set the pot by the fire, just to make the result more mysterious), and in a short time the pot and the stool were frozen together, as we shall very shortly find it to be the case here. And all because salt has the power of lessening the attraction between the particles of ice. Here you see the tin dish is frozen to the board—I can even lift this little stool up by it.
This experiment cannot, I think, fail to impress upon your minds the fact, that whenever a solid body loses some of that force of attraction by means of which it remains solid, heat is absorbed; and if, on the other hand, we convert 
Fig. 21.a liquid into a solid, e.g., water into ice, a corresponding amount of heat is given out. I have an experiment shewing this to be the case.
