confidence and hope to our researches for such usefulness in every part of the creation. They have thus a peculiar value in adding connexion and imiversality to our perception of beneficial design.

7. There is a peculiar circumstance still to be noticed in the changes from ice to water and from water to steam. These changes take place at a particular a11d invariable degree of heat ; yet they do not take place suddenly when we increase the heat to this degree. This is a very curious ar- rangement. The temperature makes a stand, as it were, at the point where thaw, and where boiling take place. It is necessary to apply a con- siderable quantity of heat to produce these effects; all which heat disappears, or becomes latent, as it is called. We cannot raise the temperature of a thawing mass of ice till we have thawed the whole. We cannot raise the temperature of boiling water, or of steam rising from it, till we have converted all the water into steam. Any heat that we apply while these changes are going on is absorbed in producing the changes.

The consequences of this property of latent heat are very important. It is on this account that the changes now spoken of necessarily occupy a considerable time. Each part in suc- cession must have a proper degree of heat applied to it. If it were otherwise, thaw and evaporation must be instantaneous: at the first touch of