It is this—that caloric, which produces heat, is an extremely subtile fluid, of so refined a nature that it possesses no weight, yet is capable of diffusing itself among the particles of the most solid bodies.
It is also believed that—all bodies are subject to the action of two opposing forces: one, the mutual attraction of their particles; the other, the repulsive force of caloric—and that bodies exist in the æriform, fluid, or solid state, according to the predominance of either the one or the other of these opposing forces.
329. How do we measure the quantity of caloric in any substance?
It is impossible to determine the amount of caloric which any body contains. Our sensations would obviously be deceptive, since, if we dipped the right hand in snow, and held the left hand before the fire, and then immersed both hands in cold water, the water would feel warm to the right hand and cold to the left hand.
But, as caloric uniformly expands substances that are under its influence, one of the bodies most sensitive to calorific effects has been selected to be the indicator of the amount of caloric. This substance is quicksilver; and the scale of measurement, and the apparatus for exhibiting the rise or fall of the quicksilver, constitute the thermometer.
330. If it is impossible to measure the amount of caloric in any substance, how can it be said that ice absorbs 140. deg. in becoming water?
Those figures simply record the amount of calorie indicated by the thermometer. The instrument will show with sufficient accuracy the relative amount of caloric in various bodies, or in the same bodies under different circumstances, but it can never determine the precise amount of caloric in any one body.
"Great is the Lord, and greatly to be praised in the city of our God, in the mountain of his holiness."—Psalm xlviii.