on some of the leading Doctrines of Caloric, Fc. 185 
additional elongation should have been produced, instead of four 
times as found by experiment. “¢ Since for all practical purposes 
uniform increments of bulk, or expansions of solids by heat, cor- 
respond to uniform increments of this power ;” then each of our 
old successive intervals of 90° may, for all practical purposes, be 
held te correspond to equal increments of temperature. 
Mr. Daiton’s intervals from 32° to 482° Fahr. are as before 
given, 102°-4; 77°-6; 63°°9; 55°-7; 50°-5=390°-1. . Now, 
if we call the first quantity 1-00, it will produce on a metallic 
rod a corresponding effect in expansion=1:00. The next in- 
terval of Mr, Dalton’s scale (equal always to 90° Fahr.) can pro- 
duce only 3 of the effect of the first, or as 75 to 100. The 
third, fourth, andsfifth intervals will give the fractional expan- 
sions in reference to the first, of 3%2,, 754,, and about -5%, or 
merely a half. 
No such diminution of effect was observed in the experiments ; 
from 392° to 482° F., the rod elongated as much as from 32° to 
122°, or double the quantity compatible with the Daltonian hy- 
pothesis. Thus therefore we have a rigid, and I think unan- 
swerable demonstration of the general correctness of the com- 
mon scale of temperature, and of the extreme inaccuracy and 
inapplicability of Mr. Dalton’s geometrical substitute. Should 
the preceding statement leave any doubt or obscurity concerning 
the legitimacy of the inference now drawn, I trust it will be en- 
tirely removed, wheu the details of the experiments are published, 
with drawings of the apparatus, in my treatise on pyrometry. 
Yet though the mercury in the thermometer tube move, pari 
passu, with a metallic rod, deemed uniform in its expansion, it 
does not prove perfectly equal uniformity of expansion to belong 
to the mercury. It will seem, no doubt, a paradoxical assertion, 
that of two bodies marching together, hand in hand, one of them 
may have an equuble pace, while that of the other is regularly, 
but very slowly accelerated. Yet I think the position just. It 
proceeds from a circumstance in the thermometer sufficiently 
obvious, but which seems to have escaped our systematic writers. 
I do not rest the proposition on any imperfection of workman- 
ship, or supposed irregularity in the expansions of the glass. 
Let us take a thermometer, the calibre of whose stem is per- 
fectly uniform, and whose scale is exactly divided. Let it have 
a range from zero to the 656th degree, at which mercury boils, 
by the accurate experiments of Creighton, At 32°, let the mer- 
cury stand at the bottom of the ivory scale, where of course the 
graduations commence. The bare part of the instrument is con- 
sequently the plunging limit, in most chemical researches on the 
temperature of liquids. Immerse the bulb in common oil, or 
oil 
