Halliday & Matthiessen (1999: 543):
If we look at Newton's "Opticks", from which these are taken, we find that it consists of three simultaneous discourses interspersed. In one of these phases, Newton describes his experiments; in another he draws conclusions from the experiments; and in the third he provides mathematical explanations. … The examples just cited of grammatical metaphor are typical of the second phase. It is here that Newton is proceeding by logical steps through a reasoned argument; and he frequently needs to summarise the argument up to that point, or in anticipation of what is to come. A typical sequence would be the following:
… when Light goes out of Air through several contiguous refracting Mediums as through Water and Glass, … that Light … continues ever after to be white. … … the permanent whiteness argues, that …
The metaphorical nominalisation permanent whiteness summarises the earlier sequence of inductions.