Bacon distinguishes the labour of human power — superinducing a new nature on a body, such as making silver yellow like gold — from the labour of human knowledge: discovering the form or cause responsible for a nature wherever it occurs. The two are, for Bacon, functionally identical projects viewed from different ends; knowing a form just is knowing how to produce or remove the nature it governs.
This is the same ambition Bacon had already sketched, more briefly, in The Advancement of Learning's discussion of metaphysic. Novum Organum's Book II is his attempt to actually deliver a working procedure for it — tables of presence, absence, and degree, applied first, at exhaustive length, to the nature of heat.
Drawn from Book II, Aphorism I of Novum Organum, opening Bacon's account of the discovery of forms.