578 REGNAULT ON THE 
These two series of experiments are notably different when 
the relative values are compared; but the absolute differences 
are really very small, and may be classed amongst the errors of 
observation. They suffice, I imagine, to show that the tension 
of mercurial vapour at 100° C. is about 0°5 millimetre, and that 
at a temperature of 50° it is scarcely 0°10 millimetre ; below 
50° it is therefore scarcely worthy of notice, and I considered 
it unnecessary to introduce the correction into the following 
Tables :— 
TaBLe II. 
Series A. 
Temperatures. Tensions. 
tempera- Difference. 
on Thermom.| “tures, _| Observed. | Calculated. 
