected in the following 
manner. Within the fmall tube of the thermometer, above 
the furfaee of the mercury on either fide, immerfed in thefpirit 
©f wine, is placed a- lmall index, fo fitted as to pafs up and; 
down as occalion may require : that furfaee of the mercury 
which riles carries up the index with it, which index does not 
return with the mercury when it defeends ; but, by remaining' 
fixed, fhews diftinftly, and very accurately, how high the- 
mercury had rifen, and confequently what degree of heat or 
cold had happened. Fig. 2. reprefen t-s one of thele indexes 
drawn larger than the real ones, to render it more diftinch, 
ci is a fmall glafs tube, three quarters of an inch long, herme- 
tically fealed at each end, inclofing a piece of fteel wire, nearly 
of the fame length ; at each end cd is fixed a fhort piece of a< 
tube of black glafs, of fuch a diameter as to pafs freely up 
and down within the fmall tube of the thermometer. The 
lower end, floating on the furfaee of the mercury, is carried 
up with it when it riles, while the piece at the upper end, 
being of the fame diameter, keeps the body of the index pa- 
rallel to the fides of the thermometrical tube.' From the upper 
end of the body of the index at c is drawn a fpring of glafs to 
* The divifions below the freezing point are taken by means of a mixture of 
it'a fait and ice, a? deferibed by nollet, ue luc, and others. 
the 
