Professor Adams on the Theory of the Thermometer. 123 
The investigations connected with the hypothesis, that 
caloric is a material substance, appear to have given rise 
somewhat extensively among writers, to what, itis believed 
will be considered, upon examination, an erroneous view 
of the construction of the thermometer. What is intend- 
ed by this communication, may best be accomplished, by 
first making quotations from several writers, and by after- 
wards making such remarks upon them, as the occasion 
_ renders necessary.- ~ Sine ee 
Dr. Henry says, ‘‘ the experiments. of De Luc have 
shown, that the ratio of expansion does not strictly keep 
pace with the actual increments of temperature ; and that 
the amount of the expansion increases with, the temper- 
ature. Thus if a given quantity of mercury, in being 
heated from 32° to 122°, the first half of the scale, be éx- 
panded 14 parts, in being raised from 122° to 212°, the 
higher half, it will be expanded 15 parts.” 
“From the inquiries of ‘Mr. Dalton,” ‘continues the 
same writer, it ‘‘ appears to follow, that the irregularity of the 
expansion of mercury is considerably greater than has been 
stated by De Luc.” V pbrtiagy: 
Again, ‘‘ making due correction for this circumstance,” 
that is, the expansion of the glass in the thermometer, “Mr. 
Dalton has been-led to conclude from his experiments, 
that notwithstanding the apparent diversities of expansion 
in different fluids, they all actually expand according to the 
same law ; viz. that the quantity of expansion is as the 
square of the temperature from their respective freezing 
points, or from their point of greatest density. If then a 
thermometer be constructed, with degrees corresponding to 
this law, they will be found to differ very considerably from 
those of the common mercurial theremometer, in which the 
space between freezing and boiling is divided into 180 equal 
parts. In the appendix, will be found a table showing the 
correspondence between the old scale, and the new one 
constructed on Mr. Dalton’s principle.* 
Dr. Gorham says, Chem. I. 74, “the thermometer as 
commonly constructed with equal divisions, is not to be 
considered as perfectly correct in its indications of temper- 
ature. Jiquids not only differ in their expansibilities, but 
* Chemistry, Vo}. 1. Chap. HI. Sect. I. 
