4. A maximum capacity for receiving, transmitting, storing and carrying away heat.
5. Freedom from tendency to decompose or to change in composition by gumming or otherwise, on exposure to the air (79) while in use.
6. Entire absence of acid or other properties liable to produce injury of materials or metals (77) with which they may be brought in contact.
7. A high temperature of vaporization and a low temperature (83) of solidification.
8. Special adaptation as to speed and pressure of rubbing surfaces under which the unguent is to be used.
9. It must be free from grit and from all foreign matter.
The author will add that for use in horology:
10. It must possess a minimum variation of viscosity (84) in varying temperatures.
The writer can see no reason why a mineral oil which has been properly refined and of the proper consistency, either alone or mixed with animal oil, could not be used to great advantage in horology. Indeed, the possibilities in this direction seem to be so pregnant with promises of good results that some space will be devoted to the matter.