Article #42 - What is the reason that iron becomes heated by being hammered?

   It is a well known fact that when bodies pass from a dense to a ?? rare state, their capacity for caloric or heat is increased, heat is consequently absorbed, and cold is produced, but when bodies pass from a soft to a hard state, their capacity for caloric or heat is diminished, consequently the heat which was before latent, is thrown off and becomes sensible, when air is compressed forcibly in a tube the heat which was before latent becomes sensible, because the condensation lessens its capacity for caloric.

            For the same reason, when a piece of lead or iron is beaten with a hammer it becomes hot, because the metal in consequence of the hammering has its capacity for caloric reduced, and

thus the heat which was before latent becomes sensible.

                                    Jabez Baily